Essay by Eric Worrall

Two for the price of one? The weather will be record cold with melting ice.

Climate change is the worst. Here’s just how bad it got this year.

By Hannah Osborne

The big news in Earth science this year was all about climate change, with extreme weather, flooding and drought attributed to warming. Scientists also warned about much worse to come if we don’t rein in carbon emissions.

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Climate change devastation edging closer

But some of the scariest news about the planet isn’t what happened this year but rather what could occur if we don’t stop spewing carbon into the atmosphere. A study published in June suggested ecological tipping points — such as the collapse of the Greenland Ice Sheet and the transformation of the Amazon rainforest into savanna — could be reached in just 15 years if climate change isn’t controlled.

In October, scientists penned an open letter warning about the risk posed by the collapse of a key Atlantic current. In it, researchers urged policymakers to address the threat posed by the weakening Atlantic Meridional Overturning Circulation (AMOC) — a giant ocean conveyor belt that transports heat to the Northern Hemisphere, and the breakdown of which could cause temperatures across Europe to plummet.

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Read more: https://www.livescience.com/planet-earth/climate-change-is-the-worst-heres-just-how-bad-it-got-this-year

My question, how can you have a Greenland ice sheet collapse and a weakening AMOC at the same time?

if AMOC is weakening, wouldn’t this slow the delivery of heat to Greenland?

I tracked down the study which allegedly predicted the Greenland ice sheet collapse, the study appears a little less explicit than Live Science portrays. The study mentions Greenland ice sheet collapse as one of a range of erratic climate events the authors believe could start to occur sometime between 2035 – 2047, but doesn’t appear to put an explicit date on that collapse.

Published: 22 June 2023

Earlier collapse of Anthropocene ecosystems driven by multiple faster and noisier drivers

Nature Sustainability volume 6, pages 1331–1342 (2023)Cite this article

Abstract

A major concern for the world’s ecosystems is the possibility of collapse, where landscapes and the societies they support change abruptly. Accelerating stress levels, increasing frequencies of extreme events and strengthening intersystem connections suggest that conventional modelling approaches based on incremental changes in a single stress may provide poor estimates of the impact of climate and human activities on ecosystems. We conduct experiments on four models that simulate abrupt changes in the Chilika lagoon fishery, the Easter Island community, forest dieback and lake water quality—representing ecosystems with a range of anthropogenic interactions. Collapses occur sooner under increasing levels of primary stress but additional stresses and/or the inclusion of noise in all four models bring the collapses substantially closer to today by ~38–81%. We discuss the implications for further research and the need for humanity to be vigilant for signs that ecosystems are degrading even more rapidly than previously thought.

Read more: https://www.nature.com/articles/s41893-023-01157-x

An additional issue, claims of an imminent AMOC collapse and an imminent Greenland ice sheet collapse at the same time seems inconsistent. If the Tropics are supposed to be overheating, a hotter tropical belt would surely strengthen the AMOC pump by increasing the temperature difference available to power the heat engine, regardless of any salinity issues at the cold end of the engine. However, a slowing AMOC should slow down the delivery of heat to Greenland, which should reduce the rate of melting.

Even if an AMOC collapse did somehow occur simultaneously with a big Greenland ice melt, how quickly do they expect that mile thick ice sheet to melt?

I bought too much milk a week ago, so I put a 6 pint plastic container of milk in the freezer. Yesterday I pulled that milk out of the freezer. That milk sat on my kitchen counter all day yesterday, yet there is still a big lump of ice in it. My house is pretty warm, the aircon is struggling with the hot subtropical Aussie Summer. Of course I blame global warming, it absolutely wasn’t my fault for not investing in a bigger aircon.

Obviously that milk would melt a lot faster if I put it under a stream of hot water, but if AMOC collapses, the delivery of “warm” water to Greenland will be reduced.

Of course we still have a long time to wait to see if these predictions are true. According to the study above, disasters like the Greenland Ice Sheet collapse are not supposed to start happening until 2035 – 2047.

A deferred start date is nothing new in climate science, the climate disaster is a bit like nuclear fusion, always 10+ years in the future, except when they try to hype up some contemporary photogenic weather disaster.

Scientists who get their fingers burned with an overly aggressive ice melt prediction usually appear to have the grace to retire or otherwise fade into the background, or if they want to keep playing they tend to push their updated disaster prediction date a safe distance into the future.