Reality of Climate Change - Hacked E-mails Debunked

Originally posted by -PLB-
This answers my question, thanks. My assumptions on how they calculated the increase in radiative forcing caused by doubling CO2 was incorrect. But still, I can nowhere find how they did calculate it. I read the paper linked on Wikipedia, but it pointed to the IPCC report. In that report I could not find it. If anyone can give me the page in the report where it is calculated, or knows a paper or article that explains it, it would be very welcome.

You're talking about climate sensitivity: it's been estimated by both modelling/physics and observations. I would suggest looking up Ray Pierrehumbert's book on the physics. It's still available online for free. Moreover, I haven't watched it all, but there's a lecture series online as well (not sure how deep it goes into the maths, it's for a non-science majors).

geoflop.uchicago.edu...

Could be worth the bother. And for the observations, James Annan has done some work on combining data from various studies (IIRC, Annan & Hargreaves, 2006).

reply to post by melatonin


Climate sensitivity is used to calculated the temperature change as result from the radiative forcing. So climate sensitivity is not what I am looking for, I am looking for calculations of radiative forcing itself. Currently the radiative forcing by CO2 is about 1.6W/m2. According to the IPCC, a doubling of CO2 results in an increase of 3.7 W/m2 in radiative forcing. So doubling the CO2 levels results in more than tripling the radiative forcing (from ~1.6 to 5.3).

I did find the paper on which the values of the IPCC are based, however, I can not access it. It can be found here: www.agu.org...

Originally posted by -PLB-
So climate sensitivity is not what I am looking for, I am looking for calculations of radiative forcing itself.

Righteo.

F = 5.35 ln(C/Co)

Where 5.35 is the constant derived from radiative transfer models (e.g., MODTRAN) using the HITRAN database; C = target concentration; Co = baseline concentration.

F = 5.35 ln(560/280)

F = 5.35 ln(2)

F = 5.35 x .693

F = 3.71wm-2

You should be able to find the Myhre et al (1998) paper easily enough. And there's a version of MODTRAN on the site I gave earlier with the lectures:

geoflop.uchicago.edu...

According to the IPCC, a doubling of CO2 results in an increase of 3.7 W/m2 in radiative forcing. So doubling the CO2 levels results in more than tripling the radiative forcing (from ~1.6 to 5.3).

If you use the higher level of CO2 as a baseline, yes.

But it's generally viewed as from 280ppm->560ppm. With 280ppm as the pre-industrial level. So if we calculate from 385->770ppm, then we'll have 3.7wm^-2 worth of forcing. But the 1.6wm^-2 is already from the 280ppm baseline (280-380?). The first doubling will be reached at 560ppm.

[edit on 14-12-2009 by melatonin]

reply to post by Long Lance

afaik, it isn't one-way at all, carbon monoxide inhalation is ample proof for that, because it bonds more readily to haemoglobin than O2, which means that relatively little is needed to reach lethal levels.

CO is a single-bond molecule like O2, and this allows it to utilize the same chemical pathways as oxygen to enter the bloodstream's hemoglobin. Once it is accepted by hemoglobin, the bonding to that hemoglobin is stronger than oxygen's bond (in large part because CO is not as stable as O2 and tends to form stronger covalent bonds tio the hemoglobin than to itself) and therefore will not release when needed. The hemoglobin that accepts a CO molecule is for all practical purposes a dead weight in the blood supply and must be replaced.

CO2 contains two covalent bonds and cannot use this chemical pathway.

You are correct, though. This is a good example of how low some people will stoop to perpetuate the "CO2 is bad" mythology. I will not allow such claims to go unchallenged.

TheRedneck

reply to post by melatonin


Those are of course not the actual calculations, but the result of the calculations. I finally found the paper I mention above, but it is kind of hard to find how they come to that value of 5.35. I have to say that I haven't finished the whole paper yet, but I kinda get idea there are immensely complex models behind it, and it would be very hard to verify it. But still, it is basically one of the most important values in the whole MMGW theory, so it would be nice if there was some sort of general explanation.

About the doubling, thanks for explaining it (although it was also explained in that paper, but still).