R QUIRK states several fallacies (Letters, March 12, ‘What Greta doesn’t realise’) when he jumps to the conclusion that zeroing carbon dioxide emissions in Britain would not change the climate.

CO2 causes warming despite being a small proportion of the atmosphere. Would R Quirk eat a poisoned meal because there’s only a small amount of cyanide in it? Small things can have important effects.

Yes, manmade CO2 is small compared to naturally produced CO2. But CO2 produced naturally is matched by the CO2 absorbed naturally, by plants and oceans. And the natural world cannot absorb all manmade CO2, so atmospheric CO2 levels are rising.

Britain’s CO2 is a small proportion of the world’s, but the hope is that by example and by dialogue we can persuade other nations to act too. For the alternative is the tragedy of the commons: increasing CO2, increasing warming, irreversible tipping points and our eradication from the planet.

We can and must, despite climate-change deniers, change things for the better.

Nigel Coe