The following comment by Paul Williams provides a different perspective on the question asked by Walter Starck a couple of days ago.
"I think we argue over AGW because there's so many unanswered questions, such as:
1. Where are the climatic catastrophes we've been hearing about?
2. Why are the AGW proponents using dodgy statistics to bolster their case? (Even though they've now "moved on")
3. Why are they proposing ineffective "solutions" for climate change, such as Kyoto?
4. Why do they constantly say the debate is over, when it obviously is not?
5. Why do they attack their opponents, rather than their opponents arguments?"
And the flea gives the elephant jungle fever and the elephant dies. Strange how something so small could upset the balance.
C20 - hmmm must be a new gas! Wonders never cease.
However one must realise that it was only less than a year ago that we discovered that the plant kingdom produced CO2 during the night and O2 during the day - reversing things. Anthropogenic forcings have not this factor incorporated into the model.
And in any case there is no discrete CO2 gas phase in the air which can be treated as a distinct physical factor. Others have argued that the behaviour is applicable at the molecular scale, but that is a furphy as we have no experimental data on the behaviour and physical properties of CO2 at the molecular scale. Principally because we cannot measure it. CO2's molecular properties are inferred from its macroscopic properties.
That said, the molecular forcing of CO2 in air is much like the assertion that some air bubbles in the ice cubes cooling your beverage influence the temperature.
And that a flea on an elephant's tail is capable of influencing its progress along its habitual path. The elephant is unaware of the flea but the flea, in its hubris, THINKS it affects the elephant.
From such intellectual molehills mountains are formed.
John, for that to be the case, the forcings from aerosols would have to show an increase up until 1975/6, followed by an abrupt decrease and a continuation at a lower level or a continued decline. At least that seems reasonable to me.
Yet the aerosol forcings, as far as I know, don't do that. There is a bit of a dip for about three years from 1980, then a continuation of the curve of increased forcings.
http://www.giss.nasa.gov/data/simodel/trop.aer/
With the booming Chinese economy, it would not be a surprise if aerosol forcings are still increasing.
1998 was the warmest recorded year last century, but it seems highly unlikely that aerosol forcings were particularly low that year. I think we would have heard a bit about it if that was so.
So I'm struggling to accept the "GHG forcings overpowered aerosol forcings" theory. If it is as you say, surely there is some understandable evidence to back it up, rather than the output of GCMs.
In the meantime, there is the correlation of temperature with changes in upwelling of deep Pacific ocean water, which is in turn correlated with changes in Rate of Change of Length of Day, correlated in turn with changes in solar system angular momentum. (Not sure if I've got that right!).
While correlation is not causation, shouldn't it carry more weight than LACK of correlation?
Well - it's an interesting point - what is "a natural cyclical fluctuation". There seems fair paleo and modelled evidence that the three Milankovitch mechanisms are cyclical and overlapping at big time scales. But apart from that - what exactly is a natural fluctuation - chaos - something we don't understand? Would have thought that El Ninos and the like are "quasi-periodic" but not cyclical/predictive/repetitive - predictive perhaps in an limited way close up to the event in an emerging season but not over years in advance.
So we're saying the climate could just "warm up" globally or "cool globally" for no real reason?? Don't sit well with me - but interested in any serious comments.
Have you got that paul?
If the temperature goes down it is"natural cyclical fluctuations".
If the temperature goes up it is"anthropogenic forcings".
Makes perfect sense!
Paul, your question was answered a couple of comments up. The decline 1940s to 1970s is attributed to a combination of sulphur + particulates and natural cyclical fluctuations. The upward trend for C20 as a whole can be explained entirely by the net impact of anthropogenic forcings.
Louis Hissink
I think you have hit the nail on the head re "redistributing wealth not climate" When you think about it Natural Variation, Solar Activity,and of course water vapour are just as likely/more likely to be the cause of any warming as CO2
but you can't have any wealth redistribution on the back of that argument!
Fosbob - whip over to James Annan and put on a bet then !
Malcolm Hill - same old same old.
Robert Cote,
I don't think anyone knows what percentage of global climate change can be attributed to humanity.
It is instructive to remember the comment made some years back by the Canadian Environment minister whjo reckoned that so what if the science behind global warming is wrong, Kyoto was always about redistributing wealth, not climate. Climate was the vehicle to implement that redistribution except that it has now been derailed.
It is also high time that the IPCC stopped adopting standards of practice that are not in accord with the norms. I refer of course to the way in which the economic stuff has been handled, which was highlighted at great length previously on this blog by Ian Castles.This is particularly so when the emphasis is always to the melodromatic and extreme.
The pro-warmers might be more credible if for once they could acknowledge that there might also be some benefits of being warmer,with slightly higher levels of C02, and these benefits have economic value. But no, they cant even yield to common sense on that point.
But to then come up with an idiotic solution called Kyoto, as the answer to an already dubious problem, shows that whatever the final answer might be, it sure as hell has been handled appallingly badly by the IPCC and the Brigade of Euro spivs driving it.
Another UN/Europe stuff up.