In a summary of their survey on the opinion about global warming among Earth scientists (see Eos, 90(3), 20 January 2009), Peter Doran and Maggie Kendall Zimmerman conclude that the debate on the role of human activity is largely nonexistent, and that the challenge is “how to effectively communicate this fact to policy makers” and to the public. However, I argue that neither of these conclusions can be drawn from the survey. For example, one issue that is much discussed in the public debate is the role of greenhouse gas emissions in global warming. Perhaps there is not much debate about this issue among scientists, but this cannot be concluded from the survey, in which nothing is said about such emissions. In the second question of their survey, Doran and Kendall Zimmerman refer only to “human activity.” Furthermore, even if scientists agree that the effect of human activity is “significant,” which is the word used in the second question, they can have very different beliefs as to how large, and how dangerous, this effect is.