Detection and Attribution of Anthropogenic Changes in Climate Extremes and Variability

Duke University, Durham NC

Investigators

Abstract

Climate models are widely used to predict future climate changes associated with increasing greenhouse gas emissions and other anthropogenic influences on climate. Detection and attribution of climate change provides a rigorous evaluation of the ability of climate models to realistically simulate past climate change associated with natural and anthropogenic influences. Detection methods also provide a means for estimating the probability distribution of future changes based on observed changes, and to estimate the contribution from greenhouse gas forcing to changes in the risk of extreme events. Scientific Objectives and Intellectual Merit: The research aims at detecting and attributing large-scale changes in the statistics of climate that describe extremes. The first thrust of the work is to apply fingerprint detection and attribution approaches to changes in hot days and nights, and projected global-scale increases in heavy precipitation, particularly over several days. Results will be used to estimate anthropogenic changes in the risk of heat waves and rare temperature extremes. A second thrust of work is to explore changes in climate extremes and variability that have been determined as potentially important for impacts on ecosystems and society. Examples are heat waves, false springs, or droughts resulting from decreases in growing season rainfall or combined rainfall and temperature changes. The work is now feasible because of recent improvements in the quality and quantity of observational data sets and climate model simulations. A large set of the latest climate model simulations has recently become available from simulations performed for the 4th IPCC assessment report. These can provide estimates of climate change signals and model uncertainties in these signals. Furthermore, indices of daily temperature and rainfall extremes are being collected that cover an increasing area of the global land mass. Also, long station data are becoming available that allow to test internal climate variability estimates from climate models. Broader Impacts: Climatic extremes have large impacts on society, agriculture, and ecosystems, and many impacts of climate change may be directly related to changes in climate extremes. Therefore, it is of great importance to society to understand the variations in climate extremes encountered over the 20th century, and to evaluate the ability of climate models to simulate such changes. Detection of anthropogenic changes in climatic extremes is essential for understanding emerging risks in the current climate, and realistically predicting further changes and their uncertainties. The activity also has impacts on teaching and education. The budget contains funding for a graduate student, and thus for training a student in important problems of climate research, societal impacts associated with it, and applying up-to-date statistical techniques.