The winters of the early 1970s were very cold and snowy in the northeastern United States where I grew up – as elsewhere around the US and Europe. I remember snowfalls that came up to my chin (though, of course, I was only a few feet tall back then). We now call those “old-fashioned winters”, precisely because they have grown so rare as a consequence of – yes – global warming.
If you’re younger than I am (I became a demi-centenarian three years ago), those winters are likely to be outside the range of your experience. And so it may seem plausible to you that cold snaps, that in reality simply reflect the sort of weather that was commonplace just decades ago, might constitute “record” or “unprecedented” cold.
Such a myopic view of weather extremes can be exploited by those who look to cast doubt on the overwhelming scientific consensus behind human-caused climate change. Very much in that vein, Donald Trump recently asserted in a tweet about the cold spell in the midwest that “windchill temperatures are reaching minus 60 degrees, the coldest ever recorded”. He added: “What the hell is going on with Global Waming [sic]? Please come back fast, we need you!”
Neglect, for the moment, that “global waming” isn’t a thing and that, as we have come to expect, almost none of the claims in Trump’s tweet are true – the coldest wind-chill temperatures recorded for the midwest are close to minus 70F (minus 57C), and for the US overall below minus 100F (minus 73C). Might he have a point?
For example, if we were seeing more frequent cold extremes, would this contradict the theory of human-caused global warming? No. Scientists increasingly think that climate change may cause a more frequent breakdown of the “polar vortex” of the northern hemisphere (the tight band of winds in the upper atmosphere that, typically, confine the cold North Pole air masses to the Arctic, loosely associated with the jet stream). The amplified warming of the Arctic caused by the melting of sea ice reduces the temperature contrast between the equator and pole. It is that contrast that maintains the polar vortex and jet stream. As the vortex breaks down, the jet stream slows and exhibits broader north-south wiggles, just as a river crossing almost level territory exhibits broad meanders as it snakes its way to the coastline.
That makes it easier for pieces of the cold Arctic air masses to break off and wobble down into middle-latitude continental regions such as North America and Europe, precisely what happened with the recent cold air outbreak in the US. But let’s return to the other first question: are we seeing an increase in record cold? So far, in the first month of 2019, two all-time cold records were set – in towns in Illinois. Meanwhile, there have been 35 all-time records for heat (many of them set in the extreme summer heatwave that is baking Australia and scorching cities such as Adelaide). That’s a ratio of 18 hot records to each cold record.
In the absence of planetary warming, that ratio should be one to one. Maybe, you say, it’s a fluke. After all, it’s only one month of data. But the ratio of warm to cold records is roughly two to one for the past decade.
We can now go a step further, “attributing” record warm spells to global warming by employing climate models to quantify the incidence of extreme events, both with and without the effect of human-caused greenhouse warming. The extreme European heatwave last summer was, according to one such estimate, made twice as likely by human-caused climate change. (In reality, this is probably an underestimate because the models do not capture some of the effects of a slowing jet stream analysed in some of my own recent research). So we’re seeing a trend toward more record heat, not record cold. And, even if we were seeing an increase in cold winter outbreaks in certain parts of the US and Europe, it wouldn’t necessarily contradict the case for climate change – it might even be symptomatic of it, associated with the breakdown in the polar vortex.
Let us return to Trump’s tweet, for it does not stand in isolation. It is part of a several-years-old pattern of denying the basic scientific evidence for human-caused climate change. Trump is plainly not the “genius” he has claimed to be, but he knows that climate change is real. We know this because he cited it as a reason to be granted a special dispensation to build a wall – a wall to protect his golf course in Ireland from the damaging effects of a rise in sea level.
So, if it’s not due to ignorance, what is responsible for Trump’s continued climate-change denial? Could it be the same thing responsible for him outsourcing his energy and environmental policy to fossil fuel interests? Could it have something to do with Russian influence that some have suggested helped get him elected?
We may have some answers to these questions when special counsel Robert Mueller completes his investigation into Russian meddling in the 2016 US presidential election.
In any case, Trump’s repeated dismissive comments about human-caused climate change are an example of what I have referred to as “the weaponisation of ignorance”. The ignorance in this case isn’t Trump’s. He appears to know better. It’s the electorate’s.
Only with an ill-informed citizenry could you plausibly dismiss the consensus of the world’s scientists based upon a single cold spell. Trump and, more to the point, the fossil fuel interests whose bidding he is doing have weaponised the public’s poor understanding of science.
The great Carl Sagan presaged this very scenario in his classic work The Demon-Haunted World. Sagan feared a descent into ignorance and expressed his apprehension of a future in which “no one representing the public interest can even grasp the issues”.
He worried about the emergence of a citizenry that is unable to differentiate between “what feels good and what’s true” and is therefore vulnerable to pseudo science and anti-science.
With the election of Donald Trump, have we finally arrived in the future that Sagan so feared? And if so, is there any escape from it? That remains to be seen.