That mirrors global average temperature in general for that time period. Apparently it was because we were pumping sulfates into the atmosphere at an amazing rate from the 1940's until the EPA was born. Sulfates block sunlight and so mask the overall warming, at the cost of polluting the atmosphere.
It has been proposed to intentionally resume injecting sulfates into the upper atmosphere in order to mitigate global warming[0]. (This is a horrible idea, but the jury's still out on whether it's better than the alternative.)
CO2-Emissions have been growing at an accelerating speed. Cumulative emissions double every 20-30 years. Half of CO2-emissions since 1750 have happened just since 1993.
Doesn’t that suggest sea transportation may be a bigger contributor than greenhouse gasses? Industrial production was at its limits during that period, but I would imagine cross ocean cargo was down significantly.
It would be interesting to see what pandemic years looked like with thousands of ships sitting for months off shore.
One more edit: container ships are effectively giant heat sinks with a ton (literally tons) of surface area (corrugated containers), sucking heat from the air and dumping it into the ocean. If that hypothesis has merit, I would expect the LA ports to have an increase in temperature during that same period.
