Global Warming Level of Emergence and related population exposure to temperature and precipitation extremes

Abstract

<p>Communicating the uncertainty of natural climate variability to the public and researchers from other fields remains challenging. In this context, the concept of time of emergence (ToE) i.e., the year or decade when the climate signal emerges from the natural climate variability, has been well established over the past years. In addition, global warming levels (GWLs) are used more and more frequently to define the future projection horizon. However, only a few studies combined these two approaches. In this study, we utilize multiple initial condition large ensembles from CMIP6, to more robustly sample extreme events and account for natural climate variability, to estimate the global warming level of emergence (GWLoE) of various ETCCDI indicators. These indicators were selected to represent both precipitation and temperature extremes. Further, we analyze the impact of incremental temperature changes on the emergence of these indicators. Additionally, the GWLs are analyzed in relation to changes in the probability risk ratio to highlight that every degree of additional warming counts. Different scenarios for population changes are applied to estimate the population affected by the emergence of indicators as well as for a doubling in probability risk ratio. The combined GWLoE of all large ensembles highlights considerable regional differences among the individual ensembles. Similarly, regional differences arise for the GWL related to a doubling in probability risk ratio. The changes in population affected by these changes in risk ratio highlight the need to limit global warming as much as possible.</p>