the current or past long-term weather conditions characteristic of a region or the entire Earth.

Some greenhouse gases are emitted naturally. However, greenhouse gases are also emitted when fossil fuels, such as petroleum and coal, are burned. Many people believe that humans need to use alternative fuels so they will burn fewer greenhouse gases. They believe that doing this could slow down the rate of global warming.

North Africa and Southwest Asia are large producers of fossil fuels. If people start to use less coal and petroleum in an attempt to reduce greenhouse gases, the economies of North Africa and Southwest Asia could suffer. The same is true of the economies of China and North America. Scientists have reported that these two countries are the world’s largest producers of greenhouse gases. For all areas of the world, alternative fuels may someday be the only way to decrease greenhouse gas output without negatively impacting people or the world's economies.