I’m going to say something controversial. As a climate scientist, I predict a sustained, noticeable, and severe cooling trend across the Northern Hemisphere. The cold will begin soon, if it hasn’t already, and last until at least the end of the year. Some regions will freeze, it will snow, and climate deniers will gloat. The cause is a phenomenon that, while mysterious, is known to science. We call it “winter.”
I won’t be sad to see the end of this summer. It’s been brutal: heatwaves in London and Tokyo, scorching temperatures and melting permafrost in the Arctic, wildfires ravaging California and Greece. A city in Oman saw temperatures exceeding 108 degrees F. At night. I wonder if this could be the year the world finally wakes up to the reality of climate change. And then I remember last summer, when hurricanes flooded Houston and devastated Puerto Rico and the US Virgin Islands. And the year before: the hottest ever recorded. Something is clearly happening here. I think, when we talk about it, we need to keep four things in mind.
Weather is not climate
As Marshall Shepherd brilliantly puts it, “weather is your mood, climate is your personality." Weather is short-term and impossible to predict far in advance. I have no idea what the weather will be like in New York City on January 20, 2021. But I’m fairly confident it will be chilly, because New York winters are cold. Climate is just the average weather over a long time. A freakishly warm January day doesn’t make New York a winter vacation paradise. And a cold day, month, or even year doesn’t mean the climate’s not heating up.
Weather is affected by climate
Because of this, many people are nervous when talking about extreme weather events in a climate context. But a changing climate can “load the dice” on weather, making certain kinds of extreme event more likely. For example: the amount of water vapor that the atmosphere can hold increases with temperature. Heat it up by 1° F, and the moisture content increases by about 3 percent. The result? More intense rainstorms. Similarly, heat waves happen more often when the planet as a whole gets warmer.
Does one torrential storm or one bad heat wave prove climate change is happening? Of course not. Multiple long-term lines of evidence do that. But climate change will make heavy rainfall even heavier, and heatwaves hotter and more frequent. It’s reasonable to suspect that climate change plays a role in recent events.
Ask the right question
Lance Armstrong is very good at riding his bike. Even completely clean, he’d win a lot of races. It’s not inconceivable that he could have won seven Tours de France. But we know he was doping, and, most importantly, we know what doping does. So we feel confident in stripping him of his titles.
When an athlete tests positive for a banned substance, we don’t try to figure out exactly how they would have placed on a race-by-race basis, letting them keep some titles and downgrading others to third or ninth or sixty-second place finishes. Sure, we might be able to do a statistical analysis on every individual race, but mostly, we agree that this isn’t the right question to ask.
It’s the same with climate and weather. Hurricanes, heat waves, floods, and droughts have happened before and would happen again, even if humans didn’t exist. We can- and do- use clever statistics to calculate the increased risk of these events in a warming climate. But “would this have happened without climate change?” is seldom a yes-or-no question. Instead, we should be asking ourselves what we’re doing to the climate. Because when records fall this often, you have to suspect doping is involved.
It’s never just climate
Extreme events don’t matter on an empty planet, and climate change doesn’t happen in a pristine world. It’s our presence that turns weather events into disasters. And we’re complicated. Climate change will result in more wildfires, but the way we manage land is a huge contributor to their severity. Warming sea surface temperatures may fuel stronger hurricanes, but where we choose to live and build will determine the damage they cause.
Climate change happens in the world we build for it. It’s a complex place, shaped by powerful political, demographic, and economic forces. Climate change is almost never the only factor contributing to the cost of natural disasters. But that doesn’t mean it doesn’t matter.
So as this Northern hemisphere summer turns into winter, spare a thought for the poor climate scientists who are going to have to explain the falling temperatures to smug relatives and disingenuous politicians. But more importantly, remember the fires and heat waves and droughts of this angry summer. They’re a sign of things to come.