The counterintuitive finding highlights the influence of airborne particles, or aerosols, that block incoming sunlight.
When emissions of aerosols dropped last spring, more of the Sun’s warmth reached the earth , especially in heavily industrialized nations, like the USA and Russia, that normally pump high amounts of aerosols into the atmosphere.
“There was an enormous decline in emissions from the foremost polluting industries, which had immediate, short-term effects on temperatures,” said NCAR scientist Andrew Gettelman, the study’s lead author. “Pollution cools the earth , so it is sensible that pollution reductions would warm the earth .”
Temperatures over parts of Earth’s land surface last spring were about 0.2-0.5 degrees Fahrenheit (0.1-0.3 degrees Celsius) warmer than would are expected with prevailing weather , the study found.
The effect was most pronounced in regions that normally are related to substantial emissions of aerosols, with the warming reaching about 0.7 degrees F (0.37 C) over much of the USA and Russia.
The new study highlights the complex and sometimes conflicting influences of various sorts of emissions from power plants, automobiles , industrial facilities, and other sources.
While aerosols tend to decorate clouds and reflect heat from the Sun back to space, CO2 and other greenhouse gases have the other effect, trapping heat near the planet’s surface and elevating temperatures.
Despite the short-term warming effects, Gettelman emphasized that the long-term impact of the pandemic could also be to slightly slow global climate change due to reduced emissions of CO2 , which lingers within the atmosphere for many years and features a more gradual influence on climate.
In contrast, aerosols — the main target of the new study — have a more immediate impact that fades away within a couple of years.
The study was published in Geophysical Research Letters. it had been funded partially by the National Science Foundation, NCAR’s sponsor. additionally to NCAR scientists, the study was co-authored by scientists at Oxford University , Imperial College, and therefore the University of Leeds.
Teasing out the impacts
Although scientists have long been ready to quantify the warming impacts of CO2 , the climatic influence of varied sorts of aerosols — including sulfates, nitrates, black carbon, and mud — has been harder to pin down. one among the main challenges for projecting the extent of future global climate change is estimating the extent to which society will still emit aerosols within the future and therefore the influence of the various sorts of aerosols 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 referred to as ECHAM-HAMMOZ, which was developed by a consortium of European nations. They ran simulations on both models, adjusting emissions of aerosols and incorporating actual environmental condition in 2020, like winds.
This approach enabled them to spot the impact of reduced emissions on temperature changes that were too small to tease call at actual observations, where they might be obscured by the variability in atmospheric conditions.
The results showed that the warming effect was strongest within the mid and upper latitudes of the hemisphere . The effect was mixed within the tropics and relatively minor in much of the hemisphere , where aerosol emissions aren’t as pervasive.
Gettelman said the study will help scientists better understand the influence of varied sorts of aerosols in several atmospheric conditions, helping to tell efforts to attenuate global climate change .
Although the research illustrates how aerosols counter the warming influence of greenhouse gases, he emphasized that emitting more of them into the lower atmosphere isn’t a viable strategy for slowing global climate change .
“Aerosol emissions have major health ramifications,” he said. “Saying we should pollute isn’t practical.”