Why wouldn't an increase in CO2 levels increase temperature?

Question

Isn't this basic physics? CO2 is transparent to visible light, but reflects heat. How could increased CO2 not warm the planet?

Answer 1

This whole CO2 idea is crazy. Don't they teach about trees and CO2 in schools any more?

Answer 2

A close examination of the CH4, CO2 and temperature fuctuations recorded in the Antarctic ice core records does in fact reveal that yes, the temperature moved first in what is, when viewed coarsely, a very tight correlation. But what it is not correct, is to say the temperature rose and then 800 years later the CO2 rose. These warming periods lasted for 5000 to 10000 years (the coolings lasted ~100kyrs) so for the majority of that time (~90%) temperature and CO2 rose together. This means that this wonderful archive of climatological evidence clearly allows for CO2 acting as a cause while also revealing it can be an effect.

The current understanding of those cycles is that changes in orbital parameters (Milankovich and other cycles) caused greater amounts of summer sunlight in the northern hemisphere. This is a very small forcing. But it caused ice to retreat in the north which changed the albedo increasing the warmth in a feedback effect. Some ~800 years after this process started, CO2 concentrations in the atmosphere began to rise and this also amplified the warming trend even further as another feedback mechanism.

You can also go here ( http://www.realclimate.org/index.php?p=1... ) for a discussion by climate scientists of exactly this question but with greater technical detail and full references to the scientific literature.

Answer 3

Actually, CO2 absorbs - not reflects - heat.  Your continued lack of understanding of the basic physics involved destroys the credibility of your claimed scientific credentials.

There is no question that CO2, by absorbing heat radiation, becomes warmer.  The question is, how much effect, if any, does a 0.00011 volume fraction increase over natural atmospheric maximum levels of CO2 have on the entire atmosphere.

Answer 4

The only thing that would prevent CO2 level increases from raising the temperature is if there were negative feedback processes that resulted from the increased CO2.  Even those legitimate (as opposed to the ignorant or for-hire ones) climate scientists (e.g. Lindzen) that pooh pooh the notion of serious consequences acknowledge that.  It's a well established principle of physics.

Computing the sensitivity (temperature rise due to doubling of CO2) is pretty straightforward and comes out to be around 1.2 C.  No scientist with any legitimacy really questions this.

The uncertainties come in when you add the complexities of feedback.  As the ocean warms slightly, what happens?  As the polar ice melts and we have less albedo effect, what happens? etc., etc.

Lindzen, for example, proposed the so-called iris-theory that clouds would effectively curb the expected warming. But his theory didn't hold up to scrutiny when other scientists tried to replicate his efforts (perhaps the cause of his somewhat curmudgeonly ways).

The current state of knowledge indicates that the balance of the various feedback mechanisms (some will have a cooling effect and some a warming effect) is positive. That means we should expect the warming to exceed the CO2-only warming of 1.2 C.

Dealing with feedbacks in any meaningful ways, is where computer modeling really comes into play. And global climate models from around the world are coming up with an estimated warming of about 1.8 - 4.0 C by around the end of the century (based on various assumptions of human activity).

Answer 5

It would. One would have to be pretty ignorant to claim otherwise.

Answer 6

Your arguments have never been about facts, and it doesn't look like they are yet, keep trying.

Answer 7

Yes, in fact we know it does.  We can see this via the runaway greenhouse effect on Venus, making it twice as hot as Mercury despite being twice as far from the Sun:

http://www.realclimate.org/index.php/arc...

Or from looking at our own planet, which would be 33°C colder if not for the greenhouse effect.  See page 5 here:

http://ipcc-wg1.ucar.edu/wg1/Report/AR4W...

Not only do we know that increased concentrations of atmospheric CO2 will cause an increase in global temperature, we also know the associated forcing, which is currently 1.6 W/m^2 from CO2 alone - approximately 14 times greater than the forcing from solar irradiance.  In fact, the greenhouse effect is the best understood forcing ("high level of scientific understanding").  See page 4 here:

http://www.ipcc.ch/pdf/assessment-report...

Answer 8

Bob--- the answer is not known--- did the increased CO2 RESULT from the warming or CAUSE the warming.

http://www.ecoworld.com/blog/2008/03/12/...

http://en.rian.ru/russia/20070115/590789...

Answer 9

It can. While we must concede that the “warming potential” of CO2 is relatively low compared to other greenhouse gases (GHGs); its concentration is much greater (more than 90% - excluding water vapor), which appears to be the reason the IPCC et al look to CO2.

But you have to keep in mind that the warming effect of CO2 is logarithmic to its concentration; therefore it has a diminishing return in effectiveness. That means the first increase of, e.g., 100 parts per million (PPM) in the atmosphere has a greater effect than the next 100 PPM, and so on. Thus the curve plotted by this behavior would be asymptotic; meaning that the net continued warming effect of increased CO2 concentration approaches zero as concentrations double, triple, etc. At some level further increasing CO2 has essentially no effect at all.  

Also, keep in mind a couple other essential facts:

1) The spectral absorption range of CO2 is overlapped by other gases, so its effectiveness is shared, causing the net effect of CO2 to be less than if it was the only greenhouse gas. Admittedly, due its greater concentration it still has greater overall effect than other GHGs - excluding water vapor.  

2) CO2 is not the only greenhouse gas, and as is rarely reported water vapor by far exceeds CO2 in the greenhouse equation. Water vapor is generally accepted among climate scientists to contribute 95% to the total greenhouse effect. CO2 falls in at less than a 4% contributor, and less than 1% of this is from human activity.

3) CO2 comprises 0.037% of the atmosphere, but the human part of that concentration is only about 5%. This means the remainder is from natural causes (arguably feedback effects) Simple math would dictate that only a very small part of the 280 PPM increase in the industrialized era is directly from humans.

Ultimately it is revealed that CO2 is only a little over a 1° C portion of the total ~33° C greenhouse effect, and human contribution to warming about 0.1% of the total – or about half of the 0.6° C warming recorded in the 20th century. And that’s being very generous in favor of CO2.

Answer 10

The thing is any change in temperature requires energy. The energy flux remains the same so it does not matter what the ratio of the gases is. It is the energy level that makes the temperature change. As to why to climate and therefore the temperature changes its because energy is in constant flux even as the overall flux is constant. Its somewhat like the wind.

Answer 11

it works both ways;

increased heat causes atmospheric CO2 concentration to rise via various bio-chemical processes, such as the carbonate/bicarbonate balance in the oceans, and increasing methane emissions from swamp lands and soils.

increased CO2 causes temperature to rise via the greenhouse effect.

this also works the other way round, with cooling and lowered CO2 concentration.

this is what it known as positive feedback, and is the main cause of the very rapid rise in temp. and co2 at the end of each ice age, and also the fall in same at the end of interglacials. (we are overdue for one of those, i wonder why...)

Answer 12

Isn't co2 being dismissed as causing global warming?

More scientist, and NASA are now saying that the Pacific ocean currents El Nino / La Nina are causing the climate to change.

1998 was a strong El Nino year, that's why it was a warm year, and this year is a strong La Nina year and this is the reason all scientists are saying that this is going to be below average temperatures.

CO2 has nothing to do with global warming, Bob.  Check out the information on the ocean currents.  You'll see this is true.

Answer 13

This is one of the great mysteries in the global warming argument.  We can observe that the climate isn't getting warmer even with a steady increase of co2.

Other factors are working on our environment that we have yet to discover.  The climate is very complex and just co2 is not the cause for temperature variations.

We need more work done to explain the climate rather than depend on the opinion of a few men and their consensus.  

We need objective facts, not subjective opinions.