If industrial carbon dioxide emissions continue unabated, atmospheric concentrations of CO2 could by 2100 reach levels not seen in at least 30 million years, when Earth’s average temperature was 25 to 30 degrees F warmer than today, according to an analysis by a U.S. scientist.
Writing in the journal, Science, Jeffrey Kiehl of the National Center for Atmospheric Research said that if carbon dioxide emissions continue to grow, atmospheric concentrations of CO2 could reach 900 to 1,000 parts per million by 2100 — triple levels two centuries ago.
Analyses of molecular structures in fossilized organic materials show that the last time atmospheric concentrations of CO2 reached those levels was 30 million to 100 million years ago, Kiehl writes. Average temperatures in much of that era were as much as 30 degrees F warmer than today, Kiehl says.
Kiehl is not forecasting such a drastic temperature increase within a century, but he warns, “If we don’t start seriously working toward a reduction of carbon emissions, we are putting our planet on a trajectory that the human species has never experienced.” Kiehl also says the planet’s climate system may be twice as sensitive to carbon dioxide as currently believed, since models do not factor in the amplifying effect that melting ice sheets and sea ice will have on warming.