Challenge syndicate: Nobel laureate who saved the ozone layer explains how you can defuse the ticking time bomb on the prime of the world

SAN DIEGO, California (Project Syndicate) – It's hard to imagine that climate change could be more devastating than the fires in California, Oregon, and Washington, or the procession of hurricanes that were approaching – and sometimes, too. devastated – the Gulf Coast. There have also been fatal heat waves in India, Pakistan and Europe and devastating floods in Southeast Asia.

But there is much worse ahead of us, particularly at a risk so great that it alone threatens humanity itself: the rapid depletion of the Arctic sea ice.

Remembering an Alfred Hitchcock film, this climate bomb, which at some point could more than double the rate of global warming, has a timer that is watched with growing fear. Each September, the extent of the Arctic sea ice reaches its lowest level before increasing darkness and falling temperatures cause it to expand again. At this point, scientists compare the extent to previous years.

The results should terrify us all. This year, measurements from the National Snow and Ice Data Center in Boulder, Colorado show that there is less ice in the center of the Arctic than ever before, and research just released shows that winter sea ice in the Arctic Bering Sea hit its lowest level since 5,500 Years in 2018 and 2019.

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In the entire Arctic, the sea ice reached the second lowest value ever on September 15. The amounts vary from year to year, but the trend is unstoppable: The September 14th with the least sea ice were all in the last 14 years.

However, sea ice not only covers less area. it's also thinner than ever. The oldest sea ice (older than four years) that is more resistant to melting now accounts for less than 1% of total sea ice cover. First year ice now dominates, making sea cover more fragile and melting faster. Scientists now expect the Arctic Ocean could be nearly ice-free within a decade or two by late summer.

The effects would be catastrophic.

In the extreme scenario, which could occur within decades, the loss of all of the ice throughout the sunlit months would create global radiant heating equivalent to adding one trillion tons of carbon dioxide to the atmosphere. To put this in perspective: In the 270 years since the beginning of the industrial revolution, 2.4 trillion tons of CO2 have been added to the atmosphere. About 30% of the Arctic warming has already been added to the climate due to the ice lost between 1979 and 2016, and warming quickly follows as more of the remaining ice is lost.

This extreme scenario would drive climate change 25 years and is hardly far-fetched. Just last month, after record temperatures in summer, a block of ice broke off the largest remaining Arctic ice shelf in northeast Greenland, which was about twice the size of Manhattan.

Meanwhile, the Greenland ice sheet on land is also in danger. With the Arctic warming at least twice as fast as average global warming, the rate of melting in Greenland has at least tripled in the past two decades. This is believed to become irreversible in a decade or less. Ultimately, this melting will cause sea levels to rise up to seven meters and drown coastal cities, although this peak will most likely not be reached for hundreds of years.

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The problem of accelerating Arctic warming is exacerbated by the self-reinforcing risk of feedback from the thawing of permafrost. With around twice as much carbon trapped in the permafrost as it is in the atmosphere, releasing even part of it can be catastrophic. Thawing permafrost would also release even stronger greenhouse gases: nitrous oxide and methane. As global temperatures rise, it is also possible that even more methane will be emitted from the shallow seabed of the East Siberian Arctic Shelf.

It is clear that urgent action is needed to mitigate these enormous – even existential – risks. A rapid reduction in CO2 emissions is necessary, but far from sufficient. In fact, studies show that even quick CO2 savings would only reduce CO2 warming by around 0.1-0.3 ° C by 2050.

For this reason, it is also important to reduce emissions of so-called short-lived climate pollutants: methane, soot, fluorocarbons (HFCs) and tropospheric ozone. Such a measure could reduce the sixfold warming by reducing CO2 emissions by 2050. Overall, eliminating the emissions of these super pollutants would cut global warming in half and reduce projected Arctic warming by two thirds.

Some progress is being made. Almost four years ago, in Kigali, Rwanda, 197 countries passed an amendment to the Montreal Protocol that focuses on HFC phasing out. (The Montreal Protocol has already facilitated the leakage of nearly 100 chemicals that fuel global warming and threaten the ozone layer.)

In addition, the US Senate last month reached a non-partisan deal to cut HFC production and imports by 85% by 2036. California, for its part, has cut soot emissions by 90% since the 1960s and will cut the remainder in half by 2030. And the US Climate Alliance – a non-partisan group of 25 governors – has set a goal of reducing methane emissions by 40% to 50% by 2030 % to lower.

These are laudable goals. To achieve them – let alone the more ambitious targets needed to contain the rise in global temperature – we will have to overcome stiff headwinds, starting with the administration of President Donald Trump speaking out against emissions reduction targets.

Even if Trump loses next month's elections, the Arctic – and the entire planet – is in grave danger unless the new administration radically steps up its efforts to reduce carbon and short-lived climate pollutant emissions.

People around the world are already losing their homes and livelihoods to deadly fires, floods, storms and other disasters. Much worse could come.

This article was published with permission from Project Syndicate – The Time Bomb at the Top of the World.

Mario Molina, 1995 Nobel Laureate in Chemistry, was a professor at the University of California at San Diego and the National Autonomous University of Mexico.

Durwood Zaelke is President of the Institute for Governance and Sustainable Development and Co-Director of the Governance for Sustainable Development Program at the University of California at Santa Barbara.

Mario Molina died while preparing this comment. Read here a tribute to his co-author Durwood Zaelke.

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