Lungs by Duncan Macmillan. ‘I could fly to New York and back every day for seven years and still not leave a carbon footprint as big as if I have a child. Ten thousand tonnes of CO2. That’s the weight of the Eiffel Tower. I’d be giving birth to the Eiffel Tower’. A couple are deciding their future. Thirty-something, educated, thoughtful, they want to have a child for the right reasons. But in a time of overpopulation, erratic weather and political unrest, what exactly are the right reasons?