Carbon dioxide (CO₂) emitted by burning fossil fuels for energy today will only be removed from the atmosphere by natural sinks – like forests and the ocean – in the next 300 to 1,000 years.
That means the climate benefits of transitioning to clean energy become apparent on far longer timescales than political term limits and election cycles.
A US study, for example, found that deep cuts to emissions from the energy sector will not result in climate cooling until after 2100.
The costs of mitigating climate change outweigh the immediate benefits to the climate. Politicians seeking recognition for their actions at climate change conferences like COP26 in Glasgow have little motive to deliver policies which slash emissions quickly.
But there is a large, short-term benefit to eradicating fossil fuels for global health.
The same fossil fuels producing the greenhouse gases warming the Earth's atmosphere also form large quantities of air pollutants. The pollutants most hazardous to health are small particles which can penetrate deep into the lungs.
These particles have diameters of no more than 2.5 micrometers, so are called PM2.5. At least 800 of these particles could fit end-to-end on the head of a pin. These fall out of the air when it rains, so they persist in the atmosphere for a much shorter time (just a few days) than CO₂.
In a study we published earlier in 2021 in collaboration with researchers at Harvard University, we estimated that exposure to air pollution from using fossil fuels globally accounts for one in five premature deaths.
Our results suggest that at least 8.7 million early adult deaths could have been avoided in a single year if countries had already abandoned fossil fuels. This is equivalent to the population of Greater London.
The health benefits of decarbonization
Our estimate of premature deaths far exceeds that of other researchers, as we used a model that simulates the sources and fate of air pollution to calculate its abundance on a much finer scale.
This gives a more accurate picture of the concentrations of air pollution breathed in by people in urban areas. We then used this to estimate excess deaths using the most up-to-date health studies, which have found that air pollution is deadlier than previously assumed.
The most common causes of premature death from air pollution exposure are heart disease and lung cancer, but researchers routinely report additional illnesses. The World Health Organization (WHO) recently published much stricter health guidelines for air quality than it last recommended in 2005 based on substantial evidence that exposure to air pollution is even worse for public health than scientists had imagined.
Our study is probably an underestimate of the possible public health benefits of abandoning fossil fuels.
We only accounted for one type of pollution, PM2.5, which arises from burning fossil fuels. A range of air pollutants form as byproducts in all other steps of the fossil fuel supply chain: from finding, extracting and processing fossil fuels, to storing and transporting them.
One example is formaldehyde gas, which is emitted during petroleum refining and flaring of natural gas. Formaldehyde reacts to form ozone in the lower atmosphere, where it is toxic and can exacerbate asthma symptoms.
We also only focused on adults. The relationship between air pollution and poor health in children isn't completely understood, but studies so far have shown that exposure to air pollution stunts growth and impedes brain and lung development in children.
In a landmark case in 2020, air pollution was directly attributed to the death of Ella Kissi-Debrah, a nine-year-old girl in London.
The health benefits of transitioning to clean energy are substantial and can emerge quickly. They offer a tantalizing opportunity for politicians to deliver immediate improvements in the lives of their voters.