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Fresh breeze on climate debate
 Opinions have shifted recently regarding the issue of climate change. The credibility of so-called climate alarmist has suffered from the critical inquiries of the broader scientific community, the so-called climate skeptics, and various incidents.
As much as I approve of the effect on re-opening the scientific discussion, I think it is probably for the same wrong reasons that led people to believe alarmist theories in the first place: primarily media sensationalism.

Science is not a popularity contest, it is simply the rigorous search of knowledge. The validity of anthropomorphic global warming theory and its predictions has little to do with mediatic debate around tornadoes, cold winters, Himalayan glaciers or a shady researcher.
In that sense Al Gore (and others) have brought this upon the AGW community with his movie, An Inconvenient Truth, by using simplistic and shocking images (hockey stick, climate instability, polar bear, drowning cities). These talking points, like much politics certainly captured people's imagination and it encouraged them to trust superficial arguments. The result is a backlash as those claims are debunked.

Now, carbocentrists (a more suitable moniker for supporters of the AGW theory, coined by author Benoît Rittaud) rightly argue that climate science is subtle and complex and that those headline-grabbing arguments are not the real core of the theory.
Fair enough, so what is the real core?

Maybe the IPCC report is not that relevant at this point, because of several faulty claims and its lack of political independence, but it at least spells out the carbocentrist theory. From what I understand, its main argument goes like this:

1. climate models incorporate the state-of-art knowledge about physical phenomenon which underly climate,
2. the models have been tuned to real-world data and produce results consistent with the temperature average measured for the last x decades,
3. known factors which are explicitly not supported by the models are not expected to negate the results,
4. CO2 is deemed the most important factor because models fail to match historical data if CO2 is not included,
5. the models all tend to forecast a warming of the average temperature, across many runs with different CO2 emission scenarios.

I hope my summary is accurate. If it's not, I would love some carbocentrists lay the logic out properly.

Assuming the above reasoning, a number of questions I can think of would have to be addressed for it to be a strong argument:

* If our physical understanding and modeling is good, why do we need multiple models?
* How do we know that models are good at forecasting?
* How do we know that the forecasts from different runs are properly distributed in terms of probabilities?
* How much out-of-sample (ie. future data) do we need to collect to even consider invalidating a model (falsifiability)?
* Given enough out-of-sample data and the wide range of predictions offered by the models, what variation between measurements and predictions would it take to invalidate a model?
* How can we rely on "ab ignorantum" argumentation to claim that CO2 is the main factor? Ignorance of a better explanation is not conclusive proof.
* Is average temperature a good measure to build scientific knowledge?
* Given the non-linear and chaotic nature of weather, how can we exclude seemingly important factors?

Finally, I understand that politics cannot be completely taken out of the discussion, but we should do our best to separate the question of what we know and understand from what we should do about it. Policy decisions relate to primarily to politics and economics, and related to climate science only for understanding the expected effects on climate of the designed behavior change.


Watch this movie:

I was already convinced about the human CO2 factor in global warming, but this movie convinced me even more. And if you want to learn more, head over to:

And sorry for not answering your questions directly.

Posted by: Paweł Gościcki (March 21, 2010 03:19 PM) ______________________________________

Hi Pawel,

I am aware of realclimate.org and a number of other sites with diverse points of view. I did not find the questions above addressed there.
That site seems to focus on individual points, rather than modelling and end-to-end methodologies.
Also, having stuff like Mann's curve (hockey stick) discussed there strikes me as partisan, since Michael Mann is part of that site.

I'll check out the video presentation. Thanks for the pointer.

Admitedly, I don't have expertise in a related field (only college-level general scientific education) to really build a firm understanding, but I have seen convincing presentations both in support of the thesis and critical of the thesis's validity, all from reputable scientists in related fields and broadly.

For some critical ones, see the ICCC presentations.

In support of the IPCC thesis, David Archer's presentation was convincing too.

Posted by: Julien Couvreur (March 21, 2010 06:43 PM) ______________________________________


Posted by: Yansky (March 21, 2010 09:29 PM) ______________________________________

I just finished watching Richard Alley's talk, which Pawel recommended.
It focuses on evaluting the relative importance of CO2 in the climate system, at the geologic time scale. His conclusion is that CO2 is one of the most important factors, from all those considered. Pretty interesting analysis.

He also makes a good argument regarding the cosmic ray theory, showing a time period were Earth was left vulnerable to full-strength cosmic rays, but climate apparently didn't budge.


Posted by: Julien Couvreur (March 21, 2010 11:14 PM) ______________________________________

For me the only question worth answering is the one linking CO2 to the rise of global temperatures. And this one is cleverly answered in the aforementioned video. All other questions are easily answered. Did we have a global temperature rise during the last few decades? Yes, of course. Did we have a global rise in CO2 levels during that time? Yes, of course. Is the rise of CO2 caused mostly by human activity? Yes, of course.

Ergo, we are dealing with an anthropogenic global warming.

Posted by: Paweł Gościcki (March 22, 2010 02:51 AM) ______________________________________

For me the only question worth answering is the one linking TELEVISED SPORTS to the rise of global temperatures. . All other questions are easily answered. Did we have a global temperature rise during the last few decades? Yes, of course. Did we have a global rise in TELEVISED SPORTS during that time? Yes, of course. Is the rise of TELEVISED SPORTS caused mostly by human activity? Yes, of course.


Posted by: thatsettlesit (March 23, 2010 02:09 PM) ______________________________________

Supposing the climate debate with all its argument is wrong, should that be a reason for us to stop our engagement for nature? Many people think more about our environment, and I think that´s really good. So even if they do it for the wrong reason, they do something good, and that´s actually why the debate should not be stopped, even if it´s wrong.

Posted by: Dave (March 26, 2010 08:42 AM) ______________________________________

@thatsettlesit: sure, but Richard B. Alley in the aforementioned video does not mention any TELEVISED SPORTS. Only CO2. And that video is pretty convincing. Really.

Posted by: Paweł Gościcki (March 28, 2010 03:29 PM) ______________________________________

@Dave: Protecting the environment is a laudable goal. But how much is the right amount or trade-off?

If not for the AGW question, there are probably more urgent issues to be solved than CO2 emissions (environmental, poverty and health related).

Crisis situations are used to inspire fear into people and justify massive government interventions, when most regular environmental problems can be solved more economically by private property.

Posted by: Julien Couvreur (March 31, 2010 04:00 PM) ______________________________________

Actually, to a certain degree, science is popularity building. It is inherently social, thriving on the peer review process, revision, and consensus. It is the convergence of this consensus that is the very nature of scientific "knowledge", and this can be a slow and laborious process (though sometimes it can be fast, as Kuhn's "The Structure of Scientific Revolutions" makes clear). As more data accumulates, it is analyzed against existing models, and these models are refined or corroborated accordingly (note, I don't mean computational models specifically, but rather the theoretical framework that informs them). I'm skeptical of worldviews that espouse scientific realism, but with any luck the "knowledge" hard earned through this process will hopefully track objective reality at least accurately enough for our purposes. The thing to note is that this is an ongoing process. As the consensus builds we give more epistemic weight to the model or claim being made, but it can of course only approach "certainty" asymptotically.

The thing I find fascinating is how people without the proper expertise would side with the small minority of experts who go against the grain. It's a similar phenomenon we see in conspiracy theories. People with little or no expertise and in possession of few facts concocting wild theories. There may be something of our psychological desire to root for the underdog going on to. More than likely in this case it is all political and economic. There are a certain class of people who would like to think we can all be totally independent and we don't need to cooperate with each other at all, and that the world can experience unending economic growth.

I mean, scientific consensus can be and has been wrong, but none of the alternative approaches to discovering objective truths have proved very successful in the past.

One thing is for sure, the consensus on climate change among the experts is strong enough at this point that if it turns out they are wrong people will rethink the role of science as our top epistemic authority.

Posted by: eHead (April 21, 2010 01:54 PM) ______________________________________

Yes, it can literally take generations to naturally flush out old misconceptions from the scientific community. But I think it is fair to say that the measure of a theory in natural sciences is not a vote of experts, but rather how it measures up to evidence, scrutiny and testing.

Although I agree about your comment about non-experts taking chiming in, I am not as sure as you on climate change. In particular, I don't understand how saying "CO2 is the only variable that we have found so far that lets our models generate historically-compatible global temperature averages" (paraphrasing based on my understanding) would be sufficient to call the case closed.
I can understand that would make this the prevalent theory, but the result would be much stronger if the models could accurately predict some unexpected future event. The less likely and the more accurate the prediction, the more credible the confirmation you get from such a test.
At least, that is how things worked for natural sciences in the past, no? I'm thinking of Galileo's and Einstein's theories for example.

When it comes to economics, I don't know of any single group of people that think that individuals don't need cooperation.
Regarding an assumption unending growth, you may want to clarify your point. Do you know of any group of people that contend that natural resources are not limited and don't constrain economic activity (which is obviously true)?

Posted by: Julien Couvreur (April 22, 2010 01:23 AM)
