This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic.
Objection:
Correlation is not proof of causation. There is simply no proof that CO2 is the cause of the current warming.
Answer:
There is no "proof" in science, that is a property of mathematics. In science, one must look at the balance of evidence and formulate theories that can explain this evidence. Where possible scientists make predictions and design experiments to confirm, modify or contradict their theories and must modify these theories as new information comes in.
In the case of the theory of Anthropogenic Global Warming, what we do have is a theory (first conceived over 100 years ago) that is based on well established laws of physics, it is consistent with mountains of observation and data, both contemporary and historical, and it is supported by very sophisticated and refined Global Climate Models that can successfully reproduce the climate's behaviour over the last century.
Given the lack of any extra planet Earths and a few really large time machines, it is simply impossible to do any better than this.
Aside: It is usually interesting to ask just what observations or evidence your skeptic would consider "proof" that Global Warming is indeed caused by the rising CO2 levels. Don't be surprised if it an impossible request!
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic.
"There is no Proof that CO2 is Causing Global Warming" was first published here, where you can still find the original comment thread. This updated version is also posted on the Grist website, where additional comments can be found, though the author, Coby Beck, does not monitor or respond there.
Environment
Politics
Comments
Co2 does not correlate to temperature over the last 150 years,or the last 1000 years,or the last half-million years[Vostok ice cores].There were times in the past when co2 was 5 times or even 10 times more abundant in the atmosphere,and the earths temperture was far lower than it is today.Al Gore's attempt to correlate them was nothing less than scientific fraud as it is well known that co2 follows temprature,and not the other way around which is what the AGW theory requires.
Posted by: Tim Wells | August 19, 2008 6:12 AM
Please read these: geological history,
CO2 lags, not leads,
historical examples of CO2-caused temperature rise,
no correlation last century.
Posted by: coby | August 19, 2008 11:08 AM
none of the links in this article take me to the evidence that CO2 is causing the warming. I keep asking everywhere- what is the evidence that CO2 is to blame? Nobody has an answer.
So, Mr Coby, since you have set yourself up as an expert and spokesman on this issue, I want to hear from you.
What... in your words... is the evidence that C02 is causing the global warming?
Posted by: daddy dave | October 15, 2008 8:35 PM
daddy dave:
Given the absorption spectrum for CO2, how is it possible for increasing atmospheric CO2 not to increase the mean temperature of Earth?
Posted by: Richard Simons | October 20, 2008 4:17 PM
Richard Simons:
Co2 is a greenhouse gas ofcourse,and it does add a small amount of warming.But it has not been shown that the .7C rise in the last century is attributable to CO2.It is simply not a strong enough greenhouse gas.CO2's radiative effect is,as you know,logarithmic and so has less of an effect for each given volume that is put into the atmosphere.The majority of the radiative effect of CO2 is already done as the absoption wavelengths are now close to saturation.
Posted by: timwells | October 20, 2008 10:26 PM
timwells,
"CO2's radiative effect is,as you know,logarithmic and so has less of an effect for each given volume that is put into the atmosphere."
Yes, we know that. And you know we know it. So why bring it up? The CO2 forcing estimates which are used to attribute warming to CO2 already include this effect. The forcing is still large enough. "Increases slower than linearly" doesn't mean "negligible".
I detect a pattern of errors here. Climate scientists know that CO2 forcing is logarithmic in concentration. They know that temperature rises can cause CO2 increases. And they know that CO2 levels have been larger in the past. Your assumption seems to be that scientists don't know any of these well known facts, or else they ignore them because Al Gore told them to.
In reality, as coby pointed out, these facts don't prove what you want them to prove. But upon having this pointed out, you simply ignore those points and move on to new "arguments" that scientists are supposedly unaware of.
After being corrected once, you should have reconsidered your "global warming is disproven by this well known fact unknown to scientists" strategy, but you stuck to it. It shows that you'd rather quote-mine arguments off skeptic websites than think about the actual science involved.
Posted by: Ambitwistor | October 21, 2008 10:59 AM
Mr Ambitwistor - I'm very happy debate the science involved.
TimWells suggests that of the 0.7 degrees rise in the last century, the portion of this that can be attributed directly to CO2 is small (only that which occurred between the late 1970s to the late 1990s can possibly be due to it for starters). I have asked this question myself on this site
http://scienceblogs.com/illconsidered/2008/09/arctic-sea-ice-recovered-in-2008.php#comment-1146376
– inertia is only answer I have had so far, an explanation I am not convinced by, though that particular subject is no doubt complex.
At least those commenters gave me a vaguely plausible explanation. However, your answer to TimWells appeared to be:
- state that TW said something you agree with (real zinger that one!).
- then put words in his mouth that he clearly didn’t mean ie. " Increases slower than linearly" doesn't mean "negligible".” We all know this.
- then say that TW makes the claim that scientists do not know a series of three facts despite the fact that, erm, TW explicitly used the phrase “as you know” in his post with regard to one of the facts, explicitly stated in his post another of these facts (that CO2 “does add a small amount of warming”), and didn’t mention anything in connection with the third.
- I could go on…..
There are no substantitive points in your post. There is only one person in this twosome that I think ought to “think about the actual science involved”.
Posted by: paul | October 24, 2008 3:07 AM