Yarrow Axford is an assistant professor of earth and planetary sciences at Northwestern University. She wrote this article, which originally appeared in U.S. News & World Report on January 25, 2014.
With December snow still sitting on my Chicago lawn, and the latest blast of arctic air now moving through most of the country, more reasonable weather seems a distant memory.
To make temperatures that freeze your nostril hairs even less welcome, the lousiest weather every winter brings out a corresponding blast of hot air from climate change skeptics, who annually present the seasons as evidence that modern science is a scam. Take Donald Trump’s recent tweet, for example, delivered to his almost 2.5 million followers, that “global warming [bulls**t] has got to stop. Our planet is freezing...”
The Donald is wrong, but many people may share his misperception. There appears to be a psychological basis for the way our collective concern about global warming tends to fall with the autumn leaves and rise whenever the mercury does. A 2011 study by researchers at Columbia University found that study participants who described the day they were surveyed as warmer than usual expressed more concern about global warming, and were willing to donate more money to a relevant charity. The opposite effects were observed in participants who described the day as colder than usual.
A recent follow-up study sought to understand the underlying reasons for this effect, and found that study participants showed a preference for forming opinions based upon accessible and simple information (like today’s temperature), rather than complex and impersonal data (which probably describes anything you’ve ever heard about the science of climate change).
Unfortunately, although winter marks the end of many things — fall semester, baseball season, wearing sandals in Chicago — even the frostiest winter cold snaps do not stop or even slow down global warming.
Climate change is a painstakingly well-documented long-term global trend, in which each recent decade has been warmer than the decade before. This is generally true for most parts of the globe, but more importantly is true when one considers the Earth as a whole.
As the Intergovernmental Panel on Climate Change described in its Fifth Assessment Report released last September, “Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850,” and “In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years.”
Despite the overwhelming evidence that our planet is warming, there are two points of perpetual confusion that combine with our psychology to make winter weather a seasonal boon for climate skepticism. For one, a cold snap where we live should not be confused for a global event.
While the recent polar vortex weirdness had communities across the eastern U.S. scrambling to deal with frigid weather earlier this month, it may have seemed to Americans like the whole world was locked in an icy grip. It was easy to forget that only hours before the arrival of that record-setting cold, parts of the eastern U.S. were enjoying unseasonably warm temperatures. And while Midwesterners were bundling up against the frigid cold, unusually warm winter temperatures were making the news in parts of Europe, including Russia, leading to (likely premature) speculation that the Olympic Winter Games in Sochi might not be wintery enough for winter sports.
Farther away, Australia was baking in a record-setting continent-wide heat wave, which later led to suspension of play during the Australian Open due to the risks of dangerous heat for athletes. While I was worrying about my bathroom plumbing freezing up in Chicago, a friend in Adelaide wrote to say, "Just to warm you up, it is currently >110 F.”
Not only has this winter’s seemingly epic cold weather been matched nearly point-for-point by unusually warm weather in other places, but there is an even more important point to keep in mind: climatically speaking, all weather should be considered short-term noise superimposed over longer-term climate.
Lately, that means superimposed over the unmistakable decades-long warming trend described by the Panel on Climate Change. Even if it is a global event, a cold season or cold year alone does not give us a cooling climate. Similarly, the evidence for a warming climate is not based upon a single warm season or year. Take Arctic sea ice, for example. As can be seen clearly in data available from the National Snow and Ice Data Center, in recent summers sea ice has covered about half to two-thirds the area of the Arctic Ocean as it did in summers of the late 1970s and early 1980s.
The downward trend is astonishing when one views the data over decades. Last year saw the sixth smallest ice extent ever recorded — better news than the record low reached in 2012, but by no means the “global cooling” touted by climate skeptics.
Of course, the same faulty conflation of short-term weather and longer-term climate sometimes goes in the opposite direction, applied to hot weather. One very bad year for Arctic sea ice will not necessarily be followed by another equally bad year. A hot summer in one part of the country is not, by itself, evidence for climate change — although hotter and more frequent heat waves are an expected consequence of global warming and the probability of hot summers is going up, up, up.
The bottom line is that the problem of climate change has not gone away, despite the fact that some of us can’t remember what our yards look like without snow or our spouses look like without long underwear. Given that we may be wired to worry more about climate change when we’re warm than when we’re cold, maybe it was a blessing that Trump’s misinformed tweets made me so angry and hot under the collar.