"I'm not here to debate what's not debatable," Ernest Moniz declared early in his tenure as President Obama's secretary of energy. "The threat from climate change is real and urgent."

That was then. Now we have a president who famously described climate change as a hoax advanced by the Chinese to undermine the US economy. Also an energy secretary, Rick Perry, who wrote a book in which he referred to climate-change science as a "contrived phony mess." And an Environmental Protection Agency chief, Scott Pruitt, who told CNBC just the other day, "no, I would not agree that [human activity] is a primary contributor to the global warming that we see."

To be fair, it's still not clear exactly where the Trump administration will land. Secretary Perry, for instance, who presided over the greatest expansion of wind capacity in the country during his 14 years as governor of Texas, acknowledged in his confirmation hearing that climate change is real, and that "man-made activity" is at least partly to blame.

That said, the federal government today, with all its power to regulate, fund research, devise tax policies, and otherwise set the tone for business, has staked out a position on climate change that's nowhere near the territory occupied by the Obama Administration. What does that mean for companies operating in the rapidly emerging multi-trillion-dollar market for clean energy technology?

Kevin Knobloch, just back from three-plus years in Washington as former Secretary Moniz's chief of staff, made the following points when he spoke recently to an audience of energy company owners and operators outside Boston.

It's not easy to change the rules: "By the time we left," Knobloch said, "we had strengthened and finalized some 50 energy-efficiency rules over two Obama terms reaching into every corner of the economy." President Trump can't just sign all that away. It's a complex process, involving a lengthy period for public comment, and often generating legal challenges. The only exceptions would be certain regulations enacted in the waning days of the Obama administration that are subject to expedited reversal under the Congressional Review Act. It's an arcane legislative procedure that before this year had been deployed but once, under President George W. Bush in 2001, to overturn a Clinton-era regulation designed to combat repetitive stress injury. So far the current Congress has invoked the act to reverse three Obama-era regulations, with four more pending. Any regulations finalized as late as June 2016 are potentially at risk.

Green jobs, red states: Solar employment grew 25% nationally in 2016, according to the DOE, to just under 374,000 jobs, and wind grew 32%, to 102,000 jobs. That's still a fraction of the total energy workforce of 6.4 million, but it's where most of the action is these days. In fact the fastest growing occupation in America is wind turbine service technician. What's key, a disproportionate percentage of green-energy job growth is occurring in politically conservative parts of the country. (One example: Of the four states with the most wind power, three--Texas, Iowa, and Oklahoma, which together are responsible for 40% of US wind capacity--voted for Trump in 2016.)

Two of the most important pieces of federal legislation supporting wind and solar are the Production Tax Credit and the Investment Tax Credit, both of which were extended for five years in 2016, with bipartisan support. "[Iowa Republican Senator] Chuck Grassley isn't going to sit aside idly when somebody goes after the PTC and ITC," Knobloch said.

194 markets: President Trump has said that he wants to pull out of the Paris climate accord. That's easier said than done, given the way the agreement is structured. But even in a worst case scenario, the U.S. is only one of 194 signatories, all of which have committed to significant CO2 reductions by 2025. "Those in my view are 194 markets for renewable energy developers," Knobloch said, adding, "it's going to take a very significant growth in renewable energy over the next decade plus" to meet those goals. Knobloch's bottom line for those on the front lines of the green energy revolution? Don't despair.

And don't let up: "I think the renewable energy sector is very key in these coming weeks and months," he said. "Very key. In maintaining and building on the bullishness we all feel and that we've seen in this market."