Future Arctic temperature change resulting from a range of aerosol emissions scenarios

Heat-induced SIRT1-mediated H4K16ac deacetylation impairs resection and SMARCAD1 recruitment to double strand breaks

Hyperthermia inhibits DNA double-strand break (DSB) repair that utilizes homologous recombination (HR) pathway by a poorly defined mechanism(s); however, the mechanisms for this inhibition remain unclear. Here we report that hyperthermia decreases H4K16 acetylation (H4K16ac), an epigenetic modification essential for genome stability and transcription. Heat-induced reduction in H4K16ac was detected in humans, Drosophila, and yeast, indicating that this is a highly conserved response. The examination of histone deacetylase recruitment to chromatin after heat-shock identified SIRT1 as the major deacetylase subsequently enriched at gene-rich regions. Heat-induced SIRT1 recruitment was antagonized by chromatin remodeler SMARCAD1 depletion and, like hyperthermia, the depletion of the SMARCAD1 or combination of the two impaired DNA end resection and increased replication stress. Altered repair protein recruitment was associated with heat-shock-induced γ-H2AX chromatin changes and DSB repair processing. These results support a novel mechanism whereby hyperthermia impacts chromatin organization owing to H4K16ac deacetylation, negatively affecting the HR-dependent DSB repair.

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H4K16ac deacetylation during hyperthermia is conserved in human, Drosophila, and yeast

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Dynamic regulation of the chromatin functions during hyperthermia is SIRT1-dependent

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SIRT1 function is negatively impacted by SMARCAD1

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Hyperthermia increases replication stress and impacts DNA resection, impairing DSB repair

Estimating Arctic Temperature Impacts from Select European Residential Heating Appliances and Mitigation Strategies

The use of residential heating devices is a key source of black carbon and other short-lived climate forcer emissions in Arctic and other high latitude regions, with important impacts to the Arctic climate and human health. The types of combustion technologies and fuels used varies by region, which impacts the emission profiles of these pollutants and thus the magnitude of Arctic climate responses. Using emission inventory data from 14 European countries, we derive wood-fueled residential heating emissions of black carbon, organic carbon, and sulfate from six appliance types in 2016. Using previously derived equilibrium Arctic temperature responses, we estimate Arctic temperature influences from each appliance type. Using the 2016 appliance emission data as a baseline, we compute the emission mass and Arctic temperature mitigation potential from hypothetical stove conversion scenarios. A total of 43.2 gigagrams (Gg) of black carbon, 175.7 Gg of organic carbon, and 10.3 Gg of sulfate were emitted in 2016 from the six appliance types in the 14 countries. The combined emissions increased Arctic surface temperatures by +2.8 millikelvin. If each country converted its appliance fleet to the technologically advanced pellet stoves and boilers, the combined black carbon, organic carbon, and sulfate emissions from heating appliances could be reduced by 94% and the Arctic temperature response reduced by 85%. The specific source and originating region of emissions are important factors in resolving the magnitude of their impacts. Improved country-level accounting of specific appliances and their emission characteristics can lead to a better understanding of potential mitigation options.

Climatic Responses to Future Trans-Arctic Shipping

As global temperatures increase, sea ice loss will increasingly enable commercial shipping traffic to cross the Arctic Ocean, where the ships' gas and particulate emissions may have strong regional effects. Here we investigate impacts of shipping emissions on Arctic climate using a fully coupled Earth system model (CESM 1.2.2) and a suite of newly developed projections of 21st-century trans-Arctic shipping emissions. We find that trans-Arctic shipping will reduce Arctic warming by nearly 1 °C by 2099, due to sulfate-driven liquid water cloud formation. Cloud fraction and liquid water path exhibit significant positive trends, cooling the lower atmosphere and surface. Positive feedbacks from sea ice growth-induced albedo increases and decreased downwelling longwave radiation due to reduced water vapor content amplify the cooling relative to the shipping-free Arctic. Our findings thus point to the complexity in Arctic climate responses to increased shipping traffic, justifying further study and policy considerations as trade routes open.