Someone I know posits that there’s no science showing that CO2 contributes to greenhouse effect:
Please post cites to studies that show the role of CO2 as a forcing greenhouse gas.
Please do not debate the topic, as a debate would belong in GD. This is merely a request for cites. My guess is that there are folks here who know right where to look, and I’d appreciate it.
If people want to post studies that refute the role of CO2, that’s great too. Please make that clear, though.
It really goes all the way back to Tyndall in the 1850s/1860s.
Contributions to Molecular Physics in the Domain of Radiant Heat (1872)
Check out pg. 231 onwards…
For the modern reader, Carbonic acid gas is carbon dioxide, carbonic oxide is carbon monoxide, and carbonic acid is H[sub]2[/sub]CO[sub]3[/sub] (aqueous carbon dioxide, if that helps.)
Your acquaintance has picked a line of argument that can be falsified by anyone with an IR spectrophotometer and a gas cell. Hell, your local community college probably has those items.
The second part, having to do with calculating that absorption by CO[sub]2[/sub] is sufficiently large in magnitude to influence the climate, originally comes from…
On the influence of carbonic acid in the air upon the temperature of the ground (1896)
There’s a lot of very dense writing there, but Arrhenius believed doubling atmospheric CO[sub]2[/sub] would increase temperatures in the range of 5 or 6˚C. After some argumentation back and forth with Knut Angström, he eventually revised that to close to 2˚C by the early 1900s.
Thanks! Big help.
I also found this high-school lab project. Seems to me this should work:
http://www.starhop.com/library/pdf/studyguide/elementary/GloJar-7.pdf
But this shows a very similar experiment that fails:
Perhaps I should try the experiment myself.
Wouldn’t the glass reflect most of the heat we’re trying to measure absorption of? Seems to me the test should use visible light with say, black construction paper on the bottom.
CO[sub]2[/sub] is transparent to visible light.
My job involves a lot of measuring photosynthetic rates, which we do by measuring change in carbon dioxide concentrations (inferred by IR absorption). This is something I literally observe just about every week.
As wevets says, go to your local community college and check out some of their equipment.
Global warming was predicted by Svante Arrhenius over a hundred years ago, for what it’s worth, and was originally predicted based on mechanistic, theoretical arguments rather than observational data.
I just skimmed it and it’s possible that they’re correct and Gore faked the experiment, but that’s a climate change denialist site with a poor track record when it comes to facts.
Right. That’s why it lets it in. Why doesn’t it let it all back out? Because the radiation outward isn’t visible light, it’s much lower frequency radiated heat, which the CO2 absorbs.
Thus my suggestion to use black construction paper. Visible light passes through the glass and through the CO2-containing air, strikes the black paper and is radiated back outward as heat. Some of this heat gets absorbed by CO2. Some gets reflected back by the glass? Perhaps – but we have a control for that.
I’d also add a 4th jar, filled by breathing air into it using a tube, and allowed to reach equilibrium with all the jars in the dark, before putting in sunlight. We couldn’t measure the amount of CO2, but we could see if increasing the CO2 content makes a notable difference.
Then we’d see the effect of water in the presence of a GHG, and we’d also see a difference based on additional GHG. Gee, add a 5th jar, with breath but no glass of water. Then we can control for two independent variables, and expect to see a synergistic effect when using both.
[BTW, after a moment’s thought, I realize my objection to glass (heat bouncing off it and not entering) is silly, or greenhouses wouldn’t work. I need to think before hitting that “post” button!]
BTW, above I said ‘high school’ but it’s targeted for elementary and middle school.
At the end, the author says he believes the theory but wanted to address the authenticity of the two presenters (Gore, Nye).
I think I’m gonna have to get myself some jars and thermometers!
Thanks!
So he’s the guy who came up with:
ΔF = α Ln(C/C_0)
His work bears closer study. Thanks again! Ignorance fought.
Yeah, but wouldn’t it take a lot less time if you use direct sunlight to heat your jar instead of visible light? I’ve never tried to heat black construction paper with visible light, but I doubt it’s a very efficient process.
Do also drop your local community college an email or give them a call. They may already have chemistry or environmental science students doing this with an FTIR and save you some effort.
I suppose I should clarify: CO[sub]2[/sub] in your jar is not going to block all the incoming IR, especially if you use sunlight.
Visible spectrum of carbon dioxide:
I couldn’t find one, but it looks pretty darn clear and colorless to me, even at high pressure.
Infrared spectrum of carbon dioxide:
http://webbook.nist.gov/cgi/cbook.cgi?ID=C124389&Type=IR-SPEC&Index=1#IR-SPEC
I would be very interested in reading these. There are plenty of reasons why a greenhouse gas would not cause climate change, or why it would contribute to climate change in a way that wouldn’t be worth doing anything about. But claims that physics has stopped working are new to me, at least in this regard. Hence my curiosity.
On re-reading the OP, I see I didn’t really address the friend’s complaints.
Triple posting like a pro today :smack:
And also not what the OP asked, but:
Your friend noted that methane has 25x the GWP of CO2 (by mass). The updated IPCC 100-year GWP is 34x. For 20 years it’s 86x. It deviates from exponential due to depletion of hydroxyl radical.
Right – the classroom lab experiment uses sunlight, and that makes the most sense (but is less repeatable). For repeatability, a heat lamp or grow light might be better, but one would have to take into account the spectrum of the particular light. I’d rather use sunlight.
[quote=“Ruken, post:13, topic:682348”]
Infrared spectrum of carbon dioxide:
http://webbook.nist.gov/cgi/cbook.cgi?ID=C124389&Type=IR-SPEC&Index=1#IR-SPECGreat chart, thanks!
Yeah, me too. Here’s what he actually claimed:
Then an ally of his proposed a test measuring the radiative values of the GHGs and said that they’d be too small (which everyone knows is true, if we ignore the forcing effect on the equilibrium level of water vapor.)
Good point; thanks for bringing that up. I had forgotten about the complexity introduced by depletion, which reduces the GW contribution for molecules that don’t last long.
Increase the contribution in this case. Methane has a pretty short lifetime (<13 years IIRC). The primary mode of decomposition is a reaction with ·OH. However [·OH] decreases as you pump in more methane, delaying the decomposition, and increasing the radiative forcing from what you’d expect.
It’s not HUGE differences, although it does affect the cost benefit analysis for burning natural gas vs other hydrocarbons, depending on leakage rates and the discount rate.
Neither here nor there though, sorry.
I’d have to disagree that sunlight is less repeatable. Pick a clear day (if you’re in an area with clear days… it is winter after all) and the sunlight will be very comparable.
This may not work for you if you’re in an area where it stays overcast all winter.
In any case, if you get the chance, do the experiment with both sunlight and the visible light lamp - it doesn’t cost extra to put jars out in the sunlight for a couple hours - I’ll bet you the sunlight will provide more rapid, more easily discernable results (you’re less likely to get a temperature difference to small to measure with whatever thermometers you’re using,) and be easily repeated.