Horizon - Global Dimming/Warming

The program should have been right, if they should have given details about what the different aerosols do. Sulphate aerosols are of particular interest, as they attract water and may seed clouds. These reflect more sunlight back to space. Other aerosols (natural or human-induced) like sea-salt, Sahara sand, fertiliser,... reflect sunlight, but don't attract water. Soot aerosols absorb sunlight and thus heat the surrounding air. The net effect is that sulphate aersols have the highest direct and indirect (on clouds) cooling impact, followed by the others for mainly direct impact, while soot aerosols have a net warming effect. See the graphs 1d-1h of the IPCC for the different results of human-induced aerosols at:

Ferdinand

While our pollution certainly doesn't help, it is worth noting that in Roman times grapes were grown in Southern Scotland and in Dickens' time the Thames regularly froze over. While dealing with polution is a must, it is also important to factor in the (seemingly) regular climate changes before coming to a conclusion - not a trait of TV programmes that try to imply they are giving all the facts.

Just my 2p's worth.

Richard

...and wheat was grown in Greenland too.

Steve

But those facts water down the argument so they have to be left out. Same with the vapour trails thing - requires specific atmospheric conditions for them to form at all, and even more specific conditions for them to form, persist and spread. Most often the specific conditions for formation occur above existing cloud anyway so it makes absolutley no difference. No denial that they do affect the temp range when they form and spread on an otherwise clear blue day, but the conditions are local (certainly not USA wide, as the programme suggested) and certainly no worse than a whiff of cirrus or the build-up of cumulus on an otherwise clear and beat day.

If you've got an axe to grind, it's dead easy to find some facts and statistics that you can quote to support the swing of that axe, especially if you quote them in isolation from any non-supportive arguments, facts and statistics. I noticed how the "scientist" had his focus on one specific little patch of California with four or five trails across it. Probably got a PhD out of it too. They'll be banning fox hunting next and pretending that badgers don't spread TB into cattle!!

Steve

So Steve was, like

Nah, could never happen here....