Climate Sensitivity to Change Underestimated in Last IPCC Report - Study

We hear a lot of talk these days about climate sensitivity.  It is often considered the most important measure for predicting how much the Earth's temperature will increase as we emit heat-trapping gases like carbon dioxide.

A paper just published in Nature Climate Change provides some guidance on climate sensitivity.  The study was completed by Dr. Drew Shindell from NASA, and what he found was exciting.  It turns out, not all Watts are equal.  Energy changes to the Earth system from changes of sun-reflecting particulates or from ozone have a different impact than energy changes from carbon dioxide.

The reason for this seemingly strange behavior is that aerosols are largely located near industrialized areas in the Northern Hemisphere.  This hemisphere also happens to contain much more land area than the south – and land regions are more sensitive to changes in energy, at least in the near term.  In short, particulates and ozone impact more sensitive parts of the planet.  Carbon dioxide, on the other hand, spreads out uniformly across the globe – it doesn't accumulate in one hemisphere or another.

What does this have to do with climate sensitivity?  Well, it means that studies based on observed warming (such as the recent low climate sensitivity studies) have underestimated the sensitivity because they did not account for the greater response to aerosol forcing.  Multiple lines of evidence are now consistent showing that the climate sensitivity is very unlikely to be at the low end of the range.  The consequences of climate change are thus likely to be towards the more damaging end of the estimates, unless we take action to quickly reduce our emissions.

Climate Sensitivity to Change Underestimated in Last IPCC Report - Study