No, Man-Made Climate Change Is NOT Responsible for Half of Arctic Sea Ice Loss
A new study from University of Washington, together with University of Santa Barbara and federal scientists, revealed that natural variability is to blame for the substantial loss of Arctic sea ice in recent decades.
The study, published in the journal Nature Climate Change, showed that up to half of the Arctic sea ice loss since 1979 is due to shifting wind patterns caused by natural variations in atmospheric circulation.
"Anthropogenic forcing is still dominant -- it's still the key player," said Qinghua Ding, a climate scientist at the University of California Santa Barbara who holds an affiliate position at the UW and lead author of the study, in a press release. "But we found that natural variability has helped to accelerate this melting, especially over the past 20 years."
For the study, the researchers focused the effects of the so-called "hot spot" to the Arctic sea ice in September, when the ocean reaches its maximum area of open water. The hot spot is a large region higher pressure over Greenland and the Canadian Arctic. In this region, air is squeezed together so it becomes warmer and can hold more moisture, bringing more heat to the sea ice below.
Using a new sea ice model experiment they developed, the researchers determined how much of sea ice loss the past decades were caused by natural variation and how much were lost due to climate change. The researchers found that shifts in wind patterns over the Arctic are to blame for about 60 percent of sea ice lost in the region since 1979.
The researchers found that some of the shifts in wind pattern over the Arctic were influenced by climate change. However, a good fraction of the sea ice melt during September in the past decades is most likely caused by natural variations in the atmospheric circulation. The researchers estimated that 30 to 50 percent of the observed sea ice loss since 1979 was caused by natural variations in the large-scale atmospheric pattern.
Despite the large percentage of sea ice lost due to natural variation of wind patterns, the researchers cautioned that the internal natural variability is going to be overwhelmed by the increasing levels of greenhouse gases within 50 to 100 years.