The "skeptics" and "deniers", with some important exceptions, do not deny outright and in total the validity of climate science, which would be necessary to draw a valid equivalency between them and the Intelligent Design crowd. Many, perhaps most, don't even have a serious alternative theory, they're just pointing out what they think is wrong with AGW.
The important exceptions are:
As far as I know, the computer models that predict serious AGW just don't work. They don't "predict the past", i.e. you feed them historical data and they don't then predict what actually happened, and now that we can test their predictions they aren't working either. E.g.:
"The fact is that we can’t account for the lack of warming at the moment and it is a travesty that we can’t. The CERES data published in the August BAMS 09 supplement on 2008 shows there should be even more warming: but the data are surely wrong." http://www.eastangliaemails.com/emails.php?eid=1048&file...
ESR comments (http://esr.ibiblio.org/?p=1473): "Eyebrows have quite rightly been raised over this quote. It is indeed a travesty that AGW theory cannot account for the lack of warming, and bears out what I and other AGW critics have been saying for years about the fallaciousness and lack of predictive power of AGW models.
"But the second sentence is actually far more damning. “The data is surely wrong.” This is how and where most scientific fraud begins."
And that brings us to the second big issue, how good is the data and based on that what can it be used for. The proxies are very iffy, especially when they get out of the historical period and can be compared to fairly solid actual temperature measurements ("hide the decline" of the tree ring proxies).
Then there's the questions of older thermometers, where researchers are trying to tease fractional degrees out of instruments with hand painted lines. That goes many times over for the proxies.
And the problem with badly situated ground monitoring stations, especially the urban heat island problem.
Then there's the demonstrated poor to impossible quality of the CRU data and their loss of the original data; as the detailed in the HARRY_READ_ME.txt file (http://www.anenglishmanscastle.com/HARRY_READ_ME.txt), they can't even reproduce their own massaging of the original data....
And as I understand it, the NASA satellite data has been calibrated against these poor ground station data sets, not e.g. weather balloons, but I could be wrong there. This is important since instruments can drift over time, and when they're in an inaccessible satellite....
This just hits the highlights of the problems with the data, before we get into a whole lot of what looks like at worst case outright fraud.
These things including fraud don't throw climate science per se into doubt as a discipline, but they do engender skepticism and denial of AGW, which as noted is another thing altogether.
Anyway, I'll repeat the call many people are making: open it up. Retrieve the original lost records, do the science in the open, publishing all methods, code and data, and let the chips fall where they may.
When an author of a published "science" paper refuses to share his raw data, methods and code (and we're not talking about e.g. chemistry/chemical engineering where there's competitive advantage on the table for chemical companies), people legitimately wonder and discount what he says. When scientists give "the dog ate my homework" excuses, you might believe them about that (I think it's very possible WRT to the CRU ... but it says something that they didn't consider it important to archive it carefully), but I don't see how you're obliged to treat their unconfirmable results with any respect.
Add the bad faith that's manifest in the CRU emails....