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The global warming issue will not go away. Evidence continues to mount that some type of warming is occurring, maybe temporarily or of longer duration. But, is it caused by man and can anything be done about it? Environmental activism to reduce carbon dioxide emissions has reached a new intensity. The U.S. Supreme Court is being asked to rule on a suit which demands that the Environmental Protection Agency regulate the release of carbon dioxide as part of its air pollution responsibility. The president is being heavily lobbied to subscribe to the Kyoto Protocol which would require the U.S. to emit less carbon dioxide than it released in 1990. A book and a movie with the titles, An Inconvenient Truth, which press the case for global warming were released during 2006 by Al Gore, former vice president of the United States. 1,2 He makes the case that man's actions in burning fossil fuels are projected to increase the concentration of carbon dioxide in the atmosphere to the highest levels in history. He insists that uncontrolled releases of carbon dioxide will eventually melt the polar caps completely, raising sea level and inundating many coastal communities like New York, Miami, New Orleans, and Los Angeles; and drastically changing agricultural patterns because of redistribution of temperature and precipitation. And finally, on February 2, 2007, the Fourth IPCC Assessment Report on global warming was released. Interestingly, the report reduced the alarmist rhetoric because climate modelers found that they had overestimated the rise in global temperature and observations did not support the predictions.
Measures of Global Warming
For many years I have been a skeptic of global warming because the climate record available to assess the effects of increased carbon dioxide emission has been too short to say with confidence that the effect is real. There is no question that the concentration of carbon dioxide shown in Figure 1 has been increasing exponentially for almost 50 years now. These data were collected by C. C. Keeling of the Scripps Institute of Oceanography at the Mauna Loa Observatory, Hawaii. ³

Fig. 1. Atmospheric Carbon Dioxide Concentration.

Fig. 2. Sea-surface Temperature.

Fig. 3. Frequency of Hurricanes.

Fig. 4. Extent of Sea Ice.

However, it is still unclear if the conclusions are valid that this increase in carbon dioxide is due to man's burning of fossil fuels and that it is causing the apparent recent warming trend which is melting the polar caps. Several questions continue to nag researchers in the climate community. Is the globe really warming? Are the polar caps really melting? How much of the increase in carbon dioxide is due to man's influence? If man were to attempt to reduce carbon dioxide emissions would it actually do any good? And finally, are there any other possible explanations for the apparent global warming? These are not simple questions and it will require a much longer period of record to be confident in any conclusions.

In order to answer the first two questions, massive amounts of global data must be averaged over a relatively long period of time. And because the effects of global warming are so small compared to the global average, great care must be taken to avoid bias in collection and analysis of the data. Many pitfalls in this process have already occurred which have produced a lack of confidence in the results.

I determined to take another look at the evidence and see if I could detect any recent trends in the atmosphere, ocean, and cryosphere which would seem to support the concept of global warming, choosing to select several small data sets. The data sets I used are limited in spatial and temporal scope making them relatively easy to analyze without bias. However, the results need to be qualified because they don't necessarily reflect long-term, global trends.

The three data sets I analyzed were (1) the sea-surface temperature in the Gulf of Alaska, ⁴ (2) the frequency of hurricanes in the southeastern Atlantic and Caribbean, ⁵ and (3) the polar extent of sea ice in the Arctic Ocean. ⁶
Analysis
If global warming is occurring then sea-surface temperature should also be increasing, hurricane frequency should be on the rise, and polar sea ice should be melting. Figures 2-4 show that the trends for all three processes seem to be consistent for at least the short term. Sea-surface temperature in the Gulf of Alaska has increased about 3% over the past 30 years. Hurricane frequency in the western Atlantic appears to have increased about 3% over the past 150 years. And, the Arctic sea-ice extent has decreased about 5% over the past 25 years. Note, within the general trends, however, shorter period oscillations occur. Hurricane frequency is the most variable, with 30-40 year periods of lower and higher frequency. This has become particularly noticeable since about 1995 when a sudden increase in the frequency of hurricanes hitting the southeastern U.S. followed a 30-year period of lower hurricane frequency. These shorter period oscillations are normal in most geophysical phenomena and are evident in the sea-surface temperature and Arctic sea-ice extent as well, although with less fluctuation.

Based on these limited observations, it appears likely that global warming seems to be occurring over at least the past 30-50 years. I would be quick to add, however, that because of the limited spatial coverage and short time period of these data, it is still not possible to say if these trends will continue. There may be even longer-period fluctuations which we don't yet see in the data. When long-period records of data are plotted, oscillations for many periods are often seen.

These data do not address the question about man's part in causing the warming trend. It is true that increased carbon dioxide concentration in the atmosphere would be expected to increase the greenhouse effect and possibly cause warming. It is unclear whether global warming is due to increased carbon dioxide concentration or if carbon dioxide concentration is the result of global warming. The oceans contain thousands of times more carbon dioxide than the atmosphere and can release significant quantities of carbon dioxide if they are warmed or the pH altered. If some, as yet, undiscovered process is warming the ocean, it could initiate the release of carbon dioxide from the ocean to the atmosphere which, in turn, is warmed even more by radiational heating.

One possible scenario may be found in a recent series of articles by Henrik Svensmark and Nigel Marsh, cosmic ray specialists from Denmark, who have shown an indirect connection between galactic cosmic ray (GCR) intensity and global temperature. 7,8,9 They are studying the influence of the Sun on the flow of GCR to Earth. The Sun's changing sunspot activity influences the magnetosphere surrounding the Earth permitting more GCR to strike the Earth during high periods of activity. When the Sun is active, the intensity of GCR striking the Earth is increased, causing more ionization in the atmosphere, creating more carbon-14, and possibly creating more cloud condensation nuclei (CCN). This increase in CCN, in turn, appears to create more low-level clouds which cool the Earth. When the Sun is quiet the GCR intensity striking the Earth is reduced, allowing the Earth to warm. Svensmark and Marsh have shown a striking statistical correlation between sunspot activity and global cooling and warming over the past 1000 years. The recent rise in global temperature may partially be due to current low solar activity supplemented by a recent increase in carbon dioxide concentration measured at Mauna Loa. The connection which still needs further study is the production of CCN and clouds by GCR.
Conclusions and Recommendations
So, what can we conclude? I believe it is safe to say that:

Global warming appears to have been occurring for the last 30-50 years.

This warming may only be a short-term fluctuation but could be a longer-term trend.

Evidence is still inconclusive whether man is causing the warming.

No "natural" causes for global warming have been confirmed.

One possible new theory is that galactic cosmic radiation (GCR) modulated by solar activity affects low-level cloud cover and is causing the warming.

Global warming may affect some parts of our society negatively but would likely benefit others. In fact, the current warming trend may be returning our global climate closer to that prevalent in the Garden of Eden. Compared to climate changes which have occurred in earth history, a temperature rise of a few degrees is a small fluctuation which will not lead to a complete melting of the polar caps or another ice age. Earth has a stable environmental system with many built-in feedback systems to maintain a uniform climate. It was designed by God and has only been dramatically upset by catastrophic events like the Genesis Flood. Catastrophic climate change will occur again in the future, but only by God's intervention in a sudden, violent conflagration of planet Earth in the end times (II Peter 3:1-12).

1. Gore, A. 2006. An inconvenient truth: The planetary emergence of global warming and what we can do about it. Emmaus, PA: Rodale Press.

2. Gore, A. 2006. An inconvenient truth. Paramount Vantage and United International Pictures, Theatrical Distributors.

3. Keeling, C. D., et al. 2004. Carbon Dioxide Research Group, Scripps Institution of Oceanography (SIO), University of California, La Jolla, CA. http://cdiac.esd.ornl.gov/ftp/maunaloa-co2/maunaloa.co2.

4. NOAA National Data Buoy Center 2006. Buoy #46001, Kodiak, AL. http://www.nodc.noaa.gov/BUOY/46001.html.

5. Best Track data documentation tape from the National Hurricane Center 2006. http://weather.unisys.com/hurricane/atlantic/index.html.

6. Nimbus-7 satellite SMMR files of NASA Goddard Space Flight Center 2006.

7. Svensmark, H. 2000. Cosmic rays and Earth's climate. Space Science Reviews. 93: 155-166.

8. Marsh, N., and H. Svensmark. 2003. GCR and ENSO trends in ISCCP-D2 low cloud properties. Journal of Geophysical Research. 108(D6): 1-11.

9. Marsh, N., and H. Svensmark. 2003. Solar influence on Earth's climate. Space Science Reviews. 107: 317-325.

*Dr. Vardiman is Chairman of the Astro/geophysics Department at ICR.
Cite this article: Vardiman, L. 2007. Evidence for Global Warming. Acts & Facts. 36 (4).

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Introduction The global warming issue will not go away. Evidence continues to mount that some type of warming is occurring, maybe temporarily or of longer duration. But, is it caused by man and can anything be done about it? Environmental activism to reduce carbon dioxide emissions has reached a new intensity.

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Is Global Warming Real? Top 5 Arguments in Favor and Against it - Conserve Energy Future

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Global warming is a hot topic these days. Understanding if global warming is real and its impact is important to meet the challenges posed by it. Here are the top 5 arguments for and against global warming.

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Review the resources provided, and create a chart indicating facts/support for and against Global Warming. Add to our Class Chart by clicking the image below. Make sure to include your evidence to support and refute Global Warming.

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How did global warming discussions end up hinging on what's happening with polar bears, unverifiable predictions of what will happen in a hundred years, and whether people are "climate deniers" or "global warming cultists?" If this is a scientific topic, why aren't we spending more time discussing the science involved? Why aren't we talking about the evidence and the actual data involved? Why aren't we looking at the predictions that were made and seeing if they match up to the results? If this is such an open and shut case, why are so many people who care about science skeptical? Many Americans have long since thought that the best scientific evidence available suggested that man wasn't causing any sort of global warming. However, now, we can go even further and suggest that the planet isn't warming at all.

1) There hasn't been any global warming since 1997: If nothing changes in the next year, we're going to have kids who graduate from high school who will have never seen any "global warming" during their lifetimes. That's right; the temperature of the planet has essentially been flat for 17 years. This isn't a controversial assertion either. Even the former Director of the Climate Research Unit (CRU) of the University of East Anglia, Phil Jones, admits that it's true. Since the planet was cooling from 1940-1975 and the upswing in temperature afterward only lasted 22 years, a 17 year pause is a big deal. It also begs an obvious question: How can we be experiencing global warming if there's no actual "global warming?"

2) There is no scientific consensus that global warming is occurring and caused by man: Questions are not decided by "consensus." In fact, many scientific theories that were once widely believed to be true were made irrelevant by new evidence. Just to name one of many, many examples, in the early seventies, scientists believed global cooling was occurring. However, once the planet started to warm up, they changed their minds. Yet, the primary "scientific" argument for global warming is that there is a "scientific consensus" that it's occurring. Setting aside the fact that's not a scientific argument, even if that ever was true (and it really wasn't), it's certainly not true anymore. Over 31,000 scientists have signed on to a petition saying humans aren't causing global warming. More than 1000 scientists signed on to another report saying there is no global warming at all. There are tens of thousands of well-educated, mainstream scientists who do not agree that global warming is occurring at all and people who share their opinion are taking a position grounded in science.

3) Arctic ice is up 50% since 2012: The loss of Arctic ice has been a big talking point for people who believe global warming is occurring. Some people have even predicted that all of the Arctic ice would melt by now because of global warming. Yet, Arctic ice is up 50% since 2012. How much Arctic ice really matters is an open question since the very limited evidence we have suggests that a few decades ago, there was less ice than there is today, but the same people who thought the drop in ice was noteworthy should at least agree that the increase is important as well.

4) Climate models showing global warming have been wrong over and over: These future projections of what global warming will do to the planet have been based on climate models. Essentially, scientists make assumptions about how much of an impact different factors will have; they guess how much of a change there will be and then they project changes over time. Unfortunately, almost all of these models showing huge temperature gains have turned out to be wrong.

Former NASA scientist Dr. Roy Spencer says that climate models used by government agencies to create policies "have failed miserably." Spencer analyzed 90 climate models against surface temperature and satellite temperature data, and found that more than 95 percent of the models "have over-forecast the warming trend since 1979, whether we use their own surface temperature dataset (HadCRUT4), or our satellite dataset of lower tropospheric temperatures (UAH)."

There's an old saying in programming that goes, "Garbage in, garbage out." In other words, if the assumptions and data you put into the models are faulty, then the results will be worthless. If the climate models that show a dire impact because of global warming aren't reliable -- and they're not -- then the long term projections they make are meaningless.

5) Predictions about the impact of global warming have already been proven wrong: The debate over global warming has been going on long enough that we've had time to see whether some of the predictions people made about it have panned out in the real world. For example, Al Gore predicted all the Arctic ice would be gone by 2013. In 2005, the Independent ran an article saying that the Artic had entered a death spiral.

Scientists fear that the Arctic has now entered an irreversible phase of warming which will accelerate the loss of the polar sea ice that has helped to keep the climate stable for thousands of years....The greatest fear is that the Arctic has reached a "tipping point" beyond which nothing can reverse the continual loss of sea ice and with it the massive land glaciers of Greenland, which will raise sea levels dramatically. Of course, the highway is still there.

Meanwhile, Arctic ice is up 50% since 2012. James Hansen of NASA fame predicted that the West Side Highway in New York would be under water by now because of global warming.

If the climate models and the predictions about global warming aren't even close to being correct, wouldn't it be more scientific to reject hasty action based on faulty data so that we can further study the issue and find out what's really going on?

Recommended

Trending on Townhall Video

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5 Scientific Reasons That Global Warming Isn't Happening

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How did global warming discussions end up hinging on what's happening with polar bears, unverifiable predictions of what will happen in a hundred years, and whether people are "climate deniers" or "global warming cultists?" If this is a scientific topic, why aren't we spending more time discussing the science involved?

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Climate change is often treated as a political issue, but it shouldn't be.

The facts are these: The climate of our planet is changing at a pace unlike anything seen in the natural fluctuations traced across geological records, and scientists have overwhelmingly traced this global warming trend to human activity.

Unless you're a supercomputer, you'll find it virtually impossible to keep an eye on every single indicator of climate change. Here are a few that scientists use to monitor the planet:
For more, check out this story on how we know climate change is happening-and that humans are causing it.
For more on what we know about climate change, check out this story's companion piece-and our ongoing series on the Environmental Protection Agency.

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Six irrefutable pieces of evidence that prove climate change is real

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Climate change is often treated as a political issue, but it shouldn't be. The facts are these: The climate of our planet is changing at a pace unlike anything seen in the natural fluctuations traced across geological records, and scientists have overwhelmingly traced this global warming trend to human activity.

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Too often, the media focus their attention on climate-change deniers, and as a result, when scientists speak with the press, it's almost always a discussion of whether climate change is real. Unfortunately, that can make it harder for those who recognize that climate change is a legitimate threat to fully understand the science and impacts of rising global temperatures.

I recently visited the National Center for Atmospheric Research in Boulder, CO and met with climate scientists Dr. Kevin Trenberth and CU Boulder's Dr. Brian Toon to have a different discussion. I wanted better answers about what climate change is, what its effects could be, and how can we prepare for the future.

The discussion that follows has been edited for clarity and brevity, and I've added occasional comments for context. You can also listen to the podcast above or read the full transcript here for more in-depth insight into these issues.
Our discussion began with a review of the scientific evidence behind climate change.
Trenberth: "The main source of human-induced climate change is from increasing carbon dioxide and other greenhouse gases in the atmosphere. And we have plenty of evidence that we're responsible for the over 40% increase in carbon dioxide concentrations in the atmosphere since pre-industrial times, and more than half of that has occurred since 1980."

Toon: "I think the problem is that carbon dioxide is rising proportional to population on the Earth. If you just plot carbon dioxide in the last few decades versus global population, it tracks almost exactly. In coming decades, we're increasing global population by a million people a week. That's a new city in the world of a million people every week somewhere, and the amount of energy that's already committed to supporting this increasing population is very large."
The financial cost of climate change is also quite large.
Trenberth: "2012 was the warmest year on record in the United States. There was a very widespread drought that occurred, starting here in Colorado, in the West. The drought itself was estimated to cost about $75 billion. Superstorm Sandy is a different example, and the damages associated with that are, again, estimated to be about $75 billion. At the moment, the cost of climate and weather related disasters is something like $40 billion a year."
We discussed possible solutions to climate change, but while solutions exist, it was easy to get distracted by just how large - and deadly - the problem truly is.
Toon: "Technologically, of course, there are lots of things we can do. Solar energy and wind energy are both approaching or passing the cost of fossil fuels, so they're advantageous. [But] there's other aspects of this like air pollution, for example, which comes from burning a lot of fossil fuels. It's been estimated to kill seven million people a year around the Earth. Particularly in countries like China, it's thought to be killing about a million people a year. Even in the United States, it's causing probably 10,000 or more deaths a year."
Unfortunately, Toon may be underestimating the number of US deaths resulting from air pollution. A 2013 study out of MIT found that air pollution causes roughly 200,000 early deaths in the US each year. And there's still the general problem that carbon in the atmosphere (not the same as air pollution) really isn't something that will go away anytime soon.
Toon: "Carbon dioxide has a very, very long lifetime. Early IPCC reports would often say carbon dioxide has a lifetime of 50 years. Some people interpreted that to mean it'll go away in 50 years, but what it really meant was that it would go into equilibrium with the oceans in about 50 years. When you go somewhere in your car, about 20% of that carbon dioxide that is released to the atmosphere is still going to be there in thousands of years. The CO2 has lifetimes of thousands and thousands of years, maybe tens or hundreds of thousands of years. It's not reversible."

Trenberth: "Every springtime, the trees take up carbon dioxide and there's a draw-down of carbon dioxide in the atmosphere, but then, in the fall, the leaves fall on the forest floor and the twigs and branches and so on, and they decay and they put carbon dioxide back into the atmosphere. People talk about growing more trees, which can certainly take carbon dioxide out of the atmosphere to some extent, but then what do you do with all the trees? That's part of the issue. Maybe you can bury some of them somewhere, but it's very difficult. It's not a full solution to the problem."

Toon: "The average American uses the equivalent of about five tons of carbon a year - that's an elephant or two. That means every year you have to go out in your backyard and bury an elephant or two."
We know that climate change is expected to impact farming and sea levels. And we know that the temperature changes and increasing ocean acidification could cause many species to go extinct. But for the most part, scientists aren't worried that climate change alone could cause the extinction of humanity. However, as a threat multiplier - that is, something that triggers other problems - climate change could lead to terrible famines, pandemics, and war. And some of this may already be underway.
Trenberth: "You don't actually have to go a hundred years or a thousand years into the future before things can get quite disrupted relative to today. You can see some signs of that if you look around the world now. There's certainly studies that have suggested that the changes in climate, and the droughts that occur and the wildfires and so on are already extra stressors on the system and have exacerbated wars in Sudan and in Syria. It's one of the things which makes it very worrying for security around the world to the defense department, to the armed services, who are very concerned about the destabilizing effects of climate change around the world."
Some of the instabilities around the world today are already leading to discussion about the possibility of using nuclear weapons. But too many nuclear weapons could trigger the "other" climate change: nuclear winter.
Toon: "Nuclear winter is caused by burning cities. If there were a nuclear war in which cities were attacked then the smoke that's released from all those fires can go into the stratosphere and create a veil of soot particles in the upper atmosphere, which are very good at absorbing sunlight. It's sort of like geoengineering in that sense; it reduces the temperature of the planet. Even a little war between India and Pakistan, for example - which, incidentally, have about 400 nuclear weapons between them at the moment - if they started attacking each other's cities, the smoke from that could drop the temperature of the Earth back to preindustrial conditions. In fact, it'd be lower than anything we've seen in the climate record since the end of the last ice age, which would be devastating to mid-latitude agriculture.

"This is an issue people don't really understand: the world food storage is only about 60 days. There's not enough food on that planet to feed the population for more than 60 days. There's only enough food in an average city to feed the city for about a week. That's the same kind of issue that we're coming to also with the changes in agriculture that we might face in the next century just from global warming. You have to be able to make up those food losses by shipping food from some other place. Adjusting to that takes a long time."
Concern about our ability to adjust was a common theme. Climate change is occurring so rapidly that it will be difficult for all species, even people, to adapt quickly enough.
Trenberth: "We're way behind in terms of what is needed because if you start really trying to take serious action on this, there's a built-in delay of 20 or 30 years because of the infrastructure that you have in order to change that around. Then there's another 20-year delay because the oceans respond very, very slowly. If you start making major changes now, you end up experiencing the effects of those changes maybe 40 years from now or something like that. You've really got to get ahead of this.

"The atmosphere is a global commons. It belongs to everyone. The air that's over the US, a week later is over in Europe, and a week later it's over China, and then a week later it's back over the US again. If we dump stuff into the atmosphere, it gets shared among all of the nations."

Toon: "Organisms are used to evolving and compensating for things, but not on a 40-year timescale. They're used to slowly evolving and slowly responding to the environment, and here they're being forced to respond very quickly. That's an extinction problem. If you make a sudden change in the environment, you can cause extinctions."
As dire as the situation might seem, there are still ways in which we can address climate change.
Toon: "I'm hopeful, at the local level, things will happen, I'm hopeful that money will be made out of converting to other energy systems, and that those things will move us forward despite the inability, apparently, of politicians to deal with things."

Trenberth: "The real way of doing this is probably to create other kinds of incentives such as through a carbon tax, as often referred to, or a fee on carbon of some sort, which recognizes the downstream effects of burning coal both in terms of air pollution and in terms of climate change that's currently not built into the cost of burning coal, and it really ought to be."

Toon: "[There] is not really a question anymore about whether climate change is occurring or not. It certainly is occurring. However, how do you respond to that? What do you do? At least in the United States, it's very clear that we're a capitalistic society, and so we need to make it economically advantageous to develop these new energy technologies. I suspect that we're going to see the rise of China and Asia in developing renewable energy and selling that throughout the world for the reason that it's cheaper and they'll make money out of it. [And] we'll wake up behind the curve."

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Here's What Real Climate Scientists Have to Say About Global Warming

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Too often, the media focus their attention on climate-change deniers, and as a result, when scientists speak with the press, it's almost always a discussion of whether climate change is real. Unfortunately, that can make it harder for those who recognize that climate change is a legitimate threat to fully understand the science and impacts of rising global temperatures.

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Dear EarthTalk: I keep meeting people who say that human-induced global warming is only theory, that just as many scientists doubt it as believe it. Can you settle the score?
-- J. Proctor, London, UK

So-called "global warming skeptics" are indeed getting more vocal than ever, and banding together to show their solidarity against the scientific consensus that has concluded that global warming is caused by emissions from human activities.

Upwards of 800 skeptics (most of whom are not scientists) took part in the second annual International Conference on Climate Change-sponsored by the Heartland Institute, a conservative think tank-in March 2009. Keynote speaker and Massachusetts Institute of Technology meteorologist Richard Lindzen told the gathering that "there is no substantive basis for predictions of sizeable global warming due to observed increases in minor greenhouse gases such as carbon dioxide, methane and chlorofluorocarbons."

Most skeptics attribute global warming-few if any doubt any longer that the warming itself is occurring, given the worldwide rise in surface temperature-to natural cycles, not emissions from power plants, automobiles and other human activity. "The observational evidence...suggests that any warming from the growth of greenhouse gases is likely to be minor, difficult to detect above the natural fluctuations of the climate, and therefore inconsequential," says atmospheric physicist Fred Singer, an outspoken global warming skeptic and founder of the advocacy-oriented Science and Environmental Policy Project.

But green leaders maintain that even if some warming is consistent with millennial cycles, something is triggering the current change. According to the nonprofit Environmental Defense, some possible (natural) explanations include increased output from the sun, increased absorption of the sun's heat due to a change in the Earth's reflectivity, or a change in the internal climate system that transfers heat to the atmosphere.

But scientists have not been able to validate any such reasons for the current warming trend, despite exhaustive efforts. And a raft of recent peer reviewed studies-many which take advantage of new satellite data-back up the claim that it is emissions from tailpipes, smokestacks (and now factory farmed food animals, which release methane) that are causing potentially irreparable damage to the environment.

To wit, the U.S. National Academy of Sciences declared in 2005 that "greenhouse gases are accumulating in Earth's atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise," adding that "the scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action." Other leading U.S. scientific bodies, including the American Meteorological Society, the American Association for the Advancement of Science and the American Geophysical Union have issued concurring statements-placing the blame squarely on humans' shoulders.

Also, the Intergovernmental Panel on Climate Change (IPCC), a group of 600 leading climate scientists from 40 nations, says it is "very likely" (more than a 90 percent chance) that humans are causing a global temperature change that will reach between 3.2 and 7.2 degrees Fahrenheit by the end of this century.

CONTACTS: Heartland Institute, www.heartland.org; Science and Environmental Policy Project, www.sepp.org; U.S. National Academy of Sciences, www.nas.edu; IPCC, www.ipcc.ch.

EarthTalk is produced by E/The Environmental Magazine. SEND YOUR ENVIRONMENTAL QUESTIONS TO: EarthTalk, P.O.Box 5098, Westport, CT 06881; earthtalk@emagazine.com. Read past columns at: www.emagazine.com/earthtalk/archives.php. EarthTalk is now a book! Details and order information at: www.emagazine.com/earthtalkbook.

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Dear EarthTalk: I keep meeting people who say that human-induced global warming is only theory, that just as many scientists doubt it as believe it. Can you settle the score? -- J.

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What the science says...

Consensus on Consensus - Cook et al. (2016)

Authors of seven climate consensus studies - including Naomi Oreskes, Peter Doran, William Anderegg, Bart Verheggen, Ed Maibach, J. Stuart Carlton, and John Cook - co-authored a paper that should settle the expert climate consensus question once and for all. The two key conclusions from the paper are:

1) Depending on exactly how you measure the expert consensus, it's somewhere between 90% and 100% that agree humans are responsible for climate change, with most of our studies finding 97% consensus among publishing climate scientists.

2) The greater the climate expertise among those surveyed, the higher the consensus on human-caused global warming.

Expert consensus is a powerful thing. People know we don't have the time or capacity to learn about everything, and so we frequently defer to the conclusions of experts. It's why we visit doctors when we're ill. The same is true of climate change: most people defer to the expert consensus of climate scientists. Crucially, as we note in our paper:

Public perception of the scientific consensus has been found to be a gateway belief, affecting other climate beliefs and attitudes including policy support.

That's why those who oppose taking action to curb climate change have engaged in a misinformation campaign to deny the existence of the expert consensus. They've been largely successful, as the public badly underestimate the expert consensus, in what we call the "consensus gap." Only 16% of Americans realize that the consensus is above 90%.

Skeptical Science's 2013 'The Consensus Project'

Scientists need to back up their opinions with research and data that survive the peer-review process. A Skeptical Science peer-reviewed survey of all (over 12,000) peer-reviewed abstracts on the subject 'global climate change' and 'global warming' published between 1991 and 2011 ( Cook et al. 2013) found that over 97% of the papers taking a position on the subject agreed with the consensus position that humans are causing global warming. In a second phase of the project, the scientist authors were emailed and rated over 2,000 of their own papers. Once again, over 97% of the papers taking a position on the cause of global warming agreed that humans are causing it.

Lead author John Cook created a short video abstract summarizing the study:

Oreskes 2004 and Peiser

A survey of all peer-reviewed abstracts on the subject 'global climate change' published between 1993 and 2003 shows that not a single paper rejected the consensus position that global warming is man caused ( Oreskes 2004). 75% of the papers agreed with the consensus position while 25% made no comment either way (focused on methods or paleoclimate analysis).

Benny Peiser, a climate contrarian, repeated Oreskes' survey and claimed to have found 34 peer reviewed studies rejecting the consensus. However, an inspection of each of the 34 studies reveals most of them don't reject the consensus at all. The remaining articles in Peiser's list are editorials or letters, not peer-reviewed studies. Peiser has since retracted his criticism of Oreskes survey:

"Only [a] few abstracts explicitly reject or doubt the AGW (anthropogenic global warming) consensus which is why I have publicly withdrawn this point of my critique. [snip] I do not think anyone is questioning that we are in a period of global warming. Neither do I doubt that the overwhelming majority of climatologists is agreed that the current warming period is mostly due to human impact."

Doran 2009

Subsequent research has confirmed this result. A survey of 3146 earth scientists asked the question "Do you think human activity is a significant contributing factor in changing mean global temperatures?" (). More than 90% of participants had Ph.D.s, and 7% had master's degrees. Overall, 82% of the scientists answered yes. However, what are most interesting are responses compared to the level of expertise in climate science. Of scientists who were non-climatologists and didn't publish research, 77% answered yes. In contrast, 97.5% of climatologists who actively publish research on climate change responded yes. As the level of active research and specialization in climate science increases, so does agreement that humans are significantly changing global temperatures.

Most striking is the divide between expert climate scientists (97.4%) and the general public (58%). The paper concludes:

"It seems that the debate on the authenticity of global warming and the role played by human activity is largely nonexistent among those who understand the nuances and scientific basis of long-term climate processes. The challenge, rather, appears to be how to effectively communicate this fact to policy makers and to a public that continues to mistakenly perceive debate among scientists."

Anderegg 2010

This overwhelming consensus among climate experts is confirmed by an independent study that surveys all climate scientists who have publicly signed declarations supporting or rejecting the consensus. They find between 97% to 98% of climate experts support the consensus ( Anderegg 2010). Moreover, they examine the number of publications by each scientist as a measure of expertise in climate science. They find the average number of publications by unconvinced scientists (eg - skeptics) is around half the number by scientists convinced by the evidence. Not only is there a vast difference in the number of convinced versus unconvinced scientists, there is also a considerable gap in expertise between the two groups.

Vision Prize

The Vision Prize is an online poll of scientists about climate risk. It is an impartial and independent research platform for incentivized polling of experts on important scientific issues that are relevant to policymakers. In addition to assessing the views of scientists, Vision Prize asked its expert participants to predict the views of their scientific colleagues. The participant affiliations and fields are illustrated in Figure 3.

As this figure shows, the majority (~85%) of participants are academics, and approximately half of all participants are Earth Scientists. Thus the average climate science expertise of the participants is quite good.

Approximately 90% of participants responded that human activity has had a primary influence over global temperatures over the past 250 years, with the other 10% answering that it has been a secondary cause, and none answering either that humans have had no influence or that temperatures have not increased. Note also that the participants expected less than 80% to peg humans as the primary cause, and a few percent to say humans have no influence - the consensus was significantly better than the participants anticipated (Figure 4).

Scientific organizations endorsing the consensus

The following scientific organizations endorse the consensus position that "most of the global warming in recent decades can be attributed to human activities":

The Academies of Science from 80 different countries all endorse the consensus.

13 countries have signed a joint statement endorsing the consensus position:

Academia Brasiliera de Ciencias (Brazil)

Royal Society of Canada

Chinese Academy of Sciences

Academie des Sciences (France)

Deutsche Akademie der Naturforscher Leopoldina (Germany)

Indian National Science Academy

Accademia dei Lincei (Italy)

Science Council of Japan

Academia Mexicana de Ciencias (Mexico)

Russian Academy of Sciences

Academy of Science of South Africa

Royal Society (United Kingdom)

National Academy of Sciences (USA) (12 Mar 2009 news release)

A letter from 18 scientific organizations to US Congress states:

"Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver. These conclusions are based on multiple independent lines of evidence, and contrary assertions are inconsistent with an objective assessment of the vast body of peer-reviewed science."

The consensus is also endorsed by a Joint statement by the Network of African Science Academies (NASAC), including the following bodies:

Other Academies of Sciences that endorse the consensus:

Update January 28, 2017:
Some broken links were updated in the rebuttal. In addition, please check out the recent article Joint Statements on Climate Change from National Academies of Science Around the World published by Peter Gleick on his Significant Figures blog.

Last updated on 29 January 2017 by dana1981. View Archives

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That humans are causing global warming is the position of the Academies of Science from 19 countries plus many scientific organizations that study climate science. More specifically, around 95% of active climate researchers actively publishing climate papers endorse the consensus position.

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In recent years, global warming and climate change have been the subject of a great deal of political controversy, especially in the U.S. But as the science becomes clearer and consensus grows impossible to ignore, debate is moving away from whether humans are causing warming and toward questions about how best to respond.

Temperatures rising

Evidence of rising temperatures is pervasive and striking: Thermometer records kept over the past century and a half show Earth's average temperature has risen more than 1 degree Fahrenheit (0.9 degrees Celsius), and about twice that in parts of the Arctic.

That doesn't mean temperatures haven't fluctuated among regions of the globe or between seasons and times of day. But by analyzing average temperatures all over the world, scientists have demonstrated an unmistakable upward trend.

This trend is part of climate change, which many people consider synonymous with global warming. Scientists prefer to use "climate change" when describing the complex shifts now affecting our planet's weather and climate systems. Climate change encompasses not only rising average temperatures but also extreme weather events, shifting wildlife populations and habitats, rising seas, and a range of other impacts.

All of these changes are emerging as humans continue to add heat-trapping greenhouse gases to the atmosphere.

How is climate change measured?

Although we can't look at thermometers going back thousands of years, we do have other records that help us figure out what temperatures were like in the distant past. For example, trees store information about the climate in the place they're rooted. Each year trees grow thicker and form new rings. In warmer and wetter years, the rings are thicker. Old trees and wood can tell us about conditions hundreds or even thousands of years ago.

Windows on the past are also buried in lakes and oceans. Pollen, particles, and dead creatures fall to the bottom of oceans and lakes each year, forming sediments. Sediments contain a wealth of information about what was in the air and water when they fell. Scientists reveal this record by inserting hollow tubes into the mud to collect layers of sediment going back millions of years.

For a direct look at the atmosphere of the past, scientists drill cores through the Earth's polar ice sheets. Tiny bubbles trapped in the ice are actually samples from the Earth's past atmosphere, frozen in time. That's how we know that the concentrations of greenhouse gases since the Industrial Revolution are higher than they've been for hundreds of thousands of years.

Computer models help scientists to understand the Earth's climate, or long-term weather patterns. Models also allow scientists to make predictions about the future climate by simulating how the atmosphere and oceans absorb energy from the sun and transport it around the globe.

We are the reason

Several factorsaffect how much of the sun's energy reaches Earth's surface and how much of that energy gets absorbed. Those include greenhouse gases, particles in the atmosphere (from volcanic eruptions, for example), and changes in energy coming from the sun itself.

Climate models are designed to take such factors into account. For example, models have found that changes in solar irradiance and volcanic aerosols have contributed only about two percent of the recent warming effect over 250 years. The balance comes from greenhouse gases and other human-caused factors, such as land-use changes.

The speed and duration of this recent warming is remarkable as well. Volcanic eruptions, as an example, emit particles that temporarily cool the Earth's surface. But they have no lasting effect beyond a few years. Events like El Niño also work on fairly short and predictable cycles. On the other hand, the types of global temperature fluctuations that have contributed to ice ages occur on cycles of hundreds of thousands of years.

The answer to the question, "Is global warming real?" is yes: Nothing other than the rapid rise of greenhouse gas emissions from human activity can fully explain the dramatic and relatively recent rise in global average temperatures.

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Global warming: Is it real? Get the facts.

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Scientific consensus is overwhelming: The planet is getting warmer, and humans are behind it.

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Climate Change: Vital Signs of the Planet

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The rate of change since the mid-20th century is unprecedented over millennia.

Earth's climate has changed throughout history. Just in the last 800,000 years, there have been eight cycles of ice ages and warmer periods, with the end of the last ice age about 11,700 years ago marking the beginning of the modern climate era - and of human civilization. Most of these climate changes are attributed to very small variations in Earth's orbit that change the amount of solar energy our planet receives.

This graph, based on the comparison of atmospheric samples contained in ice cores and more recent direct measurements, provides evidence that atmospheric CO2 has increased since the Industrial Revolution. (Credit: Luthi, D., et al.. 2008; Etheridge, D.M., et al. 2010; Vostok ice core data/J.R. Petit et al.; NOAA Mauna Loa CO2 record.) Find out more about ice cores (external site).

The current warming trend is different because it is clearly the result of human activities since the mid-1800s, and is proceeding at a rate not seen over many recent millennia. It is undeniable that human activities have produced the atmospheric gases that have trapped more of the Sun's energy in the Earth system. This extra energy has warmed the atmosphere, ocean, and land, and widespread and rapid changes in the atmosphere, ocean, cryosphere, and biosphere have occurred.

Do scientists agree on climate change?

Yes, the vast majority of actively publishing climate scientists - 97 percent - agree that humans are causing global warming and climate change.

detailed answer

Earth-orbiting satellites and new technologies have helped scientists see the big picture, collecting many different types of information about our planet and its climate all over the world. These data, collected over many years, reveal the signs and patterns of a changing climate.

Scientists demonstrated the heat-trapping nature of carbon dioxide and other gases in the mid-19th century. Many of the science instruments NASA uses to study our climate focus on how these gases affect the movement of infrared radiation through the atmosphere. From the measured impacts of increases in these gases, there is no question that increased greenhouse gas levels warm Earth in response.

"Scientific evidence for warming of the climate system is unequivocal."

- Intergovernmental Panel on Climate Change

Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that Earth's climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks. This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly 10 times faster than the average rate of warming after an ice age. Carbon dioxide from human activities is increasing about 250 times faster than it did from natural sources after the last Ice Age.

References

References
Header image shows clouds imitating mountains as the sun sets after midnight as seen from Denali's backcountry Unit 13 on June 14, 2019. Credit: NPS/Emily Mesner

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Climate Change Evidence: How Do We Know?

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Vital Signs of the Planet: Global Climate Change and Global Warming. How do we know it's happening? Here's the evidence.