About half of the world’s population will be electing leaders this year.More than 40 countries that are home to about half of the world’s population — including the United States, India and South Africa — will be electing their leaders this year.My colleagues at The Times report that it’s “one of the largest and most consequential democratic exercises in living memory,” which “will affect how the world is run for decades to come.”Climate is front and center on many of the ballots. The leaders chosen in this year’s elections will face daunting challenges laid out in global climate commitments for the end of the decade, such as ending deforestation, tripling renewable energy capacity and sharply reducing greenhouse gas emissions.Here are the issues and races to watch closely:Major climate policies at stakeClimate change is one of the issues on which Republicans and Democrats are farthest apart.President Biden signed what many called the most powerful climate legislation in the country’s history. Former President Trump, who is likely to be the Republican presidential candidate — especially after his victory in the Iowa caucuses — withdrew the United States from the Paris Agreement, the 2015 treaty that guided much of the world’s progress in curbing climate change.Republicans have also prepared a sweeping strategy called Project 2025 if Trump wins back the White House. As my colleague Lisa Friedman wrote last year, “the plan calls for shredding regulations to curb greenhouse gas pollution from cars, oil and gas wells and power plants, dismantling almost every clean energy program in the federal government and boosting the production of fossil fuels.”Ursula von der Leyen, the European Commission president, is expected to seek re-election.Martin Divisek/EPA, via ShutterstockEuropean Union incumbents will also be defending their climate policies, known as the Green Deal, in elections for the European Parliament in June. Ursula von der Leyen, the European Commission president who is expected to seek re-election by the European Parliament, kicked off a series of policies designed to ensure the bloc achieves carbon neutrality by 2050. But opposition to these policies is growing. Farmers in several countries have tried to block measures to restore natural ecosystems, while homeowners have grown increasingly worried about the cost of the green energy transition.Opinion polls analyzed by Reuters in a commentary piece suggest far-right lawmakers, who oppose Green Deal policies, will grow in number but remain a minority. Climate may also play a role in elections in Britain, which may happen in the second half of the year. They became a key point of disagreement between the Labour Party and the governing Conservative Party, which are trailing in the polls, after Prime Minister Rishi Sunak rolled back some of the country’s most ambitious climate policies.The future of coalCountries that rely heavily on coal as a source of energy, such as India, Indonesia and South Africa, are also going to the polls this year. In South Africa, elections could influence how fast the country is able to switch to renewables. Any shake up to the ruling African National Congress’ hold on power could boost the shift to renewables, my colleague Lynsey Chutel, who covers South Africa, told me.Environmental activists demonstrated outside of Standard Bank South Africa in Johannesburg, South Africa, in September.Kim Ludbrook/EPA, via ShutterstockRight now, one of the party’s most powerful leaders is an energy minister who has fiercely defended the country’s continued use of coal. Many voters are angry at the A.N.C. for its inability to address an energy crisis partially created by aging coal plants.There seems to be less room for a shift in the elections in Indonesia and India. My colleague Suhasini Raj, who is based in India, told me that, despite high rates of pollution and the pressure on India to let go of coal, the current prime minister Narendra Modi is likely to be re-elected and continue his pro-coal policies.In Indonesia none of the candidates running for president have put forward a concrete plan to transition to clean energy, Mongabay, an environmental news service, reported. The country is by far the world’s biggest exporter of coal. Oil on the ballotFor leaders in oil producing nations around the world, balancing climate policies and drilling has been a delicate act that will be tested on the ballot.President Biden risked losing the support of many climate-conscious voters when he approved Willow, an $8 billion oil drilling project on pristine federal land in Alaska. But Biden’s support for more drilling has been, at least in part, an effort to curb inflation, which angers many more voters.Claudia Sheinbaum’s presidential campaign in Mexico is also balancing climate proposals with her country’s dependence on oil. A climate scientist who is now the mayor of Mexico City, Sheinbaum is a protégé of President Andrés Manuel López Obrador, whose administration has tried to boost the oil sector’s role in the country’s economy.Claudia Sheinbaum, running for president in Mexico.Carlos Lopez/EPA, via ShutterstockSheinbaum, a favorite to win in June, has vowed to act to protect the climate. But it’s unclear how much Obrador’s oil legacy will color her policies. “We are going to keep advancing with renewable energies and with the protection of the environment, but without betraying the people of Mexico,” she told voters, according to Bloomberg.The oil industry is also on the ballot in Venezuela and Russia, where it lends strength to authoritarian leaders.Vladimir Putin’s re-election — and his disregard for the climate — seems to be a foregone conclusion. But, in Nicolás Maduro’s Venezuela, there is tiny window for change, though it seems to be closing fast.Venezuela freed five political prisoners in October after the United States vowed to lift some sanctions to its oil industry if it holds free and fair elections. But the main opposition candidate is still banned from running.It may sound contradictory, but some investment in Venezuela’s oil sector could help clean it up. As my colleagues reported last year, government dysfunction has left the industry unable to maintain minimum safeguards, with devastating consequences to the environment.We will report back with key developments on these races throughout the year. When it comes to the climate crisis, even far-off elections have implications for us all. Plaintiffs in the Loper Bright Enterprises case, from left, William Bright, Wayne Reichle and Stefan Axelsson, in Cape May, N.J.Rachel Wisniewski for The New York TimesA Supreme Court case could dismantle federal regulationThe Supreme Court is set to hear arguments on Wednesday for a case that could severely curb the federal government’s regulatory power, with potentially drastic repercussions for the climate.The case is about a group of commercial fishermen who oppose a government fee designed to help prevent overfishing. But a victory for the fishermen could achieve a long-sought goal of the conservative legal movement: undermining a longstanding legal doctrine known as the Chevron deference.That could have implications for the environment, but also health care, finance, telecommunications and other sectors, legal experts told my colleague Hiroko Tabuchi.“It might all sound very innocuous,” said Jody Freeman, founder and director of the Harvard Law School Environmental and Energy Law Program. “But it’s connected to a much larger agenda, which is essentially to disable and dismantle federal regulation.”The Chevron deference was created by a 1984 Supreme Court ruling involving the oil and gas giant. It empowers federal agencies to interpret ambiguities in laws passed by Congress. Weakening or eliminating the Chevron deference would limit the agencies’s ability to interpret the laws they administer. A victory for the fishermen would also shift power from agencies to judges, my colleague Adam Liptak wrote.The lawyers who have helped to propel the case to the nation’s highest court have a powerful backer: the petrochemicals billionaire Charles Koch. Court records show that the lawyers who represent the New Jersey-based fishermen also work for Americans for Prosperity, a group funded by Koch, who is a champion of anti-regulatory causes.In their briefs, the groups supporting the fishermen pointed out that the Chevron deference has fallen out of favor at the Supreme Court in recent years, and several justices have criticized it.Justice Clarence Thomas was initially a backer of the Chevron deference, writing the concurring opinion in 2005 that expanded its protections. But Thomas, who has close ties to the Koch’s political network, has since renounced his earlier ruling. Other climate newsNearly a quarter of humanity were living under drought in 2022 and 2023, the United Nations estimates.The Biden administration announced a plan to charge oil and gas companies a steep fee for emitting methane.John Kerry, President Biden’s special envoy for climate, plans to step down in the spring.A U.S. government map that show extreme weather threats now frequently covers almost the whole country.Chevron, the oil giant, and other companies are building an underground hydrogen battery in Utah.Denial about climate change is on the rise, according to an analysis of 12,000 disinformation videos by U.K. researchers, Grist reports.Colombia created its newest national park by befriending the traditional ranches that surround it.The Crochet Coral Reef, a long-running craft-science collaborative artwork, is the environmental version of the AIDS quilt. More