A LINEAR ESTIMATION OF A TIMING OF UNPRECEDENTED CLIMATE DUE TO GLOBAL WARMING

Abstract

Even if an external forcing is given uniformly over the globe, the corresponding climate change and feedbacks would differ by region. Thus the detection of global warming signal has been made on a regional scale as well as on a global average against an internal variability in climate system. The purpose of this study is to estimate a timing of unprecedented climate due to global warming and to analyze the regional differences therein. For this purpose, unlike previous studies that used climate simulation data, we used observational data to estimate a magnitude of internal variability and a future temperature change. We calculated a linear trend in surface temperature for 1880-2015 and a magnitude of internal variability as the largest displacement from the trend. A timing of unprecedented climate was defined as the first year when a predicted minimum temperature exceeds a maximum recorded in the observational data and remains as such since then. Presumed that the linear trend and the temperature displacement will be maintained in the future, the timing of unprecedented climate tends to be considerably different for each continent the timing over the ocean is highly affected by a large internal variability except for the high-latitude regions having a significant warming trend. Therefore, we need to consider an internal variability as well as a regional warming rate when planning a climate change mitigation and adapge against an internal variability in climate system. The purpose of this study is to estimate a timing of unprecedented climate due to global warming and to analyze the regional differences therein. For this purpose, unlike previous studies that used climate simulation data, we used observational data to estimate a magnitude of internal variability and a future temperature change. We calculated a linear trend in surface temperature for 1880-2015 and a magnitude of internal variability as the largest displacement from the trend. A timing of unprecedented climate was defined as the first year when a predicted minimum temperature exceeds a maximum recorded in the observational data and remains as such since then. Presumed that the linear trend and the temperature displacement will be maintained in the future, the timing of unprecedented climate tends to be considerably different for each continent the timing over the ocean is highly affected by a large internal variability except for the high-latitude regions having a significant warming trend. Therefore, we need to consider an internal variability as well as a regional warming rate when planning a climate change mitigation and adap