Study: China’s Clean Air Policies are Triggering Additional Global Warming

This is a photo taken in the city of Taiyuan, China shows haze on December 3, 2016. CREDIT Courtesy of Yuhang Wang

Guest essay by Eric Worrall

According to a study whose authors include Ken Caldeira, China’s efforts to eliminate its infamous air pollution could cause an additional 0.1C NH warming, because less sunlight will be reflected by aerosols. However, despite suggesting China’s improved air quality is a “climate setback”, Caldeira acknowledged cleaner air is a net improvement.

China’s Success in Improving Air Quality by Cutting Polluting Emissions May Worsen Climate Change 


China’s success in improving air quality by cutting polluting emissions may have a negative knock-on effect on climate change overall, a new study has found.

The research, by scientists from Carnegie Institution for Science, USA, Chinese Academy of Environmental Planning, China, Tsinghua University, China, and the University of California Irvine, USA, used modeling to analyze the effect China’s success in reducing emissions such as sulfur dioxide, black carbon, and organic carbon, has had on global climate change. Their results are published today in the IOP Publishing journal Environmental Research Letters.

Lead author Dr. Yixuan Zheng, from Chinese Academy of Environmental Planning, a former postdoc at Carnegie Institution for Science, said: “Economic growth and industrialization in China over the recent decades has been supported by increasing consumption of energy from coal, making China the world’s largest emitter of major air pollutants such as sulfur dioxide and black carbon. These pollutants have significant impacts on air quality and public health, so China put stringent measures in place to reduce them. The measures were effective, and aerosol pollution in China was substantially alleviated after 2013, with notable public health benefits.”

Dr. Zheng said: “Anthropogenic sulfate aerosol was estimated to cool the earth on average by half a degree centigrade in 2010, equivalent to 76 percent of all-anthropogenic-aerosols-induced cooling. Black carbon, on the other hand, absorbs heat in the atmosphere and warms the Earth. So, understanding the effect reduction in these materials could have on warming is essential for future climate mitigation strategies.”

Carnegie’s Professor Ken Caldeira, also a co-author, said: “Cleaning up aerosol emissions has tremendous health benefits, but unmasks some global warming. While this may seem like a climate setback, we need healthy people to help tackle the climate problem, and if we are to have more resources to allocate to better energy systems, we need to be spending less on the health damage caused by our aerosols. Helping people to become healthier can be a win for the climate system, even if it does directly lead to some warming.”

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The abstract of the study;

Climate effects of China’s efforts to improve its air quality

Yixuan Zheng, Qiang Zhang, Dan Tong, Steven J Davis and Ken Caldeira

Published 29 September 2020

Facing severe air pollution issues, China has implemented a series of clean air policies aimed to improve the country’s air quality. These policies largely focused on reducing emissions of major air pollutants such as sulfur dioxide (SO2) and primary aerosols. However, changes in such pollution also affect radiative forcing. To understand the climate consequences of these clean air actions in China, we evaluate the near-equilibrium climate response to sustained changes in aerosol (and precursors) emission rates equivalent to those that occurred in China between 2006 and 2017. During this period, China’s SO2 emissions declined by ~70%, and black carbon emissions declined by ~30%. Climate simulations that used a fully coupled ocean and atmosphere climate model indicate that China’s reductions in aerosol emission rates from 2006 to 2017 may exert a net increase in global radiative forcing of 0.09 ± 0.03 W m−2 and a mean warming of 0.12 ± 0.01 °C in the Northern Hemisphere; and may also affect the precipitation rates in East Asia and in more distant regions. The success of Chinese policies to further reduce aerosol emissions may bring additional net warming, and this ‘unmasked’ warming would in turn compound the challenge and urgency of international climate mitigation efforts.

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The study authors also claim that the lower aerosols have increased precipitation slightly, especially in the East, which has experienced severe floods this year.

It is nice to see an author of a climate paper acknowledge some things are worse than global warming.

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September 30, 2020 10:25 pm

So in this case the glass is half-full instead of half-empty.

Reply to  gringojay
October 1, 2020 1:00 am

They are going through the stage that USA and Europe went though in 60s and 70s …. when “global warming” allegedly started.

The Clean Air Act etc., initially achieved massive improvements in air quality. Now we have a chance to quantify that effect with detailed remote sensing and will then be able to subtract that effect which is currently mis-attributed to AGW.

Reply to  gringojay
October 1, 2020 1:11 am

A great illustration of the difference between clean air and “clean air” !!

At least the Chinese know the difference between truly toxic emissions you can see and non toxic “dirty ” CO2.

Reply to  gringojay
October 1, 2020 4:27 am

If I had to start my furnace up on Sept 9 this year, the earliest I have EVER turned it on, and the PM forecast through Saturday is barely mid-30s, I’d like to know just what’s wrong with a little Globull Warming? I could use it over here in my kingdom.
I’ll have to pull out the heavy comforters next. Not my idea of a good time.

September 30, 2020 10:51 pm

“It is nice to see an author of a climate paper acknowledge some things are worse than global warming.”
Mmmm I don’t think he said one was worse or more preferable than the other. But it is great to see China are keen to withdraw from the filthy coal. On another positive note it was good to hear in last nights debate (yelling match) that Trump is keen on electric vehicles ,which when combined with nuclear power and other non coal produced power, leads to cleaner air.

Reply to  Simon
October 1, 2020 12:06 am

As usual, you have it the wrong way around.

Modern coal DOES NOT lead to unclean air.

Whereas, the production of wind turbines and solar panels is extremely dirty business causing massive air and other pollution.

Reply to  Simon
October 1, 2020 12:10 am

“China are keen to withdraw from the filthy coal….”

ROFLMAO.. from Dirty coal, old factories etc yes

From coal fired power.. not so much

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Reply to  fred250
October 1, 2020 1:17 am

That is what dirty coal means in a sane world. Burning coal produces filthy smoke ( I grew up in a home with a coal fire , I know what it looks like ).

Reply to  Simon
October 1, 2020 12:17 am

Not much sign of any untoward temperature change in china..

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China’s energy mix 2018.

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Reply to  fred250
October 1, 2020 1:07 am

Interesting. Apparently the early 20th c. warming 1905-1940 was a strong cooling in SW China.

Reply to  Simon
October 1, 2020 3:28 am


Maybe not.
UN Warns Of Devastating Ecological Side Effects Of Electric Car Boom

* Date: 23/04/19

Reply to  KcTaz
October 1, 2020 12:21 pm

Mmm those two articles are not the gold standard in fair reporting. Read GWPF and stopped there. Things are changing so quickly with the batteries that first article is wildly out of date(in content). If you watched Tesla’s battery day the other day you would see just how much things are moving and how exciting the whole thing field it. And while it is true we are not quite there yet (cheap environmentally friendly batteries), I wouldn’t bet against the technology.

Pat from kerbob
Reply to  Simon
October 1, 2020 9:12 pm

It’s always tomorrow land yes

So what if you bet the world on it and it doesn’t happen?

Reply to  Simon
October 2, 2020 6:13 am

“Read GWPF and stopped there.”

Yes we know you REFUSE to listen to actual scientists, slimon. !

Can’t let the actual FACTS intrude on your brain-washing.

Reply to  Simon
October 1, 2020 7:16 am

I seem to remember that in the Climate Gate emails, they wrote about how the SO2 emissions were reducing the temperatures around Chinese power plants.
So, we have that one to add to the mix, too.

Reply to  Simon
October 1, 2020 7:54 am

As usual, simon sees what it wants to see, not what is there.
China is building coal plants as fast as they can. What they are doing is putting modern filters on them.
In the west, Coal has been clean since the 70’s.

Geoff Sherrington
Reply to  Simon
October 2, 2020 2:19 am

Relatively, as a fuel, which is more dirty, animal dung or coal?
Civilisations moves from dung to coal partly because coal was cleaner.
Now, the crazies want to stop coal and increase biomass.
I wonder why people named them crazy.
Geoff S

September 30, 2020 10:52 pm

Just about anything is worse than ‘Global Warming’ including the common cold.

Reply to  nicholas tesdorf
October 1, 2020 1:16 am

Stubbed my little toe on a chair leg yesterday !

That was heaps worse. !

Reply to  nicholas tesdorf
October 1, 2020 7:56 am

Global warming is a net positive.

September 30, 2020 10:56 pm

“It is nice to see an author of a climate paper acknowledge some things are worse than global warming. ”

He doesn’t really. He apologetically points out the warming and the cleaner air, but justifies it by indicating how we need healthier people who are spending less on health care to fight climate change. Never says that people’s wellbeing is more important than maintaining the Earth’s temp at some arbitrary figure. Why is today’s temp so great? What about the higher temp of like 8000 years ago when the Sahara was a savannah and forest and the world was teeming with life? Or even hotter roughly 55 million years ago, before the ice covered Antarctica, the world was a jungle?

Reply to  PCman999
October 1, 2020 3:34 am


I really don’t get the connection he was trying to make. It seems like quite a stretch either because it sounded good or because he needed an excuse now to not go all Alarmist hysterical over alleged AGW.

Zig Zag Wanderer
September 30, 2020 11:10 pm

So, that means that the developed world, who cleaned to their age pollution in the 70s and 80s, caused additional Global Warming too. About as much as we’ve seen since then.

Looks like the concept of CAGW from CO2 is dead in the water.

Reply to  Zig Zag Wanderer
September 30, 2020 11:45 pm

More sun with less clouds.
20% more since 1980.
That is a good change due to cleaner air.

Reply to  Lasse
October 1, 2020 1:20 am

Simulations… climate model….. indicate that …. may……….

YAWN !!!

October 1, 2020 12:22 am

Temperature in rural China

minor warming in more northern place.. …

Warmer places.. not so much

October 1, 2020 12:29 am

Central china cooling

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October 1, 2020 12:40 am

Still quite a bit cooler in China than a few thousand years ago

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Someone show me a trend here please

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October 1, 2020 1:13 am

No-one can ever measure “global” temperatures to 0.1ºC accuracy.

So I guess what they are saying is it will make no measurable difference anyway.

So … why bother saying anything.!

Why even publish it !

October 1, 2020 1:52 am

Is it possible that the cleanup of European, American and other Western nations as well as Russia had the same same effect on global warming in the 20th century – boilers, smelters, railways, domestic, commercial and industrial solid fuel heating etc all belching carbon particulates, sulfur compounds. Many small scale sources but high levels of particulate and sulfur emissions. Could this be the dominant cause of the small amount of global warming we are seeing rather than CO2?

Serge Wright
October 1, 2020 3:02 am

China’s clean air policies are much like their emissions targets. All aspiration and no substance.

Reply to  Serge Wright
October 1, 2020 3:24 am

They are making no difference to temperatures in China, so how the heck are they going to make a “global” difference.

October 1, 2020 6:11 am

If global CO2 levels in the atmosphere were to become fixed at current levels of between 410 to 415 ppm what according to AGW theory and modeling would be the long term effect on the ‘global temperature’? Would the temperature continue to rise from current levels to reach a steady range of values? If the carbon dioxide output of the USA fell to zero would this have any measurable effect on world CO2 levels?

October 1, 2020 6:17 am

*Climate simulations that used a fully coupled ocean and atmosphere climate model indicate that China’s reductions in aerosol emission rates from 2006 to 2017 may exert a net increase in global radiative forcing of 0.09 ± 0.03 W m−2 and a mean warming of 0.12 ± 0.01 °C in the Northern Hemisphere*

In a recent comment on another thread (dh-mtl September 30, 2020 at 11:33 am ) I raised this specific issue.

So if the reduction in pollution from China during 12 years can cause 0.1 C warming, then how much of the 0.8 C of total Global Warming since per-industrial times could be caused by the decades of cleaning up pollution in the rest of the world from the end of the 1960s onward. I expect that it is much more than 0.1 C.

And yet we are told that the justification for believing in CO2 as the cause is that there are no ‘natural causes’ that could be responsible for the temperature increase. Well here is a ‘man-made’ cause that is fortunately self-limiting!

Nick Schroeder
Reply to  dh-mtl
October 1, 2020 7:18 am

“…no ‘natural causes’ that could be responsible for the temperature increase.”

What temperature increase?

1.5 C rise in the GMAT anomaly (Know what/how that is?) over 140 years is noise in the data, UHI, upgrades in instrumentation and procedures…….

The null hypothesis needs no explanation.

Reply to  Nick Schroeder
October 1, 2020 7:59 am

They still don’t know what caused the Roman, Minoan and Egyptian warm periods. Nor do they know what caused the Holocene Optimum. If they don’t know the causes of these warm periods, it is logically impossible for them to declare that whatever the cause, it isn’t operating during the Modern warm period.

Nick Schroeder
October 1, 2020 6:22 am

“…could cause an additional 0.1C NH warming, because less sunlight will be reflected by aerosols.”
Hmmm, less reflection equals more hotness.
Decreasing albedo, increasing hotness.
Minimum albedo (zero), maximum hotness.

Gosh, where have I heard that before?

Abolition Man
October 1, 2020 6:33 am

They are trying to make the Commifornians feel better about the massive amounts of CO2 and particulate matter their wild fires have pumped into the atmosphere! Apparently it is very important for Communists to stick together and support each other in their times of need!
I was perusing an old WUWT article about sulfur based aerosol production in the 19th and 20th Centuries and noticed that there was a short term drop in the 1930’s. Could this have been one cause of the Dust Bowl, and were both brought about by a decline in manufacturing during the Great Depression?
Did the implementation of the US Clean Air Act cause the “global cooling” trend to switch to Gullible Warming as it took effect in the mid 1970’s? Enquiring minds want to know!

Reply to  Abolition Man
October 1, 2020 11:51 am

Abolition Man:

I have a couple of peer-reviewed papers which supports your speculations that you might want to read:

“Atmospheric SO2: Principal Control Knob Governing Earth’s Temperatures” (2018)

Google the title. For an expanded version,

and “Experimental proof that Carbon Dioxide does NOT cause global warming” (Aug 2020)

October 1, 2020 7:52 am

Did they just admit that some of the post 1970 warming was due to the atmosphere being cleaned up?

Gordon A. Dressler
October 1, 2020 7:59 am

Nice photo of the haze over the city of Taiyuan, China, albeit very misleading as to the thrust of the above article.

The total area of large cities in China, say with populations above 10,000 people, capable of producing significant quantities of aerosols is, what, maybe 0.1% of China’s total land area.

This causes me to question if the study authors, including Ken Caldeira (FWIW), correctly accounted for aerosol reflectivity values.

That is, aerosol reflectivity has a concentration value-dependent optical depth, beyond which it is “saturated”. For proper calculations, one would have to know and apply the reflection dependency on altitude (almost certain to be non-linear) for the different combinations of aerosols noted in the above article and their concentration values as adjusted over China’s total range of topography. Without doing this, erroneously high values of China’s total aerosol reflectivity are probable if one just ratios the concentrations measured in the atmosphere around the cities atmosphere (in units per square km terms) to the total area of China.

Of course, this issue may pale in comparison to this biggest red flag concerning scientific credibility of the above article, stated in the first boxed excepts: “The research . . . used modeling to analyze the effect China’s success in reducing emissions . . . has had on global climate change.”

Modeling? Hey, what could go wrong with that? These author’s definitely need to get together with the IPCC.

October 1, 2020 8:36 am

The effect aerosols in the atmosphere was also demonstrated by the eruption of Mount Pinatubo in 1991, which according to Wikipedia ‘led to a decrease in Northern Hemisphere average temperatures of 0.5–0.6 °C (0.9–1.1 °F) and a global fall of about 0.4 °C (0.7 °F)’.

This paper presents the same mechanism of aerosols significantly affecting global temperatures, only this time by removing them from the atmosphere.

The magnitudes of the effects from both this paper and Mount Pinatubo leads me to question whether a good part of the ‘global warming’ seen since the 1980s, that we are told should be attributed to CO2, is not rather to be attributed to pollution reduction since the 1970s.

October 1, 2020 12:54 pm

When a settled system is disturbed, it will adjust to diminish the change that has been made to it.

Any change in status quo prompts an opposing reaction in the responding system.

Gordon A. Dressler
Reply to  Ralph Dave Westfall
October 1, 2020 3:39 pm

Except for disturbances in “settled” quantities of radioactive material that will initiate nuclear chain reactions, as employed in nuclear power reactors and fission bombs . . .

Except for disturbances in “settled” snow packs leading to avalanches . . .

Except for thermal or chemical disturbances in “settled” quantities of mixed chemicals leading to flames or explosive chemical reactions . . .

Except for disturbances in “settled” (aka quiescent) superheated or supercooled liquids, such as water . . .

Except for slight (say, around +.01%) pressure disturbances in a “settled” gas storage tank—or even kid’s balloon—that has been pressurized to within .005% of its rupture pressure . . .

Except for an electrical disturbance in a “settled” bipolar junction transistor state that triggers it to begin operating in “avalanche mode” . . .

Except for almost everything that is explainable by quantum physics and relativity . . . (just consider the “settled” system of parallel light rays from a very distant star passing near a massive body that causes the light to be bent by its likewise-“settled” gravitational field — Arthur Eddington, you listening?)

I could go on and on, but need I? Le Chatelier’s principle has its place . . . and its definite limitations.

John Harrison
October 1, 2020 3:14 pm

I’m a little bit confused….. when the global temperatures started falling in the 70s the reason given for this was that aerosols from unfiltered Western industrial and domestic combustion of fossil fuels were reflecting sunlight. Then the subsequent rise could perfectly be explained away by reason of the introduction of clean air acts reducing the particulate matter. Is there something we don’t know about the aerosols emitted by Eastern countries? Is it somehow different? I was assured that the science was settled.

John Harrison
October 1, 2020 3:25 pm

Long ago when the science was first settled we were assured that the cooling during the 70s was due entirely to aerosols from the industrial and domestic combustion of fossil fuels in Western countries. They only started to rise once more due to the enactment of clean air legislation. It seems, therefore, that Eastern aerosols must be different….

D Cage
October 1, 2020 10:01 pm

So climate scientists finally admit what engineers have said for around seventy years that warming is actually caused by the clean air laws.

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