|August 25, 2016|
How air pollution is causing the world's 'Third Pole' to melt
|In discussions about melting glaciers, most people think immediately of the vast ice sheets in Greenland and Antarctica. But there's another, less talked-about ice-filled region on Earth that's also experiencing dramatic melt, with millions of humans' livelihoods and water supply at stake. |
The snow-covered Himalaya-Hindu Kush mountains and the Tibetan Plateau, spanning a broad area in Central and East Asia, together contain the largest ice mass on the planet outside of the polar regions. In fact, it's earned itself the nickname of the "Third Pole." But as in Greenland and Antarctica, there's trouble afoot: Glaciers in the Third Pole are also shrinking.
According to remote sensing data collected and analyzed by the Chinese Academy of Sciences, about 18 percent of China's glaciers alone have disappeared over the past 50 years. And that's a big problem because meltwater from these glaciers feeds a network of rivers that supply water, directly or indirectly, to more than a billion people downstream.
Rising temperatures, the product of global warming, are certainly one threat facing the glaciers, said Shichang Kang, a professor at the Chinese Academy of Sciences' Institute of Tibetan Plateau Research. But air pollution in the region is also helping to accelerate the melting. And now, Kang and a group of colleagues have helped shed some new light on where all this pollution is coming from and how it could be stopped.
In a new study, published Tuesday in the journal Nature Communications, the researchers collected samples of black carbon --- a particulate matter created through the burning of fossil fuels and biomass --- throughout the Third Pole and analyzed them using a special chemical "fingerprinting" process that identifies what kind of burning produced them and where they originated.
Black carbon might be most famous for the range of adverse health effects it's believed to cause, including respiratory and cardiovascular problems and even premature death. But in terms of its effects on glaciers, it's known to cause snow and ice melt in a number of different ways. First, black carbon floating in the atmosphere is able to absorb sunlight and cause at least temporary regional warming as a result, Kang noted. Additionally, when black carbon deposits itself on snow and ice masses, it tends to darken their surfaces, causing them to absorb more sunlight and melt faster.
Until now, scientists have had trouble pinpointing which places are contributing pollution to which regions of the Himalayas and the Tibetan Plateau and which types of sources are causing the most damage. That's important information, not only for constructing accurate ice models to predict how the glaciers might change in the future, but also for writing new policies aimed at cutting pollution in the places that need it most.
In their new study, the researchers found evidence that both the burning of fossil fuels and the burning of biomass --- materials such as plant matter and animal dung --- have contributed to the black carbon that ended up in the Third Pole. In the Himalayas, it was split about evenly between the two sources, with most of it coming from the Indo-Gangetic Plain in northern India, while in the northern part of the Tibetan Plateau, most of the black carbon came from fossil fuel burning in China.
But in the inner, central part of the plateau, about two thirds of the sampled black carbon came from biomass burning rather than fossil fuels --- a finding that Kang noted is "very surprising." This suggests that internal Tibetan fuel-burning practices, such as burning yak dung for daily cooking and heating, are contributing more pollutants to certain parts of the Third Pole than experts previously suspected.
This is valuable data that can better inform the models used to simulate ice melt in the Third Pole and make predictions about what the region's future might look like. But according to Kang, "the most important thing is that we can provide mitigation [advice] to policymakers."
Because most biomass burning on the Tibetan Plateau is used for home energy, including cooking and heating, government investments in improving the efficiency of stoves and expanding the availability of cleaner energy sources to households in the region could make a big difference, Kang noted.
This advice isn't meant to overshadow efforts to reduce fossil fuel burning, which also has big implications for the fight against global climate change. And wider efforts to address the burning of fossil fuels in Central and East Asia are already under way in some places. In China, for instance, coal-burning still remains the country's dominant power source --- but reports suggest that coal consumption hasn't grown since 2013 and may have even declined in the last year, while the government has also placed a moratorium on new coal mine approvals for at least the next three years.
The study's results may have helped reveal some new ways governments can add to or prioritize their current efforts to cut down on black carbon production. In the meantime, careful monitoring of the Third Pole's glaciers will be critical, Kang said, especially when it comes to keeping an eye on the region's water resources and making projections for the future.
"In the future, we're definitely going to see glaciers shrink, but different regions with different climate regimes have different responses," Kang said. "This is what we want to try to figure out."