Gov. Jerry Brown has been a leader on fighting climate change. But is he doing enough?

At the Paris Climate Summit in 2015, Gov. Jerry Brown was treated like a head of state and a climate leader. Heads turned throughout the press center as aides hustled the California governor to a row of makeshift studios where the world’s leading television networks waited. As the governor of what was then the world’s sixth-largest economy (now the fifth), Brown told French TV about organizing the Under2 Coalition: 123 national, state, and local governments, representing more than a quarter of the global economy, collaborating to keep the global temperature rise under 2 degrees Celsius. Days later, the international community adopted the Paris Agreement, which pledged to limit warming “well below” that mark.

This week, on Sept. 12-14, Brown will host a follow-up meeting intended to keep the world moving toward that under-2-degree future, notwithstanding the obstructions emanating from Washington. The California Global Climate Action Summit is expected to draw thousands of people to San Francisco. Government delegations from China, India, Germany, France, the European Union, Brazil – indeed, from virtually all of the world’s major greenhouse-gas emitters, except the U.S. – will be there, along with hundreds of mayors, governors, policy experts, business executives, climate activists, journalists and citizens.

“We need catalytic events that propel states and people forward to turn the earth away from the catastrophic course we’re pursuing,” Brown says. “This summit is a step, but it’s only a step.

“Is it enough? No. Are we on a path to avoid catastrophe? No. But I want to do the maximum I can do.”

Although Donald Trump’s shadow will inevitably hang over the proceedings, this summit was planned well before his election. The idea first emerged at the conclusion of the Paris summit. Paris summit chair Christiana Figueres wanted California as the host because its record of climate accomplishments was second to none among the world’s major economies. The state was well on its way to reducing emissions to 1990 levels, and in 2015 Brown had signed a law that would go further. SB 350 requires California to double its energy-efficiency savings by 2030, and to obtain 50 percent of its electricity from non-carbon sources.

Even so, Brown now finds himself under attack by climate activists who insist that he’s not doing enough. Organizers of a campaign called Brown’s Last Chance note that in seven years, he has issued permits for 20,000 new oil wells, and received over $9 million in political contributions from energy industry special interests.

The tragedy is that Brown and his critics may both be right. Even the states and countries moving the fastest aren’t moving fast enough to outrun the gathering tsunami of climate disruption.

And because the world delayed taking meaningful action for most of the past 30 years, largely because of resistance from Washington, emissions must now be cut at a pace and a scope that will likely require massive – and perhaps politically untenable – upheaval.

MARK HERTSGAARD is the The Nation’s environment correspondent and investigative editor.