Over the past 350 years, we have placed a great deal of trust in science. You have only to look at the world in which we live to see what science has done for us. But is there a new mood in the land that is questioning that trust in science? This is important because the challenges the world faces, such as climate change, feeding a growing population, meeting the increasing demands for energy and tackling disease, are all issues in which science plays a crucial role. When society makes decisions on these issues, it is vital that they are based on science - but if the public is losing trust in science, that will be difficult to bring about.  One area where trust has been eroded to the point that science is under attack is climate science. There is strong evidence that over the past 150 years CO2 levels in the atmosphere have increased due to human activity and that this has led to a temperature rise of about 0.8C. There is a consensus among climate scientists that the temperature will continue to rise due to human activity, although by how much is uncertain.  The majority of climate scientists also think that this is likely to have a significant effect on the way we live, changing agriculture and our environment, and that there needs to be a concerted effort to control CO2 emissions to reduce these problems. This will require globally agreed action, and significant intervention in the way the world's economy is run.  Despite the evidence, there are some who disagree, probably because of their concern that such action will cause economic harm, and they have influenced a substantial swathe of public opinion.  Why is this the case? Several factors are important. The first is the complexity of the science involved, which leads to uncertainty in predicting the outcome. Climate science is complicated and it is difficult to understand fully the influence of the sun, clouds, vegetation and chemical composition of the atmosphere on overall climate change. and where there is uncertainty, alternative points of view can prosper, even if they are in a small minority.  a second factor is the greatly increased influence of people other than mainstream scientists who are posting analyses and opinions through blogs and social media. This can result in strongly argued opinion holding sway with the public even though it is not backed by robust scientific evidence.  Sometimes such polemicists will attack the consensus simply because it is the consensus. What such arguments tend to ignore is that consensus emerges within a scientific community from informed and critical discussion, and if over time the consensus view holds up, then that consensus is likely to be correct. Consensus is not a dirty word; it is a consequence of long and detailed arguments among experts.  a third factor is that if the scientific area of interest - for example, climate change, nuclear power, GM crops or the causes of and treatment of human disease - has great sociological, political or economic impact, then ideological, political and religious opinions get mixed up with scientific debate. Commentators distort sc