Manmade global warming is a fact
DR ALAN Rogers is correct in saying that global temperatures dropped between 1940 and 1970; the 0.2 degrees celsius cooling was caused by sulphate aerosols from industry and volcanoes (Letters, March 5).
But he is wrong in claiming that it disproves anthropogenic (manmade) global warming. It then shot up by 0.8 degrees during the next 30 years, when sulphate levels fell back.
Climate change deniers can’t understand that there are numerous factors influencing the earth’s climate, both natural and caused by man, and the existence of one does not disprove the existence of others.
These effects are superimposed on the global warming caused by the greenhouse effect due to rising levels of CO2 and other greenhouse gases, which is a scientific fact.
MICHAEL JOB GLENGARRIFF, CO CORK