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NATURE CLIMATE CHANGE | VOL 2 | SEPTEMBER 2012 | www.nature.com/natureclimatechange C limate models expand scientific understanding of the projected impacts of increased atmospheric concentrations of greenhouse gases on Earth's systems and serve as decision-making tools in consideration of adaptive and mitigative policy responses 1 . As such, the use of models to generate knowledge about climatic change has been described as "a central focus of climate politics" 2 and also "a lightning rod in the climate debate" 3 . These computer programs, which work through a series of time-stepped operations to solve the mathematical equations representing Earth's climatic processes, have been the target of climate science sceptics who question the validity of their projections 4,5 and the subject of long-standing debate even among non-sceptics over their use for policy decisions [6][7][8] .Under conditions of increasingly variable climatic conditions, decision-makers on all governmental levels will probably rely on model projections for policymaking on multidecadal timescales. Thus criticisms of modelling within climate sceptic arguments, as well as debates over the use of models as tools for informing policy, are directed at an aspect of climate science that is both integral to our understanding of Earth system processes 9 and likely to become increasingly important to societal decisions in adapting to and mitigating climate change 10 .Yet large proportions of the US public are unsure whether climatemodel projections can be trusted, according to a recent nationally representative survey. Of those surveyed in 2010, 64% reported either that they believed that scientists' computer models are too unreliable to predict the climate of the future (41%), or that they did not know whether to trust them (23%) 11 . Moreover, uncertainties both in climate predictions for the next few decades and in longer-range projections may widen with the use of new modelling techniques and as additional climate processes and feedbacks are incorporated to produce more realistic simulations, posing further complications to public communication efforts 12 . Here, we map the outlines of model discourses to identify problems and opportunities for the communication of climate-model science for the purposes of improved decision-making.So far, there seems to be no systematic evaluation of the treatment of climate models and their projections in public discourse, even though they have been politically contentious and are widely misunderstood, based on comparisons with more familiar forecasting tools such as weather models 11 . Popular media have become increasingly responsible for conveying complex science to the public 13 and are a primary source of climate change information for many Computer models generate projections of future climatic conditions that lie at the crux of climate change science and policy, and are increasingly used by decision-makers. Yet their complexity and politicization can hinder the communication of their science, uses and limitatio...