Arctic cools – but is it just a false alarm?

Image copyright EPA Image caption Goran Eriksson on the Greenland ice sheet

It is the Arctic region that is set to bear the brunt of climate change this century, and new evidence shows that we are losing our grip on it.

Researchers have used satellite data to pinpoint the cooling effects that man-made emissions are having on the region.

They suggest that models might be too conservative.

The study – published in the journal Geophysical Research Letters – is the first to make direct measurements of the Arctic Ocean in more than a decade.

How to make data accessible

It tracked how much heat energy was bouncing back to the surface in the areas of the sea where marine animals breed.

It is this sort of data which can help scientists explore the factors that are driving global climate change.

The reflective quality of the Earth’s atmosphere causes the more heat that reaches the surface to bounce back to the surface.

Such reflections – more highly reflective aerosols, such as water vapor, in the air, for example – mean the world’s oceans absorb significantly more heat than land-based regions.

This can result in global temperature increases of up to 10C, scientists say.

This particular study compared the record of annual ozone depletion data to measurements of warming.

It found a remarkable acceleration in marine-surface temperature warming of 1.8C since the beginning of the 21st century.

Image copyright ESA Image caption Satellite imagery shows the concentrations of greenhouse gases in Earth’s atmosphere

“The thinning ozone layer has had the effect of limiting the expansion of the upper atmosphere and pooling of heat and light below,” the study’s author, Goran Eriksson, from the University of Melbourne, told the BBC.

“In this case, the aurora borealis (the northern lights) could have reduced the light reflection to a point where the maximum amount of energy was converted to heat waves and was reflected back down towards the oceans, a process which is more pronounced in the Arctic.”

“This cooling trend in the Arctic Ocean occurred at the same time that other variables such as ozone loss and volcanic activity in the region were stable,” he added.

Could it be a false alarm?

Although it is not yet clear how long the recent cooling trend will last, Dr Eriksson believes the area around Alaska’s Aleutian Islands is the closest example to home.

Image copyright NASA Image caption A computer simulation shows the impact of CO2 emissions and the ozone hole

“Under the Russian model, we see the Arctic Ocean cooling faster than we expected,” he said.

“Our observation shows that the cooling signal is much stronger than anything we’ve seen before and could potentially make us rethink the way climate models are already constructed.”

The natural cooling effect in the Earth’s atmosphere – known as the energy budget – and the thermal expansion of Earth’s oceans are slowing down as well.

This means greenhouse gas emissions – including CO2 – are now likely to increase even more quickly.

The researchers think the consequences of this cooling could potentially last for 30 to 50 years, but admitted the exact effect of CO2 emission policy on future global temperatures is still unknown.

“[Environmental protection initiatives] could perhaps significantly reduce the intensity of such cooling once the effects of ozone depletion and the ocean thermal expansion were exhausted,” said Dr Eriksson.

“This could end up in a global temperature rise of around 0.5-1.0C over the coming decades, which would be sufficient to cause significant additional impacts such as drought, flooding and death, most of which are concentrated in the summer months.”

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