The reduction in aerosol emissions had a slight impact on warming, according to research
NATIONAL CENTER FOR ATMOSPHERIC RESEARCH / UNIVERSITY CORPORATION FOR ATMOSPHERIC RESEARCH
Research news
The lockdowns and decreased social activity related to the COVID-19 pandemic had an impact on pollutant emissions, which slightly warmed the planet for several months over the past year, according to new research by the National Center for Atmospheric Research (NCAR).
The counterintuitive finding underscores the influence of particles or aerosols in the air that block the incident sunlight. When aerosol emissions decreased last spring, more of the solar heat reached the planet, especially in highly industrialized countries like the United States and Russia, which typically pump large amounts of aerosols into the atmosphere.
“Emissions from the most polluting industries fell sharply, which had a direct impact on temperatures,” said NCAR scientist Andrew Gettelman, lead author of the study. “Pollution is cooling the planet, so it makes sense that reducing pollution would warm the planet.”
The temperatures over parts of the earth’s land surface last spring were around 0.1 to 0.3 degrees Celsius warmer than would have been expected under the prevailing weather conditions. The effect was most pronounced in regions normally associated with significant aerosol emissions, with warming reaching around 0.37 ° F (0.37 ° F) in much of the United States and Russia.
The new study sheds light on the complex and often contradicting influences of different types of emissions from power plants, automobiles, industrial plants and other sources. While aerosols tend to lighten clouds and reflect heat from the sun back into space, carbon dioxide and other greenhouse gases have the opposite effect, trapping heat near the planet’s surface and raising temperatures.
Despite the short-term warming effects, Gettelman stressed that the long-term impact of the pandemic could be to slightly slow down climate change due to the decreased carbon dioxide emissions that linger in the atmosphere for decades and affect the climate more gradually. In contrast, aerosols – the focus of the new study – have a more immediate effect that disappears within a few years.
The study was published in Geophysical Research Letters. It was funded in part by the National Science Foundation, the sponsor of NCAR. In addition to NCAR scientists, the study was co-authored by scientists from Oxford University, Imperial College and the University of Leeds.
Working out the effects
Although scientists have long been able to quantify the effects of carbon dioxide on warming, it has been more difficult to determine the climatic impact of various types of aerosols – including sulfates, nitrates, soot, and dust. One of the greatest challenges in forecasting the extent of future climate change is to estimate the extent to which society will continue to emit aerosols and what influence the various types of aerosols have on clouds and temperature.
To conduct the research, Gettelman and his co-authors used two of the world’s leading climate models: the NCAR-based Community Earth System Model and a model called ECHAM-HAMMOZ, which was developed by a consortium of European nations. They performed simulations for both models, adjusted the aerosol emissions and took into account the actual meteorological conditions in 2020, e.g. B. Winch.
This approach allowed them to identify the effects of reduced emissions on temperature changes that were too small to be filtered out from actual observations, where they might be obscured by the variability of atmospheric conditions.
The results showed that the warming effect was greatest in the middle and upper latitudes of the northern hemisphere. The effect was mixed in the tropics and comparatively small in much of the southern hemisphere, where aerosol emissions are not as widespread.
Gettelman said the study will help scientists better understand the impact of different types of aerosols under different atmospheric conditions and support efforts to minimize climate change. Although research shows how aerosols counteract the warming impact of greenhouse gases, he stressed that emitting more of them into the lower atmosphere is not a viable strategy for slowing climate change.
“Aerosol emissions have significant health effects,” he said. “To say we should pollute is impractical.”
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About the article
Title: “Climate Impacts of COVID-19 Induced Emissions Changes”
Authors: A. Gettelman, R. Lamboll, CG Bardeen, PM Forster, D. Watson-Parris
Journal: Geophysical Research Letters
This material is based on work supported by the National Center for Atmospheric Research, a major facility sponsored by the National Science Foundation and administered by the University Corporation for Atmospheric Research. All opinions, results, conclusions or recommendations expressed in this material do not necessarily reflect the views of the National Science Foundation.
On the web: news.ucar.edu
On Twitter: @NCAR_Science
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