20,000 years ago, much of the
United States was covered in
glaciers. In the United States
today, we have a warmer climate
and fewer glaciers.
Alaska's Muir glacier in August 1941 and August 2004. Significant changes occurred in the 63 years between these two photos. Credit: USGS
1895 - Swedish chemist Svante Arrhenius
became curious about how decreasing levels
of CO2 in the atmosphere might cool Earth.
In order to explain past ice ages, he wondered
if a decrease in volcanic activity might lower
global CO2 levels.
His calculations showed that if CO2 levels were halved, global temperatures could decrease by about 5 degrees Celsius (9 degrees Fahrenheit).
to his calculations,
this time investigating
what would happen
if CO2 levels were
The possibility seemed remote at the time, but his results suggested that global temperatures would increase by the same amount — 5 degrees C or 9 degrees F.
Many scientists believe, however, that with the dawn of the industrial age — and the burning of fossil fuels such as coal, natural gas, and oil—humans began to significantly add to the amounts of carbon dioxide and other greenhouse gases in the atmosphere, enhancing the planet's natural greenhouse effect and causing higher temperatures.
Advancements took place and a much more
aggressive approach to production came along
with it. This resulted in using more and more
fossil fuels to support the ever growing demand.
A newspaper clip published Aug. 14, 1912, predicts that coal consumption would produce enough carbon dioxide to warm the climate. (Image credit: Fairfax Media/CC BY-NC-SA 3.0 NZ)