‘Fund gas’ threat

Contrary to Dr Dryburgh’s claim that carbon dioxide is not a pollutant (Letters, 12 March), the dictionary definition of a pollutant is that of “a substance which has harmful or poisonous effects”. Given the effects of CO2-­induced global warming, it is safe to say that CO2 has harmful effects.

Specifically, and in more 
scientific terms, CO2 is referred to as a “fund pollutant”, as 
the environment is capable of absorbing at least a proportion of that which we release into the atmosphere.

The effects of fund pollutants become significant when their emission rates exceed the environment’s absorptive capacity for them – which has certainly been the case with CO2 throughout most of the past century into the current one.

(Dr) Gavin Whittaker