Reducing pollution worsens global warming

The fight against pollution, in other words, the disappearance of the blanket of aerosols which reflects sunlight towards the sky, aggravates warming. This could account for up to 40% of the increase in planet-warming energy between 2001 and 2019.

Bad news, a little disturbing: the drop in pollution on a planetary scale is making global warming worse. Mathilde Fontez, editor-in-chief of the scientific magazine Epsiloon, confirms to us that pollution has decreased overall in the world – the control of air quality carried out since the 1990s is bearing fruit. But today we see that this has a twisted effect.

franceinfo: This purer air, controlled for more than 30 years around the world, aggravates global warming?

Mathilde Fontez: Yes, it’s quite disturbing. The subject is in all the discussions among experts today. Especially since we are in the process of taking stock of the year 2023: a record year on all fronts, the hottest in history. And it’s – in part – because of the drop in pollution.

A series of studies have just quantified this effect, and they show that it is important: La drop in pollution would be responsible half of the current acceleration in the rate of warming.

The latest study which has just been published on April 3, 2024 by researchers from the Cicero Institute in Norway, and which is based on satellite observations, assesses that it could represent 40% increase in energye which warmed the planet between 2001 and 2019.

How does falling pollution cause warming?

When suspended in the air, pollution particles reflect light back into space, and therefore cause cooling. If we have less, there is warming. Particles can also increase the number of droplets in the air: making larger clouds, which last longer – and clouds also reflect light.

Basically, polluted Earth is more reflective. Unpolluted, it is darker, and therefore it captures more heat from the sun. These phenomena have been known for a long time. But what we are discovering today is the importance of the effect, et its complexity. It is difficult to predict precisely how this will evolve.

Researchers see that these mechanisms have an impact on global temperature, but also on atmospheric circulation, on winds, on monsoons.

Because it is not, of course, a question of stopping depolluting?

No, the experts obviously insist on this point: we do not choose between the plague and cholera. Poor air quality causes more than 4 million premature deaths on the planet each year.

But the effects of this decline must be taken into account. For example, by always combining anti-pollution measures with measures to reduce greenhouse gases. And by continuing satellite monitoring, by adding this subject to international discussions: until then, aerosols were not part of the subjects discussed at the COPs. Almost no country mentions them in its official commitments to the Paris Agreement…