This award supports research using general circulation models to test the idea that activities undertaken by humans since the advent of managed agriculture approximately 11,000 years ago have added significant amounts of carbon dioxide (CO2) and methane into the Earth's atmosphere. The researchers will attempt to simulate a cooler world that would exist today in the absence of pre-industrial and industrial-era greenhouse emissions. The researchers will also examine the impacts of large-scale clearance of Eurasian forests prior to industrial periods and analyze the impact of short-term climatic variations in a cooler and lower greenhouse gas concentration world.
Recently published research by the authors suggests that activities undertaken by humans about 11,000 years ago have added significant amounts of carbon dioxide and methane to the atmosphere. The onset of significant human emissions of these gases can be detected by the departure of atmospheric gas concentrations from natural cyclic variations that have prevailed for thousands of years.
The researchers hypothesize that if natural decreases in CO2 and methane prevailed during the middle and late Holocene, greenhouse-gas concentrations in the atmosphere would have fallen toward their natural limit and the Earth would be a considerably cooler place than it is today. One line of evidence suggests an ice sheet would be growing today in northeast Canada. This suggests that greenhouse-gas emissions from pre-industrial human activities kept climate too warm for glaciation to begin.
