 In the 1970s, a memo by the tobacco industry revealed how they confused the public about the science linking smoking to cancer. The now infamous memo said, doubt is our product, since it is the best means of competing with the body of fact that exists in the mind of the general public. It is also the means of establishing a controversy. What this is saying is the most effective way to neutralise scientific evidence is to raise doubt about the science. This same strategy has persistently and effectively confused much of the public about climate change. So what are the methods used to manufacture doubt about climate science? There are three key methods. Cast out on scientific evidence, attack the scientists themselves, and cast out on the scientific consensus. Let's look at how doubt is cast on the scientific evidence. There are a number of ways that this can be done. The first way is by misrepresenting scientific papers, claiming they say something they don't. Secondly, data can be distorted by cherry picking certain pieces of data while ignoring the full body of evidence. The third approach is to propose conspiracy theories, accusing the scientific community of falsifying their data. An alternative to casting doubt on scientific evidence is to attack the scientists themselves. An unfortunate consequence of the rejection of climate science is that scientists themselves are undergoing personal and professional attack. These can take the form of abusive emails, excessive freedom of information act requests, online attacks in blogs and online discussions, and personal correspondence being hacked and published online. Perhaps the most damage to the integrity of science comes in the form of pressure being applied to academic journals and universities. There's a growing body of literature into the nature of complaints being received by academic institutions. Why would they do this? The intent is to interfere with one of the basic principles of scientific work, the freedom to responsibly conduct research and accurately communicate the results. The immediate consequence is that some academics are now facing what amounts to scientific censorship. But there are also more subtle effects. A number of studies have documented that the aggressive attacks on the scientific community are affecting how they communicate their research. For example, an analysis found that the IPCC underestimate climate impacts 20 times more often than overestimate them. Predictions of alarming climate impacts are vigorously pounced upon by critics, whereas harmless predictions are met without hostility. The result is a tendency to underestimate the impacts of climate change in order to avoid a hostile response. The third and arguably most significant strategy is casting doubt on the scientific consensus. Public perception of scientific consensus is known as a gateway belief. What people think about expert opinion guides a range of beliefs about climate change. Consequently, the scientific consensus has been a target for over two decades. In this timeline, we see a steady procession of campaigns, reports, petitions and so on, all seeking to confuse the public about the overwhelming scientific agreement on human cause global warming. Let me draw your attention to some key moments over the last few decades. In 2002, a pollster, Frank Luntz, conducted market research into how politicians could prevent public support for policies that mitigate climate change. His solution cast doubt on the scientific consensus. In more recent years, one study from Oklahoma State University looked at the most common climate myths in newspaper opinion pieces written by syndicated conservative columnists. What they found was that from 2007 to 2010, the number one most common myth was there is no consensus. Attacking the consensus is the number one strategy for those who reject climate science. These methods have the aim of confusing the public into thinking there is still substantial scientific disagreement about human cause global warming. More broadly, intimidation of scientists and attacks on scientific evidence are designed to manufacture doubt about climate science. How should the scientific community respond to the merchants of doubt? Daylight is the best disinfectant. Academic institutions, the public and the media need to better understand the nature of the attacks directed towards the scientific community and science in general. Fortunately, a growing number of books and scholarly papers are documenting the situation. If those are to attest, some television shows and even MOOCs are picking up on it too.