The Lancet study in a nutshell: Take climate models that don’t work, and guesstimate what might happen to agriculture because of the climate we probably won’t get. Then use those guesses of food production in 2050 to fantasize what that means for human mortality. After all, we don’t know how many people are killed today by “4% less fruit and vege and 0.7% less meat”, but we can estimate what that dietary change will do in 2050 after a medical revolution, 35 years of plant breeding and agricultural changes. Not to mention a few more rounds of global food fads and phases of Vegan, Paleo, Atkins, and 5:2 Fasting. (But how did they factor in the mortality effect from another 2,000 episodes of MasterChef?)
Seriously, CO2 has increased crop yields, and will continue to do so until we hit 1000ppm (or maybe 2000). Around the planet, plants grow in warm places, and shrivel up and die in cold ones. So do people. Cold kills 20 times as many people as heat does. It must take a lot of modeling to calculate “more deaths” from two good outcomes.
Look at where fruit grows. In a warmer world, the tropics will stay a similar temperature (thanks to the evaporative air conditioner taking heat off the oceans in the tropics) but I guess the current Arctic fruit industry will be wiped out by nicer weather. I guess it’s the deathknell for the Siberian Strawberry industry and the Grapes of Greenland.