By John Parnell
Scientists have cleared up misinterpretations of a recent paper by NASA’s James Hansen on the global cooling effects of emissions from coal power stations.
A number of climate change sceptics seized on the study about the effects that sulphur and nitrogen pollution have on atmospheric CO2 levels.
Hansen was describing how these two pollutants, associated with older, dirtier coal power stations, can offset some of the climate damage done by recent greenhouse gas emissions.
The concentration of CO2 in the atmosphere has not risen as sharply as emissions of greenhouse gases. Hansen suggests that the recent gush of emissions from coal in China and India could be masking some of this impact.
The National Review gleefully suggested burning more coal to reduce global warming, a line repeated by the Tuscon Citizen’s Jonathan DuHamel and syndicated widely.
On the face of it, that may seem the case but the more complicated truth is that in the long term, the effects would be highly detrimental.
Dr Bill Collins is the Chair of Climate Processes at the Department of Meteorology, University of Reading. He told RTCC why these cooling effects would not be likely to last long.
“Aerosols, mainly sulphate, reflect sunlight and cool the plant and emitting nitrogen can fertilise the ecosystems making them draw down more CO2 from the atmosphere,” says Collins.
“Hansen is saying climate change is not as bad as it could be because we have emitted all these other pollutants that have inadvertently offset the amount of climate change caused by CO2,” he says.
The UK and many other developed countries removed sulphur from their power stations’ emissions in an effort to reduce acid rain. China is doing the same now and Collins is confident India will follow suit.
“We want to clean up these pollutants though, for health reasons and when we do that will uncover this latent warming that was there all the time only hidden,” he says.
Cleaner coal power will no longer include this ‘offset’ from sulphur and nitrogen, but will continue to pump out CO2 in the same volume.
“These pollutants kill people. That’s why the Chinese are tackling these pollutants. That’s a good argument for not burning coal as a climate mitigation strategy,” adds Collins.
Aside from that very good motivation, in the long run, it wouldn’t work out well for the planet either.
Carbon dioxide is good for the vegetation on land and bad for the oceans says Collins. The ocean can absorb more CO2 than it currently holds but it reacts in the water to form carbonic acid upsetting a delicate balance and harming marine life.
Vegetation will enjoy the benefits of additional CO2 in the short term, as proven by many experiments pumping CO2 into greenhouses.
“This won’t continue indefinitely,” says Collins. “Trees will grow as fast as the most limiting factor allows them. If that’s the CO2 level then they’ll grow faster when there is more available, but only until they run out of other nutrients.
“Then we have to remember the climate is changing so drought for example will start to limit growth as well,” he adds.
The nitrogen issue is also complex but it adds to the case for long term damage out running initial gains of increased dirty coal emissions.
“We have an initial benefit of ‘greening the planet’, only to pay later by having a much less predictable climate,” says Dr Martin Lukac, a lecturer in crop science at the University of Reading.
“The main reason for this is the longevity of the ‘positive’ effects lasting years and possibly decades, compared to the ‘negative’ effects – CO2 related warming – which last for centuries.”
Lukac and Collins explain that while adding nitrogen to crops or even to the plants in your garden at home will indeed boost their growth, adding it indefinitely will eventually upset an ecosystem.
Many plants have adapted to life without nitrogen. A sudden surge would act in the benefit of those that thrive in a nitrogen rich environment. That means grasses for example doing well at the expense of all else, not good for biodiversity or the ongoing growth of a land based carbon sink.