On a crucial issue, the first report of the IPCC speaks with two tongues. It expresses confidence in the greenhouse theory and, at the same time, says that evidence for the theory is indeterminate and inconclusive. This article addresses itself to two candidates for an explanation. The first hypothesis builds on the straightforward observation that people do not always speak their mind. But there is little reason to believe that contradictions in text can be traced to scientists' concern about boosting the credentials of the greenhouse theory. The second candidate for an explanation, which is the main contribution of the article, says that scientists may be diverted from the concern about truth because they take on tasks that are extraneous to the role of scientist. Thus, members of the IPCC are charged with providing premises for climate policy, and this may have affected both their research and the presentation of its results.