Comparisons need deep scrutiny and the whole system and associated infrastructure needs to be taken into consideration - for example, with cars you need roads, bridges etc etc - concrete/steel etc etc (concrete 8% of worldwide emissions with aviation 2.5%)
I've seen a figure of 7% for human respiration contribution to CO2 production, wonder if Comrade Corbyn has any suggestions.
http://s3-eu-west-1.amazonaws.com/me...Go+Summary.pdf