Climate Change Decadal Pause Study â€“ Accidental Climate Mitigation
Professors Jesse ThÃ© and Roydon Fraser from the University of Waterloo are initiating a study on the potential cause of the decade long pause on global warming. This is an interview with Prof. ThÃ©, as a disclosure is also ENNâ€™s Editor-in-Chief. .
ENN: What is causing this decade long pause on the average global temperature increase?
Prof. ThÃ©: First of all, note that the last decade was the warmest on record. While the maximum temperatures are not increasing as fast, we are not seeing a real pause on temperature increase, just a significant reduction on its growth rate. Second, researchers are not certain, and our work at this stage can only be placed in the scientific method as a hypothesis. Until we develop the full analysis, all my views in this interview are based on our hypothesis that the pause in the temperature increase is caused by aerosol formation form the massive burning of coal in China (50% of global consumption of coal) and India.
ENN: Please explain to our readers why the burning of coal in China and India is reducing the growth in temperature globally. Isnâ€™t this burning injecting more CO2 in the atmosphere?
Prof. ThÃ©: The additional burning of coal in China injects sulfur in the atmosphere (SO2), which turns into reflective aerosols. This causes higher reflectivity of solar radiation back to space. This is a cooling effect that more than counter balances the additional CO2 emitted from the burning of coal. In our research we will attempt to demonstrate a reduction of thermal load from the sun caused by increased this increased aerosol reflectivity. Note that if our demonstration fails to prove this cooling effect it will at least eliminate these aerosols as a significant contributor to the decadal climate change pause.
ENN: Why did you and Prof. Fraser came out with this aerosol cooling hypothesis? What are the present explanations for the pause in global temperature growth?
Prof. ThÃ©: Unfortunately there are no definitive answers to the slowdown in temperature increase. One of the main hypotheses is that the additional heat is going into the oceans. However, as I already stated, this is not universally accepted, and it might not fully account for the reduction in the atmospheric energy budget. Prof. Fraser and I understand the cooling effect from burning of coal SO2 emissions over the USA in the 1970s. This cooling effect almost disappeared after the large reduction in sulfur emissions over North America.
ENN: Do you mean to say that if China and India clean the emissions of SO2 the accelerated temperature increase will return?
Prof. ThÃ©: Yes, if our hypothesis is correct. Note that China is already implementing desulfurization of their emissions (using scrubbers) due to poor air quality on their coastal areas. Consider that this is an unplanned mitigation of global warming. It is not all good, since if we prove this hypothesis, we might see a reduction in the evaporation rates over the Pacific Ocean. Therefore, areas downwind should see significant reduction in precipitation. The theme is complex and any additional conclusion would be on the realm of speculation. One might speculate, but not assert, that the US Southwest could potentially experience more severe droughts due to this increase aerosol issue over the Pacific Ocean.
Coal fired power station on Lamma Island Hong Kong, China image via Shutterstock.