Earth Protect Blog

By David Leonhardt The New York Times, 2-17-

Much of the Pacific Northwest is blanketed in snow. Texas continues to endure frigid weather and electricity outages. Another winter storm is spreading across much of the country. Today, snow or freezing rain may fall on Washington, New York and Boston.

To make sense of this week’s cold spell and storms, I spoke with John Schwartz, a Times reporter who focuses on the climate. Our conversation follows.

Question: Let’s start with a simple question on some people’s minds — How do you think about record-low temperatures hammering parts of the U.S. at the same time that we’re experiencing global warming?

John Schwartz: It does sound counterintuitive! Those who deny climate science love to declare that there’s no such thing as climate change whenever the weather turns cold. But weather remains variable, and cold weather in winter still happens, even if the overall warming trend means that winters are getting milder.

Q: And is there any relationship between this week’s storms and climate change? I noticed that the climate scientist Katharine Hayhoe uses the phrase “global weirding.”

John: There’s interesting science that suggests the effects of a warming world have something to do with these sudden bursts of Arctic cold, as well. The cold air at the top of the world, the polar vortex, is usually held in place by the circulating jet stream. The Northern Hemisphere’s warming appears to be weakening the jet stream, and when sudden blasts of heat in the stratosphere punch into the vortex, that Arctic air can spill down into the middle latitudes.

Q: Are there any other changing patterns of winter weather that may be connected to climate change?

John: A warming atmosphere can hold more moisture, so when you do get storms you can expect to see heavier rain and snow. There’s also fascinating research that links a warming Arctic to increased frequency of the broad range of extreme winter weather in parts of the United States. It’s known as “warm-Arctic/cold-continents pattern,” a phenomenon that’s still being studied.

Q: What are the recent weather trends — during winter or not — where the evidence most strongly suggests climate change is playing a role?

John: In the United States, we’re seeing longer wildfire seasons because of hotter, drier conditions, and our hurricanes are becoming more destructive in several ways, including flooding and storm surge. It’s even worsening the misery of pollen season. We’ve always had floods, fires and storms, but climate change adds oomph to many weather events.