Of all the countries taking part, the hosts have the best sense of what the nations of the world are prepared to do to avoid dangerous climate change.
While the Prime Minister said he thought it was possible that carbon emissions could be reduced at the necessary rate, he added: “It's going to be very, very tough, this summit. And I'm very worried, because it might go wrong and we might not get the agreements that we need. It’s touch and go.”
He expressed the hope that “peer pressure” at the summit would persuade some countries to do more, which perhaps shows just how much they are open to being influenced.
As Johnson spoke, Nicola Sturgeon said the idea of extracting oil and gas “until the last possible moment… would be fundamentally wrong”, while admitting it was “tempting” for countries with significant fossil fuel reserves – like Scotland – to do so.
But although the First Minister said her government’s focus would be on “achieving the fastest possible just transition for the oil and gas sector”, she once again failed to call on the UK government to refuse permission for the Cambo oil field off Shetland to be drilled.
All this on the day that the World Meteorological Organisation revealed that greenhouse gases reached record highs last year, despite the economic slowdown caused by the Covid pandemic.
The last time the Earth had similar levels of carbon dioxide in the atmosphere was three to five million years ago, when the temperature was two to three degrees Celsius warmer than it is now.
All over the world, leaders like Johnson and Sturgeon are facing tough choices over climate change and far too many are taking what they think is the politically easy answer: continuing to burn fossil fuels and repeatedly putting off dealing with climate change.
One solution is for the public to help those in charge do the right think by exerting peaceful “peer pressure”. If the world is to rise to the greatest challenge humanity has ever faced, we must make the political price of failure abundantly clear to our leaders.