Protagoras,

Sorry but you haven't done your homework. H2O the gas may be a greenhouse gas and therefore a contributor to warmth, but the main effect of H2O is via the clouds and convection effects which are NOT well understood.

Water is liquid up to 100C but is volatile which gives it the useful cooling property that even below 100C the odd molecule can pick up energy from the surface of the planet and then behave like a warm gas and rise on a convection current, carrying that energy (i.e. heat) way from the surface before condensing into clouds and ultimately rain. Some types of clouds tend to reflect more incoming solar radiation than others, to the point that they actually have a cooling effect. Others trap heat beneath them.

See http://www.atmosphere.mpg.de/enid/3__Sun_and_clouds/-_Clouds_and_climate_ti.html

Some clouds have a net heating effect and some a cooling effect. The history of the planet, and in particular the absence of any previous 'runaway greenhouse effect', despite warmer climates and much higher CO2 levels than are conceivable today, give us reason to believe that there are strong negative feedback loops that will mitigate any warming or cooling effects, keeping temperatures within a fairly narrow range. Good old H2O is the obvious candidate.

Suggest you do some reading about this.

Hi Kalin,
glad again that you're accepting the subtleties in this, where many sceptics just volunteer that "warmer weather = more clouds = more rain = more crops, so lets warm the planet!"

I do think there are probably cloud related limits to warming and also life cycle events that can also suck Co2 back out of the atmosphere and cool the planet. Climatologists appear to still be modelling the effects of clouds, and according to what I've read from Tim Flannery and seen on Catalyst there appears to still be ongoing debate about the amount of safety net or range in temperature growth due to negative cloud forcings or positive.

But it's like we're facing Dirty Harry and the climate is asking, "Do you feel lucky, Punk?"

The trends are up, and previous geological eras were hotter than today, and experienced dieoffs as a result! See studies linked to under:
http://en.wikipedia.org/wiki/ELE#Sustained_and_significant_global_warming

For a brilliant half hour on the biological safety nets planet earth may have for preventing a Venus like runaway greenhouse event, see part 3 of "Crude" by the ABC science unit. However, as they suggest there are some NASTY side-effects of letting Co2 levels get that high and while it might be a safety valve that prevents Earth turning into Venus, Crude suggests that the safety value is no where near "safe enough" to save our civilisation and let us be ambivalent about Co2 levels.

http://www.abc.net.au/science/crude/

Again, water appears to "mostly" be a neutral forcing within the climate variation we are worried about. We *are* raising Co2 levels which will accentuate water's role. Water acting as a higher order safety valve preventing Venus is one thing. But will it prevent massive crop failure and an increase in failed states in our current civilisation? So far the literature is not clear, and does not appear to let us relax about Co2, or we'd KNOW about it!

(All those agencies I listed agree that man-made global warming being DANGEROUS!)

After watching Prof Plimer on A-PAC Mon 13/7 I found this forum and have read many posts with great interest. I like Kalin's analogy of the effect of wind on the outcome of a football game. It seems everyone is missing the most important and telling point made by Plimer - that climate warming / cooling is not driven by one or two factors. The whole system needs to be considered. Lets stop drawing simple correlations between temperature and one or two greenhouse gases and, if we really feel that we need to, start considering at the whole package including solar activity, ocean warming / cooling ....and the list goes on and on. Does Man really think he can influence the balance of such a complex system? History, and (importantly) science has already proven that even after the 5 or 6 events causing mass extinctions (read quick, massive climate change), the 'natural' balance will be restored over time. No matter what we do, we are merely ants scratching an itch on an elephant's backside.

CO2 in the venus atmosphere is about 96% by volume. http://hyperphysics.phy-astr.gsu.edu/HBASE/Solar/venusenv.html

CO2 in the Earth atmosphere is about 0.04% by volume. http://en.wikipedia.org/wiki/Carbon_dioxide_in_the_Earth%27s_atmosphere

You might think this means there's only 2400 times as much CO2 on Venus as on Earth. But the figure is actually much higher because the atmosphere of venus is Much denser. Also , there is very little H2O in the venetian atmosphere. In short venus is useless for comparison purposes. It is grossly misleading to insinuate that 'runaway global warming' could turn our atmosphere into that of venus. All the known fossil fuels reserves, if consumed tomorrow, would still leave CO2 as trace gas, albiet at much higher levels than today.

As for all those bodies agreeing that global warming is DANGEROUS, I presume by 'dangerous' they broadly mean global warming is likely to cause large scale disruptions to our social and economic systems with inevitable loss of life through famine, and geographical displacement, etc.

I expect you will accept that these same organisations must also agree that global cooling would also be as 'dangerous' for much the same reasons.

It follows then that the only 'safe' way forward is to keep the worlds climate in equilibrium.

Consider then, that most of the time, the planet is MUCH cooler than present. Absent the current fear of man made global warming, scientists would (as they were 30 or 40 years ago) worry about very significant cooling (based on geological history, likely to be as much 10C - http://photos1.blogger.com/blogger/4116/666/1600/IceCores1.gif), which is also certain to be extremely 'dangerous' and which would appear to be due relatively soon.

Clearly, the ice core records shows that climate fluctuates quite regularly and rapidly, even without our efforts to mess it up. Unfortunately, with our present or forseeable technology, we have no prospect of maintaining such a complex and huge system in a 'safe' happy equilibrium. Climate change is inevitable, as are the 'dangerous' consequences. We will just have to deal with them and it would be wiser to harness our resources to that end.

Kalin1

I suggest that you do more research on clouds in the future rather than provide us with a tired old paper published in 2003.

I prefer to glean my more up-to-date information from reputable scientists (attached to reputable climate institutes) who are sufficiently ethical to publish their corrections. While research results continue to vary, increased research and more sophisticated methods of analyses and modelling are drawing us closer to understanding the impacts that cloud compositions have on climate change.

I have concluded that you know little about anthropogenic particulates, soot and sulphate aerosols and their impacts on cloud formations and subsequently, the domino effect. I do not reiterate the “all things are bound together” from some esoteric philosophical whim.

http://www.giss.nasa.gov/research/briefs/koch_04/

Large concentrations of human-made aerosols decrease and increase rainfall as a result of their radiative and CCN activities. At one extreme, pristine tropical clouds with low CCN concentrations rain out too quickly to mature into long-lived clouds. On the other hand, heavily polluted clouds evaporate much of their water before precipitation can occur, if they can form at all given the reduced surface heating resulting from the aerosol haze layer.

I am reminded of the Asian brown “cloud” which is 10 million square kilometres wide and three kilometres thick, a fluctuating haze of man-made pollutants now spreading across the whole Asian continent and blocking out a significant proportion of the sunlight. This brown "cloud" also affects Australia's climate.

http://www.cbc.ca/world/story/2008/11/13/brown-clouds.html

Your allusion to “higher” CO2 levels in the past is also vacuous since scientists have estimated that current CO2 levels are the highest in at least 650,000 years. Humans were not around 650,000 years ago, however, seemingly you have no interest in past extinctions either where scientists (not least, the respected palaeontologist, Dewey McLean)have provided a convincing hypothesis that carbon dioxide played a significant role in past extinctions.

“Those who ignore the past are bound to repeat it.”

Riffmaninoz – Did you know that renowned geophysicist and palaeontologist, David Jablonski, estimated that the recoveries of the “natural balance,” after previous extinctions, were between 5 and 10 million years?

Nice post Protagoras! Your mentioning the CCN reminded me of this video. I love TED!
http://www.ted.com/talks/willie_smits_restores_a_rainforest.html

Just to prove I'm not a total doomer, PLEASE watch this 20 minute video as it is very inspiring and is one of my favourite things on the net right now. He builds a complete rain-forest ecology, a complete local economy, AND changes the local climate by the trees giving off chemicals that demonstrably increase rainfall.

Kalin you’ve fallen for climate myth number 4, "But they predicted an ice age in the 70's.”

First point: so what if they did? Real science changes and evolves with new data, but dogma doesn’t. Climate sceptics keep trotting out the same old dogma while climate science evolves. Go figure.

Second point: That's Monkton's strawman through and through and it's a pile of garbage. A few climatologists may have mentioned it, and then the media went nuts with it. There was no climatologist CONSENSUS though!

http://www.newscientist.com/article/dn11643-climate-myths-they-predicted-global-cooling-in-the-1970s.html

On Venus: I do understand Venus is VERY different to the earth. It's atmosphere is 96 times Earth's, and is mostly carbon dioxide. But read this next argument slowly and carefully!

"generates the strongest greenhouse effect in the solar system, creating surface temperatures of over 460 °C (860 °F).[28] This makes Venus's surface hotter than Mercury's which has a minimum surface temperature of -220 °C and maximum surface temperature of 420 °C, even though Venus is nearly twice Mercury's distance from the Sun and receives only 25% of Mercury's solar irradiance."

http://en.wikipedia.org/wiki/Venus#Atmosphere_and_climate

So much for the sun being the main driver of climate. If any planet was meant to have a "greenhouse effect" based on the sun, you'd think it was Mercury!

(Also against the sun driving climate on earth is the fact that temperatures are increasing more during the winter and night, not summer and day).