Retorts

I Don't Understand

What is a surface energy flux? ("Doubling the CO₂ content is expected to result in an increased surface energy flux of 1.2 W/m²." Climate of Opinion, Sept) This term is used as if it decisively refutes the claims of an enhanced greenhouse effect, but is not explained, nor is its relevance discussed. And "is expected" begs the question of by whom, and why, and so what? Which way is the energy flux going? Where has it come from -- the Sun, inwards or the Earth, outwards, or what?

R. N. McLean, Lower Hutt

Earlier in the article, John Daly states that the general circulation models predict that doubling the CO₂content would produce a surface energy flux of 1.2 W/m², and that this would come about as a product of surface infrared back-radiation. That is, the energy coming from the sun is re-radiated from the surface at infrared wavelengths and is then trapped by CO₂ and other greenhouse gases. However, as Daly points out, the increased surface energy flux could well be countered by evaporation, convection and cloudiness, rather than producing a rise in temperature.