June Extremes Suggest Parts of Climate System are Reaching Tipping Pointshttps://arstechnica.com/science/2023/07/june-extremes-suggest-parts-of-climate-system-are-reaching-tipping-points/June 2023 may be remembered as the start of a big change in the climate system, with many key global indicators flashing red warning lights amid signs that some systems are tipping toward a new state from which they may not recover.
Earth’s critical reflective polar ice caps are at their lowest extent on record in the satellite era, with the sea ice around Antarctica at a record-low extent by far, spurring worried scientists to share dramatic charts of the missing ice repeatedly. In the Arctic, the month ended with the Greenland Ice Sheet experiencing one of the largest June melt events ever recorded, and with scientists reporting that June 2023 was the hottest June ever measured, breaking the 2019 record by a “staggering” 0.16° Celsius.
Globally, the oceans set records for warmth on the surface and down to more than 6,000 feet deep throughout the month, with temperatures so far above the norm that the conditions elicited more graphs showing the anomaly. They’ve been shared thousands of times by scientists, policymakers and the public. And in Canada, forest areas about the size of Kentucky have burned, choking huge swaths of central and eastern North America with acrid wildfire smoke, with some of the haze even reaching Europe.
There was record-breaking heat on nearly every continent during the month, according to independent climate statistician Maximilian Herrera. Along with the deadly late June heat in Mexico and the South-central United States, extreme readings have been widespread in remote Siberia, with hundreds of daily heat records, including readings higher than 95° Fahrenheit close to the Arctic Circle. “The heat will just get worse,” he posted on Twitter.
Herrera also tracks notable regional extremes, like a historic mountain heatwave in Iran, where temperatures in late June spiked to between 100° and 120° Fahrenheit at elevations between 1,500 and 5,000 feet above sea level that are normally far cooler. During the first week of July, temperatures in Iraq are forecast to breach 120° Fahrenheit.
“These extraordinary extremes could be an early warning of tipping points towards different weather or sea ice or fire regimes,” said University of Exeter climate researcher Tim Lenton.
“We call it ‘flickering’ when a complex system starts to briefly sample a new regime before tipping into it. Let’s hope I’m wrong on that.”
In the meantime, the tropical Pacific Ocean is shifting into the warm El Niño phase of a two- to seven-year Pacific Ocean cycle that can boost the average global temperature by 0.2° Celsius, enough to stoke the planet’s fever to a dangerous new high.
“I expect a step change to higher global mean temperatures starting this year,” said atmospheric scientist Kevin Trenberth, a distinguished scholar at the National Center for Atmospheric Research and honorary faculty at the University of Auckland.
“And next year will be the warmest on record, either 1.4 or 1.5C above pre-industrial.”The higher of those levels is the amount to which the United Nations’ 2015 Paris Agreement aspired to limit climate change, but the continued upward trajectory of global temperatures could make that goal impossible to reach.
“I expect it then to oscillate about that value and not come down again,” he said.
The persistence of the startling Antarctic sea ice decline may be one of the most puzzling and worrisome of the recent cluster of climate extremes. Until recently, researchers expected less sudden changes in Antarctica, because it’s such a vast reservoir of coldness, and surrounded by a continual swirl of ocean currents and winds that have buffered the continent to some degree.
But at the end of June, getting into the heart of the Southern Hemisphere winter, an area of ice about the size of Texas and Alaska, nearly 1 million square miles, was missing. As the Southern Hemisphere’s winter set in, the sea ice grew more slowly than ever observed in the satellite era.
https://zacklabe.com/global-sea-ice-extent-conc/Other recent research shows that the Southern Ocean encircling Antarctica and extending northward to 60° south latitude, stored a disproportionately large percentage of the heat trapped in the atmosphere by greenhouse gases and then absorbed by the world’s oceans between 2005 and 2017. The study showed the Southern Ocean took up 45 to 62 percent of the heat absorbed by the world’s oceans, even though it makes up only 6.25 percent of the global ocean surface area.
In the absence of its reflective sea ice cover, the darker-colored ocean can absorb even more heat, potentially leading to earlier and more extensive melting during the next Austral summer. And as the fringe of ice around Antarctica gets smaller, warmer ocean water can more easily flow toward the floating ice shelves that buttress vast areas of inland ice that could start flowing into the sea faster to speed sea level rise.
At the top of the planet, scientists have been watching an extreme ocean heat wave in the North Atlantic just as carefully, because it could be a symptom of disruption to the Atlantic Meridional Overturning Circulation, a critical part of the global climate system that transports cold and warm ocean water between the poles. Sea surface temperatures about 9° Fahrenheit above average in the region could also contribute to heatwaves over adjacent land areas.
... “The pile of evidence linking a rapidly warming Arctic with extreme summer weather events continues to grow,” climate scientist Jennifer Francis wrote on Twitter on June 30, sharing a link to a new peer-reviewed study in Nature Communications that solidifies the hypothesis that changes in the Arctic can lead to a wavier jet stream that can trap heat domes in place.
In recent years, those patterns have sometimes persisted for months with only short pauses, including last summer, when a heat dome over Europe lasted several months and fueled that continent’s hottest summer on record.
