From – Klaus Illum3 February 2009
The time scales of the graphs above and below differ by a factor 1,000. The composition of the
atmosphere (H2O, NH3, N2O, CH4, O2, …..) has changed during the last hundreds of millions of
years. During the last hundred thousands of years the CO2 concentration has fluctuated at a
much lower level than previously. Climate change risk assessments should refer to the more
recent periods, not to periods millions of years ago when the atmosphere and life on Earth was
if the question concerned a particular issue of minor importance, I would’t interfere in this discussion within a field in which I have no professional qualifications.
However, this is not an issue of minor importance to mankind.
Therefore, as a citizen with some experience in reading and apprehending scientific assessments I have an obligation to take a stand in the climate discussion.
To take the position that the anthropogenic GHG emissions are of minor importance relative to natural phenomena is not merely taking an academic standpoint. It means to take on ones shoulders a heavy burden of responsibility for consequences which we will hardly live to experience ourselves.
In actual practice a central question is whether or not to allow the substitution of coal for declining supplies of oil and gas.
Regarding the CO2 concentration experiment, you say: “Nature has made the experiment for us.” referring to a graph in your paper.
Please see the note attached as my comment to that statement of yours.
I do not accept the notion of the long history of the atmosphere and the concurrent development of life on Earth as an ‘experiment’ made by nature which is comparable to the experiment of increasing the CO2 concentration by 50-100% in a climate system which has been relatively stable for the last 10,000 years or so.
Professor Klaus Illum