Fuel oil warming the earth rapidly, and the emissions from their combustion kill millions of people every year. So we need to release it quickly. But in a surprising way, aerosols have one benefit: They cool the atmosphere. It creates a climate imbalance. If we burn less gas, oil, and coal, we will stop filling the atmosphere with global warming gases, but we will also fill it with fewer planet-cooling aerosols.
But exactly how much cooling we get from aerosols, and how strong it will be as the planet absorbs the oil, are big questions among climate researchers. Oxford University climatologist Duncan Watson-Parris said: “People think that air pollution is very important. “And the aerosol intensity uncertainty is the biggest uncertainty in climate science.”
Last week, Watson-Parris published a paper in a journal Natural Climate Change in which he predicted how the aerosol concentration will change by the end of this century. It is thought that the less fuel we burn, the less aerosols we will produce. But they were able to control the amount of cooling the aerosols could provide. In one version of the model, which assumed that aerosols had a cooling effect, dumping them was like turning off the Earth’s atmosphere. This warming would be enough to exceed the Paris Agreement’s goal of limiting global warming to 1.5 degrees Celsius.
But if we think that aerosols have a cooling effect of 50 percent, discarding them will not be necessary, and we will have a good chance of reducing the temperature below 1.5 degrees. Demonstrating the extent of this could be important to policymakers, he says, who have spent the last two weeks at the COP27 climate conference in Egypt discussing how much carbon countries should be allowed to emit.
But nailing down that number has been difficult, due to the disruption of aerosols and Earth’s atmosphere. Burning smoke produces clouds of invisible particles, especially sulfates, that cool the climate in two major ways. Watson-Parris said: “These particles act like little mirrors, reflecting sunlight back into space. “So it’s like a parasol.” Small particles in the atmosphere protect the Earth from the sun’s rays.
The second method is more indirect: It stimulates the formation of clouds, which also affects the local climate. Watson-Parris says: “All stars are like vapors in the atmosphere that circulate and form cloud droplets.
Clouds do this naturally when water freezes around dust. But if you fill the space provided with additional aerosols, the droplets can be larger, yet smaller: There is more water vapor surrounding the particles. Smaller specks shine brighter than larger ones, causing the cloud to whiten, which causes the sun’s energy to be reflected back into the atmosphere. Watson-Parris says: “The smaller the droplets, the slower they fall, and the longer the clouds can live. “And this — we call it the whole organism — is one of the most uncertain and most likely contributors to all of this cooling.”
