22 July 2016

Evidence for Climate Change in Satellite Cloud Record

Science

Several large-scale patterns of cloud change between the 1980s and 2000s were identified in artifact-corrected satellite cloud datasets: poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops.  These changes were shown to be consistent with cloud changes robustly predicted by global climate models, and were likely to have had a warming effect on the planet.

Impact

Most of the uncertainty in how much the planet will warm in response to greenhouse gas emissions is due to uncertainty in how clouds will respond and impact Earth’s energy budget. Unfortunately, assessing how clouds have changed as the planet has warmed over recent decades is impeded by the fact that records of cloudiness from weather satellites are plagued by spurious variability, so the authors used novel techniques to remove spurious variability from the satellite cloud record.

Summary

Clouds substantially impact Earth’s energy budget by reflecting solar radiation back to space and by restricting emission of thermal radiation to space. Most of the uncertainty in how much the planet will warm in response to greenhouse gas emissions is due to uncertainty in how clouds will respond and impact Earth’s energy budget.  Records of cloudiness from satellites originally designed to monitor weather are plagued by erroneous variability related to changes in satellite orbit, instrument calibration and other factors, making them unsuitable for assessing how clouds have been responding to global warming. In this study, a partially DOE-funded team used novel techniques to remove spurious variability from the satellite cloud records. The corrected records exhibited several large-scale patterns of cloud change between the 1980s and 2000s: poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops.  These changes were found in several independent datasets, and were shown to be consistent with cloud changes robustly predicted by global climate models. All of these changes are likely to have had a warming effect on the planet, and lend credence to the amplifying cloud feedbacks that are present in nearly all climate models.

Contact
Mark Zelinka
Lawrence Livermore National Laboratory (LLNL)
Publications
Norris, JR, RJ Allen, AT Evan, MD Zelinka, CW O'Dell, and SA Klein.  2016.  "Evidence for Climate Change in the Satellite Cloud Record."  Nature, doi:10.1038/nature18273.