This article goes over his methods and why they're ridiculous:

"The fourth fatal error Nordhaus makes is the most farcical. In a 1991 paper that became a touchstone for all his later work, he assumed that, because 87 percent of GDP occurs in what he called “carefully controlled environments” — otherwise known as “indoors” — it will not be affected by climate.

...

Ignorance of systems has its way of plowing forward, juggernaut-like. Nordhaus has opined that agriculture is “the part of the economy that is sensitive to climate change,” but because it accounts for just 3 per cent of national output, climate disruption of food production cannot produce a “very large effect on the U.S. economy.” "

https://theecologist.org/2023/nov/01/when-idiot-savants-do-c...