DEAR SIR: In last week’s letters page (21 September) Tom Cook on “the role of methane gas” as a greenhouse gas claims “methane is 20 times more harmful than carbon dioxide” and “is often trapped inside the earth and it is released by mining/deforesting”. He provides no evidence for any of these statements, but he did ask for evidence for a statement in my letter of the previous week that “methane and nitrous oxide are not greenhouse gases”.
I don’t know Tom Cook or what his qualifications are, but he might like to read a paper in the journal of The New Zealand Institute of Primary Industry Management Incorporated: Volume 22, number three (September 2018 pages 3-10) ISBN 2463-3011 by Jock Allison and Thomas P. Sheahen entitled “The contributions of water vapour (H2O), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N20) to the warming of the atmosphere.” This paper quotes from fundamental research on this subject and can also be found online.
Also, unlike carbon dioxide, methane breaks down after 12 years.