Joe Biden has implored countries to do more to tackle the climate emergency, telling the Cop27 summit that world leaders “can no longer plead ignorance” and that time to confront the crisis is running out.

Biden told a large crowd of delegates at the talks, held in Egypt, that the “science is devastatingly clear – we have to make progress by the end of this decade.” The US president stated that America was taking action on cutting planet-heating emissions and that other major economies needed to “step up” to avoid a disastrous breach of 1.5C in global heating.

“Let’s raise both our ambition and speed of our efforts,” he said in his speech on Friday in Sharm el-Sheikh. “If we are going to win this fight, every major emitter needs to align with 1.5C. We can no longer plead ignorance of the consequences of our actions or continue to repeat our mistakes. Everyone has to keep accelerating progress throughout this decisive decade.”

Biden, buoyed by better than expected midterm election results for Democrats this week, said that governments need to “put down significant markers of progress” in reducing emissions. Scientists have warned that the world is heading for disastrous levels of global heating, with emissions still not falling fast enough to avoid severe heatwaves, wildfires, droughts and other impacts of the climate crisis.

“It’s been a difficult few years; the interconnected challenges we face can seem all-consuming,” said Biden, who accused Vladimir Putin of using “energy as a weapon” in Russia’s invasion of Ukraine, an action that has caused energy and food prices to soar globally. “Against this backdrop, it’s more urgent than ever that we double down on our climate commitment.”

Biden, who was briefly interrupted by a small band of whooping climate protesters, said the US was committed to helping developing countries hurt worst by climate impacts but did not mention providing payments via “loss and damage”, the hot topic of Cop27 and the most pressing issue for vulnerable communities already suffering from worsening catastrophes.

The protesters were youth and Indigenous activists from the US, calling on Biden to stop pushing fossil fuel extraction. “The president, members of congress and the state department have come to this international forum on climate change proposing false solutions that will not get us to 1.5 degrees,” said Big Wind, 29, member of the Northern Arapaho tribe in Wyoming.

“We need to accelerate the transition but that’s not going to happen by partnering with big polluters like Amazon and PepsiCo, and so we needed to call that out,” he said, in reference to an announcement earlier this week by US climate envoy John Kerry, the Bezos Earth Fund, and PepsiCo among others about plans to design an Energy Transition Accelerator.

Biden used the speech to unveil a number of new measures, including a plan to slash emissions of methane in the US, support new early warning systems for extreme weather disasters in Africa and a deal to back new solar and wind projects in Egypt in return for the country decommissioning gas power plants and cutting its emissions.

The standout pledge made by Biden is the plan to reduce methane, a powerful greenhouse gas that routinely leaks from oil and gas drilling operations, the burning of gas itself and from agriculture. Methane doesn’t last as long in the atmosphere as carbon dioxide but traps 80 times more heat, on average, in the 20 years after it is emitted.

The new methane cuts could be undercut elsewhere. A slew of new gas projects in the US, approved by the federal government, could cause a 500% increase in methane emissions in the decade to 2030 if all planned developments go ahead, according to Bill Hare, chief executive of Climate Analytics.

“So while it’s all very well and good to clean up the methane fugitives from the oil and gas industry, let’s be clear – the US is ramping up its gas production at a time when it should be working out how to cut it,” Hare said.

The newly strengthened standards will help slash methane emissions by 87% by 2030, compared with 2005 levels, according to the US Environmental Protection Agency, through new regulations to curb gas flaring and leaks of methane from oil and gas drills and pumps. A new program will require oil and gas companies to respond to third-party reports of methane leaks.

Environmental groups called upon Biden, still facing the possibility of Republican control of Congress following midterm elections, to more aggressively wield the unilateral power of the presidency to shift away from fossil fuel use.

“The new methane reduction plan is welcome and long overdue, but President Biden must bring far more to these negotiations,” said Jean Su, director of the Center for Biological Diversity’s energy justice program. “It’s past time for Biden to declare a climate emergency and stop approving new fossil fuel projects that will release more methane into the atmosphere, even with these standards.”

It’s proved a mixed Cop27 for the US in Sharm el-Sheikh. The American delegation has been keen to tout the reputation-boosting passage of the Inflation Reduction Act, a sweeping package of clean energy support and the first major climate bill ever enacted by the US. John Kerry, the US climate envoy, has called the law “transformational” and “one of the most important bills in the past 50 years”.

But critics have pointed out that the US has yet to provide anywhere near the level of climate finance that befits its role as the world’s economic superpower and largest emitter of carbon pollution in history. Even the $11bn already promised by the US to support developing countries ravaged by climate-driven storms, fires and drought, which Kerry has admitted is not enough, is uncertain given the possible makeup of Congress.

The issue of “loss and damage” – funds for repair and reconstruction paid by wealthy countries to poorer nations suffering unavoidable depredations due to the climate crisis – made it on to the agenda at Cop27 but US officials have said discussions over any sort of funding mechanism could take another two years.

“We have a responsibility, we made a commitment,” Nancy Pelosi, for now the speaker of the House of Representatives, said of developing countries in a visit to Cop27. But, she added, “it is a challenge, and we haven’t succeeded yet, to get the global funding that we need to be good neighbours on this planet.”

Alice Hill, a former climate adviser to Barack Obama, said: “President Biden wants to keep the 1.5C goal, insisting that every emitting nation do its part. He announced a slew of new climate programs, but he couldn’t deliver what the developing world most wants – enough money to adapt to climate extremes. He will need Congress to cooperate to accomplish that.”

Activists from around the world at Cop27 said the US needed to do far more but planet-heating emissions in the US are expected to rise about 1.5% this year, due to a surge in gas use and a rebound in air travel following the depths of the Covid pandemic.

“The US is the biggest historic polluter and has the financial and technological wherewithal to solve the climate crisis yet has failed time and time again to honour its pledges,” said Mohamed Adow, director of the thinktank Power Shift Africa.

“We are paying for the crimes of corporations and the global north, who have made Pakistan a hub for climate disasters,” said Farooq Tariq, a veteran climate activist from Pakistan. More than a third of his country has been inundated by flooding since June, displacing more than 30 million people, and scientists have said global heating likely worsened the disaster.

“We don’t want any more words, we want debt suspension, we want reparations, we want climate justice,” said Tariq.