Recent analyses of the possible adverse effects of climate change on agriculture in developing countries have raised food security concerns, especially for farm households whose crop productivity is expected to fall. The present study uses the GTAP global economy-wide model to capture at the same time the expected positive effects on temperate zone crop productivity, which will more or less offset the upward pressure on farm product prices from yield falls in developing countries. Also modelled is an expected adverse effect of higher temperatures and humidity on the productivity of unskilled workers in the tropics, but since they work in nonfarm as well as farm activities the net effect of that shock on agriculture’s competitiveness is an empirical matter. The results suggest there may be less cause for concern over food security than some earlier studies indicated, but the degrees of uncertainty involved in such modelling are sufficient to warrant a precautionary approach.