Hindering harvests Using such data researchers have now compiled an estimate of global changes in crop yields which can be put down to recent increases in temperature and decreases in rainfall (the world as a whole is getting wetter, but the rain has stayed away from some agricultural plains). The bad news is that they find that climate change has lowered the amount of maize (or corn, if you prefer) and wheat produced in a given area. The good news is that the effect is so far reasonably small.