Recent research suggests that global warming has slowed down in recent years â€“ but not because weâ€™re getting better at controlling global COâ‚‚ emissions. It seems that the concentration of stratospheric aerosols is increasing, thus having a cooling effect on the planet.
An aerosol is a particle that floats in the air, and according to John Daniel of the National Oceanic and Atmospheric Administration â€œ[acts] to keep warming from being as big as it would have been.â€
A natural way for stratospheric aerosols to form is when sulphur dioxide (SOâ‚‚) is emitted into the atmosphere following a volcanic eruption. When it reaches the middle layer of the atmosphere â€“ or stratosphere â€“ it dilutes into droplets of sulphuric acid, thus becoming an aerosol. When Mount Pinatubo erupted in 1991, it spewed ten cubic kilometres of gas, ash, and SOâ‚‚ into the atmosphere, cooling the planet for a year. Other less active volcanoes emit SOâ‚‚ into the atmosphere on an intermittent basis, having less pronounced impacts on the environment.
But one of the most common ways for SOâ‚‚ to find its way into the atmosphere now is through human combustion of coal. Coal consumption has increased multi-fold over the past few decades, thus contributing to the concentration of stratospheric aerosols in the atmosphere. In fact, now that China is emitting more SOâ‚‚ than ever because of its large-scale construction of coal-fired plants, it has single-handedly been cancelling out the warming effects of rising COâ‚‚ emissions.
The recent global â€œstratospheric hazeâ€ has decreased greenhouse warming by 20 percent since 1998, or 0.07Â°C.
But what are we to make of this global cooling effect? Have we solved the problem of climate change?
Well, the answer can be quite complicated depending on which way you look at it.
There are some that are claiming itâ€™s too late to stop climate change and we are going to have to turn to geo-engineering to avert global disaster scenarios. Such is the conclusion that Gwynne Dyer came to in his recent book Climate Wars.
Without simplifying his argument too much, he basically suggests that the political will-power is not strong enough to reduce greenhouse gas emissions to safe levels, and we must therefore find some way to artificially cool the planet. There are numerous ways to do this, the most outlandish one being the installation of large mirrors outside the Earthâ€™s atmosphere to reflect solar rays away from the surface. It would seem that increasing atmospheric aerosols would be a similar geo-engineering solution, as it could reduce the effects of rising COâ‚‚ levels. Mind you, some experts argue that global warming would eventually overtake any effect that SOâ‚‚ has on global cooling.
I find I am sceptical about any geo-engineering solutions. Humans have a huge impact on how the planet functions and we should be wary about messing with it more than we already have. Rather than try to â€œcover-upâ€ our greenhouse gas emissions with geo-engineering, we should strive for a cleaner society. The technology is just about there (if not already) to dive headlong into renewable energy and less carbon intensive activities. The biggest hurdles are political will-power and vested interests that seek to maintain our addiction to fossil fuels.
But perhaps Iâ€™m being too optimistic about what we can accomplish. Perhaps geo-engineering might ultimately be the solution…
What are your thoughts?
Image CC licensed by hAdamsky: coal-fired power plant.