Just three months after the landmark summit, there is a danger that the vital pledges made will “wither on the vine”, the cabinet minister will say in a major speech.
Cop26 saw the world’s wealthiest countries fail to make commitments to keep global heating to 1.5°C – above which scientists warn runaway climate change is inevitable.
The level of CO2-cutting pledges made will result in the planet warming by up to 2.4°C, even if they are followed up with practical policies and legislation.
The Glasgow summit ended with Mr Sharma in tears – and critics warned the crisis was simply “kicked down the road”, to Cop27 in Egypt at the end of this year.
In a speech at Chatham House, the Cop26 president, will say: “There is no doubt that the commitments we secured at Cop26 were historic. Yet at the moment they are just words on a page.
“And unless we honour the promises made, to turn the commitments in the Glasgow Climate Pact into action, they will wither on the vine.
“We will have mitigated no risks. Seized no opportunities. We will have fractured the trust built between nations. And 1.5 degrees will slip from our grasp.”
The Glasgow pact, at the end of Cop26, committed countries to “phase down coal”, but the language was watered down after China and India objected to “phasing out” the dirtiest fossil fuel.
Mr Sharma, who remains president until the next summit, must also ensure that developed countries meet their promise to deliver $100bn a year to help poor countries adapt to the planet heating.
But Boris Johnson’s government has also faced criticism that it has made climate promises without the policies to deliver the carbon cuts necessary.
The advisers on the Climate Change Committee warned the UK is lagging behind on its key goal of 78 per cent cuts to greenhouse gases by 2035.
Bob Ward, policy director of the Grantham Research Institute on Climate Change at the London School of Economics, said Britain must commit itself to greater action this year.
“Although the UK already has one of the strongest pledges for 2030, it will be difficult to persuade other countries to go further without offering to do more itself,” he said.
“The UK Presidency of Cop26 needs to put pressure on all countries, particularly laggards like Australia, to increase their planned emissions cuts.”
The Glasgow Climate Pact was praised for requiring that countries bring forward new CO2 targets one year from now, rather than waiting five years.
The change is designed to put pressure on all nations to move further before they gather again in Egypt towards the end of 2022.
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