He recently described the modern world's addiction to fossil fuels as "suicidal".

But in his speech to global leaders gathered at the COP27 climate summit in Egypt on Monday, he took it a step further.

Sunak commits billions to climate fund - COP27 latest

"We are on the highway to climate hell," he said, "with our foot still on the accelerator."

There is a good reason he is using shock tactics.

After a year of perma-crisis, climate change is slipping down the agenda.

There are few better examples of this than Rishi Sunak, who initially said he wasn't even planning to attend, citing other pressing commitments - despite the UK still holding the previous COP26 presidency at the time.

He changed his mind after it emerged Boris Johnson was going, but the damage to the UK's reputation as a climate leader was done.

The problem is that a lack of political momentum, particularly among the big emitters, translates into lack of desperately needed acceleration in emissions reductions.

This is the thing that will push 1.5C of warming out of reach.

We are already being warned the world is significantly off course unless more is done.

But the other thing a lack of will translates to is a lack of cash: cash for developing nations to adapt to climate change, and cash so that developing nations can receive compensation for the damages they've suffered from a crisis they did little to cause.

Money is the fault line that runs through every COP summit.

But in Sharm el-Sheikh, it is turning into a yawning chasm.

For those in need of more help, it is a matter of faith in the UN process, but it is also increasingly a matter of survival.

Watch the Daily Climate Show at 3.30pm Monday to Friday, and The Climate Show with Tom Heap on Saturday and Sunday at 3.30pm and 7.30pm.

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The show investigates how global warming is changing our landscape and highlights solutions to the crisis.