Fresh atmosphere in 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 Beno??t 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.

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