Climate crisis: Why is the Arctic heating up much faster than anywhere else?

The Arctic is warming between two to three times faster than the rest of our planet, but what are the mechanisms causing this phenomenon, known as polar amplification?

It has long been known that one of the key causes of polar amplification is the decline in “albedo”, or reflectivity as the Arctic ice caps melt, but scientists now believe the relationship between aerosols and clouds could have more of an impact than previously thought.

The way a reduction in albedo impacts the Arctic is as follows: As less sea ice covers the Arctic Ocean, and glaciers recede and snowfall becomes less widespread or long lasting, less solar radiation is reflected off these bright white surfaces back into space.

Instead, the energy is instead absorbed by the darker open ocean and land, which leads to a rise in temperatures, and can therefore ultimately mean less ice and snow, thereby creating a cycle that pushes up local temperatures fast.

But scientists say another regional factor which is pushing polar amplification up is the extent of cloud cover.

Clouds are also highly reflective, both above and below and this means they also serve as a protective shield from solar radiation, with less cloud meaning more energy can then be absorbed by the Earth, but also they can effectively insulate the regions they cover.

But clouds depend on aerosols to form. Aerosols are tiny particles suspended in the air, and can be a wide variety of sizes and compositions. They can occur naturally such as from sea spray, marine microbial emissions or from forest fires (like in Siberia). 

They can also be produced by human activity, for example from the combustion of fossil fuels or agriculture. Without aerosols, clouds cannot form because they serve as the surface on which water molecules form droplets.

Scientists now believe aerosols are an “essential element” in regulating the climate and Arctic climate in particular.

In a new paper, published in the journal Nature Climate Change, scientists from the Swiss Federal Institute of Technology Lausanne (EPFL), say greater research on aerosols is required to understand why we are recording disproportionate warming in the Arctic.

Julia Schmale, the head of EPFL's Extreme Environments Research Laboratory and one of the paper’s authors, said: “How albedo is affected by ice is fairly well understood - there are established maximum and minimum values, for example.

“But when it comes to groups of aerosols, there are many variables to consider: will they reflect or absorb light, will they form a cloud, are they natural or anthropogenic, will they stay local or travel long distances, and so on. There are a lot of question marks out there, and we need to find the answers.”

Dr Schmale has carried out several research expeditions to the North Pole, most recently in early 2020 on the German icebreaker Polarstern. During these trips she saw first-hand that the Arctic climate tends to change fastest in the winter - despite there being no albedo during this period of 24-hour darkness. 

Scientists still don’t know why, but the researchers now suggest one reason could be that clouds present in winter are reflecting the Earth’s heat back down to the ground. 

This occurs to varying degrees depending on natural cycles and the amount of aerosol in the air. That would lift temperatures above the Arctic ice mass, but the process is extremely complicated due to the wide range of aerosol types and differences in their capacity to reflect and absorb light. 

“Few observations have been made on this phenomenon because, in order to conduct research in the Arctic in the wintertime, you have to block off an icebreaker, scientists and research equipment for the entire season,” said Dr Schmale.

The scientists have said the findings could be used to improve existing climate models, and suggested further exploration was required, while existing warming discoveries could also be used to improve current models.

“A major effort is needed right away, otherwise we'll always be one step behind in understanding what's going on,” said Dr Schmale.

“The observations we've already made could be used to improve our models. A wealth of information is available, but it hasn't been sorted through in the right way to establish links between the different processes. For instance, our models currently can’t tell us what kinds of aerosols contribute the most to climate change, whether local or anthropogenic.”

In their paper, the research team suggest creating an interactive, open-source, virtual platform that compiles all Arctic knowledge to date. 

They point to the International Arctic Systems for Observing the Atmosphere (IASOA) programme as an example. This programme coordinates the activities of individual Arctic observatories to provide a collaborative international network for Arctic atmospheric research and operations. 

“We need to improve our climate models because what’s happening in the Arctic will eventually spread elsewhere. It's already affecting the climate in other parts of the northern hemisphere, as we've seen with the melting glaciers and rising sea levels in Greenland. And to develop better models, a better understanding of aerosols’ role will be crucial. They have a major impact on the climate and on human health,” Dr Schmale warned.