A recent review of satellite data is confirming that the Earth is already warming, possibly somewhat faster in the highest latitudes than previously believed, while new modelling suggests a warming surge may be on the horizon.
Last week, a NASA review of independent satellite records reinforced the agency’s past pronouncements that the last five years have been the hottest on record, and that the planet has warmed 1.0°C since the late 1800s, the Washington Post reports.
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“We may actually have been underestimating how much warmer [the Arctic has] been getting,” said Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies and co-author of the new study in the journal Environmental Research Letters.
The Post explains that the two lead data sets maintained by U.S. government agencies are based on measurements collected by thousands of thermometers, ocean buoys, and other devices located around the world on land and sea.
“As the data sets have shown not only steady global warming also but a string of new temperature records, they have come under increased scrutiny, with occasional criticism of the high-profile findings and how they are stitched together,” writes Post climate specialist Chris Mooney. “However, the research groups have maintained that their methods are valid and that the different records agree considerably more than they disagree, suggesting that the warming trend they are showing is, more or less, correct.”
The substantiation comes from NASA’s Aqua satellite, launched in 2002, which conducts higher-resolution infrared measurement than the data sets provide. “What you end up with is a really impressive correspondence between the trends that you’re seeing in this satellite product, which is totally independent of the surface temperatures, and the interpretations of the weather stations,” Schmidt told the Post.
“These findings should help put to rest any lingering concerns that modern warming is somehow due to the location of sensors in urban heat islands or other measurement errors at the surface,” said UC Berkeley researcher and Carbon Brief writer Zeke Hausfather, who was not involved with the study. “The AIRS satellite data captures the whole surface of the planet and shows that, if anything, our surface measurements are slightly underestimating the rate of modern warming.”
Meanwhile, new models being developed for the United Nations’ next major climate assessment, due for release in 2021, suggest a surge in global warming may be in the offing.
“In earlier models, doubling atmospheric carbon dioxide (CO2) over pre-industrial levels led models to predict somewhere between 2.0°C and 4.5°C of warming once the planet came into balance,” Science Magazine reports. “But in at least eight of the next-generation models, produced by leading centres in the United States, the United Kingdom, Canada, and France, that ‘equilibrium climate sensitivity’ has come in at 5.0°C or warmer.” While modellers scramble to sort out the difference in results, the trend “is definitely real. There’s no question,” said ETH Zurich climate scientist Reto Knutti.
Not all climate scientists agree with that conclusion, noting that it isn’t supported by ice core samples or other data. The findings so far are “not sufficient to convince me,” said NASA climate scientist Kate Marvel—and the model’s developers admit they’re still “mystified” by the more alarming result.
“Even so, the model results remain disconcerting,” Science writes. “The planet is already warming faster than humans can cope with, after all.”
And “the scary part is these models might be right,” said researcher Andrew Gettelman of the U.S. National Center for Atmospheric Research. “Because that would be pretty devastating.”
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