THE use of fossil fuels must be substantially reduced to tackle the climate crisis, a delayed United Nations report warned today, leading to calls for an immediate end to investments in carbon-based energy.

UN science body the Intergovernmental Panel on Climate Change (IPCC) released the third part of its sixth assessment report, spelling out how to cut emissions by switching to increasingly cheap renewables and fuels such as hydrogen, as well as through energy efficiency, carbon capture and tree planting.

It highlights how consumers can be encouraged to make green choices – eating less meat, switching to renewable home heating, taking up walking and cycling or driving electric cars – and how cities can be made greener.

The report warns that meeting goals agreed by countries to limit temperature rises to avoid the worst impacts of climate change requires rapid, deep and immediate greenhouse gas emission cuts in all areas.

It pitches scientific findings on climate change into an ongoing heated debate over energy supplies and costs prompted by rising oil and gas prices and Russia’s invasion of Ukraine.

A meeting to agree on the 63-page summary of the report for policy-makers overran by more than two days as delegates wrangled over the texts, delaying publication, and reports emerged that governments were trying to “water down” experts’ findings.

The meeting involved scientists and representatives of 195 countries.

Many countries remain heavily reliant on fossil fuel use or revenues, but others are most vulnerable to temperatures rising to 1.5°C above pre-industrial levels, which would be a death sentence for them, meaning that finding international agreement requires difficult debates.

In Britain, the current energy crisis has provoked clashes over whether to speed up the shift away from oil and gas and towards clean heating, renewables and insulation or to boost domestic fossil fuel supplies from the North Sea or fracking.

The government is due to set out its new energy strategy on Thursday, with expectations of support for offshore wind and new nuclear reactors, but not cheap onshore wind.

The UN report says that there are still routes to curbing global warming, but only if decisive action is taken immediately.

Report co-chairman Jim Skea said: “It’s now or never, if we want to limit global warming to 1.5 degrees.

“Without immediate and deep emissions reductions across all sectors, it will be impossible.”

UN secretary-general Antonio Guterres said the report was a “litany of broken climate promises” and called for an urgent shift of investment from fossil fuels towards renewables, protecting forests and cutting methane emissions.

Global Witness said that the warnings in the report “must be the death knell for the fossil fuel age.”

Chief executive Mike Davis argued: “Harnessing technological advancements in the fight against the climate crisis should be encouraged but absolutely should not be seen as an alternative to stopping the destructive climate practices that are responsible for bringing us to this point.

“The single best method, readily available now, is to move off fossil fuels and to renewable energy, whilst rolling out mass home insulation.

“Likewise, false or unproven solutions being pushed by big oil and gas companies, such as carbon capture and storage, must not be used by the industry to greenwash.

“They risk being expensive, ineffective distractions from the real solutions the world desperately needs.”

Green Party MP Caroline Lucas said the report shows that “we already have climate solutions” and that “action now is cheaper than delay.”

She tweeted: “Time to pick a side – big polluters and those who bankroll them or the future of humanity.

“As Cop president, [the] UK must lead by leaving fossil fuels in the ground.”

In a separate report today,  “food systems expert” Duncan Williamson, who set up Nourishing Food Systems, calls for Britain to take drastic actions to reduce carbon emissions, warning that current government plans to tackle the climate crisis are “wholly inadequate” if warming is to be limited to 1.5°C.

Although red meat consumption has previously been highlighted as a strong contributor to CO2 emissions, eating poultry, pork and dairy regularly can also have dangerous impacts on the environment, Williamson says in a report commissioned by whole foods company Merchant Gourmet.

Of the world’s total CO2 emissions, a large proportion is attributed to livestock productions that come from animal feed.

Eating a plant-based diet has already been established as making a positive impact on the environment, but the new report advocates a “sustainable” diet instead. This means moving away from consuming processed plant-based or meat-free alternatives, along with reducing our meat and dairy consumption in favour of more pulses, lentils, beans and vegetables.

The footprint of a leading plant-based burger brand was calculated in the report as 3.5 kilograms of CO2 – three times that of lentils.

Switching to a sustainable diet has a “far greater impact” than those who consider food miles, shop locally and focus on packaging when it comes to food, the report said, adding that it could reduce global land use by up to 75 per cent.

It said that such popular measures adopted by consumers, and those enforced by government – such as the 5p plastic bag charge, to reduce impact on the environment – are much less effective.

The switch would also reduce the demand for land, which will benefit biodiversity, forest and mitigate climate change.

If the public swapped one red meat-based meal to a plant-based meal each week in 2022, Britain’s greenhouse gas emissions would be cut by 50 million tonnes, equivalent to taking 16 million cars off the road.

Mr Williamson said: “The first important step to reducing your carbon footprint is considering the ingredients you are selecting and where they are from.

“This is the time and opportunity to start giving them [wholefoods] a bigger role in our diet.”