How to find scientific data:

1. Do some research to find out what the two leading entry-level university textbooks are on the subject. To do this, check online course syllabi to see what they're using. Or, just do some searching. After 60 seconds on Google and Amazon, I found these two textbooks on global warming. I dunno if they're the best, but they'll probably do. Be sure to get textbooks and not single-author academic studies, which may be highly skewed toward a particular position that is not mainstream.

2. Skim the textbooks so that you get a sense for the major concepts of the field and how they relate to each other. I buy a lot of textbooks, but maybe you don't want to spend the money. In that case, you can call around to find what university bookstores have the ones you want in stock, then go there and hang out and read it in the store. Or, buy it online and sell it back. If you keep it in good condition, you sometimes end up spending only $20-$30 on the textbook. If either of these two options are inconvenient, well... that's research, yo.

3. Now that you know the standard terms involved, Google searches and Google scholar searches will do wonders.

4. Even better, any textbook worth its salt will give citations for some of the major studies that support its basic claims (they usually mention lots of large meta-analyses, for example).

5. Make a list of all the papers you want to read. Go to an on-campus library at a major university nearby (I drive 30 minutes to UCLA every couple of weeks). Usually you don't need a library card to sit down at one of their computers and download a bunch of papers (they'll have access to JSTOR, etc. on campus computers) to your flash drive. If they don't allow flash drives, upload the PDFs to your free (or paid) Dropbox account.

6. But usually, the textbooks themselves will contain a good overview of which debates are relatively solved, and which ones remain open. They will also describe what major questions need to be answered to solve the open questions, and what the evidence currently suggests. Of course, it's important to get the very latest edition of the textbook. Be sure to check The Best Textbooks on Every Subject.

7. Depending on what you want to learn, you may have to get a more advanced textbook on a narrower subject, but it will probably still help to skim a lower-level textbook to get a handle for the basic concepts involved in the larger field.

8. Did I mention textbooks?