"Six scientists from some of the leading scientific institutions in the United States have issued what amounts to an unambiguous warning to the world: civilisation itself is threatened by global warming.
They also implicitly criticise the UN's Intergovernmental Panel on Climate Change (IPCC) for underestimating the scale of sea-level rises this century as a result of melting glaciers and polar ice sheets.
Instead of sea levels rising by about 40 centimetres, as the IPCC predicts in one of its computer forecasts, the true rise might be as great as several metres by 2100. That is why, they say, planet Earth today is in "imminent peril"...
Read the complete article entitled 'The Earth Today Stands in Imminent Peril' by Steve Connor: http://environment.independent.co.uk/climate_change/article2675747.ece
The piece finishes with comment that "a feasible strategy for planetary rescue almost surely requires a means of extracting [greenhouse gases] from the air."
"Alfred Wong of the University of California, Los Angeles, at last week's meeting of the American Geophysical Union, in Acapulco, ... reckons the problem is not so much that CO2 is being thrown away, but that it is not being thrown far enough. According to his calculations, a little helping hand would turn the Earth's magnetic field into a conveyor belt that would vent the gas into outer space, whence it would never return...
Read the compete article from The Economist entitled 'Stairway to Heaven' here: http://www.economist.com/research/articlesbysubject/displaystory.cfm?subjectid=348924&story_id=9253976
I must say, as a layman, I'm thoroughly enjoying this debate, and even beginning to follow the technical aspects of it! Although my opinion is about as stable on this issue as a polonium teacup, I do take heart because of two factors:
1. the issue is far more complicated with far more factors whatever their relevance than is presented in the popular press (and it's far easier to make highly dramatised predictions of imminent failure and take comfort in the 'badness' of mankind than to accept reasonable reassurances) - not that I'm dissing the presentation of it in the media or the 'raising of awareness' (probably the worst language anyone has used in this debate so far, so I apologise) of this issue
2. With this amount of willpower studying the difficulties and problems of this issue, I don't see much difficulty in successfully addressing it one way or t'other. Naively optimistic? Possibly, but then I bet there were days when Noah's wife said 'Don't worry, dear, the rain will end one day, and you'll get the chance to own your own vineyard' and he replied 'Oh yeah? Like hell!'
Cheers, guys! Keep it up!
Fernsy
Good points Ender, but angles will be low and your suggestion that these angles must be high enough to melt ice because it already does so, only applies to the latitudes in which this currently takes place. That condition becomes less and less true the further north one goes. One cannot apply the conditions at 60N to a situation at 80N and expect a proportionate response.
And as current cloud cover is in the 60% to 80% range then one must assume that increased cover and increased density of that cover will reduce the amount of heat getting through rather than increase the amount being trapped.
The maximum warming effect of clouds takes place when scattered clouds form over the oceans while adjacent land is clear. When these clouds build up and then move over the warmed land they then trap the heat and produce a net warming. This is not the general case in the Arctic where cloud cover remains high and reflects heat before it can be trapped by either cloud or CO2.
Ian - "And this means that the times when the sun is close to the zenith angle are a much smaller portion of the days sunshine. Take a flat plane, tilt it to 45 degrees and then rotate it by 45 degrees and the resulting angle of incidence is substantially less than 45 degrees."
However we have established that the sea surface is very unlikely to be a polished mirror so the albedo will still not be near that of ice even if the sun angle is low. Quite apart from that the sun in summer even at high latitudes will be high enough for long enough - after all the ice does melt in summer so it must be doing something.
"But it is worth repeating that the melting of sea ice will, when combined with temperature increase, produce an increase in the extent of cloud cover and the volume of moisture in those clouds."
Yes and that will increase the amount of re-radiated long wave radiation being trapped as clouds both reflect radiation and trap it. That is why the function of clouds is the least understood part of the GCMs. So your feedback effect can both increase and decrease the warming at the same time - which one will prevail?