What a wonderful environmental parable is now unfolding around a meeting of 150 countries held last week in Kigali, the capital of Rwanda, to discuss an international ban on yet another greenhouse gas, to aid their wish to halt global warming.

Back in 1987, when there was a huge panic over the hole opening up in the ozone layer over the Antarctic, 197 countries signed the Montreal Protocol, the world’s first major environmental treaty, agreeing to phase out the use of chlorofluorocarbons (CFCs), used in everything from refrigerators to hair-sprays, which were supposedly causing the ozone to disappear.

How far this has actually been responsible for the fact that the ozone hole has recently been shrinking is still a matter of scientific dispute. But CFCs have been widely replaced by hydrofluorocrabons (HFCs), used in refrigeration and air-conditioning, which, because they are short-lived, were viewed not to be damaging to the ozone layer.

However the penny has finally dropped that these HFCs are even more powerful greenhouse gases than the CFCs. So the Montreal Protocol must now be amended to ban these wicked “pollutants” as soon as possible, not least in light of last December’s Paris agreement that supposedly pledged the world to prevent global temperatures rising by more than 1.5 degrees Celsius.