Here we show that the previously reported increase in global drought is overestimated because [the current method] uses a simplified model of potential evaporation that responds only to changes in temperature and thus responds incorrectly to global warming in recent decades. More realistic calculations, based on the underlying physical principles that take into account changes in available energy, humidity and wind speed, suggest that there has been little change in drought over the past 60 years.
via Climate NON-change: No increase in droughts since 1950, say boffins • The Register.