LLNL Research Suggests Global Warming May Be Underestimated – Livermore Independent
New research at the Lawrence Livermore National Laboratory (LLNL) suggests that global warming in the troposphere, or lowest level of the atmosphere, may have been underestimated over the last 40 years.
Climate scientists studied four properties of tropical climate change that should vary in correlation with one other. For example, changes in tropical water vapor should correlate with trends in both sea surface and lower tropospheric temperature, governed by well-understood physical processes.
The fourth property studied was upper tropospheric temperature.
The researchers found that the closest correlations were found in climate model simulations using datasets suggesting larger tropical warming of the ocean surface and the troposphere.
“Such comparisons across complementary measurements can shed light on the credibility of different datasets,” said LLNL researcher Stephen Po-Chedley, who contributed to the study that appears in the Journal of Climate.
“This work shows that careful intercomparison of different geophysical fields may help us determine historical changes in climate with greater precision,” according to Po-Chedley.
If climate model expectations between tropical temperature and moisture are realistic, the findings reflect either a systematic low bias in satellite tropospheric temperature trends or an overestimate of the observed atmospheric moistening signal, according to LLNL.
“It is currently difficult to determine which interpretation is more credible,” said climate scientist Ben Santer, lead author of the paper. “But our analysis reveals that several observational datasets – particularly those with the smallest values of ocean surface warming and tropospheric warming – appear to be at odds with other, independently measured complementary variables.”
LLNL collaborated on the study with researchers from several other institutions, including Remote Sensing Systems; the Canadian Centre for Climate Modelling and Analysis, Environment and Climate Change; the University of Washington; the Massachusetts Institute of Technology; University of Graz, Austria; and the National Oceanic and Atmospheric Administration.