The summit is taking place in Glasgow, Scotland.
Some 120 world leaders will meet today to tackle the climate crisis.
They're attending the COP26 summit in Glasgow in Scotland which is kicking off today.
They'll be trying to reach a deal to stop the global temperature from rising above 1.5 degrees this century.
Dublin Green Party MEP Ciaran Cuffe says it's vital that problem is solved:
World leaders are being told that failure at COP26 'is not an option' - with entire islands at risk of disappearing without tough action on climate change.
COP26 President Alok Sharma set the tone for the next fortnight with the warning, saying he wants every country to do more.
He's aiming for detailed commitments to be made by the end of it.
However, former European Commission President Jose Manuel Barroso is sceptical:
There's been no agreement in Rome to set a target to phase out domestic coal, as climate change commitments begin to be discussed ahead of Cop26.
But G20 leaders meeting in Italy, have decided to reiterate the need to limit global warming to one-and-a-half degrees Celsius.
Rising sea levels mean the Marshall Islands, located between Hawaii and the Philippines, are in danger of vanishing if global warming is not tackled.

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