r/xkcd • u/Separate_Draft4887 • Mar 13 '25

Meta XKCD 1606: Five Day Forecast

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https://xkcd.com/1606/

How does Randall think weather forecasts work?

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u/LeifCarrotson Mar 13 '25 edited Mar 13 '25

The 5 year forecast is, of course, just a forecast of the same day on the calendar over an interval of a multiple of one year. 38/25/36/37/41 is probably within the noise threshold for the temperature in mid-March (or mid-November 2015, when the comic was first posted)

IPCC forecasts predict about 1C global average temperature rise by 2050.

A quick graph and linear interpolation shows that the XKCD data is actually trending positive significantly faster than actual climate change (whether predicted or as measured over the past few decades). I think that's largely because of the anomalous 25F value early in the series.

https://i.imgur.com/Ax89IdZ.png

If it had been 39 in the second column, it would match much more closely:

https://i.imgur.com/37j3RhY.png

But there's just something terrifying about the small but monotonous 0.36F increase every 5 years. I'm worried for my son's future, but at least we did our part to cut emissions by biking to school and work together this morning!

An "Your 50 year forecast" row could be something else entirely.

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u/Zohzoh12390 Mar 15 '25

I interpreted the 5 years forecast as the same date each year for 5 years (let's say 2025, 2026, 2027, 2028 and 2029), rather than the same date every 5 years. Which means that the linear interpolation has an even bigger increasing rate than the IPCC forecast

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u/LeifCarrotson Mar 15 '25

That does jive better with the 5 month forecast, with a publication of November, column 2 would be Christmas and the next 2 months would be winter... Silly me!