Nancy Pelosi has accused Republicans of treating the climate crisis like “it’s all a hoax” while at the Cop27 climate talks in Egypt, where the US delegation is attempting to remain upbeat about continued progress on dealing with global heating despite uncertainty over the midterm election results.

Pelosi, the speaker of the House of Representatives, made a surprise appearance at the climate summit in Sharm el-Sheikh on Thursday. The trip may be one of Pelosi’s last as speaker, with most forecasts predicting Republicans will eke out a narrow majority in the House.

There has been “shall we say, a disagreement on the subject” of the climate crisis between the parties, Pelosi said at Cop27, adding that Republicans have said “‘Why are we having this discussion? There is no climate crisis. It’s all a hoax.’ We have to get over that. This is urgent, long overdue.

“So we cannot just have any political disagreement or the power of the fossil fuel industry cramping our style as we go forward with this, but to show a path that gets us to where we need to be,” Pelosi said.

Pelosi’s appearance at Cop27 comes at a critical point for the future of democracy in the US and the future of the planet. Joe Biden was able to pass the country’s most significant piece of climate legislation this year because Democrats have the majority in both the House and the Senate. With that set to change, the mounting anger at the US for obstructing meaningful global climate action, despite being the world’s largest polluter and richest country, may only get worse.

Kathy Castor, a Democrat from Florida who chairs the House subcommittee on the climate crisis, predicted Republicans would axe her committee should they gain power. “They have not really been partners in tackling the climate crisis, and it’s inexplicable because the world’s top scientists tell us we are running out of time,” Castor said.

Biden will appear at Cop27 on Friday and a delegation of his cabinet members have already descended upon Sharm el-Sheikh to stress to other, skeptical, countries that the US, which has swerved erratically on climate policy over the years and under Donald Trump completely abandoned the crisis, will still be engaged on fighting global heating even if Republicans do secure Congress.

“I think the United States is seen favorably here based on the actions taken in the last two years,” Michael Regan, administrator of the Environmental Protection Agency (EPA), told the Guardian.

Regan, who appearing at a number of events at Cop27, cited the inflation reduction act, which includes more than $370bn in climate spending, and the administration’s actions to promote environmental justice.

“Polls suggest climate change isn’t a top-tier issue, but most families are focused on keeping a roof over their heads and putting food on the table … so it’s not surprising some issues were registering a little higher than climate change,” Regan said of the midterm elections.

“But climate change hasn’t fallen off the list, it’s still a top priority. You don’t even have to trust scientists any more, you just have to look out of the window or put on the news. People are smart enough to see this isn’t some long-term conspiracy theory.”

Faced with inconclusive midterm election results, the mood among many veteran climate activists and negotiators from developing countries is one of indifference, as they have seen little difference between the Democrats and Republicans over the past three decades when it comes to the most crucial climate issues like finance and market solutions.

Representatives of developing countries have criticized the US at Cop27 for repeatedly failing to deliver promised funding to help them deal with the crippling impacts of floods, fires and droughts, as well as transition to clean energy. Poorer nations are pushing for “loss and damage” finance to help them cope with the climate crisis. John Kerry, the US climate envoy, has admitted that further funding would be unlikely should Republicans gain control of Congress.

“The main difference is that at least the Democrats don’t deny climate change, and of course it matters inside America as without the Democrats the Inflation Reduction Act would not have passed, but on the global stage it makes no difference,” said Meena Raman, a climate policy expert from Third World Network and adviser to developing countries at the Cop summits.

“It’s the same negotiators, the same blockages, the same bullying, and even now the planet is burning, the US doesn’t change and gets what it wants. It continues to deny its historic responsibility, emphasize the private sector and loans, and uses China as the bogeyman to distract attention away from its unfulfilled pledges.”

US greenhouse gas emissions are rising, with plans to vastly expand gas production and fines for oil companies which don’t up extraction.

Asad Rehman, director of War on Want and a coordinator of the climate justice groups at Cop27, said: “We are faced with a choice of Republicans who are climate denialists whilst the Democrats are mitigation denialists – happy to speak about the climate emergency but it’s simply hollow words.

“From Bush to Biden the USA continues to block real finance, tinker with its emissions and are sacrificing billions to climate catastrophe while expanding fossil fuels which will sacrifice billions to climate catastrophe.”