“Climate Problem 22”: Reducing pollution leads to global warming

Nov 2 (Reuters) – Air pollution is a global scourge that kills millions of people every year, protecting us from the full power of the sun. Getting rid of it will accelerate climate change.

That’s the unpalatable conclusion reached by scientists studying the results of China’s highly effective decade-long “war on pollution,” according to six leading climate experts.

Chinese official data showed that efforts to eliminate pollution mainly caused by sulfur dioxide emitted by coal plants have reduced sulfur dioxide emissions by nearly 90% and saved hundreds of thousands of lives. Health studies Displays.

However, after China was stripped of its toxic shield, which scatters and reflects solar radiation, average temperatures in China have risen by 0.7 degrees Celsius since 2014, leading to more ferocious heat waves, according to a Reuters review of meteorological data and scientists interviewed. Interviews.

“It’s a catch-22,” said Patricia Quinn, an atmospheric chemist at the US National Oceanic and Atmospheric Administration (NOAA), speaking about cleaning up sulfur pollution globally. “We want to clean our air for air quality purposes, but by doing so, we are further warming.”

Removing air pollution — a term scientists call “detoxing” — may have had a greater impact on temperatures in some Chinese industrial cities over the past decade than the temperature rise caused by greenhouse gases themselves, the scientists said.

Experts have warned that other highly polluted parts of the world, such as India and the Middle East, will see similar jumps in temperature rise if they follow China’s lead in cleaning the skies of sulfur dioxide and the polluting aerosols it forms.

They said efforts to improve air quality could actually push the world into scenarios of catastrophic warming and irreversible impacts.

“Aerosols are masking a third of the planet’s warming,” said Paolo Artaxo, an environmental physicist and lead author of the chapter on short-lived climate pollutants in the latest round of Intergovernmental Panel on Climate Change (IPCC) reports. ), was completed this year.

“If you implement technologies to reduce air pollution, this will accelerate global warming very significantly in the short term.”

The Chinese and Indian environment ministries did not immediately respond to requests for comment on the implications of the pollution detection.

The relationship between sulfur dioxide reduction and warming was reported by the Intergovernmental Panel on Climate Change in 2008 2021 report Which concluded that without the solar shield that protects against sulfur dioxide pollution, the global average temperature would have already risen by 1.6 degrees Celsius above pre-industrial levels.

This misses the world’s goal of limiting temperature rise to 1.5 degrees Celsius, beyond which scientists expect catastrophic and irreversible changes in climate, according to the Intergovernmental Panel on Climate Change, which pegs the current level at 1.1 degrees Celsius.

A Reuters review of Chinese data provides the most detailed picture yet of how this phenomenon plays out in the real world, based on previously unreported figures on changes in temperatures and carbon dioxide emissions over the past decade and confirmed by environmental scientists.

Reuters interviewed a total of 12 scientists about the phenomenon of unmasking globally, including four who served as authors or reviewers of sections on air pollution in IPCC reports.

They said there is no suggestion among climate experts that the world should stop fighting air pollution, a clear and present danger that the World Health Organization says causes about seven million premature deaths annually, most of them in poor countries.

They instead stressed the need for more aggressive action to reduce greenhouse gas emissions, with methane reduction seen as one of the most promising ways to offset pollution detection in the short term.

BATTLES XI “AIRPOCALYPSE”

President Xi Jinping pledged to tackle pollution when he took power in 2012 after decades of burning coal that helped turn China into the “world’s factory.” The following year, when Beijing’s record smog inspired “Airpocalypse” headlines, the government unveiled what scientists called a Chinese version of America’s Clean Air Act.

On March 5, 2014, a week after Xi toured during another severe bout of smog in the capital, the government officially declared war on pollution at the National People’s Congress.

Under the new rules, power plants and steel plants were forced to switch to coal with low sulfur content. Hundreds of inefficient factories were closed, and vehicle fuel standards were tightened. While coal remains China’s largest energy source, smokestack scrubbers now eliminate most sulfur dioxide emissions.

China’s sulfur dioxide emissions fell from a 2006 peak of about 26 million metric tons to 20.4 million metric tons in 2013 thanks to more gradual emissions restrictions. But with the war on pollution, those emissions fell by about 87% to 2.7 million metric tons by 2021.

The decrease in pollution was accompanied by a jump in global warming. The nine years since 2014 have seen China’s national average annual temperature rise to 10.34 degrees Celsius, an increase of more than 0.7 degrees Celsius compared to the period 2001-2010, according to Reuters calculations based on annual weather. Reports published by the China Meteorological Administration.

Scientific estimates differ on how much of this increase comes from detecting greenhouse gas emissions or natural climate changes such as the El Niño phenomenon.

The effects are most severe at the local level near the source of pollution. Almost immediately, China saw big jumps in global warming after pollution was detected near heavy industrial areas, according to climate scientist Yangyang Xu at Texas A&M University, who modeled the impact of aerosols on climate.

Xu told Reuters he estimated that uncovering the masks had caused temperatures near the cities of Chongqing and Wuhan, long known as China’s “ovens,” to rise by about 1 degree Celsius since sulfur emissions peaked in the mid-2000s.

During heatwaves, the effect of unmasking can be more pronounced. Computer simulations showed that the rapid decline in carbon dioxide in China could raise temperatures on very hot days by up to 2 degrees Celsius, said Laura Wilcox, a climate scientist who studies the effects of aerosols at Britain’s University of Reading.

“These are big differences, especially in a place like China, where the heat is really dangerous,” she said.

In fact, heat waves in China have been particularly fierce this year. A town in the northwestern region of Xinjiang saw temperatures of 52.2 degrees Celsius (126 degrees Fahrenheit) in July, breaking the national temperature record of 50.3 degrees Celsius set in 2015.

Beijing also experienced a record heatwave, with temperatures exceeding 35 degrees Celsius for more than four weeks.

India and the Middle East

The effects of sulfur detection are most evident in developing countries, where the United States and much of Europe have been cleaning up their skies for decades. While the warming from sulfur cleaning is strongest locally, the effects can be felt farther away. One study 2021 A study in which Xu participated found that the decline in European aerosol emissions since the 1980s may have changed weather patterns in northern China.

In India, sulfur pollution is still on the rise, nearly doubling in the past two decades, NOAA researchers calculate based on figures from the U.S.-funded Community Emissions Data System.

In 2020, when pollution fell due to coronavirus lockdowns, ground temperatures in India were the eighth hottest on record, 0.29°C higher than the 1981-2010 average, despite the cooling effects of a La Nina pattern. Climate, according to the Indian Meteorological Department. .

India aims to clean its air like China, and in 2019 launched its National Clean Air Program to reduce pollution by 40% in more than 100 cities by 2026.

Scientists said that once polluted areas in India or the Middle East improve their air quality by abandoning fossil fuels and moving to green energy sources, they, too, will lose their sulfate shield.

“You stop your human activities for a short period of time, the atmosphere clears very quickly and temperatures rise immediately,” added Sergey Osipov, a climate modeler at King Abdullah University of Science and Technology in Saudi Arabia.

Compensation for methane?

As the implications of pollution detection become increasingly clear, experts are looking for ways to combat global warming associated with it.

One proposal, called “solar radiation management,” envisions deliberately injecting sulfur aerosols into the atmosphere to cool temperatures. But many scientists worry that this approach could lead to unintended consequences.

A more common plan is to reduce methane emissions. This is seen as the fastest way to tame global temperatures because the effects of the gas in the atmosphere only last a decade or so, so cutting emissions now would produce results within a decade. In comparison, carbon dioxide lasts for centuries.

As of 2019, methane has caused temperatures to rise by about 0.5 degrees Celsius compared to pre-industrial levels, according to Intergovernmental Panel on Climate Change figures.

While more than 100 countries have pledged to reduce methane emissions by 30% by the end of this decade, few have gone beyond establishing “action plans” and “pathways” to reduce emissions. China – the world’s largest emitter – has not yet published its plan.

Michael Diamond, an atmospheric scientist at Florida State University, said that by targeting methane, the world could mitigate the greenhouse effect of lower pollution and potentially avoid catastrophic consequences.

“This does not condemn us to exceeding 1.5 degrees Celsius if we clean the air.”

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