We used text analyzers to compare the language used in two recently published reports on the physical science of climate change: one authored by the Intergovernmental Panel on Climate Change (IPCC) and the other by the Nongovernmental International Panel on Climate Change (NIPCC; a group of prominent skeptics, typically with prior scientific training, organized by the Heartland Institute). Although both reports represent summaries of empirical research within the same scientific discipline, our language analyses revealed consistent and substantial differences between them. Most notably, the IPCC authors used more cautious (as opposed to certain) language than the NIPCC authors. This finding (among others) indicates that, contrary to that which is commonly claimed by skeptics, IPCC authors were actually more conservative in terms of language style than their NIPCC counterparts. The political controversy over climate change may cause proponents’ language to be conservative (for fear of being attacked) and opponents’ language to be aggressive (to more effectively attack). This has clear implications for the science communication of climate research.