Hi Steve,
You could start with anthropogenic global warming. Most legitimate research refutes IPCC claims in that they consistently lack scientific rigor and fail in every prediction made to date. The whole IPCC propaganda machine will survive only as memory and an example of how science is not to be done - not the least of which is by a so called consensus which never existed.
Really? Last time I checked, there were statements to the contrary by (at least) 32 academies of science, the InterAcademy Council, the European Academy of Sciences and Arts, the International Council of Academies of Engineering and Technological Sciences, the Network of African Science Academies, the Royal Societies of New Zealand and the United Kingdom, the National Research Council, the American Association for the Advancement of Science, the American Geophysical Union, the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, the European Federation of Geologists, the European Geosciences Union, the Geological Society of America, the Geological Society of London, the International Union of Geodesy and Geophysics, the National Association of Geoscience Teachers, the American Meteorological Society, the Australian Meteorological and Oceanographic Society, the Canadian Foundation for Climate and Atmospheric Sciences, the Canadian Meteorological and Oceanographic Society, the UK's Royal Meteorological Society, the World Meteorological Organization, The KNMI (Royal Dutch Meteorological Institute), the American Quaternary Association, the International Union for Quaternary Research, the American Association of Wildlife Veterinarians, the American Institute of Biological Sciences, the American Society for Microbiology, the Australian Coral Reef Society, the UK's Institute of Biology, the Society of American Foresters, The Wildlife Society, the American Medical Association, the World Health Organization, the Australian Medical Association, the American Astronomical Society, the American Statistical Association, the International Association for Great Lakes Research, and many others. Oh, and yes,
NASA, of course, let's not forget that one, since you seem to think it should be taken seriously on this issue (I don't disagree). Right now there are 0 scientific bodies of any standing who take the position that climate change is not real, or not man made. The American Association of Petroleum Geologists was the last major science body to take that stance, and now they are one of only a handful to take a wishy-washy semi neutral position on the issue. Beyond that, there is social science research by people like
Doran, who showed that the level of consensus on anthropogenic climate change rises from 60% to 97% as one focuses in from general scientists to more and more climate-specialized researchers. Or
Anderegg, who showed that
97–98% of the climate researchers most actively publishing in the field support the tenets of ACC outlined by the Intergovernmental Panel on Climate Change, and (ii) the relative climate expertise and scientific prominence of the researchers unconvinced of ACC are substantially below that of the convinced researchers.
And then there is Oreskes (
2004/2005) who showed that out of all research with the subject 'global climate change' published in mainstream peer reviewed journals between 1993 and 2003, 75% took the mainstream position (that climate change is real
and anthropogenic in origin), while 25% simply did not comment either way (because it wasn't relevant to their research).
Just to name one example you might consider the 50 NASA scientist and astronauts who wrote:
“claims by NASA and GISS, that man-made carbon dioxide is having a catastrophic impact on global climate change are not substantiated, especially when considering thousands of years of empirical data. With hundreds of well-known climate scientists and tens of thousands of other scientists publicly declaring their disbelief in the catastrophic forecasts, coming particularly from the GISS leadership, it is clear that the science is NOT settled.”
See: http://www.libertariannews.org/2012/04/11/nearly-50-nasa-scientists-and-astronauts-issue-letter-rejecting-nasas-stance-on-global-warming/
While I have great respect for astronauts, you have got to be joking if you think they even remotely qualify as climate experts. As for "NASA scientists", that can be anything from an engineer to an astrobiologist. Asking non-expert scientists about this issue is no more useful than asking lawyers to comment on the validity of evolutionary theory. That's why the research I quoted above looks specifically at what
climate experts have to say about this.
Also, I don't see how paleoclimate data does anything but strongly confirm the role of CO2 as a strong driver of climate change.
Here's a cool, understandable lecture by paleoclimatologist Richard Alley that goes into the issue in more detail.
Also, there is a new theory which explains the mechanism for ice age and hot house cycles which has been under the radar for about 15 years now in spite of research at CERN which confirmed that cosmic rays generate highly reflective earth cooling low level clouds.
Svensmark: The Cloud Mystery
Svensmark's hypothesis is interesting in theory, but empirical evidence gathered thus far does not support his claims. For example,
Krivova 2003 notes that
"between 1970 and 1985 the cosmic ray flux, although still behaving similarly to the temperature, in fact lags it and cannot be the cause of its rise. Thus changes in the cosmic ray flux cannot be responsible for more than 15% of the temperature increase"
and likewise,
Lockwood 2007 points out that temperature and cosmic ray flux have for the last few decades been moving in the opposite direction from the one required. There are other problems, but I'll just point you to the
skepticalscience page on this issue, which has a lot more documentation.
EDIT: Will just add this image of cosmic rays versus temperature:

Oh darn, doesn't seem to work too well for the crucial period we're arguing about, does it. Oh well, that's science for you. Such a harsh mistress.
The ‘hockey stick’ (a stupendously erroneous concoction) conveniently removed the medieval warm period from public attention in what was a blatant abuse of scientific privilege. The MWP did happen and Michael Mann or the IPCC, try as they might, cannot make it go away.
Mann et al have not "tried" to make the MWP go away. It's there in their analysis, it's just not as hot as it is today. In fact, it seems to me that where the different paleo reconstructions diverge most prominently is not the MWP, but the subsequent cold period:

But regardless, Mann's work has been scrutinized so many times now that it's become kind of a cult phenomenon among climate contrarians. And all the while, it's been a red herring of sorts; there's not that much relevance to today's climate change.
AGW is not about science. It is about money and lots of it! Anyone at the IPCC and many other university employees who value their job, but not necessarily their integrity, know that it is about money and to keep the gravy train rolling they must insist at all costs that AGW is real.
Oh yes, climate science, that's where the big money is! Forget about, oh, say, the fossil fuel industry - if you want the big bucks, go study this obscure field of science where, if you make an effort to communicate your findings to the public, you'll face death threats, public defamation of your character by blog "scientists" and politicians, and, if you're really good at it, even legal prosecution. It's super. You'll make, like, several thousands of bucks a year. Totally worth it!
Anyway, if we're gonna continue this thingy, best to do it in another thread on the global warming subforum, so as to avoid derailing this thread too much.
Cheers.
Cheers! }|:oD