CO2 Impact Greatly Underestimated by Climate Projections

A new study claims that the Earth’s climate may be up to 50% more sensitive to atmospheric carbon dioxide (CO2) over the long term than previous climate projections, and that these projections might need to be adjusted to account for this new information.

The new research, “Earth system sensitivity inferred from Pliocene modeling and data“, studied the global temperatures from 3 million years ago and found that average temperatures were “significantly higher” than would be expected from the CO2 levels existent at that time.

“Earth is a dynamic system and climate models need to incorporate its multiple feedbacks as well as changes on both fast and long timescales.” said Dr. Dan Lunt, University of Bristol, lead author of the study

According to the authors, the long term sensitivity of the Earth system as a whole to atmospheric CO2 was not taken into account accurately in previous studies.

“We conclude that targets for the long-term stabilization of atmospheric greenhouse-gas concentrations aimed at preventing a dangerous human interference with the climate system should take into account this higher sensitivity of the Earth system.” – study authors

The reconstruction of the environmental conditions present during the mid-Pliocene warm period was provided by the U.S. Geological Survey (USGS), which allowed the researchers to test the sensitivity of the Earth system to CO2 levels in the atmosphere.

“Our research on the mid-Pliocene is the most comprehensive global reconstruction for any warm period, and scientists did so by examining fossils to determine sea surface and deepwater ocean temperatures, vegetation, sea ice extent, and other environmental characteristics during that timeframe.” –  Harry Dowsett, USGS scientist

The average global temperatures during the mid-Pliocene were about 3°C (5.5°F) greater than currently and are within the range projected for this century by the Intergovernmental Panel on Climate Change (IPCC), which means it may be one of the closest analogs in helping to understand the current and future conditions on our planet.

The research team included the USGS and was led by the University of Bristol.