Donald Trump's election as the president of the United States is going to be a "big setback" for global climate efforts, especially if he rolls back critical domestic policies like the Inflation Reduction Act (IRA), environmentalist and policy expert Sunita Narain said on Wednesday.

She also said the US has historically fallen short in global climate efforts, particularly on financing support for vulnerable countries, decarbonisation and financial commitments to the developing world, and Trump's presidency will make matters even worse.

Narain said the IRA is essential for reducing US emissions as the country remains one of the largest greenhouse gas emitters and leads in oil and gas production.

While President Joe Biden's administration prioritised domestic climate actions, Trump's campaign focus on expanding fracking and oil production poses a serious threat to US commitments, Narain said.

"Donald Trump's election as the US president is going to be a major setback for the global environmental and climate change movement. While President Joe Biden's administration showed stronger climate action domestically than internationally, our primary concern now is that Trump may roll back these critical domestic efforts, including the Inflation Reduction Act (IRA)," she said.

"The IRA is crucial because the United States remains the single-largest historical emitter of greenhouse gases and is the second-largest emitter annually. It is also the world's top producer and exporter of oil and gas, generating around 13 million barrels daily. The IRA (and its role in achieving 50-per cent emissions reduction by 2030, below 2005 levels) served as a significant signal to the world that the US could lead on climate action," Narain said.

If Trump reverses these actions, it would send a very troubling message globally. In his campaign, Trump emphasised his support for fracking, oil and gas, with "Drill, baby, drill" as a key slogan.

He dismissed climate-change concerns entirely. Rolling back the IRA and expanding oil production would be extremely harmful for international climate efforts, the climate policy expert said.

"Some might argue that Trump could hesitate to undo the IRA, as its benefits have also reached Republican strongholds. However, an increase in fracking and oil production seems likely," Narain said.

Former US president Trump is cruising towards winning the White House race in one of the greatest political comebacks in American history. According to projections, Trump is all set to receive 270 electoral college votes, blocking the chance of Democratic candidate Kamala Harris to win the polls.

Trump, who has publicly called climate change a "hoax", withdrew the US from the Paris Agreement in his first term.

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