Which is the most important mistake we've seen in climate science?

It's a difficult question because what's 'important' is subjective. As your examples show, when faulty science is done, other scientists discover the errors, and they're corrected rather quickly.

Another example is the Christy and Spencer UAH error which led them to conclude the atmosphere was cooling until another group of scientists discovered the error in their analysis. At the time this was a very important error, because 'skeptics' used their conclusions to claim the planet wasn't warming and thus oppose any kind of greenhouse gas regulation. However, now everyone is aware that all global temperature datasets including UAH agree the planet is warming (though some make the ignorant 'not statistically significant' argument).

Another was the Douglass et al. tropical troposphere hot spot paper which grossly underestimated the uncertainties in the data, and was shortly rebutted by Santer et al.

http://www.realclimate.org/index.php/archives/2008...

Personally I would say the most 'important' error would be one which results in the largest propagation of misunderstanding among the general public. If a mistake is made and rapidly corrected and few people in the public hear about it, then I don't think it's terribly 'important'.

By this definition, two potential nominees are Douglass et al. and the Loehle study you mention, because they continue to be cited by deniers to this very day. Though among the general public, I don't think very many people are aware of these papers.

Another nominee is McIntyre & McKitrick's paper criticizing the Mann 'hockey stick'. Although the paper itself may have made some valid points, as you note, the general 'hockey stick' shape remains and has been confimed by roughly a dozen subsequent temperature reconstructions.

http://www.ncdc.noaa.gov/paleo/globalwarming/medie...

Yet a large number of people think the study was fundamentally wrong and the 'hockey stick' has been debunked as a forgery. This isn't so much of a scientific mistake as a successful propaganda campaign by global warming denial groups, but it's still a completely mistaken perception which is held by a significant percentage of the population.

In addition to your list, I'll throw in the last few Chilingar et al. papers on the GHE

http://www.greencropnetwork.com/media/pdf/webcours...

http://ruby.fgcu.edu/courses/twimberley/EnviroPhil...

http://www.springerlink.com/content/vl7536426072q7...

All three contain rudimentary errors, and I have no idea how they made it past peer review. Environmental Geology may not be a high impact journal, but they shouldn't be publishing such drivel.

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On second thought, these aren't particularly important papers, though a few 'skeptics' cite them occasionally. The Douglass et al. study that Dana mentions and your number 6) are probably the most damaging. Miskolczi didn't help either. Same with Paltridge 2009.

Balliunis and Soon should be on the list as well. That was a fairly egregious error and also demonstated that skeptics, once in positions of authority in the peer-review process (i.e., de Freitas was the editor on B&S (You know, I just realized that it's literally BS)), cannot be trusted to be objective.

The most important mistake made in climate science today is believing that the temperature data used to support and perpetuate the global warming belief is accurate.

The Warming community is stubbornly hanging on to the myth that the data is correct.

There have been too many Hansen-types meddling with the data as well as little or no effort to maintain and properly locate surface temp equipment.

The most important mistake in climate science is to take your six points and claim that those "corrections" are now the truth. An easy example is that conclusion of 190cm sea level rise by 2100. The current rate of sea level rise would have to exponentially accelerate.