In Mexico, the conditions that have contributed to the largest sustained movement of humans across any border in the world will get only more common. This spring, at the start of the corn-growing season, 76 percent of Mexico was in drought, and the country was sweltering under a deadly heat dome. Finally, after too many months, summer rains started to refill reservoirs. But years and droughts like this promise to become more intense: Mexico is slated to warm 1 to 3 degrees Celsius by 2060.

When drought strikes rural corn farmers in Mexico during the growing season, they are more likely to attempt to immigrate to the United States the following year out of economic desperation, according to a study released this month in the journal PNAS. This is just the latest example of a signal in migration data that keeps getting clearer: Climate change is pushing people to cross borders, and especially the southern border of the United States. Many live on the edge of financial stability; if one of their few options to support themselves is jeopardized, they might not recover. “And climate extremes are taking away whatever option there is there,” one of the study’s co-authors, Filiz Garip, a professor of sociology and public affairs at Princeton University, told me.

Donald Trump and his incoming administration have said that limiting immigration into the United States is a priority; the president-elect intends to both close the southern border and deploy the military in order to carry out mass deportations. He is also poised to ignore the climate altogether, and likely hasten the pace of change with policies that increase oil and gas drilling. That combination is “sort of like turning the heat up on a boiling pot and then forcing the lid shut,” Ama Francis, a lawyer and the climate director of the International Refugee Assistance Project (IRAP), told me. Drought and other climate disasters will help propel more people north; U.S. immigration policies will attempt to block them, but migrants won’t stop coming. Part of the argument for dealing with climate change, and doing so in partnership with the rest of the world, is that it will mitigate these sorts of pressures before they become even more dramatic conflicts. The next administration could be setting the country up for the opposite.

Climate isn’t usually the only factor that drives people to move, but it can be a tipping point that clinches their decision. Like many places in the world, Mexico is becoming a harder place to live because of both drought and extreme rainfall, which leads to flooding. These are particular challenges for rural farmers whose crop depends on the seasons progressing as they have for hundreds of years. More may make the desperate choice to leave. And more who have left may stay for longer in the United States. Garip’s study found that climate extremes will delay migrants from returning to their communities. “I was really taken aback by how strong the return results were,” she said. “These weather extremes continue to shape, it seems, how people think about whether to remain a migrant or whether to go back to their communities.”

Climate factors are not what many immigrants first cite as a reason for leaving their home. Violence and racial or political persecution will often come up before drought, for example. But start talking through the deeper roots, and in many cases, “climate-related factors do come up,” Alexander de Sherbinin, an expert on climate and human migration at Columbia University, told me. Francis’s organization, IRAP, which gives migrants legal support, recently co-published a report based on interviews with more than 3,000 clients, nearly half of whom had experienced a climate disaster in their home country before leaving. The most common of these was extreme rainfall, followed closely by extreme heat.

Even when demographers control for other characteristics in a person’s life, climate change still emerges as a statistically significant factor of migration, says Lori Hunter, the director of the Institute of Behavioral Science at the University of Colorado at Boulder, who has studied migration data for decades. The pattern is clear, Hunter told me: “If we disinvest from the climate, the pressure to migrate will intensify.”

Conversely, a certain subset of the potential immigrant population, if their climate desperation could be alleviated, may not choose to come to the United States. In the long term, dramatically lowering the U.S.’s emissions would help limit climate stresses, but the warming the world has already experienced is driving weather extremes right now. Adapting to new climatic normals is now necessary. Migration is one way of adapting. But people could, with assistance, adapt in place. Among the corn farmers Garip and her colleagues studied, those who had access to some form of irrigation infrastructure, such as a reservoir, were less likely to leave, even when faced with drought conditions. It was mostly rural, smallholder farmers entirely dependent on rainfall who decided to make the perilous trek north. With investment for projects to install irrigation in those communities, “these decisions could really be different,” Garip said. “Unless we do something, then we’re just pushing more people into this dangerous journey.”

Indeed, the biggest topic at the global COP29 climate negotiations, under way in Baku, Azerbaijan, is the dollar amount that developed countries, responsible for the majority of historical emissions, will transfer to developing countries, which are bearing the brunt of the climate crisis and require at least $1 trillion of outside funding per year to build more renewable energy and respond to climate-driven disasters. Many at COP assume that the U.S. won’t contribute to those funds at all, and the meeting, now at its halfway point, is by all accounts at a deadlock, with little leadership from wealthy countries materializing. The Biden administration had plans to fund $3 billion worth of climate adaptation internationally each year, with a special focus on water security—and explicitly framed that as a tool to “address key drivers of migration.” Those plans are unlikely to continue into the next Trump presidency.

Climate finance is a nebulous category, and a lack of transparency about how the funds get spent can undermine the process. But other research has found that remittances—money that migrants send home—tend to be spent on things that improve climate resilience, such as air-conditioning. To Hunter, that remittance data suggest that international climate finance could be spent in ways that would help people adapt to climate change where they live, and remove one of the factors that force them to leave. If a motivated government made a real effort to supply that funding in the first place, perhaps those communities would not feel that they had to send a family member north. It wouldn’t stop migration altogether, but it could help reduce the pressures the incoming Trump administration is so eager to address.

Financing is one of the main sticking points at the COP29 conference in Azerbaijan.

Call for change comes after host country Azerbaijan's president calls oil and gas a 'gift of God'

French Ecology Minister Agnes Pannier-Runacher says she will not take part in the COP29 climate talks in Azerbaijan.

Top UN court confirms jurisdiction to hear the two countries' mutual discrimination claims over Nagorno-Karabakh.

Azerbaijan's president said countries should not be blamed for having fossil fuel reserves.

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The United Nations climate summit has kicked off in Azerbaijan.

Delegates gather in Azerbaijan for UN climate conference.

In what will probably be the warmest year in recorded history, in a month in which all but two U.S. states are in a drought, and on a day when yet another hurricane was forming in the Caribbean, Donald Trump, a climate denier with a thirst for oil drilling, won the American presidency for a second time. And today, delegates from around the world will begin this year’s global UN climate talks, in Baku, Azerbaijan. This UN Conference of Parties (COP) is meant to decide how much money wealthy, high-emitting nations should channel toward the poorer countries that didn’t cause the warming in the first place, but the Americans—representing the country that currently has the second-highest emissions and is by far the highest historical emitter—now can make no promises that anyone should believe they would keep.

“We know perfectly well [Trump] won’t give another penny to climate finance, and that will neutralize whatever is agreed,” Joanna Depledge, a fellow at the University of Cambridge and an expert on international climate negotiations, told me. Without about a trillion dollars a year in assistance, developing nations’ green transitions will not happen fast enough to prevent catastrophic global warming. But wealthy donor countries are more likely to contribute if others do, and if the U.S. isn’t paying in, other large emitters have cover to weaken their own climate-finance commitments.

In an ironic twist for a president-elect who likes to villainize China, Trump may be handing that nation a golden opportunity. China has, historically, worked to block ambitious climate deals, but whoever manages to sort out the question of global climate finance will be lauded as a hero. With the U.S. stepping out of a climate-leadership role, China has the chance—and a few good reasons—to step in and assume it.

The spotlight in Baku will now be on China as the world’s biggest emitter, whether the country likes it or not, Li Shuo, a director at the Asia Society Policy Institute, said in a press call. The Biden administration did manage to nudge China to be more ambitious in some of its climate goals, leading, for example, to a pledge to reduce methane emissions. But the Trump administration will likely shelve ongoing U.S.-China climate conversations and remove, for a second time, the U.S. from the Paris Agreement, which requires participants to commit to specific emissions-reduction goals. Last time around, Trump’s withdrawal made China look good by comparison, without the country necessarily needing to change course or account for its obvious problem areas, like its expanding coal industry. The same will likely happen again, Alex Wang, a law professor at UCLA and an expert on U.S.-China relations, told me.

China is, after all, the leading producer and installer of green energy, but green energy alone is not enough to avoid perilous levels of warming. China likes to emphasize that it’s categorized as a developing country at these gatherings, and has fought deals that would require it to limit emissions or fork over cash, and by extension, limit its growth. But with the U.S. poised to do nothing constructive, China’s position on climate looks rosy in comparison.

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By cutting off its contributions to international climate finance, the U.S. also will give China more room to expand its influence through “green soft power.” China has spent the past five years or so focused on the construction of green infrastructure in Africa, Latin America, and Southeast Asia, Wang said. Tong Zhao, senior fellow at the Carnegie Endowment for International Peace, told Reuters that China expects to be able to “expand its influence in emerging power vacuums” under a second Trump term. Under Biden, the U.S. was attempting to compete in the green-soft-power arena by setting up programs to help clean-energy transitions in Indonesia or Vietnam, Wang noted. “But now I suspect that those federal efforts will be eliminated.”

[Read: Why Xi wants Trump to win]

Most experts now view the global turn toward solar and other clean energy as self-propelled and inevitable. When Trump first entered office, solar panels and electric vehicles were not hot topics. “Eight years later, it is absolutely clear that China dominates in those areas,” Wang said. China used the first Trump administration to become the biggest clean-tech supplier in the world, by far. The Biden administration tried to catch up in climate tech, primarily through the Inflation Reduction Act, but even now, Shuo told me, Chinese leaders do not see the U.S. as a clean-tech competitor. “They have not seen the first U.S.-made EV or solar panel installed in Indonesia, right?” he said. “And of course, the U.S. lagging behind might be exacerbated by the Trump administration,” which has promised to repeal the IRA, leaving potentially $80 billion of would-be clean-tech business for other countries—but most prominently China—to scoop up. In all international climate arenas, the U.S. is poised to mostly hurt itself.  

[Read: How Trump's America will lose the climate race]

More practically, Baku could give China a chance to negotiate favorable trade deals with the EU, which has just started to impose new carbon-based border tariffs. But none of this guarantees that China will decide to take a decisive role in negotiating a strong climate-finance deal. Climate finance is what could keep the world from tipping into darker and wholly avoidable climate scenarios. But news of Trump’s election is likely to lend COP the air of a collective hangover. EU countries will surely assume a strong leadership posture in the talks, but they don’t have the fiscal or political might to fill the hole the U.S. will leave behind. Without surprise commitments from China and other historically begrudgingly cooperative countries, COP could simply fail to deliver a finance deal, or, more likely, turn out a miserably weak one.

The global climate community has been here before, though. The U.S. has a pattern of obstructing the climate negotiations. In 1992, the Rio Treaty was made entirely voluntary at the insistence of President George H. W. Bush. In 1997, the Clinton-Gore administration had no strategy to get the Kyoto Protocol ratified in the Senate; the U.S. has still never ratified it.

But although President George W. Bush’s administration declared Kyoto dead, it in fact laid the groundwork for the Paris Agreement. The Paris Agreement survived the first Trump term and will survive another, Tina Stege, the climate envoy for the Marshall Islands, told me. The last time Trump was elected, the EU, China, and Canada put out a joint negotiating platform to carry on climate discussions without the United States. That largely came to nothing, but the coalition will now have a second chance. And overemphasizing U.S. politics, Stege said, ignores that countries like hers are pressing on with diplomatic agreements that will determine their territories' survival.

Nor is the U.S. defined only by its federal government. Subnationally, a number of organizations cropped up in the U.S. during Trump’s first administration to mobilize governors, mayors, and CEOs to step in on climate diplomacy. These include the U.S. Climate Alliance (a bipartisan coalition of  24 governors) and America Is All In: a coalition of 5,000 mayors, college presidents, health-care executives, and faith leaders, co-chaired by Washington State Governor Jay Inslee and former EPA Administrator Gina McCarthy, among other climate heavy hitters. This time, they won’t be starting from scratch in convincing the rest of the world that at least parts of the U.S. are still committed to fighting climate change.