Contrary to what you say, I am not looking to downplay the NIPCC report, and have only skim read it and the IPCC report. The reason I mention that it is the best example of a report summarising the case against climate change. It does talk about politics and whether evidence is circumstantial, the IPCC report does not - this does not mean I believe one report is objectively better than the other.

The level of scientific content is significantly less than the IPCC report, although I agree there is some and had I more time to review would certainly be interested to look in more detail. It is reactive to the IPCC report and at a first reading the IPCC report looks significantly more robust and extensive in its coverage. I am open to be convinced otherwise, but based on my (subjective) reading I still find the NIPCC to have a lower quality and depth of scientific reasoning than the IPCC.

Incidentally, the main reason I am dismissive about the petition is that accuracy in science is not the result of a popularity contest. All the scientists I know personally certainly have much more than a PhD, so I am sceptical about the qualifications of the petitioners here. Some no doubt are more qualified than me, however a petition is hardly the way to demonstrate their expertise! In any case I am surprised if there are more convincing reports that these have not been more thoroughly publicised.

As you say, it would be better for the NIPCC people to make their report apolitical, if the problem is really about the science. If it is about the politics then the strongest way to improve their case against climate change would be to improve the science on their side.

Regarding whether the science leads or the politics leads, it is clear to me that both are important. My response highlighted that some of the political problems that you speak about are evidence of likely flaws in the way that the science is done. However, I do not believe that these are fundamental issues. I believe more science rather than less science is the way forward. I totally acknowledge there are incentives on both sides (even if the science should prove to be completely wrong), however it is probably worth remembering that many climatologists are likely highly trained and employable even if climate research funding decreases.

If the science is correct, there is potentially a very big problem for the world. The eventual impact is potentially on the order of trillions of USD per year based on a couple of reports I've looked at (see https://en.wikipedia.org/wiki/Economic_impacts_of_climate_ch..., http://www.schroders.com/en/sysglobalassets/digital/us/pdfs/... for examples). Now, again, these estimates could be wrong, and are referring to impacts far down the line, however if they are even remotely indicative, the IPCC budget (~60MM USD since 2001 according to http://www.cnsnews.com/news/article/us-taxpayers-cover-nearl...) and total US spending on climate change (of the order of 10B USD per year, according to http://www.gao.gov/key_issues/climate_change_funding_managem...) is not completely unreasonable.

Now even if you feel the science is suspect in parts, I assume you would not want to throw away all of it? It is clear that something is happening to the climate - lack of ice in the arctic being one example, but others such as death of corals in the Great Barrier Reef being another. We also have political choices on how much funding to give to research and economic reform. We live in a polluted world, and it appears very much in our interests to fund research into ways to mitigate climate change and reduce pollution.

I can see that debate on this can be productive, and I would prefer a more open debate than is currently possible. However, this does appear to me to be an area where we are probably underfunding rather than overfunding the scientific (and political!) debate. The consequences of climate change if it proves to be close to the scientific consensus are horrendous, and really one of the most critical issues facing the planet. The benefits of much of the mitigation strategies are large regardless of the science.