There is no way to even ballpark what percentage of global warming is caused by CO2 gases.

Most global warming fans will admit that CO2 (both natural and man-made) is just one of the many factors that contribute to global warming, both present and past. Most will also admit that long before cars and factories came about, wild temperature swings in both directions occurred under relatively stable CO2 levels. Additionally, most will admit there is no reason to believe these natural (non-CO2) factors are not contributing to the current warming trend. If this is the case, the percentage of warming caused by CO2 gases (in comparison to other natural factors in play) is entirely unknowable. We are only sure that CO2 (man-made or otherwise) is responsible for somewhere between 0 and 100 percent of the current warming trend.

My opponent claims that we can not determine to any accuracy the effect of CO2 on our current period of global warming. However, this is blatantly false.

First, we can at least make a good estimate based on tests in a lab. We know from such tests that CO2 absorbs a certain amount of energy from the infrared spectrum.

We know that the radiation coming down on earth from the sun is mostly in the form of UV and Visible light. We also know that the radiation that comes off the earth towards space is mostly in the form of infrared. Here is a visual aid:

http://en.wikipedia.org/wiki/Image:Atmospheric_Transmission.png

On the top graph there, we see that the upgoing thermal radiation, that is to say, heat that would otherwise escape, is largely absorbed. We can also see from this graph that CO2 absorbs radiation with wavelengths ~10-20 micrometers very well, and that this wavelength range is indeed included in the upgoing thermal radiation.

It's also true that the wavelengths absorbed by CO2 are absorbed by water vapor as well, but as we can see from that same graph, water vapor only absorbs roughly half of the radiation on this wavelength [reperesented by the halfish-height in that area for the water vapor graph].

So that should at least establish that it can be figured out at least ROUGHLY how much warming CO2 is causing [which is all I'm charged with doing]. However, I will bring more points.

Here is another graph.

http://en.wikipedia.org/wiki/Image:Vostok-ice-core-petit.png

The blue and green lines are the most important ones here. Green is CO2 levels, Blue is temperature. This is for the last 400,000 years [the data is from ice cores].

Notice anything strange? How about the VERY close correlation between the two?

Just another information source from which we can at least make a good estimate of the effect of CO2 on global temperature change.

Hopefully that is enough for you. We can make good estimates on how much gloabl warming is caused by CO2 based on what wavelengths of radiation it absorbs, what other substances absorb those same wavelengths, and the amount of energy at those wavelengths present in upgoing thermal radiation.

You did a great job of explaining how the greenhouse effect works, but I'm we are not debating that. You then cited studies that draw correlations between CO2 and climate change. But you have yet to tell me what the ballpark percentage of CO2 influence is in comparison to addition natural factors (both known and unknown) that may be influencing the recent warming trend. Why not just give me a percentage and show me how you (or anyone else) were able to arrive at it? It would seem a tall order without knowing the other factors and the extent to which THEY are responsible for heating the earth's atmosphere?

CO2 is currently responsible for roughly 9-26 percent of the greenhouse effect. This range represents a difference in how we look at it, not a lack f accuracy [If we have no other GH gases, CO2 alone amounts to 26% of current greenhouse effect, if we still have all the other gases and only take out CO2, it only reduces it by 9%] We can know this, because of what I showed last round. However, it's true that I have not shown how much of an effect the greenhouse effect has on global warming.

However, we do know the amount of heat the greenhouse effect keeps in that would otherwise escape. Or we at least have a very good estimate of this.

Knowing this, it would be possible to determine roughly how many joules of heat energy the greenhouse effect is giving us. And based on basic math, it would be possible to determine exactly how many degrees, on average, this amount of energy is increasing our climate.

WE don't need to know all the 'unknown' factors of our climate change. We know how much our temperature is increasing. We know how much the greenhouse effect is increasing our temperature [at least a good estimate]. We know how much CO2 contributes to the greenhouse effect.

With all that data, it is quite possible to ballpark what percentage of gloabl warming is caused by CO2. I'm only charged with showing you that it is possible, not doing it myself, so don't bother asking me for a percentage. I've presented data that shows that there is in fact a way to ballpark what percentage of global warming is caused by CO2 gases. That is all I must do, as that is a clear negation of te resolution. My opponenty claims there is no way to ballpark such a figure, I have provided a way.

If it were a perfect world, and all this data you mentioned were currently attainable, scientist might dare to guess what percentage of global warming is due to CO2 emissions. But since the extent of human impact on the environment is such an important question, I suspect that the reason no one has come up with this percentage is because we do not have reliable methods to accurately collect the data you claim we can so easily plug into your "basic math" problem. Let's see if I'm wrong.

"CO2 is currently responsible for roughly 9-26 percent of the greenhouse effect."

Who says?

"It's true that I have not shown how much of an effect the greenhouse effect has on global warming. However, we do know the amount of heat the greenhouse effect keeps in that would otherwise escape."

Oh, how much is that? And again, who says?

"Knowing this, it would be possible to determine roughly how many joules of heat energy the greenhouse effect is giving us.

Maybe, if anyone were actually capable of "knowing this." But with no support for your claim, it is just another claim.

"And based on basic math, it would be possible to determine exactly how many degrees, on average, this amount of energy is increasing our climate."

Yes it would be, if the rest of the fairytale were true.

"With all that data, it is quite possible to ballpark what percentage of global warming is caused by CO2."

Yes. And the key phrase there is "with that data," but you have not shown that you or anyone else has a reliable source for obtaining it.

"I'm only charged with showing you that it is possible, not doing it myself, so don't bother asking me for a percentage."

Well, you are actually charged with demonstrating that currently there IS a way to do it, not that it might be possible if someday we had access to particular data. I will not hold you to giving me the specific percentage (which must secretly exist somewhere since it can be so easily obtained). However, I will need support for your claims.

My opponent's first question is 'who says' the effect of CO2 is 9-26% of the total greenhouse effect.

The greenhouse effect is the trapping of the upgoing thermal radiation, which would otherwise escape into space, inside our atmosphere. This is caused by greenhouse gases.

We ave a good understanding of how the greenhouse effect works. We have a good understanding of what wavelengths are present in the upgoing thermal radiation. We have a good understanding of the effect of CO2 on this upgoing thermal radiation. Energy in certain wavelengths is absorbed by the CO2, trapping the heat energy here on earth.

Based on A> What wavelengths and what intensities are generally present in upgoing thermal radiation, B> what wavelengths are absorbed by CO2 and how efficiently they are absorbed, C> what other greenhouse gases also absorb these wavelengths, and D> how much CO2 is in the atmosphere, we can indeed come up with values for how much of the greenhouse effect is caused by CO2.

However, as I said last round, this alone does not give us a good estimate of the effect on global warming, since it is still possible that we don't know how much temperature change the greenhouse effect causes.

Next, my opponent asks me just how much the greenhouse effect affects global warming.

To answer this, I would have to provide some type of evidence for what the temperature of the earth is without an atmosphere. Luckily, it's right here:

http://apollo.lsc.vsc.edu/classes/met130/notes/chapter2/te_earth.html

255 kelvin, ladies and gents. That's -18C. The average temperature of the Earth, however, is about 16-17C in actuality. Thus, the greenhouse effect is responsible for about 35C of our extra heat, and CO2 is responsible for either ~9 or ~26% of that depending on how we establish responsiblity. [No atmosphere except CO2 would have 26% the effect our current atmosphere does, but removing CO2 and keeping the rest of it only reduces the effect by ~9%]

By the 26% standard, CO2 is responsible for ~9C of our temperature, and by the 9% standard it is responsible for ~3C of it.

My opponent has constantly referred to mysterious 'unknowns', but there is very little we cannot measure.

I have done more than my burden - not only have I explained HOW we can find out what percentage of global warming is caused by CO2, I have actually done it. And all my opponent asked for was a method to get a ballpark percentage.