Sulphates: The light in the dark

Not all aerosols warm. Sulphate particles, for example, can cause a dip in surface temperatures as a result of their ability to reflect infra-red radiation. For geoengineering purposes (Solar radiation management) or a “quick fix” against climate change, sulphates have provided a shining light as a new method to combat rising temperatures. Aerosols, injected into the atmosphere, reflect solar radiation back into space, thus preventing it reaching the earth’s surface. This is hoped to contradict the warming effects of greenhouse gases.

Najafi et al (2015)

So back to the Arctic…

Warming is occurring at an amplified rate within the Arctic. A study recently published in Nature Climate Change suggests aerosols could be used as a method of slowing the rising temperatures. The paper highlights the ability of aerosols to scatter radiation and cause clouds to form. Modelling results suggests greenhouse gases were going to cause a 3 degrees Celsius warming over the Arctic, yet the rise in temperature currently stands at only 1.2. The difference between predicted and observed can be accounted to the cooling influence of sulphates. This demonstrates the potential of SRM schemes, especially in the Arctic.

It is important to remember SRM, as a method of mitigating climate change, does not come without risks. A friend of mine covers the topic of Solar Radiation Management in her blog and highlights the risks associated with this type of geoengineering. Aerosols only influence the climate for approximately 2 years before being removed, from the atmosphere, by precipitation. A greater concentration of sulphates can result in a lower pH rainwater (acid rain). Secondly, the uncertainty associated with these methods is still high and the failure of these schemes could subject the earth to rapid warming, at a greater rate and to higher temperatures than current.

Thoughts:

Before I began engaging with the literature surrounding this topic I recorded my initial opinion as I was interested to see if it had changed: “I believe geoengineering is not a good mitigation strategy. Messing with the natural climate system will only end badly and the negative impacts of aerosols (in the Arctic especially) has not been considered holistically. Based on what I have read this is not going to be a long term fix for climate change. In the Arctic, aerosols have a series of negative effects including changes to the composition of clouds, which has not been considered.”

I started this blog seeing all types of pollution as negative, but after reading this I have been shown that aerosols are not all bad. Any method which can slow the warming in the Arctic must be positive! However the future isn’t so bright. Predictions show anthropogenic productions of aerosols are predicted to decline (whilst greenhouse gases continue to rise), indicating rate of warming within the Arctic will increase in the near future.

This is a very controversial topic and I would be very interested to hear your opinions so please comment and let me know!