MAJOR ACCELERATION OF POLAR ICE LOSS AND ITS CONSEQUENCES

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26 february 2019

[4C Note: The following letter on the menace of Antarctic ice melt was sent to us by Dr Stephan Singer, Senior Advisor on Global Energy Policies, for the Climate Action Network International, through the "talk" list of that organization.]

Dear all,

Ela Smith and Climate Analytics alerted us yesterday so eloquently on the threat to the potential rapid and deep melting rates of the Himalayan glaciers based on the recent ICIMOD study even under a 1.5 degree trajectory.

The threat of unexpected rapid melting even under 1.5 C is also reflected in the recently published research on the Antarctic and Arctic.

Here is my personal summary and conclusion on the issues below. I do fear from a scientific view that we are already on the brink of irreversible ecosystem changes caused by climate change…..

There is emerging evidence that climate change impacts – here glacial melting and sea level rise – are likely and significantly stronger in future than anticipated by the recent IPCC 1.5 C report even under lower levels of warming. Therefore our political asks as CAN network have to adapt to that such as asking for faster full decarbonisation of energy sector well before 2050 with aggressive growth of renewables and energy efficiency and a fast move to the Natural Solutions in land use sector while halting deforestation asap.

Many of us and in scientific community thought that the Antarctic might be more resilient to global warming, due to its large size and lower temperatures than in the Arctic. Bloody wrong.

Recent published research (January 2019) shows that annual net ice mass losses in the Antarctic were (and probably still are) rapidly increasing and same order of magnitude than Greenland.

https://www.pnas.org/content/116/4/1095

A multilateral and multidisciplinary team of scientists now show the continued losses of terrestrial ice of Antarctica over the last decades.

The total ice mass loss increased from 40 Gt/y on average in 1979–1990 to 50 Gt annually in 1989–2000, jumping to 166 Gt/y in 1999–2009, and were about 252 Gt annually in recent years of 2009–2017. A six-fold increase in 40 years.

Although this rapid Antarctic melt represents so far “only” about 1.4 cm of sea level rise over the last 4 decades, its increase is highly worrying, particularly the acceleration in last 20 years of a five-fold increase of ice mass loss displays an unexpected heavily exponential development resulting very likely from only global warming.

And there is still the Arctic – the Greenland terrestrial ice shield to be precise. Which if melted completely would add another 7 meter of sea level rise.

The Greenland Ice Sheet and its outlying ice caps were losing mass at a rate of about −102 Gt/y in early 2003, but 10.5 y later this rate had increased nearly fourfold to about −393 Gt/y”. 4 times. Another science contribution a few days ago.

https://www.pnas.org/content/116/6/1934

or here from National Geographic

https://www.nationalgeographic.com/environment/2018/12/greenland-ice-sheet-is-melting-faster-than-in-the-last-350-years/

https://www.nationalgeographic.com/environment/2019/01/greeland-ice-melting-four-times-faster-than-thought-raising-sea-level/

And despite a break in high melting rates between 2013 and 2014, the magazine concludes:

Data from NASA’s GRACE satellites and GPS stations scattered around Greenland's coast showed that between 2002 and 2016, Greenland lost approximately 280 billion tons of ice per year. This average annual ice melt is enough to cover the entire states of Florida and New York hip deep in meltwater, as well as drowning Washington, D.C. and one or two other small states

In the 20th century, Greenland has lost around 9,000 billion tons of ice in total, accounting for 2.5 millimeters of sea-level rise

And we need to keep in mind that terrestrial glacial ice loss is reacting with delay of decades to contemporary global warming. Hence the present rates of global warming are likely not a reflected part of the ice retreat. Some scientists fear, we are already on an almost irreversible run-away climate change pathway (the “Hothouse”), or are close to “Tipping Points” (https://www.nytimes.com/2019/01/21/climate/greenland-ice.html)

A hypothetically continued and randomly estimated further six-folding and four-folding of the Antarctic and Greenland terrestrial ice melting rate in next decades might discharge about 2.3 trillion tons of ice annually into world oceans by mid-century or earlier. This would mean an annual rate of about 7 mm sea level rise because approx. 350 billion tons of melted land ice increase sea level by about 1 mm – which is rather close to the estimated sea level rise by the IPCC AR5 scenarios of very high warming. And thermal expansion of warmer surface water following higher temperatures add to that sea level rise threat.

We are still significantly far away from an average 1.5 C global warming. But once that ecological change is triggered (well below 1.5 C ?) and once the irreversibility is put in place, the system enters a new equilibrium – and we are in deep trouble, to say that diplomatically. If Antarctica would melt completely, this would raise global sea level by more than 50 meters. The “good news” is that this is unlikely to happen in next couple of hundreds of years….But already sea level rise by end of century of “only” one meter or less is a “live or die” situation for many poor people living in low-lying coastal areas and Islands.

The IPCC in its recent 1.5 C report and based on earlier scientific literature assumes a sea level rise of 26 – 77 cm by end of century based on the various 1.5 C scenarios compared to twenty year average sea level in 1986-2005. And IPCC says correctly in report:

There is high confidence that sea level rise will continue beyond 2100. Instabilities exist for both the Greenland and Antarctic ice sheets, which could result in multi-meter rises in sea level on time scales of century to millennia”.

And this implies in the absence of effective adaptation that…:

With a 1.5°C stabilization scenario in 2100, 62.7 million people per year are at risk from flooding, with this value increasing to 137.6 million people per year in 2300”.

And further:

At least 136 megacities (port cities with a population greater than 1 million in 2005) are at risk from flooding due to sea level rise with magnitudes of rise possible under 1.5°C or 2°C in the 21st century, unless further adaptation is undertaken“.

The IPCC continues about the assumed costs and provided that there are not sufficient additional protection levels:

Coastal flooding is projected to cost thousands of billions of USD annually, with damage costs under constant protection estimated at 0.3–5.0% of global gross domestic product (GDP) in 2100 under an RCP2.6 scenario (which comes close to a 1.5 C scenario). Risks are projected to be highest in South and Southeast Asia…”

Now, if present melting rates of terrestrial polar ice are considerably higher than thought earlier, then future melting rates will be very likely higher, too, even under low warming/1.5 C scenarios. Hence, if resulting sea level also will rise higher, then the numbers of affected cities and populations by floods will also be bigger and similarly the anticipated costs larger than expected under 1.5 C – not to talk about higher temperatures……

Lessons to learn on the necessary enhancement of the NDC. Cutting net CO2 emissions by 45% by 2030 globally, as suggested by IPCC for 1.5 C, is probably not good enough. Phasing out fossil fuels by 2050 might be too late to avoid bad surprises. Holy cow – we are getting into rough waters. But who should ask for the “politically impossible” but ethically mandatory if not us NGO?

Cheers

Stephan


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