New research from California-based research group Remote Sensing Systems may explain discrepancies between satellite data and ground temperatures in a study that points to faster overall global temperature rise. The new data reveals the 1976-2016 warming rate to be about 30 percent higher than previously believed, with one scientist claiming the data shows a 140 percent increase since 1998.
The difference in ground and satellite data has long been used by climate skeptics as evidence against global climate change. Unlike ground temperatures, which are relatively consistent among studies, satellite data is less reliable and tends to record significantly lower temperatures.
The discrepancies in temperatures are believed to be caused by the equipment used to record them.
Due to a phenomenon called orbital decay, satellites do not always record temperatures in a given location at the same time each day.
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"As these satellites circle the Earth, their orbits slowly decay over time due to drag from the upper atmosphere," wrote data scientist Zeke Hausfather, Ph.D., in an article on Carbon Brief, the Independent reports. "While the satellites are designed to fly over the same spot on the Earth at the same time every day -- a precondition to accurately estimating changes in temperatures over time -- this orbital decay causes their flyover time to change."
Hausfather claims the orbital drifts of some satellites can vary several hours from the time they were taken the previous day.
Using satellite data, scientists Carl Mears, Ph.D., and Frank Wentz at Remote Sensing Systems devised a way of accounting for orbital changes. Their study, published in the Journal of Climate, found little discrepancy between ground and satellite data when applying the new method.
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The new data suggests a yearly change of 0.31 degrees Fahrenheit between 1976 and 2016, compared to the previous record of about 0.24 degrees.
"This change is primarily due to the changes in the adjustment for drifting local measurement time," the scientists wrote. "The new dataset shows more warming than most similar datasets constructed from satellites or radiosonde [weather balloon] data."
Hausfather told Carbon Brief the data shows a 140 percent increase since 1998. The Washington Post reports that previous satellite studies showed a "warming hiatus" for this time period, suggesting global temperature rise had slowed.
In addition to rapid temperature rise, Hausfather noted that the data shows 2016 to be the warmest year on record.
The study's results are particularly significant given that previous satellite data are frequently referenced by climate change skeptics. Republican Sen. Ted Cruz of Texas and head of the Environmental Protection Agency Scott Pruitt are among those who have cited satellite studies, The Washington Post reports.
As scientists, even the authors of the study note that people should remain objective when interpreting the study.
“The improved consistency leads us to have confidence that we are moving in the right direction, though the existence of further problems in the data set, which might result in further upgrades, is not in any way ruled out,” said Mears.