China and India’s “crazy bad” smog has been masking global warming

Reducing some kinds of air pollution could actually speed up global warming.
Reducing some kinds of air pollution could actually speed up global warming.
Image: AP Photo/Andy Wong
We may earn a commission from links on this page.

World leaders are busily trying to avert future environmental catastrophe at the climate summit in Paris this week. But while they discuss what the atmosphere should look like decades from now, people in New Delhi and Beijing are struggling just to breathe the air of today.

Both Delhi and Beijing are choked with heavy smog that exposes their combined 40 million residents to dangerously high concentrations of fine particles that can penetrate deep into human lungs. The toxic soup was so thick on Dec. 7 that authorities took the unprecedented step of issuing a “red alert” for Beijing, shutting down schools and construction sites to curb exposure to particulate levels over 10 times the World Health Organization’s recommended threshold. Delhi’s levels have been spiking just as high, leading authorities there to propose limiting the use of personal cars to alternate days.

These are just the latest stopgap measures being used to address a global air pollution emergency that cuts short the lives of over 7 million people every year. But solving this mounting crisis poses a puzzle for policymakers. That’s because cleaning up certain kinds of air pollution could actually hasten global warming.

To understand the problem, it’s important to first understand that smog comes in a variety of shades.

The sooty winter air in Beijing is infamously dark—so dark it blots out the sky and obscures buildings at a distance of a few dozen yards. That smoke actually contains a mix of lighter-colored particles, like sulfur dioxide, and darker ones, like black carbon.

Both are products of inefficient combustion. But they have very different effects on the climate.

Sulfur dioxide and other light-colored aerosols reflect incoming sunlight back into space, effectively cooling Earth’s atmosphere. Black carbon, on the other hand, is a powerful warming agent, hundreds of times more efficient at turning sunlight into heat than the same amount of carbon dioxide.

Scientists warn that emissions of sulfur dioxide and other light-colored particles have been “masking” the warming caused by carbon dioxide and other greenhouse gases to date. In fact, a study from 2008 estimated that 2.4° C (4.3° F) of warming is already locked into the climate system. We just haven’t felt it yet, thanks to all the light-reflecting pollution we’ve been churning out.

As developing economies reduce sulfur emissions from coal burning, concentrations of light-colored particles in the atmosphere will decline. This means that proportionately more light will reach the Earth’s surface and get trapped as heat—resulting in a burst of accelerated warming, like a coiled spring being released. A study published last month predicts that the expected reduction in sulfur dioxide and other light-reflecting pollutants will be responsible for up to 40% of expected Arctic sea-ice melt by the end of this century.

The upshot: As we stop producing so much of these light-colored aerosols, our day of reckoning will arrive, and in a hurry.

Now, no one is suggesting China slow down its recent efforts to reduce its “crazy bad” pollution. After all, it makes no difference to human lungs whether particles are light or dark.

But there is a way out of this weird trap we’ve set for ourselves. By prioritizing the reduction of smoke richest in black carbon, we can offset some of the anticipated “unmasked” warming–and save millions of lives in the process.

Since black carbon has a short lifespan in the atmosphere, settling out after a week on average, cutting its emissions would immediately slow down the rate of warming. The benefits would be greatest in vulnerable regions like the Arctic and the Himalayas, where black carbon accelerates melting by reducing the light reflected off snow and ice.

By quickly enacting measures to reduce black carbon emissions, we can avoid 0.25° C (0.45° F) of anticipated warming in the Arctic by 2050. To achieve that goal, I have a proposal that takes Bill Gates’ newly launched $2 billion clean energy fund as inspiration.

Gates and some of his fellow billionaires launched the fund with the goal of developing new “moonshot” technologies to put the world on a zero-carbon path. It may very well pay off. But while we wait to find out, I propose that nations gather together to launch a different kind of project: a particle-removal accelerator devoted to the rapid removal of black carbon from the skies above India, China, and other developing nations.

This international donor facility would target the types of smoke heavy in black carbon, including diesel exhaust (a carcinogen), fumes from kerosene lamps used for lighting many parts of Africa and South Asia, and the thick pall produced by the inefficient dung, wood and coal fires that nearly 3 billion people depend on for cooking and heating.

The accelerator would deploy proven, effective technologies. Truck and bus fleets could be outfitted with filters that trap harmful diesel particles—or better yet, the vehicles could be replaced with electric hybrids. Solar-powered LED lights could be substituted for kerosene lamps. Gas, electric, biogas, and clean biomass cooking stoves would replace the open fires and traditional stoves used by 40% of the world’s population.

A host of creative entrepreneurs are already delivering some of these cost-effective solutions at a small scale. They are starved for low-cost finance and institutional support to reach the scale that could truly transform public health, and make a serious dent in the near-term warming of our planet.

Let’s hope the talks in the City of Light generate enough momentum to give us a shot at maintaining a livable climate. In the long run, carbon dioxide is our primary threat, and we can’t afford to take our collective eye off that ball for a moment.

But let’s not look past the immediate problem of black carbon, and the plight of the many millions struggling right now to breathe under dark skies.