Washington: Earth`s hot past indicates a much hotter future than projected if the pace of greenhouse emissions continues unabated.
The study warns that if CO2 emissions continue at their current rate through the end of this century, atmospheric concentrations will reach levels that existed about 30 million to 100 million years ago.
Building on recent research, National Center for Atmospheric Research (NCAR) scientist Jeffrey Kiehl examined the link between global temperatures and high levels of CO2 tens of millions of years ago, reports the journal Science.
Global temperatures then averaged about 29 degrees Fahrenheit (16 degrees Celsius) above pre-industrial levels, according to an NCAR statement.
Kiehl said that global temperatures may take centuries or millennia to fully adjust in response to the higher carbon dioxide levels.
The study, based on recent computer model studies of geochemical processes, says elevated levels of CO2 may remain in the atmosphere for tens of thousands of years.
The study also indicates that the planet`s climate system, over long periods of times, may be at least twice as sensitive to CO2 as currently projected by computer models, which have generally focused on shorter-term warming trends.
The work was funded by the National Science Foundation (NSF), NCAR`s sponsor.