World crop yields are up year on year, according to the USDA. See Table 01 World Crop Production Summary here:

https://apps.fas.usda.gov/psdonline/circulars/production.pdf

Interesting, although year to year is a bit of a small scale to compare. Also the first sentence mentions a drought that dropped 5% of Russian wheat from the previous month, but that left the yield 4% higher than the previous year. It's possible that the increases from higher temps offset the longer droughts in some cases. If variance in rain and temperature continue to increase there will eventually be a tipping point where yields are severely reduced.

Well sure, there must be a tipping point somewhere, but the earth has been a lot hotter in the past than it is now, and biomass was in much greater quantity at such times.

It's glacial maximums that are really concerning to me personally. It's very unlikely that we could feed so many billions of people as we do now if we ever enter another ice age.