Chelsea Harvey, on December 20, 2017, writes in Scientific American about a study that has found that snowfall in Alaska has increased over the past 150 years due to climate change. Chelsea notes that the study found summer snowfall rose 49% since the mid-19th century, and winter snowfall has increased by a whopping 117 percent.
It may sound counterintuitive — after all, Alaska is experiencing the fastest rate of warming in the country, and the central part of the state has already seen its temperatures climb by 2 to 3 degrees over the last 50 years. But warmer air can hold more moisture, the researchers say, allowing for greater amounts of precipitation, including snow.
Scientists say it's not just the local warming that's played a role. The study suggests that rising temperatures in the western Pacific and Indian oceans might be an even bigger factor, helping to strengthen a low-pressure system in the Gulf of Alaska that drives warm, moist air — perfect conditions for snowstorms — north across the state. It's another reminder that the effects of climate change in one location can sometimes produce rippling effects around the world.
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"When there's warmer temperatures in the tropical ocean, that leads to enhanced convection — basically, air rising up into the upper atmosphere — and that creates a sort of anomaly that propagates through the atmosphere," Winski said. In south-central Alaska, the result is an increase in storms.
The scientists say that precipitation is being affected in other areas than just Alaska. Even as the warming oceans are bringing more snow to Denali, other research has suggested that they may also be causing a decrease in Hawaiian rainfall at the same time. In Alaska, the new study provides some of the starkest evidence yet of the region's continuous response to human-caused climate change, corresponding with 150 years of greenhouse gas emissions.
It’s important to note that Alaska’s glaciers are not getting a reprieve. They are still melting and retreating at an alarming rate.
h/t GreenPeace Canada for title
Ice Loss and the Polar Vortex: How a Warming Arctic Fuels Cold Snaps
When winter sets in, "polar vortex" becomes one of the most dreaded phrases in the Northern Hemisphere. It's enough to send shivers even before the first blast of bitter cold arrives.
New research shows that some northern regions have been getting hit with these extreme cold spells more frequently over the past four decades, even as the planet as a whole has warmed. While it may seem counterintuitive, the scientists believe these bitter cold snaps are connected to the warming of the Arctic and the effects that that warming is having on the winds of the stratospheric polar vortex, high above the Earth's surface.
Here's what scientists involved in the research think is happening: The evidence is clear that the Arctic has been warming faster than the rest of the planet. That warming is reducing the amount of Arctic sea ice, allowing more heat to escape from the ocean. The scientists think that the ocean energy that is being released is causing a weakening of the polar vortex winds over the Arctic, which normally keep cold air centered over the polar region. That weakening is then allowing cold polar air to slip southward more often.
The polar vortex has always varied in strength, but the study found that the weaker phases are lasting longer and coinciding with cold winters in Northern Europe and Russia.
"The shift toward more persistent weaker states of the polar vortex lets Arctic air spill out and threaten Russia and Europe with extreme cold," said the study's lead author, Marlene Kretschmer, a climate scientist with the Potsdam Institute for Climate Impact Research. "The trend can explain most of the cooling of Eurasian winters since 1990."
President Obama's Science and Technology Advisor, Dr. John Holdren, explains the polar vortex in 2 minutes—and why climate change makes extreme weather more likely going forward.
