Are stratospheric polar vortex disruptions what they seem?
A weak or distorted stratospheric polar vortex (SPV) is often associated with severe winter weather in Northern Hemisphere continents. Traditional metrics of the SPV state, however, may conflate influences from both the stratosphere and the troposphere below, obfuscating attribution of weather extremes. In a new paper, published this month by Climate Dynamics, researchers present a new method that more clearly separates variations in the two atmospheric layers and their contributions to severe winter weather.
Depending on your feelings toward cold and snow, the headline “The Polar Vortex is Coming!” may instill dread or delight. The Polar Vortex first entered dinner-table conversations during the extreme winter of 2013/14, the coldest North American winter of the 21st century, and has since been used—often incorrectly—as shorthand for any cold or snowy spell. The polar vortex is a pool of frigid air encircled by strong westerly winds that sits high above the polar regions during winter only, and normally it has little influence on weather at the surface. But when it becomes disrupted from its typically circular shape—either stretched to an oblong, split into separate swirls, or greatly weakened—extreme winter weather can ensue, including severe cold, snow, and even winter heat waves.
One of the ways scientists track the behavior of the stratospheric polar vortex is to monitor the height of a constant pressure surface that exists within the stratosphere. Pressure decreases at higher altitudes because there are few air molecules above that level. The height of a pressure surface bulges and shrinks depending mainly on the temperature of the air below it: warmer air expands and cooler air contracts. Height fluctuations of a level in the stratosphere, then, are caused by temperature changes in the whole column of atmosphere below that level, not only in the stratosphere. Disruptions to the SPV detected using pressure heights, therefore, may be misleading as to their cause.
“As I explored the role of stratospheric disruptions on extreme winter weather, it occurred to me that there might be a better way to measure those disruptions,” said Dr. Jennifer Francis, Senior Scientist at Woodwell Climate Research Center and lead author. “Focusing on the stratosphere itself rather than the whole atmospheric column helps separate the influences from the two layers, which often behave independently.”
The authors analyzed the thickness of a layer in the stratosphere using an AI-based approach to identify representative patterns in the SPV, including various types of disruptions.
“The new metric revealed an increased occurrence of strong and abnormally cold SPV patterns,” added co-author Natasa Skific, Researcher at the Woodwell Climate Research Center. “This is different from findings in earlier studies based on pressure heights. Our findings make sense because higher concentrations of greenhouse gases cool the stratosphere, causing a stronger SPV.”
Paper co-author Dr. Judah Cohen, Research Scientist at MIT Parsons Lab and Director of Seasonal Forecasting at Atmospheric and Environmental Research, noted the previously underappreciated common occurrence of vortex stretching, which often contributes to cold spells in the U.S. and central Eurasia.
“The results of our study fit with other work highlighting the importance of stretched-vortex states on severe winter weather. Our new metric helps isolate the stratosphere so we can better understand its dynamics and connections with weather extremes, atmospheric blocking, and amplified Arctic warming.”
Fire on ice: The Arctic’s changing fire regime
The number of wildland fires burning in the Arctic is on the rise, according to NASA researchers. Moreover, these blazes are burning larger, hotter, and longer than they did in previous decades.
These trends are closely tied to the region’s rapidly changing climate. The Arctic is warming nearly four times faster than the global average, a shift that directly impacts rain and snow in the region and decreases soil moisture, both of which make the landscape more flammable. Lightning, the primary ignition source of Arctic fires, is also occurring farther north. These findings are detailed in a report published in 2025 by the Arctic Monitoring and Assessment Programme (AMAP), a working group of the Arctic Council.
Trump is leaving UN environmental bodies. What that means for the climate
On Wednesday night, President Trump announced that the U.S. would be withdrawing from the United Nations Framework Convention on Climate Change (UNFCCC), a landmark global treaty that sets a legal framework for international negotiations to address climate change.
The move comes after the Trump Administration asked the State Department to review the country’s involvement in various international organizations last February. The result is that the president has now withdrawn the United States from a total 66 international organisations, including 31 United Nations entities. Other groups included U.N. Oceans, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, and the International Renewable Energy Agency.
Mass. home insurer of last resort sees spike in enrollment
Combination of growing climate risks and inflation likely led to roughly 15,000 new policies added to FAIR Plan in fiscal year 2024
Don’t pull the fire alarm yet, but new data on home insurance in Massachusetts is turning heads across the industry.
Massachusetts enrolled more than 173,000 policies in its insurer of last resort, known as the FAIR Plan, in fiscal year 2024 — marking the first year-over-year increase for the insurer since 2017 and its largest single-year jump since 2007. In fiscal 2023, the FAIR Plan enrolled 158,660 policies.
Continue reading on Commonwealth Beacon.
John Holdren awarded 2026 AIP Karl Compton Medal
Prize for leadership in physics to be given to Harvard professor and former OSTP director for engaging the public and promoting sound governmental policies.
AIP’s 2026 Karl Taylor Compton Medal for leadership in physics is being awarded to Professor John Holdren of Harvard University and former Chief Science & Technology Advisor to President Obama.
Named after prominent physicist Karl Taylor Compton, the medal is presented by AIP every two years to a highly a distinguished physicist who has made outstanding contributions to physics through exceptional statesmanship in science.
Holdren was chosen by the selection committee “for his scientific leadership in engaging the public and promoting sound governmental policies and key international agreements.”
Read more on the American Institute of Physics’ website.
COPs need a science track – not a seven-year science lag
At COP30 in Belem, negotiators have again been asked to shape the planet’s future using climate science that does not reflect latest high-quality research. The problem is not the evidence itself. It is the way we organise it for global climate diplomacy.
Read more on Carbon Pulse.
Grazing lands as climate solutions: Key practices for carbon and biodiversity
A new review of U.S. grazing land practices explores how land stewardship and ranch management practices can help fight climate change. The study identifies promising strategies—such as wetland restoration, planting legumes in pastures, and adjusting grazing intensity—that could boost soil carbon, cut greenhouse gases, and deliver co-benefits for biodiversity, water quality and soil health. But it also underscores a critical need for more research to guide long-term sustainable management.
Read more on Cool Green Science.
What the COP30 climate summit in the Amazon delivered for forests and Indigenous people
Brazil insisted on hosting this year’s COP30 climate summit in the Amazonian city of Belem to put rainforests at the heart of negotiations on how to curb global warming.
But as delegates from almost every country concluded tense talks under the rainforest’s humid heat, the outcome for trees and their guardians, though unprecedented, was bittersweet.
