Predictability of weather and climate

Abstract:

The response of the Euro-Atlantic wintertime circulation to climate change is deeply uncertain. The Atlantic jet is caught in a “tug-of-war” between rapid warming trends in both the tropics and the Arctic leading to debate over the changing “waviness” of the jet, which is subject to strong non-linearity and internal variability. From the complementary perspective of weather regimes, there is considerable uncertainty in how atmospheric blocking will alter under climate change. By applying the hybrid approach of geopotential-jet regimes to 6th phase of the coupled model inter-comparison project projections, we show that the centers of action of anticyclonic regimes hardly alter even under severe warming. Instead, regimes are expected to become less persistent, with zonal flow conditions becoming more prevalent, although models disagree on the details of regime changes. Finally, we show the regime response can be captured qualitatively in a simple Lorenz-like model, emphasizing the conceptual link between observed regimes and those in basic mathematical systems.

Abstract:

As the climate warms, a new hazard, compound flood-heat extreme (CFH) events, characterized by the rapid succession of devastating floods and deadly heat (or vice-versa), are becoming increasingly frequent, threatening infrastructure and ecosystems. However, how this CFH hazard will change under future anthropogenic warming in China and their potential population and economic exposures remains unexamined. Here, we systematically quantify the projected changes in bivariate CHF hazards for 187 catchments in China during the 2071–2100 period relative to the 1985–2014 period and investigate the potential population and gross domestic product (GDP) exposure, by developing a climatic-hydrological-socioeconomic modelling chain. We find that there is a nationwide increase in CFH hazards and the historical 30-year CFH episodes are projected to increase by 10 times in southern catchments. Under the synergistic impacts of changing CFH episodes and population (GDP), a mass of people in southern (0.79–2.13 thousand/km²) and eastern (1.68 thousand/km²) catchments and an enormous sum of GDP in eastern catchments (400–912 million/km²) will be exposed to increasing CFH hazards. Our results highlight the necessity of improving both societal resilience and mitigation solutions to address such weather-related hazards.