Extreme cold gripping Midwest does not debunk global warming, experts say – NBC News
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By James Rainey
The massive cold weather front that has descended over the Midwest this week has commentators straining for analogies (“deep freeze,” “arctic outbreak” and “ice age”), and at least some people wondering what has become of global warming.
President Donald Trump and radio provocateur Rush Limbaugh seemed bemused by the notion that the climate is warming at a time when most of America is hunkering down against subfreezing temperatures.
But climate experts, including those inside Trump’s government, said the record-setting cold does nothing to contradict the consensus on climate change. According to a tweet Tuesday morning from the National Oceanic and Atmospheric Administration: “Winter storms don’t prove that global warming isn’t happening.”
The discussion of climate and weather, and how much one influences the other, has become charged at a time when some political conservatives have rejected the scientific consensus about climate change: that greenhouse gases have warmed Earth’s atmosphere and helped fuel heat waves, extreme storms, droughts and extreme wildfires.
This week’s blast of cold air has been linked to a familiar phenomenon — the polar vortex.
That is the mass of cold air that typically blows counterclockwise over the Arctic Circle. When the flow of the jet stream slows, it can be reconfigured and push the frigid air south, into the continental United States.
That’s how Chicago can end up with a forecast for minus 22 degrees, as cold as the South Pole, with Milwaukee expected to get even colder — minus 28.
Scientists from inside and outside the U.S. government said Tuesday that it is important not to conflate individual weather events with longer term climate trends, without further evidence of connectivity.Craig Lassig / EPA
Trump made note of the extreme chill in a tweet Monday that concluded: “What the hell is going on with Global Waming? (sic) Please come back fast, we need you!”
On his Tuesday morning radio program, Limbaugh picked up the thread. “What Trump is basically saying is, ‘How the hell can there be any global warming when we’re gonna have record low temperatures and wind chills for two days in a row?’ ” opined the man who calls himself “El Rushbo.” In an extended monologue, Limbaugh said that the term “climate change” was created because “warming has stopped” and that liberals want a catchall phrase to explain weather abnormalities.
One NOAA official denied that the agency’s tweet about the cold snap was intended to refute Trump’s declarations on the issue. “Our mission is to share timely and relevant contextual information with the public,” said David Herring, who is program manager of the Climate.gov website for the science agency. “We get questions routinely when there are extreme weather events, and whether there is a connection to climate science.”
“A cold snap in the teeth of global warming is no more unusual than a cool day in summer. Both happen,” said Ben Strauss, CEO and chief scientist at Climate Central, a science education nonprofit. “It’s a bit like opening the freezer door — it cools you off if you stand there, but it tells you nothing about whether someone is turning up the room thermostat.”
Accounts about the polar vortex and other weather events focus on the here and now. But climate scientists study patterns over decades, centuries, even millennia. And scientists said the data clearly show long-term temperature increases on Earth.
“We ARE seeing an increase in record heat, and we are NOT seeing an increase in record cold,” Michael E. Mann, a professor of atmospheric science at Penn State, said via email. “The trend is in exactly the direction we would expect as a result of a warming planet. Over the past decade in the U.S., we have broken high temperature records TWICE as often as cold temperature records.”
In a stable climate, the ratio of new record highs to new record lows is approximately even, scientists said. But in the past year in the U.S., the clear warming trend has remained in evidence, with record high temperatures recorded almost twice as often as record lows. Several days of low temperatures this week will not be nearly enough to reverse that trend.
Gavin Schmidt, a climate scientist who is director of NASA’s Goddard Institute for Space Studies, agreed that anomalous cases should not distract from what has become the norm. “The basics — it’s getting warmer on average, there are more anomalous highs than anomalous lows and there is more intense rainfall — covers 90 percent of the cases,” Schmidt said.
Agreeing that a Midwestern cold snap does not debunk climate change, some scientists are trying to determine whether overall climatic shifts could actually help bring on more extreme cold.
The theory goes this way: Temperatures in the Arctic have warmed more dramatically than anywhere else on Earth. Those higher temperatures have made temperatures in the Arctic closer to the temperature in the lower latitudes. The lowering of the temperature disparity weakens the atmospheric barrier that kept the jet stream flowing in a relatively straight path around the globe. The troughs in this “wavier” jet stream dip into the Northern Hemisphere, bringing more cold weather. And the systems tend to linger, because the jet stream has slowed.
“There is a scientific discussion going on as to whether climate change is actually making it more likely for the jet stream to sometimes shoot Arctic air at us,” Climate Central’s Strauss said.
Trump has given no indication he is aware that scientists within his government are routinely affirming the general warming trend and the resulting challenges presented to humanity.
Jerry Taylor is president of the Neskanen Center, a libertarian-leaning Washington think tank that supports action to reduce greenhouse gas emissions. He said Trump’s putdowns of climate science solidify his ties to a right-wing base, in which “climate denialism is now a fundamental matter of identity.”