Slate’s Russell Jacobs looks at the end of Dark Sky, a popular weather app that is shutting down and will no longer be supported after today. Apple bought it in 2020 and has since folded many of its features into the default weather app. While it had its devotees (it was never available in Canada, so I couldn’t use it), it was, at best, “sometimes accurate”: Jacob enumerates plenty of cases where Dark Sky’s forecast failed him in one way or another. (Predicted storms failing to appear is one thing; the opposite is much worse.) It turns out that their forecasts were based not on meteorological modelling but on image processing: it treated the weather systems on radar maps as shapes. Jacobs: “Dark Sky simply monitored changes to the shape, size, speed, and direction of shapes on a radar map and fast-forwarded those images. ‘It wasn’t meteorology,’ Blum said. ‘It was just graphics practice.’” My father the retired meteorologist is no doubt twitching as he reads this.
Weather & Climate
The Gulf Stream Myth
If the Gulf Stream were somehow to shut down—something that it is hypothesized would happen due to climate change, as Greenland’s melting glaciers dump a ton of fresh water into the North Atlantic, disrupting the current1—it would not, it turns out, plunge Europe into a new ice age. That, at least, is the contention of Richard Seager, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory. He argues that European winters are 15 to 20 degrees warmer than North American winters at the same latitudes for two reasons: one, the effect of the Rocky Mountains on air currents, which bring cold air south in North America but warm air north into western Europe; and two, the seasonal release of heat stored by the Atlantic Ocean itself. The Gulf Stream itself is responsible for only a few degrees’ warming; if it were taken away, the cooling effect would not be enough to overwhelm the much larger warming effect from climate change.
The Rise of the 28-Day Weather Forecast
Most long-term weather forecasts cover no more than seven to ten days; the further ahead into the future they look, the less accurate they are. But thanks to increasingly powerful supercomputers (forecasts are based on computer modelling), meteorologists are developing “subseasonal” weather forecasts that look as far as four weeks into the future. They rely on different factors than normal forecasts—ocean temperature and currents, soil conditions, global climate phenomena—and they do have some limitations: so much processing power is required that these forecasts are much less granular.
‘Colder Than Mars’
I have a bone to pick with news stories that declare, hyperbolically, whenever a location is in the midst of a deep freeze, that it’s “colder than Mars”—stories like this one from CTV News or this one from The Atlantic.
What exactly do they mean by “colder than Mars”? Mars is a planet—one that, like Earth, has an atmosphere, albeit thin, and weather and seasons. Mars can get as cold as –143°C (–226°F) and as warm as 35°C (95°F) in spots. Mars’s mean temperature is
It turns out that what reporters really mean is the current temperature at Gale Crater, as measured by the Rover Environmental Monitoring Station on the Curiosity rover. It also turns out that there’s a handy widget that gives the current conditions as measured by REMS. As I write this, the air temperature on Mars is –19°C and the ground temperature is –6°C (the difference is because the air is so thin).
Since it’s –19°C right now where I live, yes, Mars—or at least Gale Crater, which is not the same thing (again: apples to oranges)—is just as cold. But temperatures as high as 20°C (68°F) and as low as –127°C (–197°F) have been recorded at Gale Crater. It’s no trick for a Martian summer to be warmer than a Canadian winter, but even the daytime highs of a Martian winter can be warmer than a Canadian winter. Because the air is so thin, the Martian surface heats quickly when it’s sunny, and the temperature can swing as much as 100 degrees.2
I know that hyperbole is an essential part of talking about how goddamn cold it is out there (see also: using wind chill instead of temperature), but honestly, Mars isn’t a useful point of reference.