Climate Scientists at Lawrence Livermore National Lab have found that satellites may have been underestimating global warming for the last 40 years, according to a new study that was published in the Journal of Climate on May 20. The inconsistencies in the observational data recorded by satellites came to light when the team of researchers used the latest climate modelling technique against the old model and observational data.
According to the new technique, in which scientists used an ensemble of the latest climate models, there could be “systemic low bias” in the satellite temperature trends of the lowest layer of the Earth’s atmosphere — troposphere. The researchers compared the climate data trends predicted by the 6th phase of the Coupled Model Intercomparison Project (CMIP6)with the satellite data or CMIP5.
CMIP is an initiative of the World Climate Research Program that “provides a community-based infrastructure in support of climate model diagnosis, validation, intercomparison, documentation and data access,” according to its mission statement. Using the multi-model ensemble, scientists studied the relationship among four climate indicators — water vapour, sea surface temperature, lower tropospheric temperature and mid-to-upper tropospheric temperature.
Scientists found that if the observed ratios between water vapour and temperature are to be believed, new simulations indicated a larger tropical global warming of the sea surface than estimated by CMIP5 or satellite data. The behaviour of these indicators, which were simulated using the multi-model ensemble, are governed by basic physical processes indicating a higher probability of accuracy.
However, “It is currently difficult to determine which interpretation is more credible," said Ben Santer, a climate scientist at the Lawrence Livermore National Lab and the lead author of the study. However, he added that the team’sanalysis has revealed how “several observational datasets appear to be at odds with other."