Asked by: Nick Pullen, Braintree
Cigarettes are made from tobacco leaves that originally absorbed all their carbon from the atmosphere as they grew. When you smoke them you're just returning this carbon so the net effect is zero. But tobacco agriculture also generates greenhouse gases of its own, in the form of CO2 from the diesel used in farm machinery and NO2 from fertiliser - not to mention the CO2 attributed to packaging, distribution and advertising.
On the other hand, smokers live 10 years less than non-smokers on average. If those people didn't smoke, they would have lived for another decade driving their cars, using electricity and buying things. This would generate much more CO2 than all the cigarettes they ever smoked. So smoking actually reduces global pollution, simply by eliminating the polluters!
Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.