Methodology

Search the Web of Science [WoS: university access required] as follows:

Step 1
Search with:
Topic = "global climate change" (quotation marks essential)
Publication Year=1991
Document Type=Article
Enhanced Science Index only

On November 10, 2012 this gives 40 results.

Step 2
Repeat this search but substitute Topic="global warming". This gives 131 results.

But some articles will have used both "global warming and "global climate change" and these must be subtracted otherwise they are counted twice.

Step 3
Search with Topic="global warming" AND Topic=" global climate change" in the second field. Use Publication Year=1991 and add a field for Articles or refine the search for articles only. This gives 11 results.

Therefore the total number of unique records for 1991 is 40 + 131 - 11 = 160

Repeat for each year. Or, one could do the three searches for the entire period, 1991-2012, then combine the searches to remove the double counting.

Read some combination of titles, abstracts, and entire papers as necessary to judge whether a paper "rejects" human-caused global warming or professes to have a better explanation of observations.

The Web of Science also lists the number of times each article has been cited, and much more. At the bottom of the search page, you can export the results to an Excel file.

Note that some papers that one might expect to find listed were classified as "Review" or "Editorial Material" by WoS. I did not count these.