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Arctic ice melt doesn’t boost sea levels, so do we care? – FRANCE 24

Paris (AFP)

US government scientists reported Monday that the Arctic Ocean’s floating ice cover has shrivelled to its second lowest extent since satellite records began in 1979.

Until this month, only once in the last 42 years has Earth’s frozen skull cap covered less than four million square kilometres (1.5 million square miles).

The trend line is clear: sea ice extent has diminished 14 percent per decade over that period. The Arctic could see it’s first ice-free summer as early as 2035, researchers reported in Nature Climate Change last month.

But all that melting ice and snow does not directly boost sea levels any more than melted ice cubes make a glass of water overflow, which gives rise to an awkward question: who cares?

Granted, this would be bad news for polar bears, which are already on a glide path towards extinction, according to a recent study.

And yes, it would certainly mean a profound shift in the region’s marine ecosystems, from phytoplankton to whales.

But if our bottom-line concern is the impact on humanity, one might legitimately ask, “So what?”.

As it turns out, there are several reasons to be worried about the knock-on consequences of dwindling Arctic sea ice.

– Feedback loops –

Perhaps the most basic point to make, scientists say, is that a shrinking ice cap is not just a symptom of global warming, but a driver as well.

“Sea ice removal exposes dark ocean, which creates a powerful feedback mechanism,” Marco Tedesco, a geophysicist at Columbia University’s Earth Institute, told AFP.

Freshly fallen snow reflects 80 percent of the Sun’s radiative force back into space.

But when that mirror-like surface is replaced by deep blue water, about the same percentage of Earth-heating energy is absorbed instead.

And we’re not talking about a postage stamp area here: the difference between the average ice cap minimum from 1979 to 1990 and the low point reported today — more than 3 million km2 — is twice the size of France, Germany and Spain combined.

The oceans have already soaked up 90 percent of the excess heat generated by manmade greenhouse gases, but at a terrible cost, including altered chemistry, massive marine heatwaves and dying coral reefs.

And at some point, scientists warn, that liquid heat sponge may simply become saturated.

– Altering ocean currents –

Earth’s complex climate system includes interlocking ocean currents driven by wind, tides and something called the thermohaline circulation, which is itself powered by changes in temperature (“thermo”) and salt concentration (“haline”).

Even small changes in this Great Ocean Conveyor Belt — which moves between poles and across all three major oceans — can have devastating climate impacts.

Nearly 13,000 years ago, for example, as Earth was transitioning out of an ice age into the interglacial period that allowed our species to thrive, global temperatures abruptly plunged several degrees Celsius. They jumped back up again about 1,000 years later.

Geological evidence suggests a slowdown in the thermohaline circulation caused by a massive and rapid influx of cold, fresh water from the Artic region was partly to blame.

“The fresh water from melting sea ice and grounded ice in Greenland perturbs and weakens the Gulf Stream,” part of the conveyor belt flowing in the Atlantic, said Xavier Fettweis, a research associate at the University of Liege in Belgium.

“This is what allows western Europe to have a temperate climate compared to the same latitude in North America.”

The massive ice sheet atop Greenland’s land mass saw a net loss of more than half-a-trillion tonnes last year, all of it flowing into the sea.

Unlike sea ice, which doesn’t increase sea levels when it melts, runoff from Greenland does.

That record amount was due in part to warmer air temperatures, which have risen twice as fast in the Arctic as for the planet as a whole.

But it was also caused by a change in weather patterns, notably an increase in sunny summer days.

“Some studies suggest that this increase in anticyclonic conditions in the Arctic in summer results in part from the minimum sea ice extent,” Fettweis told AFP.

– Bears on thin ice –

The current trajectory of climate change and the advent of ice-free summers — defined by the UN’s IPCC climate science panel as under one million km2 — would indeed starve polar bears into extinction by century’s end, according to a July study in Nature.

“Human-caused global warming means that polar bears have less and less sea ice to hunt on in the summer months,” Steven Amstrup, lead author of the study and chief scientist of Polar Bears International, told AFP.

“The ultimate trajectory of polar bears with unabated greenhouse gas emissions is disappearance.”

© 2020 AFP

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Arctic essentially

Arctic heat wave “essentially impossible” without human-caused climate change, study finds – CBS News

Less than a month ago the world was shocked when the temperature in the Arctic Circle reached a record-breaking 100.4 degrees Fahrenheit. While remarkable in its own right, it was merely the exclamation point on an astonishing, prolonged and widespread heat event across all of the Siberian Arctic.

The extreme and unusual warmth in this region alarmed scientists worldwide, prompting a group of 14 scientists from six countries to collaborate in a study to figure how something this out-of-bounds could occur. On Wednesday, the researchers released their findings in a comprehensive climate attribution study, declaring, “This large-scale prolonged event would have been essentially impossible without climate change.”

To put it into perspective, the team found that if, hypothetically, you lived in this region before around 1900, when human-caused climate change began to emerge, a heat event this widespread, prolonged and intense would only occur once every 80,000 years — or about once every 1,000 lifetimes. 

RUSSIA-FIRE-CLIMATE-DISASTER
Firefighters work to extinguish forest fires near the village of Batagay, Sakha Republic, also called Yakutia, in Russia’s Siberia region. Freakishly warm weather and dry conditions across large swathes of Siberia have contributed to a resurgence of wildfires in the summer of 2020.

RUSSIAN EMERGENCY MINISTRY/AFP via Getty Images


The study determined the likelihood of experiencing a regional heat event of this magnitude today, as compared to 1900, is 600 times greater. And even in today’s warmer climate, it would only be expected to happen once every 130 years.

“The findings of this rapid research — that climate change increased the chances of the prolonged heat in Siberia by at least 600 times — are truly staggering,” said Andrew Ciavarella, the lead author of the research and senior detection and attribution scientist at the U.K. Meteorological Office.

The study examined the role of human-induced climate change in the likelihood and intensity of two specific events: the persistent warmth across the Siberian region from January to June, and the record temperature of 100.4 degrees Fahrenheit set at Verkhoyansk, Siberia, on June 20.

Over the first six months of this year, temperatures across the great expanse of Siberia — an area larger than the entire United States — averaged 10 degrees Fahrenheit above normal. The image below shows the study area (outlined in the rectangular box) and above-average temperatures in the orange-red shading, using degrees Celsius.

siberia-temps.jpg

Andrew Ciavarella et al.


To illustrate the unusual persistence of the warmth, the visual below, from Arctic climate expert Zack Labe, shows the departures from average temperatures over Siberia for each month from January to June. The darkest shade of red indicates temperatures of 15 degrees Fahrenheit above normal.

Monthly temperature anomalies over Siberia for the first half of 2020. While the ‘warmth’ has moved around a bit, the persistence is just so striking…

[Data from JRA-55 reanalysis] pic.twitter.com/GfX2egeznE

— Zack Labe (@ZLabe) July 8, 2020

To investigate the climate abnormalities, the research team examined both observational surface temperature records and recreated the climate using dozens of climate computer models. 

To measure the effect of climate change, the scientists ran computer simulations to compare the climate as it is today with the climate as it would have been in 1900, when there was much less in the way of heat-trapping greenhouse gases and pollution.  

On the question of how likely the 100.4-degree record in the town of Verkhoyansk was to occur in June, the study found it to be around a 1-in-140-year event in our current warmed climate, and several thousand times more likely than it would have been early in the Industrial Revolution, before humans substantially warmed the planet.

On the question of how likely a regional heat event of this year’s magnitude is, the study found it to be a 1-in-130-year event in today’s warmed climate — 600 times more likely than it would have been in 1900. 

The study also found that from 1900 to 2020, human impact on the climate made the regional heat event approximately 4 degrees Fahrenheit warmer. And it estimates that in the future, if a similar heat wave were to occur three decades from now, in 2050, the intensity could be around 10 degrees Fahrenheit warmer compared to 1900.

“These results show that we are starting to experience extreme events which would have almost no chance of happening without the human footprint on the climate system,” explained Professor Sonia Seneviratne, from ETH Zurich. “We have little time left to stabilize global warming at levels at which climate change would remain within the bounds of the Paris Agreement.”

 

The results of the study were so dramatic that even one of its most experienced climate attribution authors, Dr Friederike Otto, deputy director of the Environmental Change Institute at the University of Oxford, was surprised. 

“It is by far the strongest change in an individual event I have seen compared to everything else I’ve studied so far,” she said.

As a result of the remarkable heat and dryness, 8,000 square miles of Siberia have ignited in wildfires — significantly more fire coverage than last year up to this point. In June alone, these fires spewed 56 megatons of heat-trapping carbon dioxide into the atmosphere — more than the yearly emissions of Switzerland. This leads to a dangerous feedback loop in which the extra carbon in the atmosphere further warms the planet.

The extensive heating is also causing another feedback loop in the Arctic by melting sea ice at a prolific rate. Right now, sea ice extent adjacent to Siberia in the Laptev Sea  is not only in record decline, it has metaphorically fallen off a cliff. 

The extreme event near Siberia continues to unfold – summer 2020 is already a memorable year in the #Arcticpic.twitter.com/HbRFoG0LRh

— Zack Labe (@ZLabe) July 14, 2020

Disappearing sea ice results in less sunlight being reflected from the light-colored ice back into space; instead, more heat is absorbed by the Earth’s exposed, darker surfaces. As a result, the Arctic is warming three times faster than the global average. This phenomenon is called Arctic Amplification.

These drastic changes drive home the degree to which humans have become a force of nature, warming the climate through the burning of fossil fuels that release heat-trapping greenhouse gases and driving extremes previously unimaginable in our history.

“We are now seeing events far outside of what our societies are adapted to,” said Otto. “Climate change is here now, it is not only a problem for someone else, somewhere else, but heat waves are threatening lives and livelihoods everywhere.” 

Although she doesn’t feel climate change will wipe out the human race entirely, she warns it will lead to dangerous instability and increasingly compromise the most vulnerable: “It exacerbates inequalities and thus is a multiplier of other threats to our societies, as it is always those who are anyway marginalised that pay the highest price.”

Stunning photos of climate change


Stunning photos of climate change

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