There has been so much conflicting and erroneous information on both sides that I don't think anyone really "knows" what is going on with global warming (or cooling?).
Here is what I know--or at least think I know:
1. We have a theory that looks good on paper.
2. The climate system is extremely complex.
3. Models, by their nature simplify the real world and in doing so cut corners and use assumptions where real knowledge is scant or non-existent. Example, water vapor is the most abundant greenhouse gas, but they know little about it, so they have made assumptions of a positive feedback, i.e., the warmer it gets, the warmer water vapor will make it. But they really don't know.
4. Some of those assumptions are likely wrong and may be very important.
5. Historic records of temps are non-existent for much of the world and even where they exist they only cover a few hundred years, so "proxies" have to be used. The validity of these proxies (ice cores, tree rings) is questionable, especially for tree rings which are produced only during the growing season.
6. There has been a lot of fiddling with the data and fudging of information in the IPCC reports, including using advocacy group publications as references (just came out that the IPCC repeatedly cited World Wildlife Fund pubs that were not peer reviewed).
7. Temperature data bases are invalid, with 90% of US weather stations having siting errors that produce evidence of warming just because of where they have located the station. Examples: Nearby air conditioners added after the station was located, they paved formerly grassed areas near or even under the stations. Stations were relocated to rooftops. Most of these changes have happened during the period when the data began to show warming. Errors can skew results as much as 5 deg. C.
8. There is a huge amount of money involved.
9. If human caused global warming is actually happening, the proposed solutions will have little effect--about 1/2 degree C by the year 2100 and the cost to our economy will be very high for little benefit.
11. If human caused warming is not happening and we believe it is, we really screw things up unnecessarily.
12. Global warming "science" has become a huge industry with 10's of millions of dollars going to researchers whose jobs depend on producing evidence of warming or impacts of warming.
12. The IPCC report for 2001 showed the medieval warming period and the little ice age that followed, but the 1004 report erased that data so they could show the "hockey stick" that has since been discredited. This is not honest, straightforward science.
13. Climate models assume CO2 produced today will reside in the atmosphere for 100 or 300 years, depending on who you listen to, but studies following atmospheric atom bomb tests showed carbon 14 to last about 25 years. Overstatement of CO2 residence time can skew model results and overstate warming tremendously. And by golly, they have sent satellites up to find the "missing" CO2. Hmmm. Are they missing something in their models?
14. I have probably forgotten lots of relevant points. Oh, yes, the "models all agree". Of course they do. There are 3 databases, 2 of which are based on a third, so they are all using almost the same database. And since there are so few studies of the necessary factors to put into the models, they use pretty much the same inputs. I drive a 2005 Toyota Tacoma, you drive a 2006 Tacoma. They look pretty much alike, don't they? Same with the models.
15. The latest IPCC report is 2500+ pages long. Citations are just as important as the text, but you have to know the science to evaluate the citations. This I don't "know', but would give odds on: Very few, if any, reporters have read the report, much less looked at the citations. They read the executive summary and leafed thru the text, looked at the pretty graphs and wrote up their story. Hardly anyone in the world has actually carefully read and evaluated the report and it's references. You can download it. Anyone here, advocate or skeptic want to take a look? I thought not.
