If the world was much warmer 3 to 5 million years ago with the same level of CO2 does that mean that if we had not had the industrial revolution would the world now be much colder?

No, the world would probably be a just a little bit cooler than it is now. It would even most likely a tiny bit cooler than it was before the industrial revolution.

The reason it is not yet a lot warmer is, as Tom says, because of thermal inertia. It takes time for things to warm up, particularly the oceans.

It's not about insulation it's about radiative induced warming in compound gas molecules.

Posted By: eniacsI often wonder what real difference C02 in such small concentrations can do. When i see numbers like 400ppm it makes me wonder why we dont fill our window units with pure C02, since it must be amazingly insulative stuff...

Of course, scientists who study climate change don't wonder about this at all. They just make up an answer without given the matter any thought at all. Or maybe they've looked into the matter in increasing detail over the last 150 years or so and very carefully calculated the effects of the different atoms and molecules in the atmosphere at each of the wavelengths, pressures and temperatures applicable to radiation moving upwards, sideways and downwards at levels between the surface and some height where the atmosphere becomes negligible.

Anyway, you wonder about comparison with gas in a window. So let's do the arithmetic. Air is made up mostly, to within a couple of percent, of nitrogen (about 80%) and oxygen (the remain 20%) diatomic molecules. Nitrogen atoms have a standard atomic weight of about 14 (and a tiny bit) and Oxygen (a tiny bit short of) 16 so air has an average molecular weight of 14 × 2 × 0.8 + 16 × 2 × 0.2 = (4 × 28 + 32) / 5 = 144 / 5 ~= 29. In other words, a mole of air has a mass of about 29 grams.

Surface pressures are typically about 100 kPa. Therefore, the column of air above a square metre of surface has a weight of about 100 kN. With the force of gravity being about 10 N/kg that's 10'000 kg (10 tonnes or 10 Mg) per square metre or, at 29 g/mol, about 345 kmol/m².

CO₂ at 400 parts per million would therefore be 345'000/1'000'000 * 400 = 138 mol/m². That is, the total amount of CO₂ in the atmosphere above one metre squared of the surface is about 138 moles. Since the molar mass of CO₂ is about 44 g/mol that's about 6 kg/m².

A mole of gas at standard pressure has a volume of about 23 litres:

https://en.wikipedia.org/wiki/Molar_volume

23 litres is 23 dm³ or 23×10⁻³ m³.

So to get as much CO₂ in your double-glazed horizontal skylight as there is in the atmosphere above it you'd need a thickness of 138 mol/m² × 23×10⁻³ m³/mol = 3.174 metres.

Bit inconveniently thick, I think.

There's also the point that it's not doing an awful lot of insulation, anyway. The total of the whole greenhouse effect (caused by CO₂, water vapour and other gases) is to raise the average temperature of the Earth's surface from, roughly, -15 °C to +15 °C. This is relative to the depths of space which have an effective temperature of about -270 °C. The heat absorbed by the Earth from the Sun and therefore the amount which needs to be radiated to space in equilibrium is about 250 W/m².

Thinking in building terms, the U-value of the vacuum of space would therefore be 250/(270 - 15) = 0.9804 W/m²·K. Adding our 3 and a bit metres of CO₂ brings this down to 250/(270 + 15) = 0.8772 W/m²·K. Not impressed.

Or, in SI R-values, we've gone from 1.02 m²·K/W to 1.14 m²·K/W, an increase of 0.12 m²·K/W. To get the same effect with mineral wool (k = 0.035 W/m·K) we would need 4.2 mm of insulation.

I hope this is right - first time I've done this calculation in this form so be interested to see if anybody can spot any blunders.

<blockquote><cite>Posted By: eniacs</cite>However I'm a sceptic regarding how much the change from 280 to 400ppm will affect the planets weather.</blockquote>This is the really big problem that faces climate scientists. It is called Sensitivity.
With several thousand feedback mechanisms, some positive and, negative and very few fully understood, any prediction is going to have a large uncertainty on it (and it looks worse on the Celsius scale).
Science never claims to be 100% accurate, it just shows/predicts as best it can. If it is not right then the model is revisited and modified.
One thing that is worth noting is that just using historic data and plotting the strongest correlations is not science. What is science, is finding a cause and working from that. Finding the cause, or causes is not easy.

Tom;
Got to disagree with you there i think.

Anything if given the right quantity is a pollution. Salt occurs naturally in the sea, but if i dumped salt in a big pile in the middle of the english countryside it would start to pollute the environment killing plants animals and fish.

Arsenic in high quantities is a horrible pollution, but arsenic in very tiny quantitys mixed in with organic matter, is called earth and therefor not pollution.

Its all in context. I think in the context of emmiting 29 billion tons of somthing per year, even though it is diluted in the atmosphere it is still a pollution. Plants or animals would not survive if in a C02 atmosphere.

ST; This is the problem I face in my mind. C02 is a small amount and the climate models can be swung wildly in either heating or cooling directions by adjusting the tiny details.

How much, and how C02 will affect us is still undecided I feel.


How long do people think it will take to go back, that is after we stop producing C02 in vast quantities, probably after 2100. How long do we think it will take for the planet to return to its pre 1900 C02 levels?

Posted By: eniacsHow long do we think it will take for the planet to return to its pre 1900 C02 levels?

That's the big problem - even bigger than our current addiction to GHG production. Even if it were do-able to stop producing GHGs tomorrow, their effect has hardly got going yet - much much more to come. Cumulative, self-sustaining major climate change is inevitable, like we've barely seen yet.

But it will take the planet's natural processes just a short while (in planetary terms) to restore the balance (or equilibriate at a new one). Trouble is, a short while in planetary terms is 10,000s of years - and humans (and many animals and plants) may not be able to sustain their survival on earth for that long, with what's coming meantime. And the new equilibrium may not suit us anyway.

It's fair to assume that human survival on earth can only be sustained (maybe) by a huge effort - to not merely slow or stop the present accumulating ecological /environmental damage, but to actively assist the planet (and its plants) to clean up our mess on a timescale of 1000s or 100s of years, rather than 10000s.

When people bandy about the word 'sustainable', the only real, relevant meaning of it is
'can human existence on earth be sustained?'

Posted By: eniacsI'm all for reducing C02 output as it is pollution, regardless as to its actual effect on the planet, I dont like it. However I'm a sceptic regarding how much the change from 280 to 400ppm will affect the planets weather.

Todays news:
http://www.telegraph.co.uk/earth/environment/climatechange/9787662/Global-warming-at-a-standstill-new-Met-Office-figures-show.html" rel="nofollow" >http://www.telegraph.co.uk/earth/environment/climatechange/9787662/Global-warming-at-a-standstill-new-Met-Office-figures-show.html

Well if you read that article it says "However, it is thought that factors such as ocean current patterns may be behind the slowdown and scientists say the “variability” in climate change does not alter the long-term trend of rising temperatures."

Some context:

http://www.skepticalscience.com/CFCs-global-warming.htm

See comments 4 and, particularly, 5 about this paper.

I wonder if this paper explains:

1) Why COâ‚‚ is _not_ causing warming?

2) Why the oceans are warming now?

More commentary on the QB Lu paper:

http://www.climatesciencewatch.org/2013/05/31/qing-bin-lu-revives-debunked-claims-about-cosmic-rays-and-cfcs/

Posted By: tonyHow come we are suddenly talking about such a small amount of warming?

Who is?

Is there anything interesting in that which hasn't already been discussed in this thread?

Posted By: eniacsI hadnt read that C02 was increasing vegetation befor.

Only up to a point, if it gets too warm then the growth rate decreases.

Also it has to be remembered 'how' the higher temperature is made up from the weather.
It is not expected to just add a couple of degrees to everything with the variation between seasons being the same. What is expected to happen is that the variation will get greater (bigger difference between maximum and minimum temperatures) but with more incidences of higher temperatures.
It is these incidences of higher temperatures that cause the problems. We all like a sunny day when we are at the beach, but imagine that for 2 months with the reduction is rainfall and our infrastructure starts to get stressed.
It is very hard to think globally, but climate change is a global phenomena, what happens Norwich is not the same as what happens in Truro weather wise, and Oxford does not have an inbetween climate, or weather.

What may be a better way of thinking about climate would be more numbers attached to the headline figures. So rather than say the temperature will be 0.1°C above the long term norm, it may be better to say that not only is is 0.1°C above the norm but is has 30 days at 5°C below the norm and 75 days 4°C above the norm. This is why climate science tends to use descriptive statistics to describe the climate rather than just one number.

Seret: if we start the century with between 6 or 7 billion people and all but a tiny fraction of them die by the end of the century yet we end the century with 10 billion that's nigh on 17 billion for starters. Add a few who are born and die within the century and it's 20 billion, easily, people who are around (alive) at some time or other this century.

Posted By: eniacsIf the below article is true, perhaps we should burn more C02 producing material in order to keep the suns heat as much as possible:

Sorry, are you seriously quoting WUWT? A blog that manages to have negative credibility? A blog for which other blogs exist simply to point out its stupidity? A blog that published this?

http://wattsupwiththat.com/2010/05/06/hyperventilating-on-venus/

Who knows what the Sun's going to do? Yes, we might be in for a period of low solar activity which might cause some cooling which would at least give us a bit longer to sort things out. But the effects will likely be tiny compared to the heating we're already producing.

And perhaps it would be a good idea to think about the effects of ocean acidification this extra COâ‚‚ will cause.

Posted By: eniacsEd, I can see that you feel strongly about this,…

Might be worthwhile discussing why it gets me so wound up.

Firstly, I think the basic science of the matter is beyond reasonable doubt. That is, if you've got some idea of why it might all be wrong you're into extraordinary claims territory needing appropriate evidence. Just thinking of something which “might” be true or pointing out some correlation without a convincing cause doesn't count.

(However, what the consequences will be is harder to say and worth some discussion.)

1) Unlike most forms of pollution it affects everybody over a long period of time. Most other forms of pollution only affect the societies which are producing them and their immediate neighbours (e.g., countries on the same continent) and fade away pretty quickly - within decades at most. With AGW the people likely most affected, particularly in the third world, are those who don't even benefit from the pollution much, if at all. Further, it hangs around for a long time and takes a long time to take effect so those affected don't even get to moan about it to the original polluters without the use of a time machine.

2) The sheer bloody-minded irrationality of the objections. For some reason people feel they can make up any old nonsense and expect to be treated politely. It's hard enough dealing with the world when everybody's making a reasonably effort to get things right - when you've got people just making stuff up then getting all hurt when you yell at them … well, I tend to find that a bit stressful.