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Current greenhouse gas mitigation ambition is consistent with ~3°C global mean warming above preindustrial levels. There is a clear need to strengthen mitigation ambition to stabilize the climate at the Paris Agreement goal of warming of less than 2°C. We specify the differences in city-level heat-related mortality between the 3°C trajectory and warming of 2° and 1.5°C. Focusing on 15 U.S. cities where reliable climate and health data are available, we show that ratcheting up mitigation ambition to achieve the 2°C threshold could avoid between 70 and 1980 annual heat-related deaths per city during extreme events (30-year return period). Achieving the 1.5°C threshold could avoid between 110 and 2720 annual heat-related deaths. Population changes and adaptation investments would alter these numbers. Our results provide compelling evidence for the heat-related health benefits of limiting global warming to 1.5°C in the United States.

Given the Paris Agreement it is imperative there is greater understanding of the consequences of limiting global warming to the target 1.5° and 2°C levels above preindustrial conditions. It is challenging to quantify changes across a small increment of global warming, so a pattern-scaling approach may be considered. Here we investigate the validity of such an approach by comprehensively examining how well local temperatures and warming trends in a 1.5°C world predict local temperatures at global warming of 2°C. Ensembles of transient coupled climate simulations from multiple models under different scenarios were compared and individual model responses were analyzed. For many places, the multimodel forced response of seasonalaverage temperatures is approximately linear with global warming between 1.5° and 2°C. However, individual model results vary and large contributions from nonlinear changes in unforced variability or the forced response cannot be ruled out. In some regions, such as East Asia, models simulate substantially greater warming than is expected from linear scaling. Examining East Asia during boreal summer, we find that increased warming in the simulated 2°C world relative to scaling up from 1.5°C is related to reduced anthropogenic aerosol emissions. Our findings suggest that, where forcings other than those due to greenhouse gas emissions change, the warming experienced in a 1.5°C world is a poor predictor for local climate at 2°C of global warming. In addition to the analysis of the linearity in the forced climate change signal, we find that natural variability remains a substantial contribution to uncertainty at these low-warming targets. [ABSTRACT FROM AUTHOR]

The article focuses on the circulation pattern that drives cold outbreaks as well as severe frost risk in southwest Western Australia in September 2016. Topics being presented include thermodynamic changes as well as the effect of human influence on cold extremes and rising temperatures of the climate mean state and forced changes to circulation is presented,

Flood hazard is a global problem, which in some regions may be exacerbated byclimate change. In south Asia, where livelihoods are highly dependent on waterresources, people can be affected disproportionally. The 2017 monsoon flooding in theGanges-Brahmaputra-Meghna (GBM) basin, with record river levels observed,resulted in ∼1200 deaths, and dramatic loss of crops and infrastructure. Climatemodel scenarios representing the Paris Agreement targets were investigated andthe changes in extreme precipitation were quantified over the GBM region. Largeensembles of climate simulations using different models and experimental designs wereused to evaluate the range of possible changes. These estimates were linked toa high-resolution flood hazard model to determine the corresponding changes inflood hazard. The simulations of 1.5∘C and 2∘C warming indicate an increase inextreme precipitation and hence flood hazard over the GBM basin compared to thecurrent climate. So even with global warming limited to 1.5∘C, there is a detectableincrease in the likelihood in flooding for extreme precipitation events such as the southAsian crisis in 2017. The additional ∼0.6C warming needed to take us from currentclimate to 1.5∘C highlights the changed flood risk even with low levels of warming. [ABSTRACT FROM AUTHOR]