As we well know, many things seem continuous though their composition is discrete. I give lectures about this, starting with the bouncing molecules that make up our gases and liquids. The cover image of Trefethen’s Index Cards illustrates how impossible it can be, in borderline cases, to decide which is the right truth.

Atop your head is another good example. In English and Spanish your hair is singular, in French and German it’s plural.

[25 November 2024]

Global warming is always in the news, and we are told that average temperature has gone up 1.3 C or 1.4 C since preindustrial times. We hear constantly about these numbers.

I’ve never heard it mentioned that such small figures don’t seem to fit our own experience. When I was a kid we skated on the pond all winter; now it usually doesn’t freeze. The Dutch no longer skate on their rivers the way they used to. The ski industry is in trouble worldwide because of lack of snow. Europe, Asia, and the US have deadly summer heat waves lasting weeks, far above the temperatures we grew up with. Novembers and Marches are warm where they used to be cold. How can all this fit with an average increase as small as 1.4 C?

I’ve been asking around to try to find the answer. A common expert’s reaction is: young man, you don’t understand statistics. I push past that, and provisionally, I have learned two surprising things especially from https://data.giss.nasa.gov/gistemp/maps/:

• There has been more warming on land than over ocean;
• There has been more warming in the north than in the tropics and the south.

On the maps, these two effects are quite striking. Put them together, and it seems the warming experienced by many of us has in fact been closer to 3-4 C.

[22 November 2024]