From Andrew Glikson, Australian National University
I would like to respond to your report that the Earth is undergoing a “beneficial greening” as a result of human-made carbon emissions (8 June, p 14). In part, greening of subtropical regions, such as the southern Sahara, may be attributed to the expansion of the tropics and a rise in humidity. The increase in humidity and in rainfall in subtropical and subpolar regions is consistent with a trend toward Pliocene-like conditions, an epoch in which temperatures were 2 to 3 °C higher than today.
This shift of climate zones towards the poles results in droughts in temperate zones where the bulk of farming takes place, examples being southern Europe, the central US and south-west Western Australia.
These factors, coupled with more extreme weather events in most climate zones, which are harmful to agriculture, hardly justify a view that carbon emissions are beneficial.
Canberra, Australia
