Human Activities Influence Precipitation at Global and Continental Scales
Climate warming induced by human activities can increase water vapor in the atmosphere, which may lead to changes in precipitation amount and intensity. Researchers, including a scientist at the U.S. Department of Energy’s Pacific Northwest National Laboratory, detected increased disparity or unevenness in annual precipitation amount and intensity at global and continental scales due to human activities. Scientists used a metric of statistical dispersion and a multi-model ensemble of global simulations of historical climate with and without the influence of human activities.
Understanding the human activity contributions to warming is important for advancing knowledge of the causes of the observed climatic trends and changes in extremes. Scientists found clear signals of human influence on the temporal variability (from year to year) of the annual precipitation amount and intensity at global and continental scales. These findings have important implications for terrestrial ecosystems, agricultural yields, and water resources that are affected not only by long-term trends in precipitation, but how precipitation varies from year to year.
This study investigated the human influence on the temporal variability of annual precipitation. Researchers compared global simulations of the historical climate for 1950–2005 with and without human influences such as greenhouse gases and land-use change. The climate simulations quantified the human contributions to the changes in temporal variability of annual precipitation amount and intensity. Researchers used a metric of statistical dispersion called the Gini coefficient. Results indicated that, over the period 1950–2005, human influences resulted in increased unevenness or disparity in annual precipitation amount and intensity at global and continental scales. Out of the 21 subcontinental regions considered, 14 and 17 regions showed significant human influences on annual precipitation amount and intensity, respectively. The results also indicated that the temporal variability of precipitation intensity generally is more susceptible to human influence than precipitation amount. The findings show that human activities have changed not only the long-term trends, but also the temporal variability of annual precipitation. This underscores the need to develop effective adaptation management practices to address the increased precipitation disparity.