We have already discussed the post-truth generated by the tobacco industry, which is plain to see today. Cigarettes continue to be sold and people continue to buy them, but we know that Big Tobacco had an influence on what was known about the connection between smoking and health and that this influence distorted the perception of the public and governments, and thus managed to postpone targeted anti-smoking action. We have also seen that things are not so clear with sugar. This is something more recent and that we are still trying to elucidate today, both in terms of the relationship between excessive sugar consumption and health and the influence of the industry on public perception. However, although we do not know how much influence it really had, the sugar industry also manipulated what was known and the way in which information was disseminated. 

Let us now turn to climate change, something that is even more complex, and for several reasons. First, it is happening, but we do not notice it in our daily lives. It is difficult for us to grasp such an abstract and sometimes counter-intuitive idea. In addition, the evidence is very complex, and probably only climate experts can understand it fully. On top of that, it is such a large-scale phenomenon that we may feel, as citizens, that there is not much we can do about it, which is very different from what happens with tobacco and sugar. When it comes to climate change, the causes, consequences and possible solutions are far removed from the average citizen. 

On the other hand, there is a significant gap between what science says and what citizens believe science says. Climate change and its public perception is a good example of a case where post-truth is at work, possibly because of the enormous political and economic interests at stake. We have made tangential references in previous chapters, but now we will dwell a little more on the post-truth mechanisms behind it. 

A number of observations lead us to conclude that the planet is undergoing very rapid climate change. The Intergovernmental Panel on Climate Change (IPCC), created in 1988 to provide "comprehensive assessments of the state of scientific, technical and socio-economic knowledge about climate change, its causes, potential impacts and response strategies," is a group of experts that evaluates scientific evidence, draws conclusions and helps define courses of action to mitigate the effects of climate change. Hundreds of climate science experts from more than 100 different countries participate in the IPCC. What they do for the IPCC is to compile research on the subject (they do not perform new studies), understand the reliability of the various pieces of evidence, synthesize them, put together detailed reports on the current situation and, on that basis, suggest possible courses of action to mitigate climate change. 

The IPCC states, based on accumulated evidence, that climate change exists and that a significantt part of it is caused by human activity (that is why we call it anthropogenic). Today, we can consider this to be an observed fact. To begin with, the global temperature is increasing. Both NASA and the National Oceanic and Atmospheric Administration (NOAA) of the United States agree that 2016 was the hottest year since we started measuring temperature in 1880 and, although there are no accurate reconstructions of global temperature on such a large time scale, some estimate that the planet has not been this hot in the last 115,000 years. 

Leaving aside some variations on very small time scales, we see that, in the 20th century and so far in the 21st century, the Earth's average temperature has been gradually increasing. Why is this so? The main cause is the greenhouse effect: the accumulation of certain gases in the atmosphere that prevent heat from escaping into space. The greenhouse effect is a natural phenomenon and one of the reasons why life is possible on our planet. The problem is its magnitude: when an excess of gases builds up and the temperature rises too fast, the effect turns against us. Where do these gases come from? Largely, but not entirely, from human activity. For example, since the Industrial Revolution, through the burning of fossil fuels that are part of the planet's natural resources, our engines and factories have been generating gases that cause this greater greenhouse effect, the main one being carbon dioxide. It is estimated that current carbon dioxide levels on the planet are the highest in the last 4 million years. 

The global temperature increase for the period from 1880 to the present is estimated to be about 1 °C, with a margin of error of a few tenths of a degree or so. This is the average increase in surface temperature of both land and oceans. For those of us who are not climate experts, the reported temperature increase does not seem too large. And here lies one of the difficulties: understanding just how serious such a global temperature increase can be. These numbers, which seem intuitively low,, have catastrophic effects on the planet. We have already mentioned that intuition does not give us very reliable answers, and this is another example. That extra degree is enough to cause the concentration of dissolved carbon dioxide in the oceans to increase, the concentration of oxygen to decrease, and the water masses to acidify. This damages the delicate ocean ecosystem and many species die or are displaced from their habitats. For example, Australia's Great Barrier Reef, the world's largest coral reef and home to great biological diversity, is rapidly dying due to water acidification and rising temperatures. When some species that are the basis of food chains die, it affects those that live off them and, ultimately, also us, who depend on fishing and related activities for our livelihoods. In addition to these changes, ocean levels are also rising. As humanity's major cities and economic zones are on the ocean coasts, rising ocean levels endanger human life and result in losses in the millions of dollars. Climate change also increases the likelihood of some types of extreme weather events, such as heatwaves and droughts. 

This phenomenon is extremely complex, and its effects are gradual. It is not easy to notice its impact day by day, but, on an appropriate time scale, a clear and perhaps already irreparable trend is apparent. Since the beginning of systematic research on this subject, predictions have been made and fulfilled, which also shows that the proposed pattern for climate change is very likely to be correct. 

The evidence is plentiful, of high quality, and available in scientific papers, specific Internet sites, and popular science books. It is a matter of looking for it. But here’s the catch: a lot of scientific evidence is available for those who want to find out, but, at the same time, this evidence is very difficult to interpret for the general public, those of us who are not experts in the field. As we said before, in these cases what we can do is to look for, and follow, the scientific consensus.¹We discuss consensus in science in Chapter IV.

Generally, scientific consensus is not measured. There are no independent organizations that are evaluating whether or not the community of experts on each subject reaches consensus. Of course, if we invented the "consensus meter" we would need consensus to know if it works, so it would not be very useful. And, if there are no apparent controversies, the issue is unlikely to become a moderately massive discussion. But the issue of climate change is different because, in the face of attacks by some groups on the existence of consensus, we finally proceeded to measure it and found that 97% of climate experts support the idea that not only is there climate change, but that one of its main causes is human activity.²See Cook, J. et al. (2013). Quantifying the consensus on anthropogenic global warming in the scientific literature, Environmental Research Letters, 8(2). An analysis of the consensus among climate scientists was recently carried out, and the results confirm this figure and show that agreement on the role of human activity in global warming increases proportionally to climate science expertise.³See Cook, J. et al. (2016). Consensus on consensus: a synthesis of consensus estimates on human-caused global warming, Environmental Research Letters, 11(4).

Knowing that the consensus among experts is so high, even if it does not reach 97%, we can use this information as a kind of indicator, and thus have an answer even if we find it impossible to understand the scientific evidence due to its complexity. 

But all this puts us, as a society and as individuals, in an uncomfortable place. It is difficult to appeal to consensus. We feel that we lose freedom, that we yield to others. Following a consensus we like is not difficult. The problem is to follow one that we do not. And here is the importance of introspection, which allows us to deconstruct our ideas at least a little to see how much of our positions are based on evidence and how much are not. 

But we must not lose our bearings: Scientific research, and the consensus of experts in a particular area, can guide us. In the case of climate change, the scientific consensus is indeed enormous. Still, opinions that oppose the idea that climate change exists and is caused by human action continue to be heard –and amplified. What do the remaining 3% of climate scientists say? Interestingly, there is not much agreement among them on a position, but rather varying views: some believe that there is no climate change, and others that there is, but that it is not caused by humans. There is no coherent alternative explanation that allows grouping this 3%, and this is another aspect of this "dissent" that, in the end, only makes the consensus stronger. 

Based on the available evidence, almost all experts agree that anthropogenic climate change is a fact. Therefore, we should accept that as well, and all the points we made about whether a consensus can be wrong apply here as well: the consensus is more likely to be right, or at least closer to the truth, than the alternative, which in this case is the opinion of some non-expert citizens and this position of a very small minority of scientists.

Like any act performed by a citizen, scientific endeavor contains political aspects that largely determine what science is done and not done. However, this does not mean that apples fall differently for Republicans in the United States, water boils at a different temperature for the Socialist Party in France, or the law of conservation of mass applies in a special way for the Worker’s Party voters in Brazil. Even if climate science were influenced by political aspects, the overall, most consensual conclusions are ultimately expected to be reliable, given that research is based on peer review of papers and constant challenge by other scientists. But that is science. What about the public perception of science? 

In 2016, the Pew Research Center studied the American public's perception of anthropogenic climate change in depth. The results showed that there is a clear difference in attitudes toward climate change issues depending on whether one is a Republican or a Democrat: Republicans express much less confidence than Democrats in climate scientists and in the existence of consensus. Moreover, the stance of each group is different depending on how much scientific knowledge a person has. While a majority of Democrats with high science literacy agree that climate change is due to human activity, less than half of Democrats with low science literacy are of the same view. Curiously, the position on climate change and its consequences is different depending on the level of science literacy only among Democrats: Republican positions on the issue seem to be similar regardless of science literacy. 

We have discussed this issue and how this difference associated with partisan positions may have emerged. One of the hypotheses was that the issue had reached society through political-partisan opinion makers, who, in this way, would have assigned a tribal component to the position. 

But beyond partisan issues, in the United States, one of the countries whose activity has the greatest impact on climate change, there is a huge consensus rift between what the science says and what society as a whole believes the science says. Non-experts believe that the disagreement among scientists is much greater than is actually the case, and this is dangerous, because post-truth creeps in. This gap between the evidence-based position of experts and that of part of the population can also be seen in other issues, such as the safety and efficacy of vaccines, the safety of food from genetically modified organisms, the effectiveness of policies to control access to firearms or evolution by natural selection of living beings. 

The information is available. There is a lot of it, and it is reliable. However, the position that there is no anthropogenic climate change appears recurrently, as if it were valid. Why does this happen? There are several possible answers. On the one hand, it may be that we citizens are not adequately prepared to understand the complexity of the evidence supporting this idea. After all, almost none of us are climate scientists. But there are also other possible causes, such as society being affected by the way the media treats the issue, or that there is a corporate lobby actively influencing public opinion. 

The largest oil companies, or companies that base their industry on the use of fossil fuels that contribute to climate change, have a presence in the media and maintain the idea that they generate "clean" energy, or express doubts regarding the existence of anthropogenic climate change. Such claims can be refuted with scientific evidence. Of course, companies have every right to advertise. The question is whether they have the right to lie. 

Companies that profit from oil, generally known collectively as Big Oil, are extremely powerful. There is evidence that they have tried to manipulate scientific research, hide results contrary to their interests and lobby politicians and opinion makers. Even with all this in their favor, they did not succeed in bending the scientific consensus. That is how strong the consensus is. The most they succeeded in doing was to sow some doubt in part of the population, particularly people who were already ideologically predisposed. Once again, creating unreasonable doubt is the pattern behind post-truth. 

Interestingly –and also worryingly–, it is possible to analyze the strategy of sowing doubt, which does not change when one moves from Big Tobacco to Big Oil. In 2010, Naomi Oreskes and Erik Conway, science historians, wrote Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming, in which they expose some of the strategies used with the explicit aim of creating doubt where there is consensus. It is not necessary to convince anyone: doubt is enough to delay decisions and actions and, sometimes, it is enough to further interests. Doubt as a product that is manufactured and propagated. 

As chess Grandmaster Garry Kasparov says, "They rarely say, 'That is false. This is the truth. It requires evidence and debate. So they say 'This is false. No one knows the truth.'"

Some oil companies have publicly stated that their goal is to become clean energy companies, and have started to diversify their investments in clean energy. From this point of view, and being extremely generous, the attempt to cast doubts is a way to buy time. But time is one of the things we don't have. 

And what is happening at the political level, particularly in the United States, one of the countries that generate the most greenhouse gasses? Even before he became president, Donald Trump referred to global warming as "a fraud". Now, as president, several members of his administration are speaking out against the scientific consensus on anthropogenic climate change, and those who do not, end up distancing themselves from his administration.⁴More on this at: http://time.com/5201421/rex-tillerson-climate-change-donald-trump/ One of the problems of a government holding positions contrary to the evidence is that it is a group of very powerful people who, therefore, are more likely to install their opinion, which, in this case, is clearly unfounded. 

This is another reason why we must fight post-truth: if we do not do so, whoever has the power –right or wrong– can, thanks to that power, spread an opinion disproportionately to its quality. 

Can we speak of intentional post-truth in the case of climate change? Let us return to the questions in Survival Guide No. 9 and briefly analyze each one. 

The first point was about what we know: "What is known about the subject and with what degree of confidence? Is there scientific consensus?". This seems to be clear. The scientific consensus not only exists, but is particularly significant, and dissenting voices do not have a unique alternative explanation nor are considered "good quality" by science. 

The second question was linked to aspects that create unintentional post-truth: "Could there be unintentional post-truth factors at work, such as beliefs, emotions, biases, tribalism, confusion about who the experts are and/or adulteration of information?" We mentioned that, at least in the United States, society thinks that there is more controversy at the scientific level than there really is, and tribal issues arise in relation to the political party with which one identifies and their position on climate change. This is an example of how, even if we are facing malicious, intentional post-truth, its effect on us would not be such if we could be more alert to the factors that make us collaborate with that post-truth without looking for it, without realizing it, without taking responsibility. There are personal beliefs at play, from people whose intuitions tell them that climate change cannot be real if higher temperatures are not evident in their locality. Also, there is confirmation bias and tribalism, as with alignment of position to political-partisan preference, and both distrust of IPCC experts and trust in what the government or certain interested parties say. Finally, information gets distorted. Clear consensus gets "lost along the way," and if we learn about climate change from the news, it may appear that there is a controversy when there is not. 

Let us move on, then, to more sensitive issues. "Can there be a conflict of interest in the way knowledge is generated and communicated? Who funded the research? Who funds the spread of information? If there is publicity, who is in charge of it?". There does not seem to have been too much conflict of interest in the generation of knowledge, but something happens in its communication to society. Sometimes, a distortion of the consensus appears, publicity from the companies most responsible for the greenhouse effect, and the U.S. government does not seem to be too committed to combating climate change. 

"Are there independent associations or expert organizations that systematically review information to seek consensus?". In the case of climate change, the IPCC is an independent organization that does this. Made up of scientists from all over the world, experts in analyzing climate, it is permanently reviewing the evidence and studying potential problems and solutions. In addition, countries often have scientific institutions that, on a smaller scale, perform similar analyses.⁵More on this at: https://climate.nasa.gov/scientific-consensus/

"Could doubt be creeping in where there seems to be certainty? Could certainty be creeping in where there seems to be doubt? Are we being distracted from the core issue by secondary aspects? How do political-economic interests fit into all this?” And here the difficulties emerge. On the one hand, there is all the evidence, and on the other, there is exaggerated uncertainty. 

One way of justifying the failure to pursue policies to reduce carbon dioxide emissions is to deny the need to do so. There are climate change denialist positions: some scientists, Government officials and oil-dependent industries support them. Sometimes, as in previous examples, the strategy they use is to cast doubt on the knowledge obtained and say that we still do not know, that science has not yet made a clear statement on the subject. As we have already said, there is no better way to discredit science than to maliciously move the goalpost of evidence required to act and "ask for more science". 

There does not seem to be much doubt that there is no valid alternative position to explain what we observe regarding climate change. The discussion is, perhaps, whether the current exaltation of the false controversy is just the innocent doubt of some actors or whether it includes a generous dose of doubt deliberately created with the aim of persuading public opinion that the issue is still debatable, so that society does not become too intent on demanding action to mitigate climate change. There is no easy solution. The intentional manipulation of public opinion looks a priori quite similar to a simple confirmation bias. This is also seen in the type of media each of us chooses to consume: we most often follow those that display ideological or political positions akin to our own. 

"Who benefits from delaying certain actions? Who benefits from defining certain actions?". Delaying action to combat climate change protects particular industries threatened by policies that should be taken to mitigate its effects. To think about the benefit of combating climate change, however, we need to understand what is involved in accepting or rejecting that it is anthropogenic. Why would it matter? Because without agreement, no action is possible. As of November 4, 2016, the Paris Agreement, which was signed in late 2015 by almost 200 countries, has been in effect. The agreement represents a commitment by countries to keep global warming below 2 °C and to try to keep that figure below 1.5 °C. In order to achieve this ambitious plan, strict policies must be put in place to reduce greenhouse gas emissions, such as regulating greenhouse gas-producing industries through carbon taxes or similar measures. Ultimately, the commitment made in the Paris Agreement entails the complete elimination of greenhouse gas emissions, which clearly implies migrating from an economy based on fossil fuels to one that uses non-greenhouse gas-emitting energies such as solar, wind and nuclear. 

Considering this framework, it is more understandable why on this issue we see a larger consensus gap among Republicans than among Democrats. There are ideological, political, and economic reasons involved, which brings us to the last point: "Could our beliefs, emotions, biases, tribalism or selection of information be influencing the answers to the above questions?" 

Probably one of the great challenges of our present is to differentiate when our confirmation bias operates internally from when it is triggered by external agents. Either way, whether the influence comes from within or from outside, we must be vigilant to prevent it.