Published: January 28, 2015
Turns out global warming is nothing new.
Solar radiation has been warming Siberian permafrost for the past 7,000 years, according to a new peer-reviewed study — long before human greenhouse gas emissions began to build up in the atmosphere.
Researchers with Germany’s Alfred Wegener Institute examined ice wedges found under Siberian tundra to examine what the winter climate has been like in the region for thousands of years. What they found was that Siberian winters have been gradually warming during that time. Not only did they find a warming trend, but they found that increased intensity and duration of solar activity in the last 7,000 years has been causing winter temperatures in the region to rise.
“We have now succeeded for the first time in using oxygen isotope analysis to access the temperature information stored in the ice and compile it into a climate curve for the past 7,000 years,” said Dr. Thomas Opel, co-author of the study recently published in the journal Nature Geoscience.
“Over the past 7,000 years, the winters in the Lena River Delta have steadily warmed – a trend we haven’t seen in almost any other Arctic climate archive,” said Dr. Hanno Meyer, the study’s lead author.
Until recently, virtually all of data scientists had of this region came from “fossilised pollen, diatoms and tree rings.” These are great ways of examining the past, but they really only tell scientists what summer temperatures were like because that’s when plants and trees grow. By examining ice wedges, scientists can get a better picture of what winter was like thousands of years ago.
“Most climate models indicate a long-term cooling in the summer and long-term warming in the winter for the Arctic over the past 7,000 years,” said Dr. Thomas Laepple, another study co-author. “But until now, there has been no temperature data to support the second claim, essentially because the majority of climate archives record information from the summer. Now we can finally demonstrate that ice wedges contain similar winter-temperature information as predicted by climate models.”
Researchers can’t say exactly how much the region has warmed in the last 7,000 years, only that there has definitely been a warming trend. Hanno said that up to the “dawn of industrialisation around 1850, we can attribute the development to changes in the Earth’s position relative to the sun.” While the sun warmed Siberian winters before the industrialized times, increases in man-made greenhouse gas emissions has caused “a major increase that clearly differs from the gradual warming in the previous phase,” according to Hanno.
German scientists are now looking to see if the sun had the same influence on winter temperatures in permafrost regions across the globe, like Alaska or the Canadian Arctic.
Findings that winters had been warming thousands of years before the Industrial Revolution of the 19th Century could provide a major breakthrough in climate science. It would also support arguments that the sun plays a large role in the Earth’s climate history.
“We already have data from an area 500 kilometres east of the Lena River Delta that supports our findings,” Laepple said. “But we don’t know how it looks for example in the Canadian Arctic. We suppose the development was similar there, but don’t yet have evidence to back up that assumption.”
