Doran and Kendall Zimmerman, 2009

A poll performed by Peter Doran and Maggie Kendall Zimmerman at Earth and Environmental Sciences, University of Illinois at Chicago received replies from 3,146 of the 10,257 polled Earth scientists. Results were analyzed globally and by specialization. 76 out of 79 climatologists who "listed climate science as their area of expertise and who also have published more than 50% of their recent peer-reviewed papers on the subject of climate change" believe that mean global temperatures have risen compared to pre-1800s levels, and 75 out of 77 believe that human activity is a significant factor in changing mean global temperatures. Among all respondents, 90% agreed that temperatures have risen compared to pre-1800 levels, and 82% agreed that humans significantly influence the global temperature. Economic geologists and meteorologists were among the biggest doubters, with only 47 percent and 64 percent, respectively, believing in significant human involvement. A summary from the survey states that:
It seems that the debate on the authenticity of global warming and the role played by human activity is largely nonexistent among those who understand the nuances and scientific basis of long-term climate processes.

Doran, Peter T.; Maggie Kendall Zimmerman (January 20, 2009). "Examining the Scientific Consensus on Climate Change". EOS 90 (3): 22–23. doi:10.1029/2009EO030002

http://www.agu.org/pubs/crossref/2009/2009EO030002.shtml