Recent aerosol reductions worsen global warming

April 8 () –

Recent reductions in emissions of tiny particles, the leading cause of air pollution globally, They have caused more heat in the Earth's climate system.

This is shown by a new international study led by CICERO (Centre for International Climate and Environmental Research) and published in Communications Earth & Environment.

Satellite measurements clearly show that more heat from the Sun enters the Earth's atmosphere compared to the amount of Earth's energy escaping into space. This so-called energy imbalance of the Earth leads to the accumulation of heat and warming of the Earth's surface.

It is well known that man-made emissions of CO2 and other greenhouse gases have been the main cause of global warming in recent decades, and that particle emissions have masked some of this warming. Most particles, especially sulfate particles, reflect sunlight and therefore act to cool the planet. However, in the last two decades, this cooling effect has reversed and now contributes to warming due to extensive measures to improve air quality in many regions of the world.

In the study, the researchers performed simulations using state-of-the-art global climate models and compared their results with satellite measurements of the trend of the Earth's energy imbalance during the period 2001-2019.

The authors found that recent reductions in human-caused particle emissions needed to be taken into account for the models to reasonably agree with satellite measurements (see figure above; black versus orange line). When the authors assumed that particle emissions did not change during the period (green line), the simulated warming of the Earth was considerably reduced.

“Our study makes novel use of models and observations to explain why Earth's energy imbalance is increasing so much. This is of utmost importance because there has been much debate about what is causing the observed doubling of the imbalance, which is driving global imbalance. Warming, sea level rise, extreme weather events, melting snow and ice and other aspects of climate change,” explains it's a statement the principal investigator of the CICERO Center for International Climate Research, Oivind Hodnebrog, lead author of the study.

“Our study underscores the importance of having continuous satellite measurements of the Earth's energy budget,” says NASA senior technologist Norman Loeb, co-author of the study.

Air pollution is a major health problem causing millions of deaths around the world, and it is important to clean the air. However, air quality improvements come at a cost. By eliminating emissions of reflective particles, the particles and their cooling effect disappear within days. However, in the case of CO2 and other long-lived greenhouse gases, The gases they warm remain in the atmosphere for centuries after their emission.

Another co-author of the study, research director Gunnar Myhre of CICERO, says that “the additional warming effect that comes from the removal of refrigerant particles is something that researchers have anticipated would happen for a long time, and it is not a surprise that”It makes sense, but now we have the evidence. “Furthermore, the strong impact that particle emissions reductions had in increasing the Earth's energy imbalance over the past two decades was an eye-opener.”

Hodnebrog says: “Continued reductions in particle emissions may lead to accelerated warming of surface temperatures as early as this decade.”