I'm getting fat and I know why....

[BlasterBates]

What pjclarke has failed to mention is that CO2 is not the main greenhouse gas, that is water vapour.

Small but significant emission, probably left out mistakenly, as not many lay people know that.

CO2 has a contribution to the Greenhouse effect of around 10% certainly no more than 30% so the increase of 30% would have an effect of around 3% maybe a bit more.

That may explain why inspite of an increase of CO2 of around 10% over the last 10 - 15 years that global temps have barely moved.

The fact that temps haven't budged for 15 years, in spite of a significant increase in CO2 is one of the main reasons why some scientists, previously banging the drum on AGW are now questioning the validity of the IPCC's projections.

[d000hg]

The way some people carry on and the ridiculous comments you hear from people lead you to believe they think air is composed of 60% oxygen and 39% carbon dioxide and that soon, carbon dioxide will be in higher concentrations than oxygen, ahhhhhh Jebus, save us!

I've never heard anyone suggest that, have you got an example?

The point is carbon dioxide barely registers as a component of air, so who cares if levels rise a little? In the grand scheme of things, the overall chemistry of air is barely changed.

True. There again you can turn clear glass any colour you like with the addition of elements at the rate of a few ppm.

Probably for the first time, WpjS (stopped clock and all that). Dramatic changes are seen throughout chemistry, physics and materials science due to additions of trace materials.

I'm sure there are many chemicals which in a similar proportion to CO2, would make the atmosphere fatal to humans.

[pjclarke]

CO2 has risen from 280ppm to 390ppm (or 0.039% if you prefer) since pre the industrial revolution, about a 40% increase, unprecedented in rate and extent for at least 600,000 years.

The difference between CO2 and water vapour in the atmosphere is mainly persistence . All other things being equal excess water vapour added to the atmosphere precipitates out in a few weeks, while CO2, once released from long term stores such as fossil fuel deposits remains in the carbon cycle for hundreds of years. Of a pulse of CO2 emitted now 25% will remain unsequestered 1,000 years later. In policy terms this equates to 'forever'.

All things are not currently equal. One of the factors that affects humidity is temperature. So if the temperature of the atmosphere rises, it can hold more water vapour. This being a powerful greenhouse gas, the increased water vapour increases the temperature further - a positive feedback. As the atmosphere is indeed warming, scientists have been looking for, and found evidence of this feedback.

The water-vapor feedback implied by these observations is strongly positive, with an average magnitude of lq = 2.04 W/m2/K, similar to that simulated by climate models [...] The existence of a strong and positive water-vapor feedback means that projected business-as-usual greenhousegas emissions over the next century are virtually guaranteed to produce warming of several degrees Celsius. The only way that will not happen is if a strong, negative, and currently unknown feedback is discovered somewhere in our climate system.

Dessler et al 2008. http://geotest.tamu.edu/userfiles/22...t_al_2008b.pdf

[BlasterBates]

It is interesting to compare two periods in history

1910-1940

In this period it is accepted that CO2 played no role in warming

From pj's favourite website:

Before 1940, the increase in temperature is believed to have been caused mainly by two factors:

Increasing solar activity; and
Low volcanic activity (as eruptions can have a cooling effect by blocking out the sun).

What caused early 20th Century warming?

Lets look at the temperature rise:



Now lets look at the temperature rise since 1980:




What do you notice?

Let me help, that the sun and volcano's can cause a rise of temperature of approx. 0.5 degree in a 30 year period.

So how can we be sure they weren't involved the recent rise?

We can't of course and that is why prominent scientists are now questioning the role of CO2.

[EternalOptimist]

I you hold out a one inch thick piece of wood on a sunny day, it will cast a shadow.
A two inch thick piece will not cast a darker shadow

It's the same with co2. Once the radiation at that particular bandwidth has been absorbed, any amount of co2 will not make a jot more difference.
And thats why quoting 390 ppm is such a load of nonsense. That bandwidth was saturated long ago.

its worth noting that the two planks I mention are short.


If the mechanism that pj mentions above were the end of the story, the planet would bootstrap itself into a permenant ice age or a permenant boiling state , like venus.
It's never happened. even in the past when there was ten times more co2 in the earths atmosphere.
And has anyone noticed how much more water vapour there is in the summer compared to the winter ? my own observations tell me that there is more precipitation in the winter and that the summer is a time of drought

[pjclarke]

We can't of course and that is why prominent scientists are now questioning the role of CO2.

Name two of them. There are some qualified people who question the size of the feedbacks, but only nutters question that increasing CO2 (and other GHGs) is a significant positive forcing.

We have good measurements of solar activity - it's gone the wrong way in recent decades to be the cause of warming, and explosive volcanic eruptions large enough to have a climatic impact, such as Mt Pinatubo, tend to get noticed .....

[BlasterBates]

Two other astronomical observations. On Mars there is three times more CO2 than on Earth, and yet Mars is cooler, also the temperature at the point in the atmosphere on Venus which has the same atmospheric pressure as the Earth's has the same temperature. i.e. what's decisive is not the composition of the atmosphere it is atmospheric pressure.

[BlasterBates]

Name two of them. There are some qualified people who question the size of the feedbacks, but only nutters question that increasing CO2 (and other GHGs) is a significant positive forcing.

We have good measurements of solar activity - it's gone the wrong way in recent decades to be the cause of warming, and explosive volcanic eruptions large enough to have a climatic impact, such as Mt Pinatubo, tend to get noticed .....

Thx for that so you admit it, because without the feedback no warming (not discernible in the natural swings up and down).

[d000hg]

I you hold out a one inch thick piece of wood on a sunny day, it will cast a shadow.
A two inch thick piece will not cast a darker shadow

It's the same with co2. Once the radiation at that particular bandwidth has been absorbed, any amount of co2 will not make a jot more difference.
And thats why quoting 390 ppm is such a load of nonsense. That bandwidth was saturated long ago.

At least we're agreed Wim's nonsense about 'trace' gases is just that, nonsense.

[EternalOptimist]

True. There again you can turn clear glass any colour you like with the addition of elements at the rate of a few ppm. Or similarly alter the radiative properties of a planetary atmosphere by increasing the concentrations of greenhouse gases by a third ...

CO2 is just a trace gas

I love that.
That is exactly what I and many others have been saying for the last 10 years. What puzzles me is how two people can see the same facts and come to so different conclusions.

Fact - add a few molecules to glass and it changes colour. It's not homeopothy its a fact. It reproduceable. There are clear rules and predictions are possible, there is a lot of science in it.
It's falsifiable. If someone comes along and says 'I can change the glass into gold by adding three ppm of dog turd' its testable.



Every single prediction they have ever made has failed - I have listed some of them ^^^^