The annual gathering of the Group of 7 (G7) in Taormina, Sicily was noteworthy in that it showed a clear division, as German Chancellor Angela Merkel pointed out, between six leaders (seven if the European Union is included) on one side, and the US on the other, on committing to the Paris Agreement on Climate Change.

That deal was reached after years of careful negotiations and has been signed by some 200 countries to try and halt the warming of our planet from man-made causes, limiting greenhouse gas emissions, providing funding for developing nations and trying to secure the environmental future of this blue planet we all share.

Former US president Barack Obama had signed onto the accord that pledged to cut greenhouse gas emissions and limit an increase in global temperature to less than 2 degrees Celsius above pre-industrial levels.

But a lot has changed in the US political landscape since Obama put pen to paper some 18 months ago. Donald Trump has long been a sceptic of the science of climate change, is an ardent supporter of fossil fuel industries, and has surrounded himself with advisers who dismiss the facts of climate science as science fiction.

While there are reports suggesting Trump is at least now willing to consider approving the agreement or is actively looking at ways to water it down, the views of his administration stand at odds with the vast majority of nations — both in the developed and developing world.

Indeed, while meeting Pope Francis I at the Vatican during his nine-day overseas trip, Trump told the pontiff that he would read the treatise on environmentalism pointedly given to him by the leader of the world’s 1.2 billion Roman Catholics.

Trump has repeatedly said that he will decide on the Paris Agreement by the end of May, and with that now upon us, the danger is that he may renege on the US commitment to adhere to its environmental responsibilities.

Should Trump baulk, the danger is that other mass emitters of greenhouse gases such as China and India will follow suit, rendering what is our best hope to negate climate change as virtually worthless. This decision by Trump is crucial — and so too how nations react. We much not let this period now be the turning point where future generations look back through the fog of their dangerously warmed up world and say: “That was the beginning of the end.”