Guest commentary

Extreme weather events remind us of our vulnerability to the truly awesome forces of nature. They reveal the weaknesses in our societal infrastructure.  Sometimes they provide valuable insights into the workings of the climate system. But the debate about whether this winter’s cold weather over the central and eastern U.S. is due to global warming has become a stumbling block in our public discourse on human induced climate change.

Like many of my colleagues in the climate dynamics community, I am not convinced that this winter’s extreme cold lies outside the range of internally generated variability of the climate system or that it was exacerbated by the recent reduction of summer Arctic sea ice coverage. The evidence linking Arctic amplification to the behavior of the wintertime polar vortex is not strong and it is not well supported by independent, peer-reviewed studies. I expressed similar reservations 50 years ago when my father asked me whether I thought that nuclear weapons tests were changing the weather.

In contrast to the situation with nuclear weapons testing, we know that global warming does affect the weather in some ways. For example, as the global mean temperature rises, all time high temperature records are being set more frequently than they would be in a constant climate. At many tropical stations, the mean temperature of the past few decades lies within the top quartile of the probability distribution of temperature at those same stations a century ago. But at sites in middle latitudes, the internal variability of the climate system swamps the human-induced global warming trend, especially during wintertime. That’s why low temperature records are still being set occasionally, even in a warming climate.

But like the the nuclear weapons testing of 50 years ago, the buildup of greenhouse gases in the atmosphere is a threat to our planetary life support system arising from the ever expanding pressures of human activities. It is notable that under the Kennedy administration above ground testing of nuclear weapons was halted, not because it was changing the weather, but because it was considered detrimental to human welfare. I look forward to the day when the unbridled consumption of fossil fuels is halted for the same reason.

But in the meantime, I disagree with those who argue that we need to capitalize on recent extreme weather events to raise public awareness of human-induced global warming. Many of the reporters who write stories about our research don’t recognize the distinction between the broad scientific consensus on climate change and the various unsubstantiated hypotheses relating to extreme weather events. When the public becomes confused, the carefully considered scientific consensus becomes vulnerable to attack by the apologists for economic growth at all costs. It didn’t take them long to learn that poking fun at the notion that global warming could lead to extreme cold is an effective tactic.

This winter’s extreme cold has been front page news not because of climate change, but because it affects the lives of hundreds of millions of people. The looming global environmental crisis, of which global warming is a part, is even more newsworthy, but that’s a different story.

The author, John Michael Wallace, is a professor of atmospheric sciences at the University of Washington.