(William M. Connolley 23:40, 13 Jan 2005 (UTC)) All this surge of editing presumably comes from the BBC horizon documentary. Which is all very well, but basing your science on a TV programme may not be a good idea.

Unqualified and unattributed editing would indeed be unwise. Checking all the sources used by the BBC would be a very good move, especially for such a potentially important topic; hopefully someone will have the time to do that. Wikipedia is, however a "work in progress" and should be treated as such. 80.42.86.119 23:53, 13 Jan 2005 (UTC)

(William M. Connolley 00:04, 14 Jan 2005 (UTC)) Yeeeessss... but perhaps checking them *before* putting them in would make some sense too?

Agreed, a practice I follow given the time to do so, especially if the source is less reputable than the BBC. Though I know even they are capable of getting basic facts wrong too...

It's not so much that popular science media like the BBC aren't reputable or honest, but simply by dint of their programming priorites they produce material of a rather lower grade of factuality than that demanded by an encyclopedia. In particular, they're prone to:

• picking the most exciting scenario from the range possible and concomitantly discounting the more prosaic.
• downplaying controversy and dissent (except where the controversy is the subject of the piece, in which case they tend to overplay it)
• willful conflation of correlation and causation

The Sept 11th thing is a case in point of this last issue. It's true that there's a correlation between this particular cessation of contrails and a change in temperature; but this doesn't by any means prove a causal link. Worse, as we have but a single datapoint, the correlation is very weak. The article said "with a consequent sudden drop in global dimming", but that's a far stronger statement that the evidence supports. I reworded that paragraph to be much less conclusory. -- John Fader 01:34, 14 Jan 2005 (UTC)

The question of checking sources is one I grapple with every time I want to edit the encyclopedia. To research everything to the level acceptable to, say, a degree level dissertation would simply mean I would never actually write anything given the time I have available.

It's important, in my opinion, to judge whether the inexact and uncoroborated information will be of more value than nothing at all. Or that the good will outweigh the bad. Or something. The fact that anything written will be ruthlessly weighed and edited by others is reassuring in this context. Like the proverbial fountain pen, many articles on which I write soon contain little of my original prose - but are nevertheless shaped by all contributions to them.

Btljs 23:32, 14 Jan 2005 (UTC)

When Horizon showed the graph before during and after the plane groundings the before and after (not during) had a noticeable difference so the difference in temperature was neglibleShiney 06:35, 14 Jan 2005 (UTC)

• My guess is that they show very simplified graphics (i.e. three values on a bar graph) but that the analysis behind these results is somewhat more thorough and we are not given that in the programme. The researcher said that it had not been observed in 30 years so it can't be negligable - the point being the way it 'jumped' then returned to what was presumably a smooth curve if we had seen the whole month for example.

Btljs 23:19, 14 Jan 2005 (UTC)

I can't find any publication by Ohmura in 1989, but he has four in 1990:

• Ohmura, A., 1990: Reevaluation and monitoring of the global energy balance. Sanderson, M. (Ed.): UNESCO Source Book in Climatology, 35-42.
• Chen, J. and Ohmura, A., 1990: On the influence of Alpine glaciers on runoff. Lang, H. and Musy, A. (Eds.): Hydrology in Mountainous Regions I, IAHS Publ., 193, 117-125.
• Chen, J. and Ohmura, A., 1990: Estimation of Alpine glacier water resources and their change since 1870s. Lang, H. and Musy, A. (Eds): Hydrology in Mountainous Regions I, IAHS Publ., 193, 127-135.
• Enomoto, J. and Ohmura, A., 1990: The influence of atmospheric half-year cycle on the sea ice extent in the Antarctic. J.Geophys.Res, 95, 9497-9511.

I'd guess that the first one is the most likely to be the relevant paper. -- John Fader 20:09, 15 Jan 2005 (UTC)

(William M. Connolley 21:02, 15 Jan 2005 (UTC)) Thanks. Now all we need is for someone to check the UNESCO book... incidentally, there is something by Ohmura in 1989 (O, Gilgen and Wild, but it looks like a tech rep not in a journal and may well be in German): Ohmura, A., H. Gilgen, and M. Wild (1989), Global Energy Balance Archive GEBA, World Climate Program—Water Project A7, Report 1: Introduction, Zuercher Geografische Schriften Nr. 34, Verlag der Fach-vereine, Zuerich, 62 pp.

The theory behind the Horizon program, that more sunlight is reflected due to (sulphate) aerosols is proven false.

As you may know, we have some satellites flowing around out of the atmosphere, which measure reflected sunlight (SW reflection) and heat (LW emission) from below. For the (sub)tropics, in the period 1985-2001 the amount of sunlight reflected by clouds reduced with ~2 W/m2. (see: http://www.atmos.ucla.edu/csrl/publications/pub_exchange/Wielicki_et_al_2002.pdf , confirmed for the 30N-30S (sub)tropics in http://pubs.giss.nasa.gov/docs/2002/2002_ChenCarlsonD.pdf ) In the same period, there was a loss of cloud cover, both in the tropics and sub tropics (and even up to 60N-60S) of 0.33% and 1.7% respectively.

If there is global dimming at the surface, the only explanation possible is that more sunlight is retained in the atmosphere. Which is (only) possible with (dark brown and black) soot particulate.

If soot particulate is to blame, then a reduction of them would have a cooling effect, not a warming effect!

See also the amount of reflected sunlight from earth on the moon ("eartshine"), which parallels the "global dimming" trend, while it should have opposite trends, at: http://www.bbso.njit.edu/science_may28.html