Climate change tipping points: back to the drawing board + Last 6 months coldest on r

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Climate change tipping points: back to the drawing board
https://www.uu.nl/en/news/climate-change...wing-table

RELEASE: We regularly hear warnings that climate change may lead to 'tipping points': irreversible situations where savanna can quickly change into desert, or the warm gulf stream current can simply stop flowing. These cautions often refer to spatial patterns as early-warning signals of tipping points.

An international team of ecologists and mathematicians has studied these patterns and come to a surprising conclusion. "Yes, we need to do everything we can to stop climate change," the authors said in full agreement with the recent IPCC report. "But the earth is much more resilient than previously thought. The concept of tipping points is too simple." The scientists have recently published their work in the authoritative journal Science.

The article builds on years of collaboration between a variety of research institutes in the Netherlands and abroad, especially between Utrecht University and Leiden University. The researchers approached the idea of a tipping point within a spatial context.

"The formation of spatial patterns in ecosystems, like the spontaneous formation of complex vegetation patterns, is often explained as an early-warning signal for a critical transition," explains lead author Max Rietkerk, ecologist affiliated with Utrecht University. "But these patterns actually appear to allow ecosystems to evade such tipping points." These findings are based on mathematical analyses of spatial models and new observations from real-world ecosystems.

Alan Turing. Spontaneously emerging patterns in nature are often referred to as 'Turing patterns', named after the renowned British mathematician Alan Turing. In 1952, he described how patterns in nature, such as the stripes on animals' coats, can develop from a homogeneous starting position.

"In ecological science, the Turing patterns are often explained as early-warning signals, because they indicate disturbance ," clarifies Leiden University mathematician and co-author Arjen Doelman. "Turing's mechanism of pattern formation is still undisputed. But the fact that a pattern is forming somewhere does not necessarily mean that an equilibrium is disrupted beyond a tipping point."

As an example of such a situation, Rietkerk refers to the transition from savanna to desert. "There you can observe all sorts of complex spatial forms. It's a spatial reorganisation, but not necessarily a tipping point. On the contrary: those Turning patterns are actually a sign of resilience."

Evading tipping points. The researchers discovered an interesting new phenomenon in ecology: multistability. It implies that many different spatial patterns can occur simultaneously under the same circumstances. Rietkerk: "And each of these patterns can remain stable under a wide range of conditions and climate change. And moreover we found that any complex system large enough to generate spatial patterns may also evade tipping points."

The question now is: which systems are sensitive to tipping, and which are not? "That means we have to go back to the drawing table to understand the exact role of tipping points," Rietkerk says. "Only then can we determine which conditions and spatial patterns result in tipping points, and which ones do not."


Antarctica's last 6 months were the coldest on record
https://www.cnn.com/2021/10/09/weather/w...index.html

EXCERPTS: In a year of extreme heat, Antarctica's last six months were the coldest on record. "For the polar darkness period, from April through September, the average temperature was -60.9 degrees Celsius (-77.6 degrees Fahrenheit), a record for those months," the National Snow and Ice Data Center (NSIDC) said.

The last six months is also the darkest period at the South Pole, which is where the name polar darkness (also called polar night) comes from. Here, the sun sets for the last time around the spring equinox, and does not rise again until near the autumn equinox six months later.

For the entire Antarctic continent, the winter of 2021 was the second-coldest on record, with the "temperature for June, July, and August 3.4 degrees Celsius (6.1 degrees Fahrenheit) lower than the 1981 to 2010 average at -62.9 degrees Celsius (-81.2 degrees Fahrenheit)," according to a new report from the NSIDC.

"This is the second-coldest winter (June-July-August months) on record, behind only 2004 in the 60-year weather record at Amundsen-Scott South Pole Station," the NSIDC said.

[...] It is important to understand weather is different from climate. Weather is what happens over shorter periods of time (days to months), such as the seven-day forecast. Climate is what happens over much longer periods of time, such as several years, or even entire generations.

"One such example is a cold snap, which can happen due to sudden changes in atmospheric circulation and may not be linked to climate change," says Tom Slater, Research Fellow at the Centre for Polar Observation and Modelling at the University of Leeds. "Texas is a good example of this; even though parts of it experienced extreme cold weather earlier this year when air from the Arctic was pushed south, looking at the long-term change in temperature tells us that Texas is 1.5 degrees warmer on average now than it was 100 years ago. That's climate."

also agree that since the 1950s extreme cold snaps do occur, but climate change is bringing far more heat records than cold records... (MORE - details)
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