According to new research by scientists at the Lawrence Livermore National Laboratory (LLNL), satellite measurements of the temperature of the troposphere, which is the atmosphere’s lowest region, might have underestimated global warming in the last 4 decades.
The research published in the Journal of Climate shows that the team examined 4 properties of tropical climate change. Each one of them is a ratio of trends in two “complementary” variables. Complementary variables usually show correlated behavior similar to tropical temperature and moisture. This behavior is driven by basic physical processes.
Four properties of climate change
The first 3 properties that the team considered showed relationships between tropical temperature and tropical water vapor (WV). These water vapor trends were compared with trends in sea surface temperature (SST), lower tropospheric temperature (TLT), and mid-to-upper tropospheric temperature (TMT).
The last property was the ratio between TMT and SST trends. All the ratios are constrained in climate model simulations, despite discrepancies in the sensitivity of climate, external forces, and natural variability. However, each ratio shows a large range when calculated with observations.
“Such comparisons across complementary measurements can shed light on the credibility of different datasets,” said LLNL’s Stephen Po-Chedley. “This work shows that careful intercomparison of different geophysical fields may help us determine historical changes in climate with greater precision.”
Realistic or an overestimation?
If the relationship between tropical temperature and moisture is real, the results of the study are either a low bias in satellite tropospheric temperature trends or an overestimation of the moisture.
Another study found out that in the last 25 years, Earth’s north and south poles have drifted about 13 feet. The study suggests that the axis started shifting significantly in 1995, speeding up the polar drift considerably. The prime reason behind the axis shift is said to be glaciers meltdowns.
“It is currently difficult to determine which interpretation is more credible,” said 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.”
