In 1995, French President Jacques Chirac, observing the presidency of Bill Clinton and his administration’s tepid response to the unfolding atrocities in the former Yugoslavia, observed, with barely concealed disgust, that “the position of leader of the free world is now vacant.”

The same thing could be said today of the presidency of Donald J. Trump. But in an unusual, and in some ways unprecedented development, a 79-year-old four-term governor and three-time presidential aspirant has swept into the void left by the inept, incompetent, and embarrassing Trump.

The governor, of course, is California’s Jerry Brown, who is about to wrap up a 10-day trip to Europe, where he made stops at the Vatican, Brussels, Stuttgart, Oslo, and Bonn, in an effort to show the international community that, despite Trump’s decision to withdraw from the Paris climate agreement, the leader of the world’s sixth-largest economy remains committed to the fight against climate change.

At a meeting of climate-change experts and religious leaders at the Pontifical Academy of Sciences on November 4, Brown explained that American state and municipal leaders have it in their power to take action. There is “not just a top-down structure that we have in the United States, there are many elements,” and, given the commitments that “we’re seeing around the world, the Trump factor is very small.”

A week later, at the United Nations Climate Change Conference in Bonn, Brown urged state and local leaders to take the initiative. “We can’t,” said Brown, “just wait for our national leaders—we need to take action together.”

Brown, who was appointed the UN conference’s special adviser for states and regions, reaffirmed the commitment of a number of American cities and states to the Paris agreement, and noted that those US businesses, states, and municipalities who remain committed to Paris represent “a bigger economy than any nation outside the US and China.”

While in Bonn, Brown also welcomed outgoing Virginia Governor Terry McAuliffe as the newest signatory to the Under2Coalition pledge. The coalition was formed in 2015 by a dozen states and provinces from across the globe, including Washington, California, Vermont and Oregon; Baden-Württemberg, Germany; Catalonia, Spain; and Ontario, Canada.

Parties to the Under2MOU (Memorandum of Understanding) pledge to pursue “emission reductions consistent with a trajectory of 80 to 95 percent below 1990 levels by 2050 and/or achieving a per capita annual emission goal of less than 2 metric tons by 2050.”

In a sense, Trump’s reckless disregard for the Paris agreement acted as a spur to action. In an interview with the author Dave Eggers this past July, Brown observed that because Trump has taken “such an outlandish position” on climate change, he has perhaps inadvertently “heightened the focus” on it. “He’s given climate denial such a bad name,” said Brown, “that he’s given the climate-action movement a thrust that it would never have generated on its own.”

Brown is under no illusions that the road ahead will be an easy one. In a talk to the German Marshall Fund in Brussels on November 9, Brown warned that with climate change “there’s a lot of easy talk,” but “unless all the major players are in, we’re not going to get there—you need India, you need China, you need Russia—everybody has to be all in.”

The problem, said Brown, is that “nobody is in charge.”

California Attorney General Xavier Becerra recently told Time magazine that these days, Brown is “a man on fire.” It is a description that is hard to dispute. From the moment Donald Trump announced his decision to unilaterally withdraw from the Paris climate accord on June 1, Brown has been in overdrive, traveling to China in June and Russia in September before taking off on this latest trip to Europe.

Perhaps in his efforts to counter, or at least partially negate, the reckless and shortsighted policies emanating out of Trump’s Washington, Brown might serve as a much-needed example to members of the so-called #resistance movement, which would be wise to spend more of its time formulating alternative solutions to pressing economic and foreign-policy challenges.

Indeed, the aforementioned Time magazine report noted that Brown does not like to use the word “resistance.” Instead, says Brown, “I’d like to reframe it as action.”

And Brown has hardly limited his own “actions” to climate change; he has also turned his attention to that other potential cause of global catastrophe: nuclear weapons.

Brown recently told a reporter at the Los Angeles Times that the ongoing threat of nuclear annihilation that we continue to live under, despite the end of the first cold war over 25 years ago, isn’t on most people’s radar because, as he puts it, “the end of the world is not news.”

But in March Brown traveled to Washington where he met with—and joined the board of—the Nuclear Threat Initiative, an advocacy group made up of distinguished nuclear scientists and foreign-policy experts that includes former US Senators Richard Lugar and Sam Nunn, former energy secretary Ernest Moniz, and former defense secretary William Perry.

For some, Trump’s reckless disregard for diplomacy and his childish saber rattling toward North Korean dictator Kim Jong-un has had the effect of bringing the risk of a nuclear war back home. As Brown put it, “You send a nuclear missile to L.A., it’s going to be a bad day for everybody. So you can’t wait for that. You’ve got to start talking.”

In a review of former defense secretary William Perry’s book, My Journey at the Nuclear Brink, Brown sounds the alarm over the risk of waging a second cold war with Russia, writing:

“Sleepwalking” is the term historians now use for the stupidities that got European leaders into World War I and for the mess they unleashed at Versailles. And sleepwalking still continues as NATO and Russia trade epithets and build their armies and Moscow and Washington modernize their nuclear overkill. A new cold war.

Brown’s cautious and historically informed worldview is, sorry to say, at odds with what passes for foreign-policy “analysis,” especially as it pertains to Russia, in the Democratic Party of 2017.

With a year left in office, reporters and pundits are already peppering Brown with questions about his legacy (a word he clearly doesn’t care for) and whether he intends to try for what would be a fourth run at the White House in 2020. But these seem to be questions with which Brown is loathe to indulge.

For now, anyway, Brown seems intent on filling the gaping void in American leadership left by the current, and most unfortunate, occupant in the White House.