More on extremes

More from Tamino.

Some things deserve repeating.

One of those things, which happened to come up in conversation recently, is that climate change has its most profound effect on extreme events. Climate change is a change in the probability function (the odds for each possible outcome) of weather, and when you look at probability functions you find that if they change in the way we expect them to, it can increase (or decrease) the chance of extremes by a surprising amount.

Zagreb-Gric, Croatia, is smack-dab in the middle of one of the fastest-warming regions of Europe. It has already warmed by about 3°C (5.4°F) since the year 1880 (here are annual averages of temperature anomaly):

 

The local warming is especially pronounced since around 1980. It’s entirely possible that by the year 2040, this region will have heated up to 4°C (7.2°F) above its pre-2000 average.

Let’s talk about the daily high temperature during the month of July. We can get a decent picture of its climate — or at least, what it used to be — by taking all the high temperatures on July days prior to the year 2000, and making a histogram:

 

Zagreb can get pretty hot during July, but not extremely so. I’ve delineated three regions: temperatures as high as 30°C (86°F), which I call “hot” days, with those reaching 35°C (95°F) being “VERY hot” and days peaking at 40°C (104°F) and above are “WICKED hot.” About 20% of July days in Zagreb reach “hot” status, while “WICKED hot” has only happened once in nearly 140 years of record-keeping.

Here’s an idea of what we’ll see, if the average increases by 4°C (7.2°F) [i.e., by another 1 degree C from today]:

 

Roughly 60% of July days will be hot days, three times as likely as they were before 2000. VERY hot (dangerously so) will be ten times as likely on a July day as it was. And “WICKED hot” temperatures will happen fifty times as often as they used to. When temperatures of 40°C (104°F) go from “once in a century” to “every other year,” there are consequences.

[Read more here]

It doesn't sound like a lot when a 1 degree C rise is bandied about.  Or, hell, 2 degrees.  But it means that very hot days will be 10 times as likely and unbearably hot days 50 times as likely. 

Tamino's stuff sometimes wrangles my brain, me being old and slow, but if you follow his arguments closely, the logic, the terrible logic, is inescapable. 

We must do something about global warming, and soon.