Response to challenge from Sir Alan
IN response to
Peter Foster’s challenge re climate change
(ODT letters,
21.4.17), I have consulted a very reputable colleague (as he suggested), and would claim Peter should know better than to pose a phoney question. Peter has asked for ‘‘any peerreviewed paper that shows CO2 having caused climate change based on evidence from observation.’’ As he should know, this is an impossible question. There is only one set of observations of the earth’s climate, which includes all the ongoing influences of greenhouse gases, solar variation, volcanoes, etc.
There is no ‘‘control’’ earth we can compare with to ascertain the direct effects of increased greenhouse gases.
In medical science, for instance, doubleblind trials can be run with and without treatment, to assess the effect of a certain drug or treatment. So one would never find a medical paper that shows a drug has had an effect, based only on evidence from observation — unless that paper reported on trials with and without the drug.
In climate science, comparisons are done using climate models, which can be run with and without greenhouse gas increase. They clearly show the warming effect of greenhouse gases. Because we have no modernday observational record that is not influenced by greenhouse gas increase, we cannot directly demonstrate the effect of greenhouse gas increase from the observational record. Alan Mark, FRSNZ, KNZM
Dunedin
BIBLE READING: Bless those who persecute you; bless and do not curse. — Romans 12.14.