Earlier this week, California Governor Jerry Brown (D) signed an executive order setting a goal of reaching net zero carbon emissions by 2045, arguably the most significant climate target ever set. But in the days after Brown’s announcement, activists took to the street to say, “Not good enough.” Hundreds marched outside the Moscone Center in San Francisco Thursday, calling on Brown to put an end to fossil fuel extraction in California, while temporarily preventing delegates to the Global Climate Action Summit from entering the building.

The scene captured the tension between advocates and policymakers, namely that climate change is so big and unwieldy that even the most ambitious policies are often insufficient. Inside the convention center, mayors, governors and business leaders gathered to discuss their plans to fight climate change, and throughout the conference, advocates called on officials to do more.

“Governor Brown preaches the climate gospel on the global stage, but his policies have allowed fossil fuel companies to create a living hell for Californians whose health and safety are threatened by toxic drilling operations,” said Cesar G. Aguirre, an organizer with the Central California Environmental Justice Network. “Governor Brown has failed, but a new generation of leaders is rising up from the grassroots and they bring the courage that politicians like Brown sorely lack.”

Responding to a question about his critics at a press conference Thursday, Brown said, “For every position, there’s a counter-position. For every counter-position, there’s a counter-counter-position.” He added, “You don’t snap your fingers and say, ‘Now it’s done.’ It takes a process. It takes stakeholder involvement, and that’s the way it is.”

At the press conference, Brown and the governors of Washington, Hawaii and Connecticut announced new commitments from the United States Climate Alliance, a group of 16 states and Puerto Rico committed to meeting their share of the U.S. pledge under the Paris agreement. Governors said they plan to better manage farms, forests and ranches that soak up carbon from the atmosphere. They also plan to cut emissions of powerful but short-lived pollutants like methane, which leaks from farms and gas drilling sites, and hydrofluorocarbons, which are used in air conditioners and refrigerators. Governors further say they plan to invest in electric-vehicle charging stations and take steps to foster the growth of solar power, which has been slowed by President Trump’s tariffs on imported solar cells.

The Global Climate Action Summit produced similar announcements from state and local leaders from across the world. Mayors declared that in 27 cities — including London, Paris, New York, Los Angeles, Boston, Chicago and San Francisco— emissions have peaked and fallen even as economies have grown, while more than 70 cities globally have pledged to hit zero net carbon emissions by 2050. Meanwhile, leaders of 21 tech companies — including Cisco, Hewlett-Packard, Lyft and Uber — pledged to draw down emissions, as leading EV infrastructure firms set a goal of installing 3.5 million charging stations in the United States and Europe by 2025. Finally, on Friday, a group of philanthropists vowed to spend $4 billion over the next five years fighting climate change.

Together, politicians, donors and business leaders are trying to forge a path forward on climate change even as President Trump throws up roadblocks as fast as he can — rolling back fuel standards, weakening emissions limits on power plants, and moving to exit the Paris Agreement, thereby undermining international efforts to stem climate change. The various alliances of mayors, governors and CEOs were formed after Trump’s election, Washington Governor Jay Inslee (D) said, “to make sure that the rest of the world understood that there is intelligent life in the United States.”

Advocates know, however, that the combined efforts of these groups will likely fall short of U.S. commitments under the Paris Agreement. A new report from Yale finds the carbon-cutting pledges of states, cities and businesses will only get the United States halfway to its goal. And, even if the United States managed to fulfill its pledge under the Paris Agreement, it would still fall short of doing its part to keep warming under 2 degrees C, the stated goal of the accord.

Given these facts, advocates say they are left with little choice but to continue to push climate-conscious leaders like Brown, no matter how much he may accomplish. The White House is undoing climate policy as fast as it can, putting the burden of progress on state and local officials. So, while inside the San Francisco summit, politicians and policy wonks celebrated incremental progress, activists outside rallied for radical change.

Several of Brown’s colleagues defended him against charges that he has done too little. “Governor Brown’s leadership on this issue over the years is second to none,” said Connecticut Governor Dannel Malloy (R). “Quite frankly, I wish I could have done as much as Governor Brown has.” To Brown’s critics on the left, Dannel said, “You’ve had one hell of run.”

It’s easy to see why governors would come to Brown’s defense. Ambitious climate policy is difficult to pass, even in deep-blue states like Washington, where, earlier this year, Governor Inslee failed to enact a carbon tax despite the fact that Democrats controlled the state legislature. Brown succeeded in California only with overwhelming support in the statehouse and a healthy dollop of political savvy.

Though he has accomplished a great deal, activists believe that even the most ambitious leader cannot stop the rise in temperature through patience and compromise. Several were arrested rallying for immediate and drastic change.

In defending himself, Brown argued that it is possible to make progress from within the system. “We’re definitely moving in the same direction as the critics,” he said. “They would just like us to go a little faster. We would like to go a little faster ourselves.”

Jeremy Deaton writes for Nexus Media, a syndicated newswire covering climate, energy, policy, art and culture. You can follow him @deaton_jeremy.