Global Dimming: Burst of Heat From Air Cleanup?—Interview w/Yangyang Xu—Radio Ecoshock 2019-01-24

You've seen pictures of crowds in Chinese cities with masks over their faces. The smog of rapid industrialization is thick, but Chinese authorities are working overtime to clear the air. But will air pollution get better or worse in a hotter world? Could cleaner air actually heat the planet?

It’s difficult to get the latest on the situation in China. But we’ve reached one of the best young scientists working on it. Dr. Yangyang Xu was educated in Beijing. He came to America to study with the legendary Ram Ramanathan at the Scripps Institution in San Diego. Now Yangyang is an assistant professor at Texas A&M University. He has already published 30 papers, with more in the works.

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I want to begin by saying this discussion is not against China. Air pollution is a problem well-known in many countries. Chinese the authorities are struggling to resolve it quickly, without damaging the economy. This science is part of that.

Let’s start with some basics. We know what the global average for carbon dioxide pollution is this year. Is there a similar global count for aerosols? Not really, pollution so regional that a global number is not helpful.

In January 2019, Yangyang coauthored a paper predicting worse pollution for East China due to increased greenhouse gases. The can haze get worse, even as the government tries to clean up because climate change disrupts weather in a way that favors the continuation of pollution. For example, yes there will be more extreme rainfall events, which do clean up the air. But there will also be more dry days in between, with wind patterns in Eastern China that do not disperse pollution well.

We discuss the relationship between air pollution and extreme rainfall events, in the past 30 years, and in the future. Dr. Xu co-authored an ambitious study, published in July 2018, attempting to explain the impacts of aerosols on rainfall, not just in China, but over Asia generally, including India.

I recall a talk in the early 2000’s by Ram Ramanathan. He said evaporation of water from pans showed a decline of about 9% in the amount of sunlight reaching the ground in Eastern China. The impacts of reducing the amount of sunlight reaching a large country are profound. Surely agricultural production would be hurt, as well as plants and animals in the wild. Isn’t that an addition cost of smog, beyond the health impacts on humans?

In the winters of 2013, 2015, and 2016, China experienced something like smog storms. Industry had to be shut down, and car traffic slashed, but the government is very aware of the problem, and citizen demand for a cleanup. Ironically, cleaner air will mean more global warming, as there are fewer aerosols to reflect sunlight back into space. We covered that last week in the interview with David Victor. Cleanup up the air is one of three reasons “Global Warming Will Happen Faster Than You Think”.

It would be ironic if humans stop polluting the air with sun-reflecting sulphates, but then feel forced to spray more sulfates in the Arctic or stratosphere to cool the planet back down. Do you think geoengineering will be necessary?


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