Air pollution cools climate more than expected – this makes cutting carbon emissions more urgent

Air pollutants kill around seven million people every year. Much of this pollution is tiny particles suspended in the air which, when inhaled, can cause people to develop heart and lung diseases, as well as cancer.

Small particles in the atmosphere also birth clouds, whether they are crystals of sea salt from the Southern Ocean or sulphate from industrial chimneys. Collectively, these particles are called aerosols. 

Moisture in the atmosphere can only condense into cloud droplets with aerosols. The aerosols that fossil fuel burning adds to the atmosphere make these droplets more numerous and clouds more reflective of sunlight, and potentially longer-lasting. All of this increases the amount of sunlight that clouds scatter back to space instead of being absorbed by the Earth. This is partly why the Intergovernmental Panel on Climate Change (IPCC) has concluded that human-made aerosols cool the climate and mask some of the warming from greenhouse gases.

This may sound like good news, but there is no cause for celebration. Aerosols (and their cooling effect) are very short-lived. While the CO₂ emitted into the atmosphere today from cars and coal power stations will still be there centuries later, the aerosols emitted as air pollution will cease to have an influence a month from now. This means that as soon as we stop emitting aerosols, their buffering effect on climate change disappears, while the greenhouse gases in our atmosphere will continue to heat the planet.

And in new research, we found that the effect of air pollution on the reflectivity of clouds may be bigger than previously assessed. If the extent to which air pollution masks the greenhouse effect is indeed bigger, delegates gathered in Sharm El-Sheikh for COP27, the latest UN climate change summit, must work even harder to reduce fossil fuel burning.

Source – The Conversation