The COVID-19 pandemic is impacting human activities, and in turn energy use and carbon dioxide (CO2) emissions. Here we present daily estimates of country-level CO2 emissions for different sectors based on near-real-time activity data. The key result is an abrupt 8.8% decrease in global CO2 emissions (−1551 Mt CO2) in the first half of 2020 compared to the same period in 2019. The magnitude of this decrease is larger than during previous economic downturns or World War II. The timing of emissions decreases corresponds to lockdown measures in each country. By July 1st, the pandemic’s effects on global emissions diminished as lockdown restrictions relaxed and some economic activities restarted, especially in China and several European countries, but substantial differences persist between countries, with continuing emission declines in the U.S. where coronavirus cases are still increasing substantially.

Background Many regions of the world are now facing more frequent and unprecedentedly large wildfires. However, the association between wildfire-related PM 2•5 and mortality has not been well characterised. We aimed to comprehensively assess the association between short-term exposure to wildfire-related PM 2•5 and mortality across various regions of the world.Methods For this time series study, data on daily counts of deaths for all causes, cardiovascular causes, and respiratory causes were collected from 749 cities in 43 countries and regions during 2000-16. Daily concentrations of wildfirerelated PM 2•5 were estimated using the three-dimensional chemical transport model GEOS-Chem at a 0•25° × 0•25° resolution. The association between wildfire-related PM 2•5 exposure and mortality was examined using a quasi-Poisson time series model in each city considering both the current-day and lag effects, and the effect estimates were then pooled using a random-effects meta-analysis. Based on these pooled effect estimates, the population attributable fraction and relative risk (RR) of annual mortality due to acute wildfire-related PM 2•5 exposure was calculated.Findings 65•6 million all-cause deaths, 15•1 million cardiovascular deaths, and 6•8 million respiratory deaths were included in our analyses. The pooled RRs of mortality associated with each 10 µg/m³ increase in the 3-day moving average (lag 0-2 days) of wildfire-related PM 2•5 exposure were 1•019 (95% CI 1•016-1•022) for all-cause mortality, 1•017 (1•012-1•021) for cardiovascular mortality, and 1•019 (1•013-1•025) for respiratory mortality. Overall, 0•62% (95% CI 0•48-0•75) of all-cause deaths, 0•55% (0•43-0•67) of cardiovascular deaths, and 0•64% (0•50-0•78) of respiratory deaths were annually attributable to the acute impacts of wildfire-related PM 2•5 exposure during the study period.Interpretation Short-term exposure to wildfire-related PM 2•5 was associated with increased risk of mortality. Urgent action is needed to reduce health risks from the increasing wildfires.

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