The UN Secretary General says the rush to use fossil fuels because of the war in Ukraine is "madness" and threatens global climate targets.
The invasion of Ukraine has seen rapid rises in the prices of coal, oil and gas as countries scramble to replace Russian sources.
But Antonio Guterres warns that these short-term measures might "close the window" on the Paris climate goals.
He also calls on countries, including China, to fully phase out coal by 2040.
In his first major speech on climate and energy since COP26, Mr Guterres makes no bones about the fact that the limited progress achieved in Glasgow is insufficient to ward off dangerous climate change.
Scientists believe that keeping the rise in global temperatures under 1.5C this century is crucial to limiting the scale of damage from global warming.
To keep that threshold alive, carbon output needs to be cut in half by the end of this decade. Instead, as Mr Guterres points out, emissions are set to rise by 14%.
"The problem was not solved in Glasgow," Mr Guterres says, in a speech delivered at the Economist Sustainability Summit.
"In fact, the problem is getting worse."
The war in Ukraine threatens to make that situation even more problematic, he says.
Europe and the UK and other countries are looking to cut their reliance on Russian oil and gas this year. Many are turning to coal or imports of liquefied natural gas as alternative sources.
But Mr Guterres warns this short-term approach heralds great danger for the climate.
"Countries could become so consumed by the immediate fossil fuel supply gap that they neglect or knee-cap policies to cut fossil fuel use," Mr Guterres said.
"This is madness. Addiction to fossil fuels is mutually assured destruction."
Countries must "accelerate the phase out of coal and all fossil fuels," and implement a rapid and sustainable energy transition.
It is "the only true pathway to energy security."
Mr Guterres says the solutions to the climate crisis mostly lie in the hands of the G20 group of richest nations, which produce around 80% of global emissions.
While many of these countries have taken great steps to slash emissions by 2030, there are a "handful of holdouts, such as Australia."
Coal must be banished, Mr Guterres says, with a full phase-out for richer nations by 2030, and 2040 for all others, including China.
Coal "is a stupid investment," according to the Secretary General, "leading to billions in stranded assets."
He says the way forward is to build coalitions to help major emerging economies to move rapidly away from fossil fuels.
He highlights the case of South Africa. During COP26 several countries including the UK, US and others agreed to an $8.5bn financing programme to end South Africa's reliance on coal.
Mr Guterres says the pieces are coming together for similar coalitions in Indonesia, Vietnam and elsewhere.
Money is one of the key problems in addressing the climate issue and Mr Guterres has called for a major ramping up in finance to help countries adapt to rising temperatures.
He points out that right now, one person in three globally is not covered by early warning systems for disasters - in Africa six in ten people are not protected.
In 2022, he argues, richer countries must finally make good on their well-worn promise to provide a $100bn a year to the developing world. (BBC)