(Image: Unsplash/Danting Zhu)

Last year’s Intergovernmental Panel on Climate Change (IPCC) report was a landmark document, a compilation of thousands of studies that painted a grim picture of the inevitable 1.5 degree of global warming, a range of future migration and foreign policy requirements, and, without a 12-year transition from coal, an exponentially worse scenario under 2 degrees on pre-industrial levels.

But the report, almost by necessity, was largely limited to the average temperature increases and direct impacts such as heatwaves, coral bleaching and permafrost.

For ANU Earth and climate scientist Dr Andrew Glikson, the report’s most pressing climatological omission is the penetration of Arctic air and ice-melt water across the Arctic boundary into southern areas — a process arising from the contrast between the flow of Arctic air and water southward and the warming of parts of the continents.

“The long-term average in the IPCC is correct, but of course we don’t live in averages, we live in the real world,” Glikson told Crikey. “[IPCC modelling is] linear, gradual and smooth as the temperature goes up.

“However, based on the studies of US climate scientists James Hansen and colleagues, the rise in temperature will induce large-scale extreme weather events, including transient freeze events consequent on the weakening of the Arctic boundary and the flow of large volumes of cold ice melt water into the North Atlantic Ocean, a process which has already begun.”

Now, the IPCC report does compare projections of the rate of arctic ice loss with the scenarios for Arctic Ocean summer ice ranging from “substantial losses” under 1 degree and “almost gone” under 2.6 degrees. But while researchers also compared the effects of melting ice shelves on sea levels and habitat destruction, there is no explicit reference to the just-below-freezing cold water now flowing from Greenland and the Arctic oceans.

A lead author of the IPCC chapter “Impacts of 1.5°C of Global Warming on Natural and Human systems”, director of the University of Queensland’s Global Change Institute Ove Hoegh-Guldberg, agrees that Glikson is quite right “in pointing out the IPCC is by nature conservative” and puts this down to the process of gaining scientific consensus across hundreds of experts and reviewers — meaning the report is highly reliable if understated.

“Naturally, many phenomena associated with anthropogenic climate change are changing at the century and millennium scale,” Hoegh-Guldberg told Crikey. “Once they start changing, however, they are unlikely to stop easily.

“This situation also emphasises the principle that if we act today, we can have a huge influence [on] how life will be on this planet centuries from today. Changes such as those seen in sea levels clearly underpin this,” and that, while hard to distinguish by mid-century, “differences between one scenario versus another could [be] in terms of tens of metres.”

Citing projections by Hansen’s 2016 Atmospheric Chemistry and Physics (ACP) investigation, as well as an observational 2015 Nature study, Glikson says this melted water will cool both large tracts of the surrounding oceanic regions and their adjacent land areas in a process that could last several decades.

Based on climate simulations, paleo-climate data, and modern observations, Hansen’s projections below paint a clearer picture of the phenomenon around a roughly 1.2 degree increase.

The process could in turn be exacerbated by atmospheric breaches in the Arctic boundary and “jet stream”, two phenomena that, pre-global warming, helped trap cold air north. As they warm with increasing Arctic temperatures, freezing air can move south, a process affecting Western Europe and North America seen during last year’s “Beast from the East” cold spell.

For Glikson, there are two major dangers associated with the redistribution of colder temperatures: firstly, and on a purely physical level, that consequent weather extremes will create destructive natural disasters, either directly through snowstorms or by increasing the likelihood of “storminess” near intermediate temperature zones. Global adaptation measures will have to follow suit.

Secondly, that the penetration of cold fronts into an otherwise warming global ocean system will be misconstrued by climate denialists.

“I have to emphasise we’re not talking about ‘global cooling’ but about the intensification of extreme weather events, including temporary transient cooling of parts of the oceans, consequent on the weakening of the Arctic boundary, as tropical and subtropical zones continue to heat,” Glikson said. “It can be misrepresented by denialists — they’re going to come and say ‘Hansen, Glikson, whoever are forecasting global cooling,’ which is not correct.

“We’re talking about extreme weather events and temperature contrasts are going to increase. This includes spells of cold freeze. The weakening of the polar boundaries is already leading to disruption of the global climate system, which allowed human civilisation to flourish.”

The idea of “global cooling” is a bizarre product of the misreporting of 1970s scientific literature and a genuine dip following the 1940s’ spike in mean temperatures. It is now only trotted out following massive heatwaves (e.g. Rowan Dean post-2016) or by denialists incorrectly throwing shade at the scientific literature (e.g. Donald Trump).

The fact that these weather extremes are a confirmation, not refutation, of the scientific consensus on global warming puts the onus on media and political figures to look more closely and not lose sight of the bigger picture

Peter Fray

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Peter Fray
Editor-in-chief of Crikey