Svante Arrhenius, a Swedish scientist, is probably the first scientist to propose that burning of fossil fuels could modify our global temperatures. In 1896, Arrhenius recognized that carbon dioxide, a byproduct of burning carbon substances such as natural gas, gasoline and oil, would act like a greenhouse gas.
A greenhouse gas traps heat by allowing energy from the sun to pass through the atmosphere and heat the surface, and then the atmosphere absorbs heat emitted by the ground. Carbon dioxide, water vapor and methane gases are examples of greenhouse gases.
Greenhouse gases occur naturally in the atmosphere. If we did not have greenhouse gases, Earth’s average temperature would be about 60 degrees colder than it is now.
Too much greenhouse gases, on the other hand, could lead to a hotter planet. Venus is an example of how large concentrations of greenhouse gases — carbon dioxide in its case — can lead to a very hot planet. The large concentrations of carbon dioxide on Venus result in an average surface temperature of about 600 degrees.
Arrhenius, a chemist, postulated that adding carbon dioxide through human activities could lead to a warmer Earth. He estimated that global temperatures could rise as much as 10 degrees.
Today, climate scientists estimate that by the end of the 21st century, increased human activities could result in a global warming of 3 to 7 degrees relative to the period between 1980-1990. Land areas will warm more than oceans, and winters will likely warm more than summers.