Nearly 20 years ago, after the world woke up to graphic evidence of holes in the ozone layer, it was in Canada's oldest city that a treaty was adopted to deal with this potentially catastrophic problem.
The Montreal Protocol of 1987 banned chlorofluorocarbons (CFCs), then widely used in aerosols and refrigerants, because these had been identified by scientists as the chief culprits in destroying the protective layer of ozone in the earth's atmosphere.
It was a technical fix, and it worked. Faced with the ban, which was grounded on conclusive evidence of the damage their products were causing, manufacturers quickly found alternatives, and the world moved on.
It is doubtful if the deal made in Montreal at the weekend by delegates attending the 11th United Nations Conference on Climate Change will be as memorable. Firstly, global warming is not susceptible to such a quick technical fix as repairing the hole in the ozone layer. Secondly, there is still huge disagreement on the way to proceed, not least in terms of adopting ambitious targets to reduce the greenhouse gas emissions blamed for causing climate change. Thirdly, the US - as the world's biggest emitter of these gases, accounting for 24 per cent of the total - has resolutely refused to play its part in the international effort to deal with this environmental problem.
But despite the continuing opposition of the Bush administration to mandatory caps on emissions, there is a groundswell of support among Americans for action to be taken. Mayors are getting involved, pledging to make deep cuts in their cities' emissions. Corporate giants such as General Electric have also seen the writing on the wall, as well as the potentially enormous returns to be made from supplying cleaner energy technologies to China, India and other rapidly developing countries. If the US was a party to the Kyoto Protocol, this type of "technology transfer" would also allow US firms to collect carbon credits to offset against their own emissions.
The Bush administration's obdurate refusal to ratify Kyoto is not only bad for the environment, but it is also bad for business. We have also witnessed a major US city - New Orleans - destroyed by precisely the type of "extreme weather event" about which scientists have been warning since the late 1980s.
"The time is past to debate the impact of climate change. We no longer need to ask people to imagine the effects, for now we can see them," Canadian prime minister Paul Martin said in Montreal last week, in a strong speech which reportedly earned him a reprimand from Washington. " The time is past to pretend that any nation can stand alone, isolated from the global community - for there is but one earth, and we share it, and there can be no hiding on any island, in any city, within any country, no matter how prosperous, from the consequences of inaction ... To the reluctant countries, including the United States, I say this: there is such a thing as a global conscience and this is the time to listen to it."