On the extreme heat, Bjorn Lomborg likes to point out that more humans globally die from cold than from heat, so increased mortality from heat waves may be more than offset by decreased mortality from cold.

The impact on crop yields are strictly tropical maize. These may be offset by increased yields at northern lattitudes in Canada and Russia. In light of Russia's recent callous disrespect for international norms, other countries may be reluctant to be totally dependent on Russian exports for their food supply.

To put the numbers on marine fisheries in perspective, the global yield of fisheries is currently about 110 million tons. Losses in ocean fishing may be offset by an increase in fish farming. In fact, it may well be that no one is eating fish any more in a few decades, all consumption of meat and fish being replaced by artificially grown substitutes that are tastier, cheaper, and more healthy.