Day: December 29, 2022

The world is getting warmer, winters included. The United States, however, has experienced severe winter storms in recent years, and experts are taking a closer look at the link between these extreme cold events and climate change.

While the link between global warming and heat waves is very direct, the behavior of winter storms is governed by complex atmospheric dynamics that are more difficult to study.

Even so, “there are certain aspects of winter storms … where the climate change linkages are fairly strong and robust,” Michael Mann, a climatologist at the University of Pennsylvania, told AFP.

For example, the warming of bodies of water — lakes or oceans — influences the amount of snowfall.

In the United States, a mechanism called “lake-effect snow” occurs around the Great Lakes region on the Canadian border. The city of Buffalo, which sits on the shores of one of the Great Lakes, was hit hard by a lethal snowstorm over Christmas weekend.

The collision between cold air from the north with the warmer water of these lakes causes convection, which leads to snowfall.

“The warmer those lake temperatures, the more moisture (is) in the air, and the greater potential for lake-effect snows,” Michael Mann wrote in a 2018 paper.

“Not surprisingly, we see a long-term increase in lake effect snowfalls as temperatures have warmed during the last century.”

Polar vortex

There is, however, no consensus on other mechanisms, such as the effect of climate change on the polar vortex and jet stream air currents.

The polar vortex is an air mass above the North Pole, located high in the stratosphere. Humans dwell in the troposphere, and the stratosphere is located just above it.

It is surrounded by a band of rotating air, which acts as a barrier between the cold air in the north and the warmer air in the south. As the polar vortex weakens, this band of air begins to undulate and take on a more oval shape, bringing more cold air southward.

According to a 2021 study, this type of disturbance is occurring more often and is reflected during the following two weeks, lower in the atmosphere, where the jet stream is located.

This air current, which blows from west to east, again following the border between cold and warm air, then meanders in such a way that it allows cold air from the north to intrude at lower latitudes, particularly over the eastern United States.

“Everybody agrees that when the polar vortex becomes perturbed or disrupted, there is an increase in the probability of severe winter weather,” Judah Cohen, lead author of the study and climatologist for Atmospheric and Environmental Research (AER), told AFP.

And this “stretched” polar vortex is exactly what was observed just before the storm that hit the United States this December, he pointed out.

The same phenomenon was seen in February 2021, when a bitter cold snap hit Texas, causing massive power outages.

‘Active debate’

But the heart of the debate lies elsewhere: What is causing these increased disturbances in the polar vortex?

According to Cohen, they are linked to changes in the Arctic, accelerated by climate change. On the one hand, the rapid melting of sea ice, and on the other, an increase in snow cover in Siberia.

“This is a topic that I have been studying for over 15 years, and I am more confident today in the link than I have ever been in the past,” he told AFP.

This last point, however, remains “an active debate within the scientific community,” Mann said.

“Climate models are not yet capturing all of the underlying physics that may be relevant to how climate change is impacting the behavior of the jet stream.”

Future studies will still be needed in the coming years to unravel the mystery of these complex chain reactions.

Source: Voice of America

As COVID-19 infections surge in China, the U.S. Centers for Disease Control and Prevention is considering sampling wastewater taken from international aircraft to track any emerging new variants, the agency told Reuters.

Such a policy would offer a better solution to tracking the virus and slowing its entry into the United States than new travel restrictions announced this week by the U.S. and other countries, which require mandatory negative COVID tests for travelers from China, three infectious disease experts told Reuters.

Travel restrictions, such as mandatory testing, have so far failed to significantly curb the spread of COVID, said Dr. Michael Osterholm, an infectious disease expert at the University of Minnesota.

“They seem to be essential from a political standpoint. I think each government feels like they will be accused of not doing enough to protect their citizens if they don’t do these,” he said.

The United States this week also expanded its voluntary genomic sequencing program at airports, adding Seattle and Los Angeles to the program. That brings the total number of airports gathering information from positive tests to seven.

But experts said that may not provide a meaningful sample size.

A better solution would be testing wastewater from airlines, which would offer a clearer picture of how the virus is mutating, given China’s lack of data transparency, said Dr. Eric Topol, a genomics expert and director of the Scripps Research Translational Institute in La Jolla, California.

Getting wastewater off planes from China “would be a very good tactic,” Topol said, adding that it’s important that the United States upgrade its surveillance tactics “because of China being so unwilling to share its genomic data.”

China has said criticism of its COVID statistics is groundless and downplayed the risk of new variants, saying it expects mutations to be more infectious but less severe. Still, doubts over official Chinese data have prompted many places, including the United States, Italy and Japan, to impose new testing rules on Chinese visitors as Beijing lifted travel controls.

Airplane wastewater analysis is among several options the CDC is considering to help slow the introduction of new variants into the United States from other countries, CDC spokesperson Kristen Nordlund said in an email.

The agency is grappling with a lack of transparency about COVID in China after the country of 1.4 billion people abruptly lifted strict COVID lockdowns and testing policies, unleashing the virus into an under-vaccinated and previously unexposed population.

“Previous COVID-19 wastewater surveillance has shown to be a valuable tool and airplane wastewater surveillance could potentially be an option,” she wrote.

French researchers reported in July that airplane wastewater tests showed requiring negative COVID tests before international flights does not protect countries from the spread of new variants. They found the omicron variant in wastewater from two commercial airplanes that flew from Ethiopia to France in December 2021 even though passengers had been required to take COVID tests before boarding.

California researchers reported in July that sampling of community wastewater in San Diego detected the presence of the alpha, delta, epsilon and omicron variants up to 14 days before they started showing up on nasal swabs.

Osterholm and others said mandatory testing before travel to the United States is unlikely to keep new variants out of the country.

“Border closures or border testing really makes very little difference. Maybe it slows it down by a few days,” he said, because the virus is likely to spread worldwide, and could infect people in Europe or elsewhere who may then bring it to the United States.

Source: Voice of America