DEAR SIR: I write regarding the recent UN climate change report and a summary article in the Economist magazine, citing the roughly equal but opposite warming/cooling effects of methane (from mainly agriculture) and sulphur (from coal power generation) emissions respectively, being a projected plus and minus 0.5°C of the projected 1.5°C targeted all-in global warming increase.

This quite depressing scientific reality means that the positive effects from the elimination of methane emissions will be largely cancelled out where sulphur emissions are also successfully eliminated – the difference being that the shorter half-life of methane means the positive impact of such changes will be faster achieved, but would still be undone in due course by the cancelled cooling effect of sulphur emissions – a case of the “hare and the tortoise” in effect.

Being a practising accountant, I have no solutions to this dichotomy, but as the agri sector faces negotiations to lower its emissions, policymakers may need to be more aware of the subtlety of these various warming/cooling components, with greater awareness that methane’s shorter half-life means such reductions will, at least, have a much quicker impact on any targeted temperature change trajectory.