China is worried about climate change, and is now the biggest global investor in green technology.
Over the past two decades China's blitz of industrialization has pulled millions of people out of poverty — and pumped millions of tons of carbon into the atmosphere. From 2008 to 2013 alone, annual energy consumption in China rose more than 50 percent.
Some 70 percent of that electricity was generated from the worst possible source: coal. China burns as much coal as the rest of the world combined, and it now emits twice as much total carbon as the U.S. (although Americans still lead the world in per capita emissions). You can see the results in the thick haze that blankets Beijing and just about every other city.
In fact, just a handful of China's 500 largest cities meet World Health Organization standards for air quality.
Air pollution kills more than half a million Chinese people every year. Runners in the Beijing International Marathon last year had to wear face masks against the smothering yellow haze, and smog alerts routinely force cities to ban driving and temporarily shut down factories.
Communist Party officials and business leaders aren't happy about the pollution, either. "Watching people wearing anti-toxin masks in the capital is pretty embarrassing," said Yun Gongmin, head of China Huadian, one of the largest state-owned energy companies. "Nobody wants to live in a polluting city for fear of getting diseases."
China's authorities are making a major push to curb emissions, both to ease the smog and alleviate the consequences of climate change. In Washington last month, Chinese President Xi Jinping announced that a national cap-and-trade program, the world's biggest, would begin in 2017. Chinese companies that emit more greenhouse gases than the allowed cap will be fined, while those that emit less can sell their credits.
China is also pouring money into renewable energy, investing $90 billion last year alone, more than any other country. It has ramped up its solar power at a staggering rate, building sprawling solar farms in the Gobi Desert.
China is already the world's largest producer of wind power, with thousands of turbines installed in the windy west and plans to more than double the number of turbines over the next five years. It's also the world's largest hydropower producer, home to half the world's 80,000 dams and building many more every year.
At a 2014 summit with President Obama, Xi pledged that China's emissions would peak by 2030 and then drop. Less than a year later, China is already ahead of that goal, with emissions now predicted to peak in 2025.
In the first few months of 2015, China's coal use fell almost 8 percent compared with last year's, a reduction equal to all the carbon dioxide emitted by the U.K.
Part of that drop came because of China's economic slowdown, but the country's new commitment to renewables means that even when the economy picks up, the extra power will come from greener sources.
China has moved so fast to expand the use of green energy that much of its new capacity is just that — capacity. Getting the energy produced hooked up to the power grid so it can be consumed will be a huge challenge. Many of the wind and solar farms, for example, are far from big cities, and authorities haven't yet worked out a way to store and transport all the energy they produce.