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Timmermann, A. et al. COVID-19-related drop in anthropogenic aerosol emissions in China and corresponding cloud and climate effects (preprint)

During the COVID-19 pandemic, China temporarily shut down much of its manufacturing and transport activities. Aerosol emissions fell to record lows, temporarily improving air quality but also affecting cloud formation, atmospheric radiation and climate.  Using a state-of-the-art Earth System Model finds a substantial increase in cloud droplet size and corresponding increase in low cloud cover over Eastern China.  This leads to intensified longwave downwelling radiation at the surface but reduced incoming shortwave fluxes, giving us insights into the Earth’s radiation balance and how the climate system might respond to future strategies to tackle air pollution.

Liu, F. et al. Abrupt declines in tropospheric nitrogen dioxide over China after the outbreak of COVID-19 (preprint)

Over Chinese New Year 2020, satellite measurements show a 48% drop in tropospheric nitrogen dioxide, primarily from fossil fuel consumption, which is 20% larger than in recent years.  The drop is found to relate to a) the first report of the virus in each province and b) the date of a province's lockdown, giving insights into the environmental and economic consequences of reduced economic activity.

Zhang, R. et al. NOx emission reduction and recovery during COVID-19 in East China (2020)

Observations from TROPOMI were used to derive NOx emission change across East China between three periods in early 2020.  Emissions during lockdown decreased by 50% compared to those immediately beforehand, then increased by 26% thereafter, although not to previous levels. NOx emissions in Wuhan showed no signs of recovering by March 12, but a few provinces, such as Zhejiang and Shanxi, have recovered fast, with emissions almost back to pre-lockdown levels.

Bauwens, M. et al. Impact of coronavirus outbreak on NO2 pollution assessed using TROPOMI and OMI observations (2020)

TROPOMI (ESA) and OMI (NASA) reveal unprecedented NO2 decreases over China, South Korea, Western Europe and the U.S. in January‐April 2020. The average NO2 column drop over all Chinese cities amounts to ‐40% relative to the same period in 2019, and reaches up to a factor of ~2 at heavily hit cities (e.g. Wuhan, Jinan).  Decreases in Western Europe and the U.S. are also significant (‐20 to ‐38%).

Liu, Z. et al. COVID-19 causes record decline in global CO2 emissions (preprint)

The decrease in global fossil CO2 emissions during the first quarter of 2020 was 5.8%, based on actual emissions data from power generation (29 countries) and industry (73 countries), and near real time activity data for road transport (132 countries), aviation and maritime transport, and on heating degree days for commercial and residential emissions (206 countries). The largest COVID-related decreases in emissions were due to industry (-7.1%), followed by road transport (-8.3%), power generation (-3.8%), residential (-3.6%), fishing and maritime transport (-13.3%) and aviation (-8.0%). Regionally, decreases in China were the largest and earliest (-10.3%), followed by Europe (EU-27 & UK) (-4.3%) and the U.S. (-4.2%). Relative decreases of regional CO2 emissions were consistent with NOx observations. Decreases in carbon intensity also suggest that carbon-intensive activities were disproportionally impacted.

Le Quére, C. et al. Temporary reduction in daily global CO2 emissions during the COVID-19 forced confinement (2020)

Government policies and activity data are used to estimate the decrease in CO2 emissions during lockdown. Daily global CO2 emissions decreased by –17% by early April 2020 compared to 2019, with just under half of this due to changes in surface transport. At their peak, emissions in individual countries decreased by –26%. The impact on 2020 annual emissions depends on lockdown duration, with a high end estimate of –7% if some restrictions remain in place worldwide until the end of 2020.