The Warmest Day of Your Life - So Far

Okay, try this with me: Bring up the memory of the hottest day in your life. Picture it: Where were you that day? What were you doing? Who was with you? How did you cope with the heat?

I'll start.

The time was August 1988, a few weeks before the start of the academic year. The Northeast was gripped by a ten-day heat wave. I went to Boston's Logan Airport, to meet my then-boyfriend, who had decided to come to the US to go back to school.

He emerged from immigration and customs wearing a thin layer of perspiration. I could tell it wasn't my lovely presence that caused him to pant slightly.

"It's so hot!" was almost the first thing he said.

"Hot?" I said, "It's cool in here; this terminal has air-conditioning."

"This is air-conditioned?" he yelped.

I could see a trace of panic come into his eyes. I suspect that at that moment he considered turning around and taking the next plane back to the pleasant Dutch climate. My poor boyfriend nearly passed out when we came outside into the heat and humidity. He spent the following days stretched out in front of a fan (I had no air conditioning then, either), while I fed him salads, iced lemonade, ice creams, everything cool.

Eventually, the heat wave passed. My boyfriend didn't turn back: he stayed, got his degree, and by and by became CelloDad. But it was a close call.

Now it's your turn.

Think back on that day, the hottest day in your life.

The fountains at the Philadephia Museum of Art, 1973


Now imagine that a time when such days happen a few times a year.
Then, a time when they happen pretty frequently.

I know, right? It makes you break out in a sweat just thinking about it. But it's coming unless we stop pumping carbon dioxide and other greenhouse gases into out planet's atmosphere, and it's coming sooner than we might think.

Climate change studies tend to depict scenarios around the year 2100: that's after my lifetime. I might not even see 2050. It's hard to wrap your head around dates that far into the future. But now a team led by Camilo Mora at the University of Hawaii at Manoa has put the data in a different light. It's eye-opening.

Climate Departure
Starting from the well-established climate data and models, Mora's team have computed the Year of Climate Departure for locations throughout the world. A place has reached climate departure when the average temperature of its coolest year from then on is expected to be higher than the average temperature of its hottest year between 1960 and 2005. It is the year in which that place has truly reached the "new normal" and its "old normal" is history.

Below is a world map with the year of climate departure indicated by colour, with a few cities highlighted. We've heard a lot about arctic sea ice melting, but this data shows that it is the tropical region which are first to reach climate departure, as early as 2020. This should worry us, because tropical species are much more vulnerable to changes in their environment than species in temperate zones. The group has posted an interactive map on which you can look up the Year of Climate Departure for your region.

When looking at data like this, we need to allow for the fact that climate scientists, like all scientists, are a careful bunch. They don't make statements that are not built on strong evidence. This is why their reports tend to understate the risks we face from climate change. They certainly don't include runaway warming scenarios. In fact, climate scientist Michael Mann has described this paper as "an overly rosy scenario". Well I'll be. Because if you look at the Climate Departure years for biodiversity, the picture is grim enough.

It's not just that we will sweat more: Our food chain might be in jeopardy within 25 years, or perhaps sooner. Before that food will merely get horrendously expensive. Species will migrate to milder climates. Well: it would be cool to have parrots and birds of paradise frequent our woods. But it won't work out that way: it's more likely that people in what are now temperate zones will be visited by scourges that are so far confined to tropical latitudes, like malaria, dengue fever, fast cockroaches and big spiders.

Canada's population is now concentrated near its boundary with the US because its northern reaches are too cold. But soon the US population might collect on the Canadian border trying to get away from the heat. Heck, at some point Canada might build a wall on its border to keep Americans out.


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