Why it worries that the poles of the Earth are less and less white

You have probably heard that one of the most serious consequences of global warming is that the poles are melting.

And maybe you’ve even heard warnings from scientists that the Arctic and parts of Antarctica are getting warmer. two to three times faster than the rest of the planet.

But do you know why the poles are important – rather, vital – for humanity?

And why are the coldest regions of the globe warming the most?

Well, possibly you intuit that the main function of the poles is to cool the Earth. And you have some reason.

But not because they act like the planet’s freezer.

The reason these vast expanses of ice cool is not that they are frozen. They cool especially because they are white. And that white reflects the heat of the Sun.

“The planet’s ice reflects just the right amount of solar energy back into space,” explains BBC naturalist popularizer David Attenborough in the documentary Breaking Boundaries: The Science of Our Planet (“Breaking limits: the science of our planet”).

“This cooling effect has been essential to keep the Earth’s temperature stable,” he remarks in the film that Netflix released in the middle of this year.

Albedo

Without the sun’s rays we could not live, but neither could we if the Earth absorbed 100% of the solar radiation.

That is why the ability of our planet to reflect part of that heat is so key, a phenomenon scientifically known as albedo.

Through this mechanism, our planet reflects 30% of the sun’s radiation.

The remaining 70% it absorbs has allowed us to maintain an ideal temperature for the development of our civilization.

But in recent decades, the world has been losing its ability to reflect the heat of the Sun, causing that perfect balance that lasted about 10,000 years – a period known as the Holocene – to be broken.

The climatologist of the Argentine Antarctic Institute (IAA) Alpio Costa told BBC Mundo that, although the main reflective barrier of solar radiation is our atmosphere, the poles play an indispensable role as the largest source of albedo on our surface.

Costa stressed that the ice is responsible for about a quarter of the total that is reflected by our planet.

But in the last half century the poles have become less and less white, reducing its reflective effect.

And it is this “reduction in albedo” that is causing these immense ice to be warming about three times more than the rest of the planet, said the expert.

Why happens

“The problem began with the industrial revolution, when we as a species began to have an influence on the climate, because we began to be an important source of greenhouse gas emissions,” explains Lucas Ruiz, geologist at the Argentine Institute of Nivology, Glaciology. and Environmental Sciences (Ianigla)

Ruiz was one of the authors of the latest report from the UN Intergovernmental Panel on Climate Change (IPCC), which unequivocally concluded that the burning of fossil fuels and other polluting actions of man are what are causing the planet to warm at a speed never seen before.

The pollution that we generate – more than half in the last 30 years (see graph above) -, not only raised the temperature of the planet, leading to the poles beginning to melt.

It also made them less white, reducing their ability to reflect the sun’s heat.

How did this happen? The reduction of the albedo occurred, on the one hand, by hydrocarbon combustion residues that deposited ollin on the ice and snow, says Ruiz.

But the same melting also darkened the surface of the ice, generating small bodies of water and encouraged the growth of algae.

“If you look at Greenland from the air, instead of seeing white, you see blue white, blue white, blue white,” Ruiz points out about the polar cap that is melting faster.

Arctic sea ice – the most extensive on the planet – is also losing mass at record speeds, exposing the ocean surface.

The problem, says the expert, is that while ice reflects 90% of the Sun’s heat, water only reflects 20% and 80% is absorbed, raising its temperatures, which also causes it to expand.

The combination of melting ice and expanding water is causing it to raise the sea level, which represents a threat to coastal cities, including several of the world’s capitals.

The IPCC estimates are that, even if the world manages to agree 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 generated will make the sea level by 2050 suba 50cm compared to 1900 levels.

“It seems little but it is very bad, because when you project it on the coastline, depending on the slope of the coast, it can be kilometers”, Affirms Ruiz.

Although it clarifies that a new work by the IPCC will only be released in February detailing which will be the most affected places, the current report foresees that “both sea level and air temperature will increase in most coastal settlements.”

Needless to say, if humanity failed to agree at the upcoming Glasgow Climate Summit (COP26) to reduce its greenhouse gas emissions, and the Earth became even warmer, the damage would be much more pronounced.

“Irreversible” vicious circle

In that sense, what worries most about the darkening of the poles is that has unleashed a vicious cycle That could prove catastrophic.

Scientists call it a “feedback process” and it works like this: as the planet warms the polar areas lose white surface, that reflects less, which produces an increase in temperature, which in turn generates more ice loss.

This phenomenon is what explains why the poles are warming between two and three times more than the rest of the planet, says Costa of the IAA.

“It has a name: it is called polar amplification”, He tells BBC Mundo.

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 today is out of our reach.

This is why scientists claim that the melting of the Arctic ice cap (Greenland) it is irreversible on a human time scale.

Costa warns that the western region of Antarctica is also melting.

And between the two, they have enough water to raise sea levels more than 12 meters.

However, there is also “good” news: these ice blocks are so massive that even if warming continues it would take tens of thousands of years to completely melt.

Instead, the most immediate danger is the disappearance of Arctic sea ice, which is less bulky -and therefore will not affect sea levels as much- but it is key to protect the Earth from the sun’s rays, since it prevents solar radiation from impacting on the ocean, absorbing it, heating and expanding .

According to the IPCC report, sea ice in the Northern Hemisphere during the driest period decreased on average about 25% in the last four decades.

Hence, many scientists believe that limiting greenhouse gas emissions is key to slowing global warming and preventing more sea ice from disappearing, critically reducing albedo.

“The loss of sea ice it is not irreversible”, Highlights Ruiz.

“If we lower the temperature, the sea ice will increase.”

The basis of the climate

Polar amplification also threatens to unbalance another vital function of the poles: climatic.

And it is that, as the climatologist Costa points out, these great ice that reflects 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 all corners of the world ”, he explains.

This phenomenon is what causes “rains very close to the equator, very dry areas in subtropical latitudes and high and low pressure passages in middle latitudes, which allows there to be different seasons there.”

For this reason, the melting of the poles and the consequent reduction of the albedo are not only increasing the temperatures of the atmosphere and threatening our coasts, but also, could cause chaos in the delicate climate balance of our planet.