Earlier this month, venture capital firm Kleiner Perkins began the process of separating its cleantech investing from the rest of its fund. It marks the end of an era. Ten years after Kleiner star John Doerr was moved to tears during his TED talk about climate change, there’s no longer any question that VCs’ interest in clean energy is waning. U.S. VC investment in cleantech “has declined sharply since 2011” according to a new analysis by the Brookings Institution. That trend is more than five years old, but it’s particularly notable given two other developments. First, another recent Brookings analysis found that U.S. cleantech innovation declined from 2014 to 2016, as measured by patents. Second, Ernst & Young, which for years ranked the U.S. as the most attractive market worldwide for renewable energy investment, this year downgraded it to third, behind China and India. America appears to be pulling back on cleantech innovation when it can least afford to do so.

Earlier this month, venture capital firm Kleiner Perkins began the process of separating its cleantech investing from the rest of its fund. It marks the end of an era. Ten years after Kleiner star John Doerr was moved to tears during his TED talk about climate change, there’s no longer any question that VCs’ interest in clean energy is waning.

U.S. VC investment in cleantech “has declined sharply since 2011” according to a new analysis by the Brookings Institution. That trend is more than five years old, but it’s particularly notable given two other developments. First, another recent Brookings analysis found that U.S. cleantech innovation declined from 2014 to 2016, as measured by patents. Second, Ernst & Young, which for years ranked the U.S. as the most attractive market worldwide for renewable energy investment, this year downgraded it to third, behind China and India.

America appears to be pulling back on cleantech innovation when it can least afford to do so.

I have a personal interest in this story, because I worked for a cleantech innovation and advocacy group several years ago. And though the idea of VCs abandoning cleantech has been around since at least early 2012, I was initially skeptical. VC funding for cleantech went down during the recession, but as a share of total VC funding it held steady at 15-17% from 2008 to 2011. Plus, I argued, other clean energy industry measures like clean energy M&A, job growth, and deployment were trending in the right direction.

Today, I am less optimistic. (Admittedly, I’m also far more removed.)

Brookings reports that cleantech VC funding has declined not just in terms of deals and dollars, but as a share of overall VC activity. In 2011, cleantech represented nearly 17% of total U.S. VC investment; in 2016 it was under 8%. “Clearly all of this reflects some sober reevaluation of the VC role in cleantech finance,” said Mark Muro, a senior fellow at Brookings, adding that “We’ve maybe asked too much of VC.”

The report goes on to say that corporations and corporate VCs are “filling in some of the gap.” But their participation in cleantech deals also peaked in 2011, and as the authors note, “These companies, with legacy businesses to protect and sustain, are unlikely to expand their involvement and pick up more of the slack in funding disruptive clean technologies.”

The Brookings report’s most peculiar finding is that VC investment in cleantech has shifted toward later-stage deals. Optimistically, maybe VCs are finding their niche – they’re realizing that certain kinds of investments don’t fit their model, especially capital-intensive, early-stage projects with unproven technology. Pessimistically, VCs are shepherding earlier investments along, but not funding as many new startups.

The bottom line, the authors write, is that:

“VC money has not been reaching many promising technologies, especially the riskiest ones, often with the heaviest financial demands, that are urgently required to address climate change.”

Perhaps that’s because VCs got distracted by the siren song of social media companies, especially after Facebook’s incredibly successful 2012 IPO. Perhaps it’s because the U.S. never put a price on carbon. Perhaps it’s because the shale boom hurt the outlook for clean energy.

Whatever the reason, it wouldn’t be of much concern to anyone outside the industry if the U.S. were otherwise doing a good job of transitioning to clean energy. But the bigger problem is in Washington. The federal government is often better positioned to fund risky early-stage technology than private companies because those companies don’t typically capture the full benefits of those investments. And the government can incentivize businesses and investors through policy, for instance by putting a price on carbon dioxide emissions to encourage clean energy investment. Yet the Brookings cleantech patenting report concludes that the U.S. government is decreasing rather than increasing its commitment to energy innovation:

At just the moment when the U.S. clean energy innovation enterprise may be hitting a flat spot, the Trump administration has proposed draconian federal budget cuts that raise new concerns about the future of the nation’s commitment to low-carbon economic development.

The current administration is also considering withdrawing from the Paris climate agreement which makes the likelihood of future international commitments to energy innovation less likely. And it has proposed steep cuts to the federal government’s energy innovation programs. Ernst & Young cites Trump’s executive order rolling back Obama’s climate regulations as one of the major developments behind the U.S.’s drop in its rankings.

“There are some things we’ve asked of VC that are properly and necessarily government activities,” said Muro. “We’ve asked VC to fund quasi-R&D activities.” For example, Muro says he opposes eliminating funding for ARPA-E, a Department of Energy program that funds energy research and commercialization, as President Trump’s budget proposed to do.

If there is a bright spot, Muro believes it’s a new breed of philanthropic and quasi-philanthropic funding sources, like Bill Gates’ Breakthrough Energy Ventures or PRIME. These efforts take different forms and have different expectations of return. What they share is a willingness to fund risky technology, and the patience that requires.

“I think we all should be hesitant about farming out huge parts of the innovation system to networks of high worth individuals,” said Muro, speaking of Gates’ initiative. “But in this case, it’s sufficient dollars and it seems like sufficient commitment that it may be part of the bridge to funding the system.”

It would be nice if VCs and the rest of the private sector would live up to their cleantech enthusiasm from a decade ago, but in retrospect Doerr’s TED talk was a high-water mark of the post-Inconvenient Truth period. “Some of this gets to this deep question that Silicon Valley is asking itself,” said Muro. “Are 140 characters enough return on all of this capital? Or is there a true appetite for solving the world’s problems?”