You’ve certainly heard that one of the most serious consequences of global warming is that the Earth’s poles are melting.
And maybe you’ve even taken notice of scientists’ warnings that the Arctic and parts of Antarctica are heating up between two and three times faster than the rest of the planet.
But do you know why the poles are important—indeed vital—for humanity?
And why are the coldest regions of the globe the hottest ones?
You possibly intuit that the main function of the poles is to cool the Earth. And there is actually some reason behind your intuition.
But you probably don’t know exactly why they act like the planet’s freezer.
The reason these vast expanses of ice cool the Earth is not that they are icy but that they are white. And that white reflects the sun’s heat.
“The planet’s ice reflects the right amount of solar energy back into space,” explains David Attenborough, naturalist and BBC presenter, in the documentary Breaking Boundaries: The Science of Our Planet (Breaking Barriers: The Science of Our Planet, in free translation).
“This cooling effect is essential to keeping the Earth’s temperature stable,” he comments in the film, released by Netflix earlier this year.
Albedo, the reflection power of surfaces
Without the sun’s rays we would not be able to live, but neither would that be possible if the Earth absorbed 100% of the solar radiation.
That’s why our planet’s ability to reflect some of this heat is so important, a phenomenon known scientifically as albedo.
Through this mechanism, our planet reflects 30% of solar radiation. The remaining 70% that the Earth absorbs allows us to maintain an ideal temperature for the development of our civilization.
But over the past few decades, the world has lost its ability to reflect the sun’s heat, causing that perfect balance that lasted about 10,000 years — a period known as the Holocene — to be broken.
Alpio Costa, a climatologist at the Argentine Antarctic Institute (IAA), states that, although the main barrier reflecting solar radiation is the atmosphere, the poles play an indispensable role as the main source of albedo on the Earth’s surface.
Costa highlights that ice is responsible for about 25% of the total solar radiation reflected by the planet. But over the past 500 years, the poles have become less and less white, reducing their reflective effect.
It is this “albedo reduction” that is causing these huge blocks of ice to heat up about three times more than the rest of the planet, explains the expert.
Why is this happening
“The problem started with the industrial revolution, when we, as a species, began to have an influence on the climate, because we became important emitters of greenhouse gases”, explains Lucas Ruiz, geologist at the Argentine Institute of Nivology, Glaciology and Environmental Sciences (Ianigla) —nivology is the study of snow and glaciology, that of glaciers.
Ruiz was one of the authors of the latest report by the IPCC (UN Intergovernmental Panel on Climate Change), which unequivocally concluded that the burning of fossil fuels and other man-made polluting actions are the main factors that explain the global warming at a speed never seen before.
The pollution we’ve produced — more than half of it in the last 30 years — has not only raised the planet’s temperature, causing the poles to start to melt.
It also caused them to become less white, reducing their ability to reflect the sun’s heat.
How did this happen? The reduction in albedo was due, on the one hand, to residues from the combustion of hydrocarbons that deposited soot on ice and snow, says Ruiz.
But the melting also darkened the ice surface, generating small bodies of water and favoring algae growth.
“If you look at Greenland from above, instead of seeing white, you’re going to see bluish-white,” notes Ruiz of the Arctic ice cap — which is melting the fastest.
Arctic sea ice — the most extensive on the planet — is also losing mass at record speeds, exposing the ocean’s surface.
The problem, says the expert, is that while ice reflects 90% of the sun’s heat, water reflects only 20% and 80% is absorbed, raising their temperatures, which also causes the water to expand.
The combination of melting ice and expanding water is causing sea levels to rise, posing a threat to coastal cities, including many of the world’s capitals.
The IPCC estimates that, even if the world manages to reach an agreement so that the planet’s temperature does not exceed 1.5°C above pre-industrial levels —today we are approaching 1.2°C—, the damage already done will cause sea levels to rise 50 cm by 2050, compared to levels in 1900.
“It seems like little, but this is very bad, because when you project on the coast, depending on the slope of the coast, it could be kilometers [de inundação]”, says Ruiz.
New work by the IPCC will be released in February, detailing which locations will be most affected. The current report, released in August, predicts that “both sea level and air temperature will rise in most coastal settlements.”
Needless to say, if humanity does not reach an agreement at the Glasgow Climate Summit (COP26) to reduce its greenhouse gas emissions, and the Earth becomes even warmer, the damage will be far greater.
‘Irreversible’ vicious circle
In this sense, what is most worrying about the darkening of the poles is that it triggered a vicious circle that could be catastrophic.
Scientists call it a “feedback process” and it works like this: as the planet warms, the polar zones lose their white surface, which reflects less, which produces an increase in temperature, which in turn leads to more ice loss. .
This phenomenon is what explains why the poles are heating up two to three times more than the rest of the planet, says Costa, from the Instituto Antártico Argentino.
“It has a name: it’s called polar amplification,” he tells BBC Mundo, the BBC’s Spanish-language services.
The bad news is that once this process is triggered, it is not enough to maintain current temperatures to slow it down. We would have to find a way to cool the atmosphere, something that is currently beyond our reach.
That’s why scientists claim that the melting of the Arctic ice cap (Greenland) is irreversible on a human time scale.
Costa warns that western Antarctica is also melting.
And considering the two poles, there is enough water to raise the sea level by more than 12 meters.
However, there is also “good” news: these blocks of ice are so large that, even if warming continues, it would take tens of thousands of years for them to completely melt.
Thus, the most immediate danger is the disappearance of Arctic sea ice, which is less bulky —and therefore will not affect sea level as much — but is critical to protecting the Earth from the sun’s rays, as it avoids the impacts of solar radiation over the ocean, which absorbs it, heating and expanding.
According to the IPCC report, sea ice in the Northern Hemisphere during the driest period has decreased by an average of about 25% over the last four decades.
Therefore, many scientists believe that limiting the emission of greenhouse gases is the key to slowing global warming and preventing more sea ice from disappearing, critically reducing albedo.
“The loss of sea ice is not irreversible”, he emphasizes. “If we slow the rise in temperatures, sea ice will increase.”
the basis of the climate
Polar amplification also threatens to unbalance another vital function of the poles: climate.
Because, as Costa points out, these large glaciers that reflect the sun are the basis of our climate.
“The difference in solar radiation between the poles and the tropics, which generates a difference in temperature, is the engine that sets the atmosphere in motion and generates what we know as climate in every corner of the world”, he explains.
This phenomenon is what causes “rainfall very close to the equator, very dry areas in subtropical latitudes and high and low pressure passages in mid-latitudes to occur, which allows for different seasons”, he adds.
So the melting of the poles and the consequent reduction in albedo not only raises atmospheric temperatures and threatens our coasts, but can also wreak havoc on the planet’s delicate climate balance.
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