Not that many years ago, a senator useda snowball gathered outside theU.S. Capitol to stand as conclusive proof that global warming didn’t exist. That’s not an argument heard much any more, even as a severe cold snap has created emergency conditions in Texas and other southern states. The connections between warming trends and extreme weather aren’t completely understood, but it’s becoming increasingly apparent that there’s a connection between climate change and rising damage from hurricanes, typhoons, rainstorms, wildfires and heat and cold.
1. What’s the connection to the Southern freeze?
The Earth’s poles arewarming faster than anywhere on the planet: The North Pole has been heating up about twice as fast as the rest of Earth for the last 30 years, according to the National Snow & Ice Data Center. In the Northern Hemisphere’s summer, this has led to a decrease in the contrast between the heat of the equator and the cold of North Pole. The strength of the summer jet stream, a river of wind that propels weather systems around the globe, depends on extreme temperature differences between these two regions. As the planet warms and this contrast diminishes, the jet stream weakens and can no longer push large weather patterns out of the way.
2. How did this send cold air south?
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In the case of the Texas cold snap, the phenomenon began in the first week of January, when air in the stratosphere above the Arctic warmed suddenly. This set up a slow-moving atmospheric chain reaction that weakened the polar vortex, the girdle of winds that keeps frigid air corralled at the North Pole, allowing it to spill out into the temperate regions of Asia, Europe, and North America. Once the cold starts rolling south, very little can stop it.
3. Can scientists prove that climate change caused this?
No. Similar events happen about six times per decade, according to the National Oceanic and Atmospheric Administration. But Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research, part of risk analytics firmVerisk, who’s spent more than a decade studying Arctic warming, maintains that climate change has increased the frequency with which the polar vortex weakens and allow the cold to air to run amok. Texas has certainly seen snow before, said Bob Henson, a meteorologist with Yale Climate Connections. But he urged observers not to be distracted by individual anomalies. “We know the climate of the central U.S. can produce events like this,” he said. “The point is, when you sum up all the events that are happening 365 days a year, that is when you see climate change most vividly.”
4. What other kind of weather do scientists tie to climate change?
The blackouts in Texas marked the second time in six months that extreme temperatures have brought grids to their knees — a heatwave across California in August caused a spike in energy demand for cooling equipment, forcing rolling blackouts for the first time since 2001. Across the U.S., severe thunderstorms and hail damage have been rising for decades. Some of that is due to increasing population, but that doesn’t explain the full extent of the increase. While scientists aren’t sure about the precise cause, there’s broad agreement that the weather is changing. In the past year, many parts of the world’s oceans reached record warm temperatures. The Atlantic produced an all-time high of 30 hurricanes and tropical storms in 2020. Vast areas the west were consumed by wildfires, including parts of Oregon and Washington that were once too wet to produce the required dry brush as fuel. Studies by reinsurers Munich Re andAon both show weather-related natural disasters around the world increasing over the years, while damage from other events such as earthquakes and volcanoes has remained the same.
5. What kind of certainty is there over the link to climate change?
It depends on what kind of disaster is being discussed. Solid correlation between global warming projections made in the 1970s or even earlier with rising temperatures make heat waves some of the most straightforward events to connect to to humanity’s greenhouse gas pollution. Forest fires are the product of heat, drought and wind, which is why scientists have become so confident that climate change is making wildfires in the western U.S., Australia, and elsewhere much worse. In the U.S. fire season is now two months longer than it was in the 1970s and 80s. Since the beginning of this century, the West has seen a 75% increase in forest area with a high fire risk, and from 1984 to 2015, the area lost to forest fires almost doubled. Hurricanes are harder to pin down, given their meteorologically complex nature and how quickly they form and dissipate. But warmer water and wetter air — both realized as complements of global warming — provide added fuel to tropical cyclones, which are expected to become more intense as the century wears on.
The Reference Shelf
- Anarticle from climate.gov in late January on the polar vortex that later led to the Texas freeze.
- Anarticle on the link between Arctic warming and extreme weather.
- TheAmerican Meteorological Society onthe link between climate change and extreme weather.
- Anarticle on climate change “Why the Polar Vortex Keeps Breaking out of the Arctic.”
- QuickTakes on blackouts in California driven bywildfires andhurricanes and climate change.
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