>>Archer uses the analogy of a partially blocked sink. Although the same amount of water is entering it (sunlight) the blockage forces the water level (temperature) higher until a new equilibrium is reached and the same amount of water leaves it as before.<<

csteele,

Thanks for the explanation - that makes sense from a physics point of view. Without having watched the videos (and I probably won't get a chance to be honest), I would imagine that as more CO2 is pumped into the atmosphere, the gravitational effect of the earth will more tightly bind the CO2 molecules into a new layer which will, in turn, act like a cloud that traps heat.

-- -- -- --

I'd like to probe into the politics of the debate a little and play devil's advocate. Over geological time there have been many volcanic events (during rifting phases of continental and oceanic plates) that have spewed many tonnes of noxious gases into the atmosphere. The atmosphere has done a pretty good job of dealing with these gases and finding an equilibrium that sustains life today. Isn't it likely that what we're doing to the atmosphere today will also reach equilibrium that sustains life down the track?

Even if the temperature did go up a few degrees globally, some places would get very hot certainly and become less habitable, but other places that are currently very cold might just become more habitable. Isn't this just swings and roundabouts? And is this really the disaster it's made out to be given that the temperature rise will play out over the next century or so?

PS: I do not have a strong view one way or the other on what the global community should do about global warming but am interested in exploring some ideas and arguments on both sides of the debate.

Sorry csteele, RobP - that's it, I'm outa here.

Let the games begin, have fun.

Dear rstuart,

Thanks for the explanation of the hotter stratosphere. Interestingly Q&A's link (thanks) talks about the cooling effect of greater levels of CO2 on it. Worryingly that cooling may have consequences for making the formation of an Artic ozone hole more likely.

I am still not quite there yet on how a cool layer can exist between 2 warmer ones even given the lack of water in the stratosphere. It seems to go against the notion that water vapour has a global warming impact. More research from myself is obviously needed.

But I might need you to tease out the notion that the stratosphere is hotter because of the fact there is no water in it. In its absence one would have thought the dropping in pressure as you went higher would have also dropped the temperature. Remembering of course as gases expand they cool.

I have just finished lecture 16 which was primarily about the chemistry of carbon. I found it fascinating that continental crusts can be over 4 billion years old but ocean crusts are never more than 100 million years old and undergoing subduction all the time.

Dear RobP,

As I said with the OP I'm keen to keep the politics at bay, at least on this thread. Obviously I'm viewing the course so I can have a more informed 'political' position but I'm just as happy for someone to have an opposite position as long as it is informed.

What I am gaining from the exercise is the ability to dismiss certain arguments that might be put to me. For instance if someone says methane and CO2 make up such a small percentage of the atmospheric gases they must not be capable of significantly changing the environment at all I now know otherwise and can explain why.

Leaving everything else aside I think it is brilliant how many people are prepared to put in countless hours getting their head around global warming. I feel it has probably lifted the gross scientific literacy of our country quite significantly.

That's my 4 x 350 limit.

it strikes me that the error in modeling..comes about by excluding night/time temp drop...we have no doudt watched their models..where the earth gets redder and redder..but the reality is..it gets red in the day...and not red at all..in the night..but not in their models

its the advantage of going..on year..[theory]..not day/night[fact]..same with the gore statements of no ice on the pole a few years ago..but the reality being..there is 25 percent more ice today

then there is the money...UK's richest man..could make more than £1bn from carbon trading scheme.
http://www.clickgreen.org.uk/news/international-news/12971-uks-richest-man-could-make-more-than-%C3%821bn-from-carbon-trading-scheme.html

laughing all the way to the bank..with his carbon credits?

New analysis released by climate change NGO Sandbag has revealed that the UK’s richest resident, Lakshmi Mittal, CEO and major shareholder of the steel giant ArcelorMittal,..could make over £1 billion between now and 2012 from his company’s participation in the EU’s Emissions Trading Scheme.

ArcelorMittal has over 14 million emissions permits that it does not need in 2008, a figure which Sandbag estimates will rise to 80 million by 2012..making it by far the biggest beneficiary of the scheme across the EU.

The carbon market..will only deliver what politicians ask it to,..so it’s up to our leaders to make it tougher and to enable it to make a much greater contribution to tackling climate change.”

the permits undeniably have huge monetary value,..they were received for free..think about who gets the money...little wonder you cant get the science...its a tax...get it...a tax for you..so the poluters can get free subsidy

RobP: "Isn't it likely that what we're doing to the atmosphere today will also reach equilibrium that sustains life down the track?"

This is covered in the lectures, lecture 15 I think csteel said. The answer is it not likely, it is certain. In roughly 100,000 years the carbon cycle will pull the CO2 levels back into balance. This issue is, 100,000 is far too long to help us.

csteele: "Thanks for the explanation of the hotter stratosphere."

Yeah, well I was wrong. Last night I went away and did some background reading because on thinking about it, what I said didn't make sense. Yes water vapour is the biggest heat carrier in the troposphere, but it acts to keep the upper layers warmer not cooler. It does this because as it condenses into clouds it releases its latent heat, then falls to the ground. This is why the layer above the troposphere, the tropopause is so cold - there is no water vapour in it to keep it warm. At least we have an answer for that bit.

So the next outstanding question is why is the stratosphere hot. Part of the answer is it contains O3 (Ozone), which is another greenhouse gas has that absorbs UV and makes it hot. Unlike the troposphere, the stratosphere doesn't mix (much) vertically so the upper layers heat up and because hot air rises they stay up the top.

And so the final question is why is the stratosphere stratified and the troposphere well mixed. I don't know. I could make guesses, but it would be better it someone else gave a more authoritative answer.

Archer, does a series of graphs that shows the peak and an extremely long decay (Absorption) of CO2 from the atmosphere.

He uses 280 ppm (Year 1700)as the base and shows the rise to peak levels then the 'rapid' fall to 25% of remaining of the peak in 1000 years. (a process known as Ocean Invasion);
a further reduction of 15% (due to Calcium Carbonate) taking between 3-10 k years;
the the remaining 10% takes 500k years. (a process he calls weathering thermostat)
i.e. It shows a peak then a long long tail.

However, when overlayed with a graph of the temperature, that remains high with a corresponding gradient drop in CO2 for the first 1000 years, of perhaps a 25% from the peak. Then a steady, but slower reduction for the reminder of the 500k years. i.e.It shows a longer peak and a shorter tail.

I know it has something to do with the chemistry, but I still don't fully grasp why the massive disconnect between the two decay rates.

Archer makes the point that filling our car with petrol today has an effect on the world for 500k years (albeit, in proportion to the graph and the effect the individual action has. Camel and straw)

Can anybody explain the why the disconnect(perhaps the chemistry) to me...I've tried to research it but no luck.