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With every winter storm, including the blizzard hitting the Northeast this week, climate change skeptics return to a familiar argument: If the world is getting warmer, why am I stuck out here, shoveling so much snow?

Climate scientists tell FRONTLINE that blizzards don't refute evidence of climate change - in fact, climate change can make blizzards more intense. The first thing people need to understand, they say, is the difference between climate and weather.

Also read: 2014 Was the Warmest Year on Record, NASA and NOAA Say

"Weather is telling us what is happening at a particular time," said Rutgers Climate Institute co-director Anthony Broccoli. "Climate is telling us the statistics of the weather we experience. One analogy that is often used is that weather determines what clothes you wear on a particular day, but climate describes what clothes you have hanging in your closet."

So what will we be wearing in the future? Climate change may mean that people in cold regions will spend fewer days in snow boots. But on the days they need them, they'll really need them.

"You have to remember that there are two factors that result in heavy snow: It has to be cold enough to snow, and the atmosphere has to be moist," said Michael Oppenheimer, a professor of Geosciences and International Affairs at Princeton University.

Also read: How Has the World Warmed Where You Live?

Winters will likely get shorter as a result of climate change, Oppenheimer said. "On the other hand," he said, "during the period when it is cold enough to snow, if you've got enough moisture in the air, you can get some wicked big snowstorms."

Why does climate change lead to more moisture?

"The maximum amount of water vapor that can be present increases with increasing temperatures. That's just a consequence of the laws of physics," Broccoli said.

Global sea temperatures have gone up about one degree Fahrenheit since the 1970s because of human activity, said Kevin Trenberth, a distinguished senior scientist in climate analysis at the National Center for Atmospheric Research.

The higher sea temperatures lead to higher temperatures above the sea surface. That warmth moves throughout the year, and at this time of year, gathers off the East Coast.

"If we have a storm that's developing, it reaches out as far as a thousand miles away and grabs the available moisture, and brings it into the storm so that it snows harder," Trenberth said. "At this time of year, this is exactly what you expect."

And what should we expect in the coming years? Perhaps the same pattern we're seeing lately, suggests Oppenheimer.

"The bottom line is in the future we'll have a shorter snow season overall but more very intense storms," he said. "Has this already started? Probably so."

If you're hunkered down for this week's blizzard, this might be a good time to nestle up with Climate of Doubt, FRONTLINE's look inside the groups that have shifted the direction of the climate change debate. You can watch it here:

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How Climate Change May Lead to Bigger Blizzards

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With every winter storm, including the blizzard hitting the Northeast this week, climate change skeptics return to a familiar argument: If the world is getting warmer, why am I stuck out here, shoveling so much snow? Climate scientists tell FRONTLINE that blizzards don't refute evidence of climate change - in fact, climate change can make blizzards more intense.

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Climate change in the 2020s: What impacts to expect

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DEPOE BAY, Ore. (AP) - Tourists, nature lovers and amateur scientists are whipping out their cameras to document the effects of extreme high tides on shorelines from the United States to New Zealand, and by doing so are helping better predict what rising sea levels will mean for coastal communities around the world.

A network of volunteer photographers fans out around the globe during so-called king tides to capture how high the waterline gets and where the water goes. They then upload the images - many with geolocation data embedded - for use by scientists, policymakers and even city planners as they study and prepare for the effects of climate change. The photos show where flooding occurs on specific roads, or give clues about whether it's safe to build new housing, for example, near an eroding bluff.

"For us, the king tide offers a look at where the water will be in about 2050, about a foot to a foot and half (30 to 46 centimeters) above normal water levels," said Skip Stiles, executive director of Wetlands Watch, a nonprofit that helped recruit 700 people to document a king tide in Norfolk, Virginia, for the first time there in 2017.

The group's efforts have since grown into a smartphone app that uses crowdsourcing to gather images and pinpoint flooding.

"What we're finding is there's a real appetite for this data. A lot of the localities here are putting together comprehensive plans for sea level rise, and I'm getting calls from them saying, 'Do you have data? Do you have photos?' That's what we're going for."

The first of these King Tide Projects involving the public began in 2009 in Australia. The idea has since spread to more than a dozen coastal states in the U.S., British Columbia, New Zealand, Mauritius and beyond.

King tides occur about twice a year in coastal areas worldwide when the sun and moon align to enhance the gravitational pull that produces normal, daily tides. These super-high tides came into sharp focus in January, when one arrived in Oregon on the same day as a major winter storm, creating 15- to 20-foot (4.6- to 6.1-meter) waves and a massive swell that sucked a man and his two young children out to sea. The woman who called 911 had been photographing the tides from her yard for the Oregon King Tides Project. The children, ages 4 and 7, died.

Citizen scientists are preparing to document this winter's final king tide Feb. 8-10 off the U.S. West Coast, followed by one in New Zealand on Feb. 12.

Flooding from king tides is a preview of how sea level rise will affect coastal communities - and warmer oceans and bigger storms could amplify those changes, said Peter Ruggiero, interim executive director of the Oregon Climate Change Research Institute. Modeling shows Oregon could experience sea level rise of as little as a foot (30 centimeters) or as great as 6 feet (1.8 meters) in a worst-case scenario, he said.

Some of these King Tide Projects, like the one in Oregon, are run by nonprofit groups, while others are in partnership with state and local governments. They all have the same goal: to educate the public and provide a clear-eyed assessment of how climate change will affect everyday life, from flooded intersections to cows grazing in knee-high salt water, to popular beaches swallowed by waves.

"A lot of the conversation around climate change was what was happening far away and not about what people were going to be experiencing in their own lives," said Marina Psaros, who helped develop California's King Tides Project. "The goal of the project was to get people thinking more about climate change locally instead of just polar bears."

In Georgia, coastal communities constantly struggle with flooding from high tides and storms - a phenomenon dubbed "sunny day flooding" in places across the U.S. South. Chatham County, home to the low-lying city of Savannah, uses dozens of sea level sensors to track tides and collect data for future city planning. It has also begun asking people to snap pictures during flooding.

"The combination of the sensor data and the photos really helps build out the story - and with that, we hope it will solidify funding decisions better," said Nick Deffley, Savannah's director of sustainability.

When Auckland, New Zealand, organized its first king tide photo event, people sent in images of flooded parks and freeway underpasses. They shared them with local government, and some of the images were used to develop a plan to reinforce a popular but rapidly eroding beach.

Last year, they expanded the program to include a series of tide gauges that are checked regularly by citizen scientists, said Ben Sheeran, founder of the New Zealand King Tide Project.

"There's no eureka moment where it all comes into play, but it's an evolving database of information that's there when needed," he said. "And the data we get are a vehicle for people to continue that conversation."

It's a conversation that remains lively in places like Oregon, where king tides mean periodic flooding of large parts of the coast.

Last year, two volunteers took photos of it from an airplane, capturing striking images of swamped farmhouses, flooded freeway on-ramps, and miles and miles of salt water-soaked agricultural land.

"That flight was my first vision of homes with water looking like it was within feet of coming up into the home. And you had pastures and farm animals out there that looked like these little dots on an island," said Rena Olson, who shot the images along with Alex Derr.

The two hope to go up again this weekend.

"Seeing that over such a large area, it really opened my eyes," Olson said. "This is impactful."

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Follow Gillian Flaccus on Twitter at http://www.twitter.com/gflaccus

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Photos of 'king tides' globally show risks of climate change

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DEPOE BAY, Ore. (AP) - Tourists, nature lovers and amateur scientists are whipping out their cameras to document the effects of extreme high tides on shorelines from the United States to New Zealand, and by doing so are helping better predict what rising sea levels will mean for coastal communities around the world.

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If there were any doubts that the climate is changing in the Colorado River Basin, 2020 went a long way toward dispelling them.

Unprecedented wildfires, deadly heat waves, withering drought - the many indicators of the climate mayhem that scientists have been warning about for years - ravaged the landscape, claiming dozens of lives and causing billions of dollars in damage.

Colorado endured an unprecedented wildfire season. And so did California, in some cases burning where the wounds were still fresh from the epic fires of 2018. Utah experienced its driest year ever, and persistent high temperatures killed more people in Arizona than ever before. Monsoon rains that typically bring relief throughout the region were a no-show for the second summer in a row and now are being called the "non-soon."

And, although the final climate data for 2020 has just arrived, forecasters are already filled with apprehension about what lies ahead for the West this year.

"We've got a pretty deep hole that 2020 has dug for us," said Jon Meyer, research climatologist for the Utah Climate Center who points to low soil moisture, high temperatures and other measures of a hotter, drier climate. "Even a good year is not going to break us out of that."

From the California coast to the eastern borders of Colorado and New Mexico, 2021 is beginning with virtually all of the Colorado River Basin in "extreme" or "exceptional" drought, conditions that haven't been eased by this winter's snowfall. Reservoir levels are so low that Lake Powell, the nation's second largest reservoir, is expected to receive just half as much runoff this year as usual.
MORE: Colorado's statewide drought "pretty dire." It'll take more than a season's snowfall to get out of it.
In Colorado, the entire state is in drought - nearly three-fourths of the landscape designated as areas in "extreme" or "exceptional" drought that are prone to large wildfires and susceptible to wind storms that rip the topsoil from the ground.

Coloradans also can look out their windows and see the "snow drought" forecasters are talking about when they say snow cover across the West is lower than at any time over the past two decades. And the poor snowpack is less than 80% of normal statewide with less than two months to keep building.

"Whatever [snow] we do get, when it comes time to melt in the spring, it's just going to soak right into the ground," said Nancy Selover, Arizona's state climatologist. "The ground is so dry, it's just gonna suck it up. We're not going to get a lot of good runoff, and we're not going to get a lot of good streamflow, reservoir infill or any of that kind of stuff, so we're concerned."

Little rain, but a 'lot of hot air''

Heat continued to dog Colorado, like most of the West, through the year. In 2020, the state experienced its seventh warmest year in more than a century of record-keeping. Average temperatures were 2.8 degrees higher than the average in the past century. Plus, 2016 through 2020 was the hottest-ever five-year period for the state, according to the NOAA's National Center for Climate Information.

The period from 2016 through 2020 was the hottest five-year period for the Colorado, according to records kept by NOAA's National Center for Climate Information. (Screenshot)

Three Colorado cities saw some of their highest average annual temperatures in 2020. Colorado Springs had its fourth warmest year; Alamosa experienced its fifth warmest; and Pueblo, its eighth warmest. And all three were at least 2 degrees hotter than the average over the past four decades.

Selover pointed out that instead of monsoon rains that raise humidity and lower temperatures through the summer, high pressure and high temperatures were relentless for the second year in a row in Arizona.

"We didn't have storms-we just had a lot of hot air," Selover said, pointing to withering 110- and 115-degree days that led to a record number of 29 nights when the low never got below 90 degrees. "The previous record was 15 days."

(Screenshot)

The relentless heat last also had impacts in Colorado, which was suffering through its fourth "non-soon," assistant state climatologist Becky Bolinger said.

"We were already in drought, but [the heat] set the stage," she said, for what would become the three largest wildfires in state history, including the Cameron Peak Fire that scorched a stunning 208,913 acres and the East Troublesome Fire that burned 193,812 acres.

As the new year begins, the soil in Colorado is starved for moisture 10 to 12 inches down, which means about half of the 20 inches of precipitation recorded so far in the Upper San Juan Basin of southwest Colorado won't become runoff this spring and summer when the environment and people need it most. Bolinger is not optimistic about a rebound.

"It's always possible," she said. "But I wouldn't say it's likely."

Record numbers of billion-dollar disasters and deaths

Heat turned out to be the biggest factor in weather- and climate-related deaths in a dozen western and central states last year, according to the latest national billion-dollar disasters tally. The drought and heat wave caused 45 deaths - most of them heat-related - said Adam Smith, who collects the data for NOAA's National Centers for Environmental Information.

Smith's analysis is fast becoming a key metric in measuring the impacts of climate change. It compiles the costs in property damage and human lives associated with increasing population, more assets in harm's way and the increased frequency of extreme weather, much of it driven by global warming. Last year the tally detailed $95 billion in costs tied to 22 events, the largest number of billion-dollar disasters recorded since NOAA began the list in 1980.

Smith said the estimate includes a broad range of quantifiable costs, such as damage to commercial and residential properties, crop losses, increased feeding costs for livestock and spending on fighting wildfires.

"It's a conservative but solid estimate," he said.

The firestorms in California, Oregon and Washington racked up an estimated $16.5 billion in costs and claimed 46 lives last year. Excessive heat across the West included a record temperature of 121 degrees in Los Angeles County and 130 degrees in Death Valley, the highest recorded globally in decades. All that heat, along with drought, came with a separate $4.5 billion price tag that included $1 billion to $2 billion associated with the three largest blazes in recorded Colorado history.

And those numbers can't account for the full range of costs, since some impacts won't be clear for months or years.

"As striking as that $95 billion figure is, I think it's really important that we remember that the human toll of climate and weather disasters is profound," said Vijay Limaye, an epidemiologist who studies the health consequences of climate change for the Natural Resources Defense Council. "It's staggering, and it's widespread."

He said extreme heat poses acute risks to human health not just through premature mortality from heatstroke, but also through a number of other health problems that aren't fully measured by the billion-dollar disaster statistics. The health care-related costs of the wildfire smoke that shrouded skies across the West last summer and fall are not included, even though the smoke triggers heart and lung problems and is sometimes blamed for premature death. Nor are the little-understood mental health consequences of drought counted, he said.

The parched landscape around Eads, Colorado, after an extended summer of extreme drought. This is a field of milo, a small usually drought-resistant grain used as a feed crop for animals. (Marc Piscotty, COLab)

A thirstier atmosphere dries out farms and drives fires

Mistie Christiansen, who oversees USDA Farm Service Agency programs in central Utah's Emery and Carbon counties, said the climate trends are disrupting life on the land and the people who depend on it.

"Ponds are dry; streams are dry; springs that would normally have supplied livestock and rangeland are dry; rivers are historically low," she said. "It's the compound factor of multiple years of this issue that's really hard. People are really struggling."

Area ranches and farms that depended on irrigation from Muddy Creek ran out of water by the end of last June. Her family cut just one crop of hay instead of the usual three and had to spend $45,000 to buy more to feed its livestock. This year, they're expecting to spend at least $30,000 to make up for what the desiccated land cannot provide. Meanwhile, the cows are weaker and pregnancy rates are down, she said.

Based on the string of rough years and how things are looking now, Christiansen said she wouldn't be surprised to see another bad year for livestock growers. "And if things don't change, you'll see a major sell off."

Despite the pain that global warming brings to rural communities like hers, Christiansen believes a higher power is changing the climate, not humans. Still, she shares one view with many climate scientists.

"There's no longer normal," Christiansen said. "I would love to see what is normal anymore, because we just swing from extremes."

Jeff Lukas, an independent climate consultant in Colorado, said the world's rapid warming is making the atmosphere thirstier "and that is so apparent in the second half of 2020."

Dry years can happen in the absence of climate change, he said. But the atmosphere's capacity to hold more water, which leads it to suck moisture from the soil, trees and snowpack, has increased significantly in response to what might seem like an insignificant amount of warming-about 2 degrees Fahrenheit.

"What [last year] will be mostly remembered for, from a weather and climate perspective, is how things dried out so much in the summer and fall as a result of both low precipitation and very high temperatures," said Lukas, who tracked climate and weather events at the Western Water Assessment for more than a decade. The dryness "led to the kind of fuel conditions and fire weather, that led to those incredible wildfires in August and September."

For Lukas, one day-long period of extreme fire behavior last year stands out: when Colorado's East Troublesome Fire ran 20 miles, expanding from 18,000 acres to 180,000 acres, eventually jumping over the Continental Divide in Rocky Mountain National Park in October. He noted that the heat, aridity and winds that set the stage for the blaze are not completely unheard of in autumn. But for such a fire to ignite and grow into the second largest blaze in state history in October, a month that is normally cool and moist, is unprecedented.

"To see it in real time, and to know that thousands of your fellow citizens are urgently trying to get themselves and their animals out of the path of this incredibly fast moving, incredibly dangerous fire, it is just stomach churning to watch it happen."

2021 set up for more heat and drought

The Bureau of Reclamation's latest 24-month forecast shows Lake Powell ending 2021 at a record low level, which is scrambling water managers in seven states to possibly launch strict drought plans and water cuts. (Jason Blevins, The Colorado Sun)

No one's started using the word "scary" yet, but all reports seem to suggest 2021 could bring more of the same:

The snowpack for the Colorado River's four Upper Basin states - Utah, Wyoming, Colorado and New Mexico - is 67% of average. That puts this year on par so far with 2018, which went on to be a terrible year for wildfire, drought and heat.

With reservoirs already low, the U.S. Bureau of Reclamation recently triggered the Upper Basin Drought Contingency Plan that requires those states to begin implementing measures to ensure Lake Powell remains capable of meeting the demand of the 40 million people who rely on Colorado River water.

The water that's flowed into Lake Powell since October is 44% of the normally expected flow.

Drought is expected to persist into spring, and odds are that Colorado River Basin states will remain warmer and drier than normal, too.

"There really isn't any good news for water resources in the Colorado River Basin right now, which is raising a lot of red flags coming into the upcoming year," said Jon Meyer of Utah's Climate Center.

"We're not totally sunk yet," he said, noting that there are still a few months for snow to start falling and snowpack to build before warmer weather begins. But, if what we've seen play out over the last two to three months continues through the spring, he added, then the pain farmers and ranchers felt last year will expand across the region, and western cities will be suffering, too.

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Climate change ravaged Colorado and the West with heat and drought in 2020. This year may be worse.

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If there were any doubts that the climate is changing in the Colorado River Basin, 2020 went a long way toward dispelling them. Unprecedented wildfires, deadly heat waves, withering drought - the many indicators of the climate mayhem that scientists have been warning about for years - ravaged the landscape, claiming dozens of lives and [...]

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Is Climate Change Going To Kill Us All In 10 Years?

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Global Warming The Future - Full Documentary 2019 HD

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Is It Too Late To Stop Climate Change? Well, it's Complicated.

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The geologic record carries a terrifying warning.

Brendan Pattengale

Photo Illustrations by Brendan Pattengale | Maps by La Tigre
Images above: Glaciers from the Vatnajökull ice cap, in Iceland Brendan Pattengale is a photographer who explores how color can convey emotions in an image. In his photo illustrations throughout this article, the colors of the original photos have been adjusted, but the images are otherwise unaltered. This article was published online on February 3, 2021.
We live on a wild planet, a wobbly, erupting, ocean-sloshed orb that careens around a giant thermonuclear explosion in the void. Big rocks whiz by overhead, and here on the Earth's surface, whole continents crash together, rip apart, and occasionally turn inside out, killing nearly everything. Our planet is fickle. When the unseen tug of celestial bodies points Earth toward a new North Star, for instance, the shift in sunlight can dry up the Sahara, or fill it with hippopotamuses. Of more immediate interest today, a variation in the composition of the Earth's atmosphere of as little as 0.1 percent has meant the difference between sweltering Arctic rainforests and a half mile of ice atop Boston. That negligible wisp of the air is carbon dioxide.

Since about the time of the American Civil War, CO ₂'s crucial role in warming the planet has been well understood. And not just based on mathematical models: The planet has run many experiments with different levels of atmospheric CO ₂. At some points in the Earth's history, lots of CO ₂ has vented from the crust and leaped from the seas, and the planet has gotten warm. At others, lots of CO ₂ has been hidden away in the rocks and in the ocean's depths, and the planet has gotten cold. The sea level, meanwhile, has tried to keep up-rising and falling over the ages, with coastlines racing out across the continental shelf, only to be drawn back in again. During the entire half-billion-year Phanerozoic eon of animal life, CO ₂ has been the primary driver of the Earth's climate. And sometimes, when the planet has issued a truly titanic slug of CO ₂ into the atmosphere, things have gone horribly wrong.

Today, atmospheric CO ₂ sits at 410 parts per million, a higher level than at any point in more than 3 million years. And humans are injecting more CO ₂ into the atmosphere at one of the fastest rates ever over this entire, near-eternal span. When hucksters tell you that the climate is always changing, they're right, but that's not the good news they think it is. "The climate system is an angry beast," the late Columbia climate scientist Wally Broecker was fond of saying, "and we are poking it with sticks."

The beast has only just begun to snarl. All of recorded human history-at only a few thousand years, a mere eyeblink in geologic time-has played out in perhaps the most stable climate window of the past 650,000 years. We have been shielded from the climate's violence by our short civilizational memory, and our remarkably good fortune. But humanity's ongoing chemistry experiment on our planet could push the climate well beyond those slim historical parameters, into a state it hasn't seen in tens of millions of years, a world for which Homo sapiens did not evolve.

When there's been as much carbon dioxide in the air as there already is today-not to mention how much there's likely to be in 50 or 100 years-the world has been much, much warmer, with seas 70 feet higher than they are today. Why? The planet today is not yet in equilibrium with the warped atmosphere that industrial civilization has so recently created. If CO ₂ stays at its current levels, much less steadily increases, it will take centuries-even millennia-for the planet to fully find its new footing. The transition will be punishing in the near term and the long term, and when it's over, Earth will look far different from the one that nursed humanity. This is the grim lesson of paleoclimatology: The planet seems to respond far more aggressively to small provocations than it's been projected to by many of our models.

To truly appreciate the coming changes to our planet, we need to plumb the history of climate change. So let us take a trip back into deep time, a journey that will begin with the familiar climate of recorded history and end in the feverish, high-CO ₂ greenhouse of the early age of mammals, 50 million years ago. It is a sobering journey, one that warns of catastrophic surprises that may be in store.

Read: Scientists have uncovered a disturbing climate change precedent
The first couple of steps back in time won't take us to a warmer world-but they will illuminate just what sort of ill-tempered planet we're dealing with. As we pull back even slightly from the span of recorded history-our tiny sliver of geologic time-we'll notice almost at once that the entire record of human civilization is perched at the edge of a climate cliff. Below is a punishing ice age. As it turns out, we live on an ice-age planet, one marked by the swelling and disintegration of massive polar ice sheets in response to tiny changes in sunlight and CO ₂ levels. Our current warmer period is merely one peak in a mountain range, with each summit an interglacial springtime like today, and each valley floor a deep freeze. It takes some doing to escape this cycle, but with CO ₂ as it is now, we won't be returning to an ice age for the foreseeable future. And to reach analogues for the kind of warming we'll likely see in the coming decades and centuries, we will need to move beyond the past 3 million years of ice ages entirely, and make drastic jumps back into the alien Earths of tens of millions of years ago. Our future may come to resemble these strange lost worlds.

Before we move more dramatically backwards in time, let us briefly pause over the history of civilization, and then some. Ten thousand years ago, the big mammals had just vanished, at human hands, in Eurasia and the Americas. Steppes once filled with mammoths and camels and wetlands stocked with giant beavers were suddenly, stunningly vacant.

The coastlines that civilization presumes to be eternal were still far beyond today's horizon. But the seas were rising. The doomed vestiges of mile-thick ice sheets that had cloaked a third of North American land were retreating to the far corners of Canada, chased there by tundra and taiga. The roughly 13 quintillion gallons of meltwater these ice sheets would hemorrhage, in a matter of millennia, raised the sea level hundreds of feet, leaving coral reefs that had been bathed in sunlight under shallow waves now drowned in the deep.

By 9,000 years ago, humans in the Fertile Crescent, China, Mexico, and the Andes had independently developed agriculture and-after 200,000 years of wandering-had begun to stay put. Sedentary settlements started to blossom. Humans, with a surfeit of calories, began to divide their labor, and artisans plied new arts. The Earth's oldest cities, such as Jericho, were bustling.

It's easy to forget that the Earth-cozy, pastoral, familiar-is nevertheless a celestial body, and astronomy still has a vote in earthly affairs. Every 20,000 years or so the planet swivels about its axis, and 10,000 years ago, at civilization's first light, the Earth's top half was aimed toward the sun during the closest part of its orbit-an arrangement today enjoyed by the Southern Hemisphere. The resulting Northern-summer warmth turned the Sahara green. Lakes, hosting hippos, crocodiles, turtles, and buffalo, speckled North Africa, Arabia, and everywhere in between. Lake Chad, which today finds itself overtaxed and shrinking toward oblivion, was "Mega-Chad," a 115,000-square-mile freshwater sea that sprawled across the continent. Beneath the Mediterranean today, hundreds of dark mud layers alternate with whiter muck, a barcode that marks the Sahara's rhythmic switching from lush green to continent-spanning desert.

Imprinted on top of this cycle were the last gasps of an ice age that had gripped the planet for the previous 100,000 years. The Earth was still thawing, and amid the final approach of the rising tides, enormous plains and forests like Doggerland-a lowland that had joined mainland Europe to the British Isles-were abandoned by nomadic humans and offered to the surging seas. Vast islands like Georges Bank, 75 miles off Massachusetts-which once held mastodons and giant ground sloths-saw their menagerie overtaken. Scallop draggers still pull up their tusks and teeth today, far offshore.

By 5,000 years ago, as humanity was emerging from its unlettered millennia, the ice had stopped melting and oceans that had been surging for 15,000 years finally settled on modern shorelines. Sunlight had waned in the Northern summer, and rains drifted south toward the equator again. The green Sahara began to die, as it had many times before. Hunter-fisher-gatherers who for thousands of years had littered the verdant interior of North Africa with fishhooks and harpoon points abandoned the now-arid wastelands, and gathered along the Nile. The age of pharaohs began.

By geologic standards, the climate has been remarkably stable ever since, until the sudden warming of the past few decades. That's unsettling, because history tells us that even local, trivial climate misadventures during this otherwise peaceful span can help bring societies to ruin. In fact, 3,200 years ago, an entire network of civilizations-a veritable globalized economy-fell apart when minor climate chaos struck.

"There is famine in [our] house; we will all die of hunger. If you do not quickly arrive here, we ourselves will die of hunger. You will not see a living soul from your land." This letter was sent between associates at a commercial firm in Syria with outposts spread across the region, as cities from the Levant to the Euphrates fell. Across the Mediterranean and Mesopotamia, dynasties that had ruled for centuries were all collapsing. The mortuary-temple walls of Ramses III-the last great pharaoh of Egypt's New Kingdom period-speak of waves of mass migration, over land and sea, and warfare with mysterious invaders from afar. Within decades the entire Bronze Age world had collapsed.

Historians have advanced many culprits for the breakdown, including earthquakes and rebellions. But like our own teetering world-one strained by souring trade relations, with fractious populaces led by unsteady, unscrupulous leaders and now stricken by plague-the eastern Mediterranean and the Aegean were ill-prepared to accommodate the deteriorating climate. While one must resist environmental determinism, it is nevertheless telling that when the region mildly cooled and a centuries-long drought struck around 1200 B.C., this network of ancient civilizations fell to pieces. Even Megiddo, the biblical site of Armageddon, was destroyed.

This same story is told elsewhere, over and over, throughout the extremely mild stretch of time that is written history. The Roman empire's imperial power was vouchsafed by centuries of warm weather, but its end saw a return to an arid cold-perhaps conjured by distant pressure systems over Iceland and the Azores. In A.D. 536, known as the worst year to be alive, one of Iceland's volcanoes exploded, and darkness descended over the Northern Hemisphere, bringing summer snow to China and starvation to Ireland. In Central America several centuries later, when the reliable band of tropical rainfall that rings the Earth left the Mayan lowlands and headed south, the megalithic civilization above it withered. In North America, a megadrought about 800 years ago made ancestral Puebloans abandon cliffside villages like Mesa Verde, as Nebraska was swept by giant sand dunes and California burned. In the 15th century, a 30-year drought bookended by equally unhelpful deluges brought the Khmer at Angkor low. The "hydraulic empire" had been fed and maintained by an elaborate irrigation system of canals and reservoirs. But when these canals ran dry for decades, then clogged with rains, invaders easily toppled the empire in 1431, and the Khmer forfeited their temples to the jungle.

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Hopscotching through these human disasters to the present day, we pass perhaps the most familiar historical climate event of all: the Little Ice Age. Lasting roughly from 1500 to 1850, the chill made ice rinks of Dutch canals, and swelled up Swiss mountain glaciers. Tent cities sprung up on a frozen Thames, and George Washington endured his winter of cold and privation at Valley Forge in 1777 (which wasn't even particularly harsh for the times). The Little Ice Age might have been a regional event, perhaps the product of an exceptional run of sunlight-dimming volcanism. In 1816, its annus horribilis, the so-called year without a summer-which brought snows to New England in August-global temperatures dropped perhaps a mere half a degree Celsius. While it is perennially plumbed by historians for insights into future climate change, it is not even remotely on the same scale of disruption as that which might lie in our future.

As Europe emerged from its chill, coal from 300-million-year-old jungles was being fed into English furnaces. Although the Earth was now in the same configuration that, in the previous few million years, had invited a return to deep, unthinkable ice ages, for some reason the next ice age never took. Instead the planet embarked on an almost unprecedented global chemistry experiment. Halfway through the 20th century, the climate began behaving very strangely.
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So this is the climate of written history, a seemingly eventful stretch that has really been the random noise and variability of a climate essentially at peace. Indeed, if you were to find yourself in an industrial civilization somewhere else in the universe, you would almost certainly notice such similarly strange and improbably pleasant millennia behind you. This kind of climate stability seems to be a prerequisite for organized society. It is, in other words, as good as it gets.

As we jump back 20,000 years-to yesterday, geologically-the world ceases being recognizable. Whereas all of recorded history played out in a climate hovering well within a band of 1 degree Celsius, we now see what a difference 5 to 6 degrees can make-a scale of change similar to the one that humans may engineer in only the next century or so, though in this case, the world is 5 to 6 degrees colder, not warmer.

An Antarctica's worth of ice now rests atop North America. Similar sheets smother northern Europe, and as a result, the sea level is now 400 feet lower. The midwestern United States is carpeted in stands of stunted spruce of the sort that would today look at home in northern Quebec. The Rockies are carved up, not by wildflower-dappled mountain valleys, but by overflowing rivers of ice and rock. California is a land of dire wolves. Where the Pacific Northwest edges up against the American Antarctica, it is a harsh and treeless place. Nevada and Utah fill up with cold rains.

During World War II, at Topaz, the desolate Japanese American internment camp in Utah, prisoners combed the flats of the Sevier Desert for unlikely seashells, fashioning miraculous little brooches from tiny mussel and snail shells to while away their exile. The desert seashells were roughly 20,000 years old, from the vanished depths of the giant Pleistocene-era Lake Bonneville-the product of a jet stream diverted south by the ice sheet. This was once a Utahan Lake Superior, more than 1,000 feet deep in places. It was joined by endless other verdant lakes scattered across today's bleak Basin and Range region.

Elsewhere, the retreat of the seas made most of Indonesia a peninsula of mainland Asia. Vast savannas and swamps linked Australia and New Guinea, and of course Russia shared a tundra handshake with Alaska. There were reindeer in Spain, and glaciers in Morocco. And everywhere loess, loess, and more loess. This was the age of dust.

Ice is a rock that flows. Send it in massive sterilizing slabs across the continents, and it will quarry mountainsides, pulverize bedrock, and obliterate everything in its path. At the height of the last ice age, along the crumbling margins of the continental ice sheets, the rocky, dusty spoils of all this destruction spilled out onto the tundra. Dry winds carried this silt around the world in enormous dust storms, piling it up in seas of loess that buried the central U.S., China, and Eastern Europe under featureless drifts. In Austria, not far from the site of the voluptuous Venus of Willendorf figurine, carved some 30,000 years ago, are the remains of a campground of the same age-tents, hearths, burnt garbage pits, hoards of ivory jewelry-all abandoned in the face of these violent, smothering haboobs. Ice cores from both Antarctica and Greenland record a local environment that was 10 times dustier than today. All of this dust seeded the seas with iron, a vital nutrient for carbon-hogging plankton, which bloomed around Antarctica and pulled gigatons of CO ₂ out of the air and deep into the ocean, freezing the planet further.
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This parched Pleistocene world would have appeared duller from space, hosting as it did a quarter less plant life. CO ₂ in the atmosphere registered only a paltry 180 ppm, less than half of what it is today. In fact, CO ₂ was so low, it might have been unable to drop any further. Photosynthesis starts to shut down at such trifling levels, a negative-feedback effect that might have left more CO ₂ -unused by plants-in the air above, acting as a brake on the deep freeze.

This was the strange world of the Ice Age, one that, geologically speaking, is still remarkably recent. It's so recent, in fact, that today, most of Canada and Scandinavia is still bouncing back up from the now-vanished ice sheets that had weighed those lands down.

In 2021, we find ourselves in an unusual situation: We live on a world with massive ice sheets, one of which covers one of the seven continents and is more than a mile deep. For most of the planet's past, it has had virtually no ice whatsoever. The periods of extreme cold-like the ultra-ancient, phantasmagoric nightmares of Snowball Earth, when the oceans might have been smothered by ice sheets all the way to the tropics-are outliers. There were a few other surprising pulses of frost here and there, but they merely punctuate the balmy stretches of the fossil record. For almost all of the Earth's history, the planet was a much warmer place than it is today, with much higher CO ₂ levels. This is not a climate-denying talking point; it's a physical fact, and acknowledging it does nothing to take away from the potential catastrophe of future warming. After all, we humans, along with everything else alive today, evolved to live in our familiar low-CO ₂ world-a process that took a long time.

How long, exactly? Fifty million years ago, as our tiny mammalian ancestors were still sweating through the jungly, high-CO ₂ greenhouse climate they had inherited from the dinosaurs, India was nearing the end of an extended journey. Long estranged from Africa and the august, bygone supercontinent of Gondwana, the subcontinent raced northeast across the proto-Indian Ocean and smashed into Asia in slow motion. The collision not only quieted CO₂-spewing volcanoes along Asian subduction zones; it also thrust the Himalayas and the Tibetan Plateau toward the stars, to be continually weathered and eroded away.

As it turns out, weathering rocks-that is, breaking them down with CO ₂-rich rainwater-is one of the planet's most effective long-term mechanisms for removing carbon dioxide from the atmosphere, one that modern geoengineers are frantically trying to reproduce in a lab, for obvious reasons.

Adding to this colossal Himalayan CO ₂ sink, the more recent buckling, tectonic mess that lifted Indonesia and its neighbors from the sea over the past 20 million years or so also exhumed vast tracts of highly weatherable ocean crust, exposing it all to the withering assault of tropical rainstorms. Today this corroding rock accounts for roughly 10 percent of the planet's carbon sink. Over tens of millions of years, then, the stately march of plate tectonics-the balance of volcanic CO ₂ and rock weathering-seems to have driven long-term climate change, in our case toward a colder, lower-CO ₂ world. As we'll see, humans now threaten to undo this entire epic, geologic-scale climate evolution of the Cenozoic era-and in only a few decades.

When Earth's blanket of CO ₂ was finally thin enough, the planet's regular wobbles were at long last sufficient to trigger deep glaciations. The ice ages began. But the climate was not stable during this period. The ice advanced and retreated, and while the descent into the wild episodes of the Pleistocene epoch could be leisurely-the depths of planetary winter taking tens of thousands of years to arrive-the leap out of the cold tended to be sudden and violent. This is where positive feedback loops come in: When the last ice age ended, it ended fast.

Coral reefs marking the ancient sea level-but today lying deep off the coasts of Tahiti and Indonesia-reveal that about 14,500 years ago, the seas suddenly jumped 50 feet or so in only a few centuries, as meltwater from the late, great North American ice sheet raged down the Mississippi. When a 300-foot-deep lake of glacial meltwater spanning at least 80,000 square miles of central Canada catastrophically drained into the ocean, it shut down the churn of the North Atlantic and arrested the seaborne flow of heat northward. As a result, tundra advanced to retake much of Europe for 1,000 years. But when ocean circulation kicked back into gear, and the dense, salty seawater began to sink again, the system rebooted, and currents carried the equator's heat toward the Arctic once more. Temperatures in Greenland suddenly leaped 10 degrees Celsius in perhaps a decade, fires spread, and revanchist forests reclaimed Europe for good.

In Idaho, ice dams that had held back giant lakes of glacial meltwater about six times the volume of Lake Erie collapsed as the world warmed, and each released 10 times the flow of all the rivers on Earth into eastern Washington. The floods carried 30-foot boulders on biblical waves, through what were suddenly the world's wildest rapids. They left behind a labyrinth of bedrock-scoured canyons that still covers the entire southeastern corner of the state like a scar. When the Earth's climate changes, this is what it can look like on the ground.

As the ice sheets of the Northern Hemisphere finally lost their grip, darker land around the melting margins became exposed to the sun for the first time in 100,000 years, accelerating the ice's retreat. Permafrost melted, and methane bubbled up from thawing bogs. Colder, more CO ₂-soluble oceans warmed, and gave up the carbon they'd stolen in the Ice Age, warming the Earth even more. Relieved of their glacial burden, volcanoes in Iceland, Europe, and California awoke, adding even more CO ₂ to the atmosphere.

Soon the Sahara would green again, Jericho would be born, and humans would start writing things down. They would do so with the assumption that the world they saw was the way it had always been. "We were born only yesterday and know nothing," one of them would write. "And our days on earth are but a shadow."

As we leap back in time again, we emerge before the final Pleistocene glaciation. We've gone tremendously far back, 129,000 years, though in some ways we've only returned to our own world. This was the most recent interglacial period, the last of many breaks between the ice ages, and the last time the planet was roughly as warm as it is today. Once more, the seas have risen hundreds of feet, but something is awry.

As the Earth's wobble and orbit conspired to melt more ice than the poles have shed so far today, the planet absorbed more sunlight. As a result, global temperatures were little more than 1 degree warmer than today's Anthropocene chart-toppers-or maybe even the same. But sea level was 20 to 30 feet higher than it is now. (A full third of Florida was sunk beneath the waves.) This is "sobering," as one paper put it.

Modelers have tried and mostly failed to square how a world about as warm as today's could produce seas so strangely high. Provisional, if nightmarish, explanations like the runaway, catastrophic collapse of monstrous ice cliffs more than 300 feet tall in Antarctica, which may or may not be set into motion in our own time, are fiercely debated in conference halls and geoscience departments.

Very soon, we may well have warmed the planet enough to trigger similarly dramatic sea-level rise, even if it takes centuries to play out. This is what the Exxon scientist James Black meant in 1977 when he warned higher-ups of the coming "super-interglacial" that would be brought about-as a matter of simple atmospheric physics-from burning fossil fuels. But our trajectory as a civilization is headed well beyond the warmth of the last interglacial, or any other interglacial period of the Pleistocene, for that matter. So it's time to keep moving. We must take our first truly heroic leap into geologic time, millions of years into the past.

We're more than 3 million years in the past now, and carbon dioxide in the atmosphere is at 400 parts per million, a level the planet will not again see until September 2016. This world is 3 to 4 degrees Celsius warmer than ours, and the sea level is up to 80 feet higher. Stunted beech trees and bogs line the foothills of the Transantarctic Mountains not far from the South Pole-the last members of a venerable line of once-majestic forests that had existed since long before the age of the dinosaurs.

What we've glossed over in our journey back to this ancient present: the entire evolutionary history of Homo sapiens, three Yellowstone super-eruptions, thousands of megafloods, the last of the giant terror birds, a mass extinction of whales, and the glacial creation and destruction of innumerable islands and moraines. As we make our way backwards in time to the Pliocene, the glaciations get briefer, and the ice sheets themselves become thinner and more temperamental. About 2.6 million years ago they all but disappear in North America, as CO₂ levels continue their slow climb.

When we arrive in the middle of the Pliocene, just over 3 million years ago, CO ₂ levels are high enough that we've escaped the cycle of ice ages and warm interglacials altogether. Lucy the Australopithecus roams a heavily forested East Africa. We are now outside the evolutionary envelope of our modern world, sculpted as it was by the temperamental northern ice sheets and deep freezes of the Pleistocene. But as to atmospheric carbon dioxide, 3 million years is how far back we have to go to arrive at an analogue for 2021.

Despite the similarities between our world and that of the Pliocene, the differences are notable. In the Canadian High Arctic-where today tundra spreads to the horizon-evergreen forests come right to the edge of an ice-free Arctic Ocean. Though the world as a whole is only a few degrees warmer, the Arctic, as always, gets the brunt of the extra heat. This is called "polar amplification," and it's why maps of modern warming are crowned by a disturbing fog of maroon. Models struggle to reproduce the extreme level of warming in the Pliocene Arctic. It's a full 10 to 15 degrees Celsius warmer in the long twilight of northern Canada, and the pine and birch woodlands of these Arctic shores are filled with gigantic forest-dwelling camels. Occasionally this boreal world erupts in wildfire, a phenomenon echoed by the blazes that today sweep ever farther north. Elsewhere, West Antarctica's ice sheet may have disappeared entirely, and Greenland's, if it exists at all, is shriveled and pathetic.

A common projection for our own warming world is that, while the wet places will get wetter, the dry places will get drier. But the Pliocene seems to defy this saw for reasons not yet fully understood. It's a strangely wet world, especially the subtropics, where-in the Sahara, the Outback, the Atacama, the American Southwest, and Namibia-lakes, savannas, and woodlands replace deserts. This ancient wetness might come down to inadequacies in how we model clouds, which are under no obligation to behave in physical reality as they do in simplified lines of computer code. Hurricanes were almost certainly more consistently punishing 3 million years ago, just as our storms of the future will be. And a more sluggish circulation of the atmosphere might have lulled the trade winds, turning El Niño into "El Padre." Perhaps this is what brought rains-and lakes-to the Mojave at this time.

Our modern coastlines would have been so far underwater that you'd have to take great pains to avoid getting the bends if you tried scuba diving down to them. Today, traveling east through Virginia, or North or South Carolina, or Georgia, midway through your drive you'll pass over a gentle 100-foot drop. This is the Orangeburg Scarp, a bluff-hundreds of miles long-that divides the broad, flat coastal plain of the American Southeast. It comprises the eroded and smoothed-out rumors of once-magnificent sea cliffs. Here, waves of the Pliocene high seas chewed away at the middle of the Carolinas-an East Coast Big Sur. This ancient shoreline is visible from space by the change in soil color that divides the states, and is visible on much closer inspection as well: To the east of this strange drop-off, giant megalodon-shark teeth and whale bones litter the Carolina Low Country. Though warped over the ages by the secret workings of the mantle far below, these subtle banks 90 miles inland nevertheless mark the highest shoreline of the Pliocene, when the seas were dozens of feet higher than they are today. But even within this warm Pliocene period, the sea level leaped and fell by as much as 60 feet every 20,000 years, to the rhythm of the Earth's sway in space. This is because, under this higher-CO ₂ regime, the unstable ice sheet in Antarctica took on the volatile temperament that, 1 million years later, would come to characterize North America's ice sheet, toying with the ancient coastline as if it were a marionette.

So this is the Pliocene, the world of the distant present. While today's projections of future warming tend to end in 2100, the Pliocene illuminates just what sort of long-term changes might inevitably be set in motion by the atmosphere we've already engineered. As the great ice sheets melt, the permafrost awakens, and darker forested land encroaches on the world's tundra, positive feedbacks may eventually launch our planet into a different state altogether, one that might resemble this bygone world. Nevertheless, human civilization is unlikely to keep atmospheric CO ₂ at a Pliocene level-so more ancient and extreme analogues must be retrieved.

We're now deeper in the past, and the planet appears truly exotic. The Amazon is running backwards, and gathers in great pools at the foot of the Andes. A seaway stretches from Western Europe to Kazakhstan and spills into the Indian Ocean. California's Central Valley is open ocean.

What today is the northwestern U.S. is especially unrecognizable. Today the airy, columnated canyons of the Columbia River in Oregon swarm with tiny kiteboarders zipping through gorges of basalt. But 16 million years ago, this was a black, unbreathable place, flowing with rivers of incandescent rock. The Columbia River basalts-old lava flows that spread across Washington, Oregon, and Idaho, in some places more than two miles thick-were the creation of a class of extremely rare and world-changing volcanic eruptions known as large igneous provinces, or LIPs.

Some LIPs in Earth's history span millions of square miles, erupt for millions of years, inject tens of thousands of gigatons of CO ₂ into the air, and are responsible for most of the worst mass extinctions in the history of the planet. They live up to their name-they are large. But these mid-Miocene eruptions were still rather small as far as LIPs go, and so the planet was spared mass death. Nevertheless, the billowing volcanoes raised atmospheric CO ₂ up to about 500 ppm, a level that today represents something close to the most ambitious and optimistic scenario possible for limiting our future carbon emissions.

In the Miocene, this volcanic CO ₂ warmed up the world to at least 4 degrees Celsius and perhaps as much as 8 degrees above modern temperatures. As a result, there were turtles and parrots in Siberia. Canada's Devon Island, in the high Arctic, is today a desolate wasteland, the largest uninhabited island in the world-and one used by NASA to simulate life on Mars. In the Miocene, its flora resembled Lower Michigan's.

The sweeping grasslands distinctive to our cooler, drier, low-CO ₂ world had yet to take over the planet, and so forests were everywhere-in the middle of Australia and Central Asia and Patagonia. All of this vegetation was one of the reasons it was so warm. Forests and shrubs made this planet darker than our own world-one still painted pallid hues in many places by bare land and ice-and allowed it to absorb more heat. This change in the planet's color is just one of the many long-term feedback loops awaiting us after the ice melts. Long after our initial pulse of CO ₂, they will make our future world warmer and more alien still.

As for fauna, we're now so distantly marooned in time from our own world that most of the creatures that inhabited this leafy planet range from the flatly unfamiliar to the uncannily so. There were big cats that weren't cats, and rhino-size "hell pigs" that weren't pigs. There were sloths that lived in the ocean and walruses that weren't related to today's walruses. Earth's largest-ever meat-eating land mammals, African juggernauts like Megistotherium and Simbakubwa, not closely related to any living mammals today, tore early elephants apart with bladed mouths.

And with CO ₂ at 500ppm, the sea level was about 150 feet higher than today. Approaching Antarctica in the middle Miocene by sea, the waters would be warmer than today, and virtually unvisited by ice. To get to the ice sheet, you'd have to hike far past lakes and forests of conifers that lined the coast. Trudging past the trees and finally over endless tundra, you would come at last to the edge of a much smaller ice sheet whose best days were still ahead of it. An axiom about this land-based Antarctic ice sheet in paleoclimatology is that it's incredibly stubborn. That is, once you have an ice sheet atop the heart of Antarctica, feedback loops kick in to make it exceedingly hard to get rid of. Barring true climatic madness, a land-based Antarctic ice sheet is essentially there to stay.

But in the middle Miocene this young Antarctic ice sheet seemed to have a temper. It might have been "surprisingly dynamic," as one paper cheerfully puts it. As CO ₂ increased from just below today's levels up to about 500ppm, Miocene Antarctica shed what today would amount to 30 to 80 percent of the modern ice sheet. In the Miocene, Antarctica seemed exquisitely tuned to small changes in atmospheric CO₂, in ways that we don't fully understand and that we're not incorporating into our models of the future. There will undoubtedly be surprises awaiting us in our high-CO ₂ future, just as there were for life that existed in the Miocene. In fact, the Antarctic ice sheet may be more vulnerable today to rapid retreat and disintegration than at any time in its entire 34-million-year history.

In the 16 million years since this mid-Miocene heat, the volcanic hot spot responsible for the Columbia River basalts has wandered under Yellowstone. Today it powers a much tamer kind of volcano. It could cover a few states in a few inches of ash and disrupt global agriculture for years, but it couldn't launch the planet into a new climate for hundreds of thousands of years, or kill most life on the surface. Unfortunately, there is such a supervolcano active on Earth today: industrial civilization. With CO ₂ likely to soar past 500ppm from future emissions, even the sweat-soaked, Siberian-parrot-populated world of the middle Miocene might not tell us everything we need to know about our future climate. It's time to go back to a global greenhouse climate that ranks among the warmest climate regimes complex life has ever endured. In our final leap backwards, CO ₂ at last reaches levels that humans might reproduce in the next 100 years or so. What follows is something like a worst-case scenario for future carbon emissions. But these worst-case projections have continued to prove stubbornly accurate in the 21st century so far, and they remain a possible path for our future.

We're now about to take our largest leap, by far, into the geologic past. We hurdle over 40 million years of history, past volcanic eruptions thousands of times bigger than that of Mount St. Helens, past an asteroid impact that punched out a gigantic crater where the Chesapeake Bay sits today. The Himalayas slump; India unhitches from Asia; and the further back we go, the higher the CO ₂ level rises and the warmer the Earth gets. The Antarctic ice sheet, in its death throes, vanishes altogether, and the polar continent instead gives way to monkey puzzle trees and marsupials. We have arrived, finally at the end of our journey, in the greenhouse world of the early age of mammals.

Today the last dry land one steps on in Canada before setting out across the ice-choked seas for the North Pole is Ellesmere Island, at the top of the world. But once upon a time there was a rainforest here. We know this because tree stumps still erode out of the barren hillsides, and they're more than 50 million years old. They're all that's left of an ancient polar jungle now whipped by indifferent Arctic winds. But once upon a time, this island was a swampy cathedral of redwoods, whose canopy naves were filled with flying lemurs, giant salamanders, and hippolike beasts that pierced the waters. At this polar latitude, on some late-fall evening of the early Eocene, the sun tried and failed to lift itself from the horizon. A pink twilight reached deep into the jungle, but soon the sun would set entirely here for more than four months. In this unending Arctic dark, the stillness would be broken by the orphaned calls of tiny early primates, who hopped fearlessly over stilled alligators that would start moving again when the sun returned from beyond the horizon. In this unending night, tapirs hunted for mushrooms and munched on leaf litter that was left over from sunny days past and that in the far future would become coal.

We have no modern analogue for a swampy rainforest teeming with reptiles that nevertheless endures months of Arctic twilight and polar night. But for each degree Celsius the planet warms, the atmosphere holds about 6 percent more water vapor, and given that global temperatures at the beginning of the age of mammals were roughly 13 degrees warmer than today, it's difficult to imagine how uncomfortable this planet would be for Ice Age creatures like ourselves. In fact, much of the planet would be rendered off-limits to us, far too hot and humid for human physiology.

Not only was this a sweltering age, but it was also one cruelly punctuated by some of the most profound and sudden CO ₂-driven global-warming events in geologic history-on top of this already feverish baseline. Deep under the North Atlantic, the Eocene epoch kicked off in style 56 million years ago with massive sheets of magma that spread sideways through the crust, igniting vast, diffuse deposits of fossil fuels at the bottom of the ocean. This ignition of the underworld injected something like the carbon equivalent of all currently known fossil-fuel reserves into the seas and atmosphere in less than 20,000 years, warming the planet by another 5 to 9 degrees Celsius. Evidence abounds of violent storms and megafloods during this ancient spasm of climate change-episodic waves of torrential rains unlike any on Earth today. In some places, such storms would have been routine, separated by merciless droughts and long, brutal, cloudless heat waves. Seas near the equator may have been almost as hot as a Jacuzzi-too hot for most complex life. As for the rest of the planet, all of this excess CO ₂ acidified the oceans, and the world's coral reefs collapsed. Ocean chemistry took 200,000 years to recover.

The most jarring thing about the early age of mammals, though, isn't merely the extreme heat. It's the testimony of the plants. In higher-CO ₂ conditions, plants reduce the number of pores on their leaves, and fossil leaves from the jungles of the early Eocene have tellingly fewer pores than today's. By some estimates, CO ₂ 50 million years ago was about 600 ppm. Other proxies point to higher CO ₂, just over 1,000 ppm, but even that amount has long bedeviled our computer models of climate change. For years, in fact, models have told us that to reproduce this feverish world, we'd need to ramp up CO ₂ to more than 4,000 ppm.

This ancient planet is far more extreme than anything being predicted for the end of the century by the United Nations or anyone else. After all, the world that hosted the rainforests of Ellesmere Island was 13 degrees Celsius warmer than our own, while the current global ambition, enshrined in the Paris Agreement, is to limit warming to less than 2, or even 1.5, degrees. Part of what explains this glaring disparity is that most climate projections end at the end of the century. Feedbacks that might get you to Eocene- or Miocene-level warmth play out over much longer timescales than a century. But the other, much scarier insight that Earth's history is very starkly telling us is that we have been missing something crucial in the models we use to predict the future.

Some of the models are starting to catch up. In 2019, one of the most computationally demanding climate models ever run, by researchers at the California Institute of Technology, simulated global temperatures suddenly leaping 12 degrees Celsius by the next century if atmospheric CO ₂ reached 1,200ppm-a very bad, but not impossible, emissions pathway. And later that year, scientists from the University of Michigan and the University of Arizona were similarly able to reproduce the warmth of the Eocene by using a more sophisticated model of how water behaves at the smallest scales.

The paleoclimatologist Jessica Tierney thinks the key may be the clouds. Today, the San Francisco fog reliably rolls in, stranding bridge towers high above the marine layer like birthday candles. These clouds are a mainstay of west coasts around the world, reflecting sunlight back to space from coastal California and Peru and Namibia. But under higher-CO ₂ conditions and higher temperatures, water droplets in incipient clouds could get bigger and rain down faster. In the Eocene, this might have caused these clouds to fall apart and disappear-inviting more solar energy to reach, and warm, the oceans. That might be why the Eocene was so outrageously hot.

This sauna of our early mammalian ancestors represents something close to the worst possible scenario for future warming (although some studies claim that humans, under truly nihilistic emissions scenarios, could make the planet even warmer). The good news is the inertia of the Earth's climate system is such that we still have time to rapidly reverse course, heading off an encore of this world, or that of the Miocene, or even the Pliocene, in the coming decades. All it will require is instantaneously halting the super-eruption of CO ₂ disgorged into the atmosphere that began with the Industrial Revolution.

We know how to do this, and we cannot underplay the urgency. The fact is that none of these ancient periods is actually an apt analogue for the future if things go wrong. It took millions of years to produce the climates of the Miocene or the Eocene, and the rate of change right now is almost unprecedented in the history of animal life.

Humans are currently injecting CO ₂ into the air 10 times faster than even during the most extreme periods within the age of mammals. And you don't need the planet to get as hot as it was in the early Eocene to catastrophically acidify the oceans. Acidification is all about the rate of CO ₂ emissions, and we are off the charts. Ocean acidification could reach the same level it did 56 million years ago by later this century, and then keep going.

When he coined the term mass extinction in a 1963 paper, "Crises in the History of Life," the American paleontologist Norman Newell posited that this was what happened when the environment changed faster than evolution could accommodate. Life has speed limits. And in fact, life today is still trying to catch up with the thaw-out of the last ice age, about 12,000 years ago. Meanwhile, our familiar seasons are growing ever more strange: Flycatchers arrive weeks after their caterpillar prey hatches; orchids bloom when there are no bees willing to pollinate them. The early melting of sea ice has driven polar bears ashore, shifting their diet from seals to goose eggs. And that's after just 1 degree of warming.

Subtropical life may have been happy in a warmer Eocene Arctic, but there's no reason to think such an intimately adapted ecosystem, evolved on a greenhouse planet over millions of years, could be reestablished in a few centuries or millennia. Drown the Florida Everglades, and its crocodilians wouldn't have an easy time moving north into their old Miocene stomping grounds in New Jersey, much less migrating all the way to the unspoiled Arctic bayous if humans re-create the world of the Eocene. They will run into the levees and fortifications of drowning Florida exurbs. We are imposing a rate of change on the planet that has almost never happened before in geologic history, while largely preventing life on Earth from adjusting to that change.

Taking in the whole sweep of Earth's history, now we see how unnatural, nightmarish, and profound our current experiment on the planet really is. A small population of our particular species of primate has, in only a few decades, unlocked a massive reservoir of old carbon slumbering in the Earth, gathering since the dawn of life, and set off on a global immolation of Earth's history to power the modern world. As a result, up to half of the tropical coral reefs on Earth have died, 10 trillion tons of ice have melted, the ocean has grown 30 percent more acidic, and global temperatures have spiked. If we keep going down this path for a geologic nanosecond longer, who knows what will happen? The next few fleeting moments are ours, but they will echo for hundreds of thousands, even millions, of years. This is one of the most important times to be alive in the history of life.
This article appears in the March 2021 print edition with the headline "The Dark Secrets of the Earth's Deep Past."

Peter Brannen is a science writer based in Boulder, Colorado. His work has appeared in The New York Times, The Washington Post, and Wired. He is the author of The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth's Past Mass Extinctions.

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The Planet Could Have Catastrophic Surprises in Store

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The geologic record carries a terrifying warning. Photo Illustrations by Brendan Pattengale | Maps by La Tigre Images above: Glaciers from the Vatnajökull ice cap, in Iceland Brendan Pattengale is a photographer who explores how color can convey emotions in an image.

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Newsela | Climate change could make blizzards more intense, scientists say

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More frequent and intense blizzards are forecast due to global climate change largely associated with higher carbon dioxide levels.

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climate change: these companies are leading the fight - cnn

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These companies are leading the fight against climate change

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The world has only until 2030 to stem catastrophic climate change. Can global companies be part of the solution?

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Jet fuel-guzzling Delta Air Lines and fossil fuel-pumping BP are vowing to go carbon neutral.

Microsoft and Ikea, behemoths of tech and furniture, have pledged to go further and actively reduce the carbon dioxide in the atmosphere. The financial giant Blackrock promises to put climate at the heart of its decisions.

In short, a slew of major corporations are making promises on climate - lofty ones.

And it's not just a case of a few headline-grabbing outliers.

More companies are disclosing their carbon emissions, and more of those companies have emissions reductions targets, according to the global nonprofit CDP (formerly the Carbon Disclosure Project).
Don't see the graphic above? Click here.
Those targets are also more ambitious. Engie Impact, a sustainability company tied to a French energy group, analyzed CDP data and found "the intensity of the commitments is rising," as Engie Impact's Mathias Lelièvre puts it.

Don't see the graphic above? Click here.

Companies are promising faster action, too. Instead of setting goals 25 years in the future - a distant target that makes accountability difficult - the average time horizon is now just eight years away, Engie Impact found.

And there's been an acceleration in the rate at which companies set " science-based targets" - specific, measurable carbon reduction goals that put a company in line with the Paris Agreement, the global climate accord aiming to hold warming at 2 degrees Celsius or lower. Coca-Cola, Nike, Best Buy, Walmart and Hilton Hotels are among the hundreds of companies with such targets.

According to one analysis, the number of Fortune 500 companies with concrete, ambitious carbon targetsquadrupled in the past four years, to 23%.
Growing pressure to act
This increase in activity comes after decades of pressure from environmental advocates - and despite a lack of action from the U.S. government.

So after all this time, what might be spurring companies to set new or newly ambitious targets?

For one thing, the effects of climate change are becoming clearer to companies as wildfires, rising sea levels, droughts and other symptoms of the crisis make headlines and affect business operations. "It's here," says Bruno Sarda, the president of CDP North America. "It's happening now, not tomorrow."

At the same time, solar and wind energy have gotten significantly cheaper, making it easier for some companies to commit to shifting away from fossil fuels.

And an increase in pressure - on multiple fronts - plays a key role.

"Investors are increasingly asking companies about this," says Kevin Moss, who runs the center for business sustainability at the World Resources Institute. "And not just the traditional activist investors who have been doing it for some time, but mainstream investors."

Pressure from customers and the general public is mounting, too, as public awareness and concern grows more intense. And while the federal government in the U.S. has backed away from climate targets, cities and states - not to mention governments abroad - are taking action.

There might be some more surprising sources of pressure, too. Children.

"I hear from business leaders all the time today that, you know, their kids come home and say, 'What are you doing, Dad?' " says Elizabeth Sturcken, a managing director at the Environmental Defense Fund who works with businesses on sustainability goals. "This makes a difference."

Employees, too, are increasingly influential. Workers at companies such as Amazon are pushing their bosses to change, and some other companies see this as a way to attract and retain talent.

Kyum Kim is the co-founder of the app Blind, where tech workers discuss their workplaces, and he says those workers are increasingly discussing issues like climate change. In a survey, half his users said a company's climate policy affects whether they want to work there.

"People talk a lot about compensation, of course, and the work culture," he says, "but I think this is a whole new segment."

There's another factor, too, according to Lucas Joppa, the chief sustainability officer at Microsoft.

He says it helps to frame climate action as an accounting problem, based on quantifying exactly how much companies emit and how much they'll need to cut.

"That really is what I see flip executives' mindsets around, is to just talk about this in terms that they understand ... a climate 'budget,' " Joppa says. "At the end of the day, what companies are really good at doing is making decisions based on numbers."
The limits of voluntary targets
Of course, setting a carbon budget is one thing. Sticking to it is another. Some climate announcements in the past - such as BP's previous rebranding as "Beyond Petroleum" - have been more PR push than actual shift in strategy, and advocates agree that follow-through and accountability will be essential if these new ambitious targets are to have an impact.

And even if companies make good on their promises, some experts say there can be a danger in relying on big corporations to drive the fight against climate change.

Shalanda Baker, a professor at Northeastern University who studies the social justice dimensions of a transition away from fossil fuels, says vulnerable and marginalized communities need to have input in how the world fights climate change - and feel the benefits of a switch to green energy.

"I'm just not sure if I have the faith, given that ... corporations are very concerned about expenses and profits, that they would really think about something that may add cost, but that may be more just," she says.

Baker says corporate action can be powerful but government policy can make sure vulnerable populations are protected.

She's not the only one who looks at these voluntary commitments and sees a need for regulation. After all, some companies taking action is nowhere near enough to stop climate change.

Elizabeth Sturcken at the EDF, who has spent two decades urging companies to act, tells companies that in addition to voluntary cuts in emissions, it's critical for business leaders to engage with policymakers and ask for government action.

Corporations from BP to PepsiCo say they support a price on carbon, one market-based policy for reducing emissions. Sturcken says companies that really want to lead on climate need to put money toward making such policies a reality.

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Better Late Than Never? Big Companies Scramble To Make Lofty Climate Promises

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Jet fuel-guzzling Delta Air Lines and fossil fuel-pumping BP are vowing to go carbon neutral. Microsoft and Ikea, behemoths of tech and furniture, have pledged to go further and actively reduce the carbon dioxide in the atmosphere. The financial giant Blackrock promises to put climate at the heart of its decisions.

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Newsela | Climate change playing havoc with monarch butterfly migration

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Climate Change 101 with Bill Nye | National Geographic

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Why Climate Change Denial Still Exists In The U.S.

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Trump on climate change report: ‘I don’t believe it’

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Government scientists warn that unchecked global warming will wreak havoc on the US economy.

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Newsela | The eerie song of Antarctica - melting ice

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The sounds coming from the Ross Ice Shelf are an early warning sign of this nightmare scenario: the disintegration of Antarctica's largest ice shelf.

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Millions of young people raised their voices at protests around the world Friday in a massive display meant to demand urgent action on climate change. Scores of students missed school to take part, some joined by teachers and parents.

Some of the first rallies began in Australia, and then spread from Pacific islands to India and Turkey and across Europe, as students kicked off what organizers were calling a Global Climate Strike.

In the U.S., where more than 800 marches were planned, thousands of young people are absent from classrooms so they can carry signs, march and shout slogans calling for a new approach to energy and emissions.

"I'd rather go protest about the Earth and how something's going wrong than sit in my classroom and act like nothing's happening," high school student Harshita Ray tells member station WOSU in Columbus, Ohio.

Instead of being at Olentangy Liberty High School, Ray joined other students for a demonstration at the Ohio Statehouse, filling the steps in front of the building and spilling out over its plaza.

Greta Thunberg, the 16-year-old Swedish activist who sparked what has become a global movement of Friday school strikes over climate change, is attending a large rally and march in Lower Manhattan.

At a rally in San Francisco, Makayla Neyon, 16, told member station KQED: "I really just hope that we bring attention to the fact that our freakin' Earth is endangered ... so that my generation and my future generation can have a planet to live on."

The protesters are marching to demand that government and businesses commit to a goal of net-zero carbon emissions by 2030. On its website, Global Climate Strike calls for a swift transition from fossil fuels to renewable energy.

Thunberg has been in the U.S. for more than a week, urging leaders to take responsibility for the environment and building momentum toward Friday's demonstrations. She recently told NPR that even with the new support, her focus remains on changing the future - for the better.

"Even though this movement has become huge and there have been millions of children and young people who have been school striking for the climate," Thunberg says, "the emission curve is still not reducing ... and of course that is all that matters."

Friday's massive march to New York City's Battery Park included 12-year-old Alexa Keys, who carried a handmade sign of the planet with the message, "Climate Change Needs to Change."

"I've never been to a march before," she told NPR's Jeff Brady. "And I think this is just amazing, that this many people gathered to protest something" on a global level, said Keys, who traveled from Warwick, N.Y., with her mother for the rally.

In Harrisburg, Pa., member station WITF reports that Natasha Sood, a medical student at Penn State, told a crowd on the steps of the Pennsylvania State Capitol: "Act as if your survival is at stake because it is! Act as if your future is at stake because it is! Act as if your kid's life is at stake because it is! Act as if your health is at stake because it is!"

The protests began in the U.S. hours after massive rallies kicked off in many European countries, from Denmark and Poland to France and the U.K.

In Germany, hundreds of thousands of marchers took to the streets in cities such as Munich, Hanover, Hamburg and Freiburg. And on the same day as the protests, Chancellor Angela Merkel's government agreed to a landmark $60 billion package designed to cut Germany's greenhouse gas emissions.

"Chanting, 'The time is now' for action on climate change, thousands of people gathered at Berlin's Brandenburg Gate, forcing police to close access to the monument due to overcrowding," NPR's Rob Schmitz reports from Berlin. "Thousands more gathered in Warsaw and Prague. In Finland, crowds of demonstrators in costumes protested outside Parliament in Helsinki. One man dressed as Santa Claus held a sign declaring, 'My house is on fire.' "

The protests come ahead of the U.N. Climate Action Summit that begins Monday in New York. In March, a similar demonstration inspired by Thunberg drew crowds around the world, including thousands of young students who skipped school to attend.

The global movement has taken root in many countries, as young people reflect on the current condition of the world - and how their lives might be shaped by the consequences of allowing global average temperatures to keep rising. On Friday, the voices included children from Abuja, Nigeria.

In Athens, waves of people gathered outside the Greek Parliament, with some of them holding signs that read, "Raise your voice, not the sea level."

In Islamabad, protesters braved a heat wave to cheer on the minister for climate change, Malik Amin Aslam, who promised to fight for the planet.

"They gathered in the late afternoon, in a nod to already unseasonably hot weather affecting the country, considered one of the world's most vulnerable to climate change impact," NPR's Diaa Hadid reports. "Protesters included teenagers in school uniforms, scouts, Red Cross volunteers and a contingent of transgender women, including a woman who raised a placard reading, 'Make The Planet Green Again.' "

Eman Ghani, 15, said she is protesting because she's angry that political leaders were complacent to the risks of global warming.

"It's mad; the people who should be bringing change in the world are not," she said. "The old people who have power are not using their power, and the young people who don't have it can only speak up."

Organizers say more than 300,000 people gathered at more than 100 rallies in cities around Australia, most notably in Melbourne, where an estimated 100,000 turned out, and Sydney, which reportedly saw 80,000 attend. Tens of thousands more are said to have marched in the capital, Canberra, as well as Perth, Brisbane and Adelaide.

The numbers of participants could not be immediately verified.

In Sydney, 18-year-old Moemoana came from Wollongong to protest on behalf of her native Samoa, one of thousands of low-lying islands around the world that are particularly threatened by rising sea levels due to climate change.

18-year-old Moemoana, (centre) has come from Wollongong to the protest, and her homeland is Samoa.
"It's a real threat and Australia needs to know that Pacifika are neighbours and Australia really needs to help out."#climatestrike pic.twitter.com/67bvwsdnuU
- Helen Davidson (@heldavidson) September 20, 2019

"The Pacific Islands are meters above sea level because of climate change and it's a scary future for our islands," she was quoted by The Guardian Australia as saying. "We want to urge people to take some action."

Australia is the world's largest exporter of coal and liquefied natural gas - both major contributors to greenhouse gas emissions. Australian Prime Minister Scott Morrison, who is in the U.S. for a state dinner with President Trump, has been criticized for not including the U.N. Climate Action Summit on his itinerary.

At least 2,000 companies in Australia gave employees time off to attend the rallies, according to The Sydney Morning Herald. Meanwhile, the country's acting prime minister, Michael McCormack, speaking in Melbourne, called the rallies "just a disruption" and expressed displeasure with students attending the protests.

"These sorts of rallies should be held on a weekend where it doesn't actually disrupt business, it doesn't disrupt schools, it doesn't disrupt universities," McCormack told reporters, according to The Associated Press.

In Kirabati, a Pacific island chain that experts fear could be inundated by sea level rise in the next 25 years, protesters carried signs that read: "We are not sinking, we are fighting."

Some 200 young activists marched to the Ministry of Environment in Bangkok, where they dropped to the ground in mock death to demand that the government declare a climate emergency.

"We're young, but we're not dumb. We know it's happening. We need change. We demand better," 11-year-old Ralyn "Lilly" Satidtanasarn told The Bangkok Post.

In India, dozens of students and activists rallied in the capital, New Delhi, outside the country's Ministry of Housing and Urban Affairs, carrying banners that read "Eco, not ego!" and chanting, "I want to breathe clean."

Thunberg has motivated millions of people to think more deeply about climate change and its future effects. And despite her young age, she makes her argument in blunt terms, seeking to cut through the entropy that has hovered around climate issues for years.

"You are not mature enough to tell it like it is. Even that burden you leave to us children," Thunberg told the grown-ups at a U.N. climate change conference in Poland last year, when she was just 15.
NPR's News Desk intern Paolo Zialcita contributed to this report.

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Young People Lead Millions To Protest Global Inaction On Climate Change

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Millions of young people raised their voices at protests around the world Friday in a massive display meant to demand urgent action on climate change. Scores of students missed school to take part, some joined by teachers and parents.

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Greta Thunberg Is Leading a Global Climate Movement

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Newsela | What will happen to the environment after the pandemic?

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Around the world people are making personal sacrifices benefiting others. Researchers say we need policies that require sacrifice for climate change.

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SYDNEY - Not long after Jack Egan's home burned down during Australia's "Black Summer" wildfires a year ago, he made a life-changing decision.

At 60, Egan quit his job so he could spend his days campaigning for stronger action on climate change, a national and global challenge he said was "akin to a war."

"I was working quite happily in aged care ... but the fires caused me to devote the rest of my life to volunteer on climate action. I took an early retirement and that's what I do full time now," he said.

Egan, whose property in Rosedale on the country's south-east coast has still not been rebuilt, recalled how "the fires had a behavior that was new to Australia, or new to me at least ... and the length of the fires - months - was really shocking."

February marks one year since Australia's catastrophic wildfire season started to ease, after leaving 34 people dead and torching at least 18 million hectares of land (nearly 44.5 million acres). It was, in the words of one state premier, "the most devastating natural disaster in living memory."

For Egan, it has been a year not only of recovery, but also of action. He spreads the word on "climate solutions and the benefits therein" around small, regional communities and was part of a delegation of survivors that took the remnants of their charred homes to Australia's Parliament House, urging politicians to do more.

"It [the Australian government] is doing as little as possible, as little as they can get away with," Egan said. "I feel ashamed of our country as it's allowed some sort of short-term cynical politics to prevent proper climate action."

Despite a chorus of scientists saying climate change is contributing to longer and more intense wildfire seasons, Prime Minister Scott Morrison refused to introduce any major climate measures after the disaster. Mass protests were held across the country calling for tougher climate action, but Morrison remained unmoved.

Morrison leads a conservative coalition government, which has been in power since 2013. His government's track record on climate includes repealing the country's carbon tax and Morrison famously bringing a lump of coal into Parliament, saying, "Don't be scared, it won't hurt you."

The prime minister's office did not respond to requests for comment.

Morrison has acknowledged the threat of climate change and routinely defends a "sensible" response. As part of the Paris climate agreement, his government committed to cutting greenhouse gas emissions by at least 26 percent by 2030 compared to 2005 levels.

But climate advocacy groups say much stronger commitments are needed, especially as Australia has one of the world's highest per capita levels of emissions and is among the biggest fossil fuel exporters.

"We know very clearly the Black Summer fires were fueled by climate change and that Australia has to play a much bigger part in addressing its contribution to that problem," Simon Bradshaw of the Climate Council, an advocacy group, said. "But we haven't seen the federal government do anything further to actually tackle the root cause of the climate crisis."

"We've seen the government refuse to strengthen its 2030 emissions reduction targets," Bradshaw added, " ... and also refuse to commit to achieving net zero emissions by 2050 or earlier. At this point, we're pretty much alone among developed countries having refused to do either of those things."

More than 100 countries have set net zero targets. This week, Morrison went as far as saying that net zero emissions by 2050 would be "preferable." But when pressed for specifics, he said, "When I can tell you how we get there, that's when I'll tell you when we're going to get there."

In the meantime, the research group Climate Action Tracker rates the government's response as "insufficient."

As a political battle around climate change is being fought in Australia, the country is also counting the cost of the wildfires on its flora and fauna.

Basha Stasak, the nature program manager at the Australian Conservation Foundation, said the disaster "really hit all swaths of the animal world."

"It's estimated that 3 billion animals were killed or displaced by the bushfires last summer," Stasak said. "This includes really iconic species that are known around the world, like the koala, which lost an estimated 30 percent of its habitat in New South Wales."

A report by WWF-Australia found that more than 60,000 koalas were affected by the infernos, which it called "a deeply disturbing number for a species already in trouble."

There is slightly better news when it comes to Australia's flora.

Patrick Norman, an ecologist at Griffith University and a researcher with the Bushfire Recovery Project, said most Australian forests have adaptations in order to survive fire.

"[Many forests] are recovering how they should, and are responding particularly well after a La Niña year, which has been excellent. Most of the areas impacted had a good, high amount of rainfall in 2020."

But he said some subalpine areas in New South Wales and Victoria, along with wetter forests in northern New South Wales were not recovering as well due to the especially brutal fire conditions.

"They [the fires] were just an enormous event," Norman said. "It's definitely scary looking into the future, at a further warming climate. We're only just starting to see the impacts now."

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One year since Australia's devastating wildfires, anger grows at climate change 'inaction'

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SYDNEY - Not long after Jack Egan's home burned down during Australia's "Black Summer" wildfires a year ago, he made a life-changing decision. At 60, Egan quit his job so he could spend his days campaigning for stronger action on climate change, a national and global challenge he said was "akin to a war."

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The Amazon rainforest lost an estimated 5 million acres in 2020, an area roughly the size of Israel, according to a recent report on the region. Experts warn that unchecked deforestation in the Amazon basin, which encompasses nine countries in South America, could trigger a tipping point in the world's largest tropical rainforest within decades.

Using satellite imagery, the report by Amazon Conservation Association and Monitoring the Andean Amazon Project, or MAAP, provides an early glimpse of deforestation in the Amazon throughout 2020. Troubling data points are highlighted, including largescale deforestation in Brazil and Bolivia, where primary forests were obliterated at rates even higher than in 2019, a year that saw prolific and highly publicized fires raging in the Amazon.

"Both in terms of deforestation and fire, the data indicate that 2020 was actually worse than 2019 across the Amazon. Over 2 million hectares (8,000 square miles) of primary forest were lost in 2020, which was much more than 2019," said Dr. Matt Finer, a researcher with Amazon Conservation and the director of MAAP.

Finer cautioned that the 2020 data are an early estimate, but added that finalized 2019 data surpassed early estimates that year.

Deforestation, spread across the vastness of the Amazonian landscape, is accelerating -- consuming ecosystems and concentrating in hotspots where hundreds of thousands of acres of forest are swallowed up for agricultural and extractive purposes by small and large actors.

"There's no smoking gun. Deforestation is not a linear wave, it's death by a thousand cuts," said Finer.

The majority of last year's deforestation occurred in the Brazilian Amazon, where over 50,000 acres of forest were lost, much of it to fires. Despite the devastation of the 2019 fires in Brazil, the ones in 2020 were worse, according to Amazon Conservation.

Of the roughly 2,500 large fires that scorched huge swathes of the Amazon last year, around 88% occurred in Brazil. A large number of those were human-caused fires created for pasture and croplands.

The report also notes massive destruction of the Bolivian Amazon. Around 205 large fires burned in Bolivia last year, engulfing over 600,000 acres of the Chiquitano tropical forest between April and November, according to the report.

Other areas of concern were in Peru, where small scale agriculture, mining and cattle ranching caused increased deforestation in the country's central Amazon. In Colombia, the illicit cultivation of coca leaf -- the raw ingredient for cocaine -- has invaded several protected forest areas.

Often described as the "lungs of the planet," the Amazon basin is twice the size of India, covering around 40% of the South American continent. Its watersheds are relied on by over 30 million, including indigenous peoples living in isolation.

Some scientists warn that the Amazon biome could soon reach a dangerous tipping point in which it no longer produces enough rainfall to support its ecosystems, eventually converting into dry savanna.

"The short answer is, the tipping point is already here," said Enrique Ortiz, tropical ecologist and co-founder of Amazon Conservation. "Not throughout the entire Amazon, but in parts."

Despite the level of destruction, Ortiz pushed back against doomsday scenarios for the Amazon.

"Deforestation is in the area of 20 or 21%," he said. "There is still probably 80% of the Amazon intact, so we have room to maneuver."

Environmental groups have placed high hope in President Joe Biden's commitment to protecting the Amazon. During a 2020 presidential debate last September, then-candidate Biden weighed in on the deforestation:

"I would be gathering up and making sure we had the countries of the world coming up with $20 billion, and say, 'Here's $20 billion, stop tearing down the forest. And if you don't then you are going to have significant economic consequences,'" Biden said.

Beyond severe mitigation of deforestation in the region, Ortiz sees political consensus and leadership among wealthy nations as another tool to help save the Amazon.

"There has been confrontation between the West and Amazonian countries. If Biden is smart and able to reverse that confrontation, then we can work together," he said.

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Amazon rainforest lost area the size of Israel in 2020

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The Amazon rainforest lost an estimated 5 million acres in 2020, an area roughly the size of Israel, according to a recent report on the region. Experts warn that unchecked deforestation in the Amazon basin, which encompasses nine countries in South America, could trigger a tipping point in the world's largest tropical rainforest within decades.

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Newsela | Cheetahs: On the brink of extinction, again

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Cheetahs have faced extinction at least two times in the past.

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COVID-19 lockdowns cause global air pollution declines

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The global response to the COVID-19 pandemic has resulted in unprecedented reductions in economic activity. We find that, after accounting for meteorological variations, lockdown events have reduced the population-weighted concentration of nitrogen dioxide and particulate matter levels by about 60% and 31% in 34 countries, with mixed effects on ozone.

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Newsela | Glacier in a fridge: Student scientists at work on climate change

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Young scientists are looking to help us adapt to climate change. One kid did this by making glaciers in the freezer.