Even as much of the United States shivered under frigid conditions last month, the planet as a whole had its warmest January on record, scientists said on Thursday.

The warmth came as something of a surprise to climate researchers. It occurred during La Niña conditions in the Pacific Ocean, which tend to lower the globe’s average temperature, at least temporarily.

Earth’s surface has now been so warm for so much of the past two years that scientists are examining whether something else in the planet’s chemistry might have changed, something that is boosting temperatures beyond what carbon emissions alone can explain.

Those emissions, the byproduct of burning coal, gas and oil, remain the main driver of global warming, which reached record levels in both 2023 and 2024.

It’s because of La Niña that scientists expected this year to be slightly cooler than the past two years, both of which experienced the opposite pattern, El Niño. The waters of the eastern tropical Pacific oscillate between El Niño and La Niña conditions, influencing weather worldwide by changing the balance between heat in the ocean and heat in the air.

But a host of other factors figure into global temperatures as well. At the moment, chances aren’t high that 2025 will end up being the hottest year on the books, Russell Vose, a climate scientist at the National Oceanic and Atmospheric Administration, told reporters recently. But this time last year, researchers were saying much the same thing about 2024, Dr. Vose said. They were wrong.

“So it’s a tough game, forecasting global temperature,” Dr. Vose said.

According to Copernicus, the European Union climate monitoring agency, last month was much balmier than usual in northern Canada, Alaska and Siberia, as well as parts of Australia and Antarctica. Abnormally high temperatures above the Hudson Bay and the Labrador Sea helped shrink Arctic sea ice to a record low for January, Copernicus said.

As scientists try to explain the unending streak of worldwide warmth, one thing they’ve focused on is reductions in air pollution.

In a report this week, James Hansen, the famed former NASA scientist, argued that cutting pollution had already played a big role in causing global warming to accelerate. The reason is a little counterintuitive: For decades, humans have not only been emitting carbon dioxide and other greenhouse gases when they burn fossil fuels. They’ve also been spewing tiny sulfate particles into the air.

These particles spur the formation of more and brighter clouds, which help shield Earth from the sun. But as regulators have curbed sulfate pollution to protect people’s lungs, this cooling effect has diminished, exposing the planet to more of the full force of greenhouse warming.

Three decades ago, Dr. Hansen was among the first scientists to draw broad attention to climate change. Speaking to reporters this week, he argued that the United Nations was ill-prepared to address accelerated warming.

The U.N.’s approach to meeting its climate goals still counts on societies to slash their carbon emissions in the coming decades, he said. Those goals now look “impossible” to achieve, Dr. Hansen said, “unless some miracle occurs that we don’t understand.”

President Trump’s brazen proposal to move all Palestinians out of Gaza and make it a U.S. territory sent shock waves around the world, where it was welcomed by Trump loyalists and members of Israel’s far right; rejected by American allies and adversaries alike; and criticized by experts as a breach of international law.

Here’s what we know about Mr. Trump’s idea for mass resettlement, and the significant obstacles it will face.

The proposal

Mr. Trump had floated the idea of Palestinians leaving Gaza multiple times since taking office last month. His suggestion that they could be moved to Egypt and Jordan was rejected last week by those countries, along with a broad group of Arab nations.

On Tuesday evening, the president went even further. Speaking alongside Prime Minister Benjamin Netanyahu of Israel at the White House, Mr. Trump said the United States intends to seize control of Gaza, displace the Palestinian population living there and turn the devastated coastal enclave into “the Riviera of the Middle East.”

But he did not say how exactly he planned to do that — offering little detail on the logistics or extensive political maneuvering that would be required.

Regional complexity

A mass relocation of Gaza’s roughly two million inhabitants is a politically explosive idea in a region with a long and bloody history of forced resettlement.

While Mr. Trump framed the matter as a humanitarian imperative and an economic development opportunity, he effectively reopened a geopolitical Pandora’s box with far-reaching implications for the Middle East. Control over Gaza has been one of the major flash points of the Arab-Israeli conflict for decades — and to Palestinians and their allies, Mr. Trump’s proposal would constitute ethnic cleansing.

Many Gazans are descendants of Palestinians who were forced out of their homes during the wars surrounding Israel’s founding in 1948, a displacement that came to be known around the Arab world as the Nakba, or catastrophe. Now Mr. Trump is suggesting that they be displaced again — insisting that Palestinians would welcome it because “they’re living in hell” in Gaza.

“I would think they would be thrilled,” he said.

But the internationally backed Palestinian Authority rejected President Trump’s proposal, as did Hamas, which has ruled in Gaza for most of the past two decades and has begun re-establishing control there since a cease-fire deal with Israel took effect last month.

“Our people in Gaza will not allow for these plans to come to pass,” Sami Abu Zuhri, a senior Hamas official, said in a statement.

The cost

Mr. Trump likened his idea about displacement to the New York real estate projects on which he built his career. “If we could find the right piece of land, or numerous pieces of land, and build them some really nice places with plenty of money in the area, that’s for sure,” he said. “I think that would be a lot better than going back to Gaza.”

Where that money would come from, however, remains to be seen. Mr. Trump suggested that other countries in the region could finance the resettlement, but he offered no details.

He also did not say who would finance and build the gleaming and modern “Riviera” he was envisioning, either. Mr. Trump again suggested that other countries would pay for the reconstruction of Gaza — a project his Middle East envoy recently said would take 10 to 15 years — but also said he foresaw “a long-term ownership position,” without explaining what that meant.

The foreign ministry of Egypt, a key U.S. partner, said in a statement that aid and recovery programs for Gaza must begin “without the Palestinians leaving.” And King Abdullah II of Jordan on Wednesday rejected any attempt to displace Palestinians and annex their land, according to the Jordanian royal court.

The legality

Mr. Trump left a number of other basic questions unanswered, like how a U.S. takeover of Gaza would be enacted, and whether the use of force would be required. He conceded that American troops might be necessary.

But experts say that his proposal would unquestionably violate international law.

The Geneva Conventions — which both the United States and Israel have ratified — prohibit the forcible relocation of populations. Forced deportation or transfer of a civilian population is defined as a violation of international humanitarian law, a war crime and a crime against humanity.

It would be a further, severe violation for the United States to permanently take over the territory of Gaza, experts say. The specifics of that violation would depend partly on whether Palestine is considered a state, according to Marko Milanovic, a professor of international law at the University of Reading in England. The United Nations recognizes Palestine as a “permanent observer state” and 146 out of 193 U.N. member states recognize Palestinian statehood, but the United States does not.

The prohibition on one state annexing all or part of another state’s territory is one of the most important, foundational principles of international law. “There’s a clear rule,” Professor Milanovic said. “You cannot conquer someone else’s territory.”

It is rare for states to violate that rule. When they have, as in the case of Russia’s invasion of Ukraine, the response has been widespread global condemnation.

That could help explain why, by Wednesday afternoon, the Trump administration appeared to be trying to soften some of the president’s more problematic suggestions.

Speaking to reporters in Guatemala City during a trip to Latin America, Secretary of State Marco Rubio said Mr. Trump was only proposing to clear out and rebuild Gaza — not claim indefinite possession of the enclave.

“The only thing president Trump has done — very generously, in my view — is offer the United States’ willingness to step in, clear the debris, clean the place up from all the destruction,” Mr. Rubio said, so that “then people can move back in.”

It was an idea, Mr. Rubio added, that “people need to think about seriously.”

President Javier Milei of Argentina announced plans to withdraw his nation from the World Health Organization on Wednesday, the latest in a series of moves by Mr. Milei that mimic President Trump’s efforts to break with international norms and alliances.

“We will never forget that they were the architects of the draconian lockdowns,” Mr. Milei wrote on X, referring to the W.H.O.’s support for broad quarantines during the pandemic. He called the lockdowns “one of the most egregious crimes against humanity in history.”

“That’s why we have decided to withdraw from such a nefarious organization,” he added, “which acted as the enforcement arm of the largest social control experiment in history.”

President Trump signed an order to withdraw the United States from the W.H.O. in the first hours of his presidency, similarly criticizing the United Nations agency’s handling of the pandemic and the cost of being a member. Mr. Milei has long criticized the W.H.O. — even writing a book condemning pandemic policies in 2020 — but he only decided to pull out of the organization weeks after Mr. Trump did the same.

If the United States and Argentina follow through on their plans, they will join Liechtenstein as the only U.N. member nations that are not also members of the U.N.’s global health alliance.

That reflects Mr. Milei’s effort to align his nation with Mr. Trump’s scorched-earth approach to the international order, even if it comes at the expense of Argentina’s previous allies and partnerships.

Mr. Milei’s spokesman said Wednesday that Argentina has also been examining whether to withdraw from the Paris Agreement, the main global pact to combat climate change, like the United States did last month. Mr. Milei, like President Trump, has publicly doubted the science showing that human activity is dangerously warming the planet.

Shortly after becoming president in 2023, Mr. Milei canceled Argentina’s plans to join the BRICS economic alliance led by China, saying he instead wanted to move his country closer to the United States.

Leaving the W.H.O. could end up costing Argentina, which is struggling under tens of billions of dollars of international debt.

Unlike the United States, which contributes roughly 15 percent of the organization’s $6.8 billion budget over two years, Argentina pays a much smaller membership fee, estimated at about $10 million a year by the Argentine news organization La Nación.

The benefits Argentina receives from membership far outweigh the cost, including tracking of outbreaks, disease prevention and sharing of technology, said Leandro Cahn, director of Fundación Huésped, a large public health organization in Argentina. “The problems the Argentine health system has won’t be resolved by not being part of the W.H.O.,” he said.

Mr. Milei’s office said Argentina would remain a member of the Pan-American Health Organization. Mr. Cahn said that may enable the country to still receive deep discounts on vaccines and medications that W.H.O. members receive, but it was unclear.

While Mr. Milei has tamed Argentina’s extreme inflation, the nation remains in a precarious financial situation. Mr. Milei has suggested that Argentina will need additional loans from the International Monetary Fund. The United States is the I.M.F.’s largest and most influential contributor.

Amid that backdrop, Mr. Milei has positioned himself as perhaps Mr. Trump’s most reliable ally on the global stage. He was one of two world leaders, along with Prime Minister Giorgia Meloni of Italy, behind Mr. Trump when he was sworn in as president last month. And Mr. Milei plans to travel to the United States this month to speak at the Conservative Political Action Conference ahead of President Trump.

Mr. Milei and Mr. Trump see eye to eye on many topics, most prominently that “woke” ideology threatens Western society. Mr. Milei gave a speech at the World Economic Forum in Davos, Switzerland, last month that sharply criticized policies that seek to help or protect people based on their gender, race or sexuality.

“The great anvil that appears as a common denominator in failing countries and institutions is the woke mind virus,” he said in the speech, imitating language from the billionaire Elon Musk. “This is the great epidemic of our time.”

He cited “feminism, diversity, inclusion, equity, immigration, abortion, environmentalism, gender ideology,” as problematic consequences of “wokeness.” He added that parents who help young children transition to different genders are “pedophiles” committing abuse. His comments against gay and transgender rights prompted large protests last week across Argentina.

Both Mr. Trump and Mr. Milei have banned gender-neutral language and many diversity policies from government.

Mr. Milei made those moves before Mr. Trump returned as president. Mr. Musk and others have also credited Mr. Milei as an inspiration for the Trump administration’s work — led by Mr. Musk — to drastically slash the size of the U.S. government. Mr. Milei has carried out a similar effort in Argentina and is expected to soon unveil plans for a second phase that would eliminate or combine 50 state agencies.

In other ways, it appears that Mr. Milei is taking cues from Mr. Trump. Mr. Milei and his ministers have recently sharpened their rhetoric against migrants. Mr. Milei’s spokesman, Manuel Adorni, said Wednesday that the government was working on new immigration laws “and more secure borders.”

Last month, an Argentine governor announced plans to build a 200-meter-long wall along a section of Argentina’s border with Bolivia that officials said is frequently crossed illegally. Mr. Milei posted the news on X, noting, “Excellent.”

Natalie Alcoba and Lucía Cholakian Herrera contributed reporting from Buenos Aires.