The Arctic sea ice has been melting faster than scientists expected in the recent decades. A new study reveals that climate change driven by human activities is not the only factor accelerating the melting. Natural variability in the atmosphere is responsible for 30%-50% of the Arctic sea ice loss during the summer. Details of the study were described in the journal Nature Climate Change.
Arctic sea ice melting faster than climate models predicted
The study was conducted by Qinghua Ding and his colleagues at the University of California Santa Barbara. It comes at a time when sea ice has been melting at a record pace at both the North and South Poles. Qinghua Ding said in a statement that though anthropogenic forcing still plays a key role, the Arctic sea ice was melting much faster than climate change models predicted. “There is a mismatch,” said Ding.
The climate models failed to capture the abrupt sea ice melting that observations showed. Scientists found in their study that natural variability had accelerated the melting, especially in the last 20 years. Past research has found that changes in the tropical Pacific Ocean have created a “hot spot” over the Canadian Arctic and Greenland that increased warming in that region.
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It’s like a flat bicycle tire
Atmospheric air in the “hot spot” is squeezed together. As a result, it gets warmer and holds more moisture, bringing more heat to the sea ice below. Ding and his team focused on how the atmospheric circulation affects the sea ice in September. To understand how more air in the “hot spot” could warm the Arctic sea, researchers cited the example of a flat bicycle tire.
The tire gets warmer and warmer when you keep pumping air into it. The tire has a certain volume. When you keep pushing air into a certain volume, it gets condensed and warmer. Now let’s say that the addition of air is warming the Arctic. How can scientists be sure that it wasn’t caused by climate change?
Climate models give accurate picture after factoring in natural forces
Neil Swart of the Environment and Climate Change Canada told AOL that if the air circulation changes are caused by human activities-led greenhouse warming or other forcings such as solar activity, aerosol emissions, and ozone depletion, there would be a clear signature when averaging multiple climate model simulations. But when Ding and his colleagues averaged together all the climate models in the given period, the changes in air circulation canceled each other out.
The climate models turned out to be accurate after factoring in the natural variations. The acceleration in the Arctic sea ice melting was due to natural variations beyond the scope of climate models. Between 30-50% of melting is because of these natural forces.