The CEO of one of the world's largest online business software companies is urging fellow technology leaders to help fight climate change.
California is the second U.S. state after Hawaii to commit to carbon-free energy.
But that is not the end of the road for the Global Climate Action Summit, the idea is to keep up the momentum.
Global warming, meanwhile, continues to gather pace: major storms bearing down on the United States eastern seaboard and the Philippines, and wildfires ravaging California, bear the unmistakable fingerprint of climate change, scientists say.
The criticism of Brown is not new and reached a crescendo in 2017 as he negotiated with some of California's largest oil producers during efforts to extend the state's cap-and-trade climate program.
"The fact that China sent a very high-level delegation to California, that was huge", said Angel Hsu, an expert on China's environmental policy at Yale. It serves to advance California's Renewable Portfolio Standard, a piece of legislation that mandates the state be powered by 50 percent renewables by 2025 and 60 percent by 2030.
Top UN officials welcomed the outcomes of the Global Climate Action Summit that concluded here on Friday, showcasing a surge of climate action and commitments from regions, cities, businesses, investors and civil society; and calling on governments everywhere to step up their efforts to tackle climate change.
In some areas, the impact of climate change is more noticeable than others and therefore it's a problem trying to convince some people to act now, she said.
In 2015, 196 countries around the globe came together under the Paris Agreement to transform their development trajectories so that they set the world on a course toward sustainable development, aiming at limiting warming to 1.5 to 2 degrees Celsius above pre-industrial levels.
"The US federal government can drive action all around the entire country, not just state-by-state", Stern said.
Nuttall, however, argues that this more than just about U.S. businesses and local and state governments stepping in and reiterating their commitment to achieving the Paris Agreement goals and climate plans and targets pledged by the Obama administration under the climate deal.
New York City Mayor Bill de Blasio followed up an earlier commitment to divest the New York pension fund from fossil fuels with a new commitment to double the fund's investments in climate change solutions to $4 billion within three years, a GCAS press release reported. Brown compared the task ahead to climbing Everest a couple of times during the summit. "We're going to collect that data".
"You don't snap your fingers and say now it's done", Brown said.
At a signing ceremony in the state capital Sacramento, Mr Brown vowed to meet the terms of the Paris agreement and to "continue down that path to transition our economy to zero carbon emissions".