Global Dimming Debate

November 23, 2021 Update: Dr. Ye Tao, RF Alumnus of Rowland Institute at Harvard, provided an update on the global dimming issue.

I'm grateful to Dave Borlace's Just Have a Think for reporting the "global dimming" climate issue may not be as serious for humans as many thought. Borlace's video contrasts with meteorologist Eric Holthaus February 8, 2018 Grist article citing this 2018 report in Geophysical Research Letters. 

Scope, intensity, timescale, and solutions regarding "global dimming" are the four main issues. In my November 24, 2019 post "Climate Equity Graph from Meinshausen et al. 2009, and Aerosol Killing / Cooling Double Bind" I wrote about Holthaus Grist article, The McPherson Paradox, and James Hansen in 2012 speaking about the aerosol problem as "Doubling Down on the Faustian Bargain" at 35:48 on this Climate One video. In my post I noted "I am uncertain about the magnitude of this problem." Even after Borlace's interesting video, I still feel this way. It seems more data and research are needed, and stakes are high enough to justify both. 

Borlace's description of "regional impacts" contrasts with Climate Scientist's David Travis' global analysis in this BBC video which originally aired in 2005 (a transcript is here). The BBC video provides a history of "global dimming" including Gerald Stanhill's research in Israel, Beate Liepert's research in Germany,  Graham Farquhar and Michael Roderick's research in Australia, Veerabhadran Ramanathan's research in The Maldives, Peter Cox's global research from the United Kingdom, and Leon Rotstayn's research about the Sahel drought whose model, according to narrator Jack Fortune, showed "what came out of our exhaust pipes and power stations [in Europe and North America may have] contributed to the deaths of a million people in Africa, and afflicted 50 million more." Rotstayn explained "The Sahel's lifeblood has always been a seasonal monsoon. For most of the year it is completely dry. But every summer, the heat of the sun warms the oceans north of the equator. This draws the rain belt that forms over the equator northwards, bringing rain to the Sahel. But for twenty years in the 1970s and 80s the tropical rain belt consistently failed to shift northwards [due to "global dimming" "pollution from Europe and North America" blocking the sun] - and the African monsoon failed."

Ramanathan explained in the BBC video "The Sahel is just one example of the monsoon system. Let me take you to anther part of the world, Asia, where the same monsoon brings rainfall to 3.6 billion people, roughly half the world's population. My main concern is this air pollution and the global dimming will also have a detrimental impact on this Asian monsoon. We are not talking about few millions of people. We are talking about few billions of people. There is no choice here. We have to cut down air pollution, if not eliminate it altogether."

In my March 3, 2018 post "Is a human life worth $450 to you?" I wrote "The highlight was when, as noted elsewhere, 'Dr. Ramanathan said it would take $450 per person per year in the top one billion people to change from our carbon economy to renewables' saving over 3 billion people that may otherwise die from exposure to 130 degree plus heat 35 years from now if humans fail to convert energy sources from coal and fossil fuels to 'solar, wind, hydro, and possibly nuclear. [ . . . . ] We have 10 to 15 years to solve the problem.'"