The scientist who uncovered acid rain in North America 50 years ago now sees a parallel struggle waging around climate change and the effects of global warming.

“The pushback was just like it is now,” ecologist Gene Likens said on Tuesday, talking about how his research in the White Mountains was received when it went public in the mid-1970s. Big vested business interests and their allies rejected his findings, he said, until he and his teams could show scientifically where the pollutants causing acid rain were coming from—industrial polluters in the Midwest.

From initial discovery to the enactment of new rules limiting those polluters took nearly a generation. Or, as Likens likes to put it, “27 years, three presidents and one pope.”

Now, he said, he’s watching something similar happen with climate change.

Likens research and his legacy are intimately tied to the White Mountains. It began in 1963 when Likens was a professor at Dartmouth College. He was the lead scientist of a team studying streamwater chemistry in the Hubbard Brook Experimental Forest outside Lincoln, the U.S. Forest Service’s forest-laboratory of the White Mountains. His team wanted to know how the forest worked, to understand the inputs and outputs, what made it tick. They weren’t looking for anything specific, Likens said, but what they they found surprised them: water infused with sulfur dioxide and nitrogen oxides, a concoction capable of leaching aluminum from the soil and depositing it downstream in lakes and rivers, and also capable of killing insects, fish and plants along the way.

What they found was acid rain.

“The very first sample of rain we collected was very acidic,” said Likens, with acidity levels 100 times above normal. “Nobody knew there was a problem,” he said. “It was pure serendipity. So much of science is that way. We didn’t set out to discover acid rain. It was there and we ran with it.”

Their research led to an article in the journal Environment in 1972. Two years later Likens, now a professor at Cornell University, replicated the experiment in the Finger Lakes region of central New York, where again they found sulfur dioxides and nitrogen oxides in the water. He and a colleague published again published their findings, this time in the journal Science.

That’s when their research got noticed.

“It was picked up by the New York Times,” Likens said. “It ran on the front page.”

The year was 1974. Acid rain for the first time was in national headlines. It would be another 16 years before Congress passed revisions to the Clean Air Act to curb the industrial pollution that was the cause.

From acid rain’s discovery in 1963 to Congressional action in 1990, all of it started in the White Mountains, in the Hubbard Brook Experimental Forest, which Likens calls one of the most studied ecosystems on the planet.

“We are much more effective stewards when we have long-term monitoring to guide us,” Likens said, “but the reality is such studies are quite rare.”

Likens research has included collecting decades of stream water chemistry data and associated rainfall information, creating one of the longest such records for any site on Earth. “And I’m still doing it,” he said.

And scientists in other disciplines have been doing similar work, leaving long records that allow researchers to see trends over time.

“So with climate change we can say what happened,” Likens said, “and what is happening.”

Birds in the forest, for example, are arriving earlier. Buds sprout earlier. Mirror Lake, “probably one of the most studied lakes in the world,” he said, is now covered by ice 20 days less each winter than in years past. The planet is definitely warming.

But when it comes to climate change some people push back against the science. And they doubt human involvement. Likens said he seen this before, that it was the same debate over causation that raged with acid rain.

But as a researcher, Likens said, his job is not to get lost in those arguments. A researcher’s job is to continue working, he said, to explore and examine, to collect data and ensure a record exists of what happens in the world.

“I’m not an advocate,” Likens said. “I’m not a politician. I’m a scientist.”

A version of this story ran in Saturday’s Conway Daily Sun.