Trends in high-frequency climate variability in the twentieth century

Abstract

HIGH-FREQUENCY climate variability is a fundamental aspect of climate. Understanding climate change demands attention to changes in climate variability and extremes¹, but knowledge of the recent behaviour of these variables has been limited by the unavailability of long-term high-resolution data. Climate simulations incorporating increased greenhouse-gas concentrations^2-9 indicate that a warmer climate could result in a decrease in high-frequency temperature variability (analogous to the decrease in variability observed from the poles to the tropics, and from winter to summer¹⁰) and an increase in the proportion of precipitation occurring in extreme events. Here we analyse high-frequency temperature and precipitation data from hundreds of sites spread over Australia, China, the former Soviet Union and the United States over the past 30 to 80 years. Day-to-day temperature variability is seen to have decreased in the Northern Hemisphere, and-at least within the United States-the proportion of total precipitation contributed by extreme, one-day events has increased significantly. We find that although the notion of a recent increase in interannual temperature variability is supported by data from the past few decades¹¹, the longer data records indicate that this trend is an aberration.