Grant,

Wen you reach a peak in something and start coming down the other side, those initial steps down the other side will also be among the highest that you've taken.

No, I am not saying that the earth has DEFINITELY started cooling but I think there are grounds for optimism about this.

Besides, it wasn't eighth hottest. In Australia it was tenth and globally it was fourth. (I'm sure that this was incidental to what you saying but let's have the facts correct.)

cheers

Snowman,
Thanks for that correction, I was too lazy to check my 'facts'.
I'm glad you're not saying 'defnitely' that the climate's cooling. But could you explain the basis for that idea? Perhaps carbon dioxide molecules have suddenly and magically stopped absorbing at infrared?
Grant

Hi Grant,

I think it is just that carbon dioxide causes less warming than many proponents of global warming would have us believe.

According to the Stefan-Boltzman equation a DOUBLING of carbon dioxide should cause an increase 0.7 degrees (or is it 0.77C ? doesn't matter much!) Since about 1800 the increase had been about one-third of that, so we can expect warming of about 0.2 degrees DIRECTLY attributable to carbon dioxide (but that doesn't mean that it has happened as you'll see below).

The dire predictions for warming are largely based on theories that certain climate elements (eg. clouds) provide positive feedback to CO2-based warming (ie. they amplify it).

Those theories are looking very doubtful but it's hard to say if there is NO feedback at all, or the feedback occurs only in some situations, or the fedback happens all the time but is far less than the theories say.

All that I think we can say for now is that other climate factors have recently been far stronger than any carbon dioxide-based warming and that the net result of those other factors has been cooling.

Note that these "other factors" may include solar emissions and that some scientists believe that solar activity is now in decline as part of its normal cycle. El Nino's could also be included in those "other factors" and the one in 1998 was particularly strong.

I hope that's enough for you for now. I can't post any more msgs here today ;-)

cheers

Snowman,

The Stefan-Boltzman equation could not predict temp increase based on CO2 concentration, since the only independent variable is temperature of the molecule, rather than the quantity of the molecule in the atmosphere. It may be a part of the very complex models that attempt to forecast climate responses. What are your qualifications in this field?

Clouds per se are a negative feedback, not positive. The theory is that warming is increasing water vapour in the atmosphere, which leads to more clouds which reflects solar radiation. That's a negative feedback.

Unfortunately, water vapour is a greenhouse gas 6 times more potent than CO2. That's a positive feedback.

The solar radiation argument is somewhat worn and is easily dealt with I think. The fact is that solar radiation does affect climate, but over periods of centuries. There is no correlation between solar activity and human time scale warming that accelerated only in about the middle of last century.

Have you considered the possibility that you are wrong? And if you are, what are the implications for us?

Grantnw,

I'll try to drag out my info on Stefan-Boltzman this evening when I have more time.

Funny you say that clouds are a negative feedback because most climatologists say they are positive. Their argument is that they trap heat, especially at night. (See also graph about 65% through http://www.john-daly.com/forcing/hug-barrett.htm) Personally I think that both positions are correct some of the time and which is happening can depend on the geometry of the situation. At night clouds trap heat, cloud increase in the late afternoon traps, cloud in morning blocks radiation and hence cools.

I agree with you about water vapour. I wonder if all the WV that human's throw into the atmosphere is enough to disturb the natural balance.

I question some of your assertions about solar radiation because they don't exactly match what I've read. (eg. see from Mar 2004 at http://www.swissinfo.org/sen/Swissinfo.html?siteSect=511&sid=5080155)

More to the point there's more to solar emissions than just radiation. One UK company makes good money from predicting weather patterns based on solar particle emissions.

Grant, can you do me a favour? Explain why the last six years of carbon dioxide emissions have not caused global temperatures to exceed their levels back in 1998.

later,

LOL ... I could ask you the same thing ... solar activity was well below average in 1998.

Of course, the reason why there hasn't been a year on year increase in temperature is the same reason the average world temperature isn't exactly the same each year - a complex system with normal stochastic variability.

Here: http://www.env.leeds.ac.uk/envi2150/oldnotes/lecture9/lecture9.html you'll find some information on the difference between CLIMATE VARIABILITY and CLIMATE CHANGE. You'll also note the solar activity chart that shows a downward (albeit cyclical) trend in solar activity since 1978.

So I'll return to my question - why was 1998 so hot when solar activity was so low?

Regards,

Grant