"More people in China thought that we should get rich first before even thinking of the environment. But now we are suffering," he says.

After decades of unbridled growth, the suffering is immense.

Rare blue-sky day

Nearly 60% of China's ground water is polluted, more than four thousand people die each year from toxic air, and soil pollution could cost more than a trillion dollars to fix.

I've come with Ma to the western outskirts of Beijing on a rare blue-sky day, heading towards the ring of mountains that skirt the capital.

"I remember when it was always like this," says Ma, who grew up here, "I saw those mountains almost every day as a child."

When I first arrived in China to live as CNN's Beijing correspondent in 2013, I didn't even know the mountains were there. It took at least a week before a stiff northerly wind cleared the haze to reveal the craggy range.

Ma points out the shuttered Shougang Steel Company, the white and red smoke stacks rising above the sprawling complex.

Shougang was a major victory for Chinese environmentalists.

The state owned company wanted to expand production to ten million tons a year, says Ma, but the acrid haze that hung over the city could be a major embarrassment for the then Olympic hosts.

So, at massive cost, the government closed it down.

Environmental crusader

Ma's work as a young journalist in the 1990s awakened him to the devastation of rampant growth.

Early on, he knew that transparency would be the key to action. With courts unlikely to press through regulations and powerful interests at play, he sought to name and shame the polluters.

But for years, the party tried to suppress pollution information and local officials, who were assessed on industrial output, frequently harassed environmental campaigners and clamped down on protests.

To be sure, environmental activists still face Communist Party wrath.

But it was hard to ignore the choking smog enveloping China's northeast.

After all, China's leaders -- when they are outside -- breathe the same air.

Clearing the haze

While I was posted in China, a notable shift became clear.

State media and Chinese citizens on social media, both heavily controlled by the state, have been given more room to expose polluters.

And Ma and his non-profit, the Institute for Public and Environmental Affairs, are already poised to take advantage.

For ten years, they have been developing a "Blue Map" app for Chinese citizens.

Ma reaches for his smart phone and swipes through the offenders. Across a map of China, they pop up as numbers in red: steel works; power plants; and state owned industrial giants.

In 2014, government agencies agreed to provide real-time emissions and pollution data of thousands of factories across China. The app allows the public to see, and report back, who the worst polluters are.

"Last year alone, we got seventy thousand records of violations," he says. "This is historical progress. Ten years ago, when we started, we knew we must get transparency."

Now a popular app, the Blue Map has millions of downloads and tens of thousands of active users, using geo-tagged photos to give evidence on suspected polluters.

It is like a virtual wall of shame, with the information fed directly to regulators.

"This demonstrates some real political will from the government to fight against pollution. Because they know if they disclose information to the public, they empower the public," says Ma.

The data is just one way in which the government is starting to act.

Cashing in on climate change

While President Trump vows to implement an "America First" policy focusing on "untapped shale, oil, and natural gas reserves" and "clean coal", China is aggressively pushing clean energy.

Recently, China announced a $360 billion investment in clean energy by 2020. The National Energy Administration says it will create jobs and curb greenhouse gas emissions.

Clean energy executives here are heartened by Trump's rise.

"It is an opportunity," says Cao Zhigang, of Xinjiang Goldwind, one of China's biggest wind turbine companies.

He says clean energy isn't just good policy -- it's good business.

Cao estimates that over the next five years the cost of wind energy will decrease enough to make it cost competitive with fossil fuels.

China is far outstripping the US in ramping up its wind power capacity, aiming to hit 200 GW by 2020, leading to some question whether it is too much too soon.

But in Hebei province, the coal powered heartland of the north, the wind turbines rising over the plum fields show where China's future lies.

Taking the lead

As the world's biggest polluter, China has a unique role to play in curbing rising temperatures. And China may also be forced to take the lead in combating climate change.

Most observers believe that Trump will turn his back on at least some of those commitments.

A key climate changer negotiator for China told me that it could push China, unwillingly, even further into a leadership position.

"The United States transition is bad news for efforts to combat climate change and it could have a negative impact," said Chai Qimin.

"China will have to take the lead, especially for developing economies," he added.

The irony isn't lost on Ma, who has made it his life's work to clean up China's environmental mess.

"Now should be a time for all of us to come together to be the guardian of mother earth, it is not the time to weaken environmental protection," he says.