For the first time, new climate observations and computer models have provided a consistent picture of recent warming of the tropical atmosphere. The data and observations were made in three separate papers published in Science Express.
The first two studies revisit temperature data obtained from satellites and weather balloons, and provide compelling evidence that the tropical troposphere has warmed since 1979. The third study, led by scientists at Lawrence Livermore National Laboratory, finds that these new observational estimates of temperature change are consistent with results from state-of-the-art climate models.
Until recently, a single satellite dataset had indicated slight cooling of the tropical troposphere since 1979. This region of the atmosphere is predicted to warm in climate model simulations that include observed increases in greenhouse gases. The discrepancy in tropical temperature trends has been used to cast doubt on the reliability of computer models.
The computer models analysed in the Livermore study show that in the deep tropics, temperature changes in the troposphere are larger than at the surface. This "amplification" effect was consistent with the findings from the new satellite and weather balloon data described in the first two Science Express papers.
"This strongly suggests that there is no longer any fundamental discrepancy between modelled and observed temperature trends in the tropical atmosphere," said Benjamin Santer, lead author of the Livermore-led paper and a scientist in LLNL's Program for Climate Model Diagnosis and Intercomparison. "The new observational data helps to remove a major stumbling block in our understanding of the nature and causes of climate change. Our work illustrates that progress toward an improved understanding of the climate system requires a combination of observations, theory and models."