In the 17th century the philosopher John Locke, writing in admiration of the great scientific thinkers of his time, remarked that he found it “ambition enough to be employed as an under-laborer in clearing ground a little, and removing some of the rubbish, that lies in the way to knowledge.” Locke was understating his considerable contribution to the new empirical and experimental sciences . Still, Locke’s observation captures an essential role philosophy plays in relation to science. A hallmark of good philosophy is the advancement of understanding through the rigorous critique and clarification of concepts. While philosophers aren’t necessarily better equipped to arrive at truth than others, they are often, by training, well-suited to detect muddled and fallacious thinking. We too often overlook the way that knowledge advances through the detection and exposition of errors — the clearing of rubbish — as much as through the discovery of facts. The fact of anthropogenic global warming, for instance, bears existential and ethical implications that require our immediate attention , yet misconceptions must be clarified in order for informed public discourse to advance. In what follows I address three common confusions that are often encountered in public and political discourse regarding climate change.
Confusion One: “Consensus has nothing to do with science”
This erroneous claim plays on the ambiguity of the term consensus. In popular parlance consensus often refers to a simple (or merely popular) agreement. In science, the term is appropriately used when a clear-cut majority of researchers recognize that converging lines of evidence confirm the same conclusion. That is precisely what is meant when we hear that there is overwhelming consensus among scientists regarding human activity as a cause of global warming . Scientific consensus is not a matter of popular opinion. A scientific consensus represents broad acknowledgment among experts that a particular claim bears strong evidential support. Humanity’s collective store of knowledge is increased once a scientific consensus is reached.
It follows that if a consensus does not exist, the scientific questions under investigation remain unsettled. Individual researchers, teams of researchers, and peer-referees are all subject to error; it is all the more important for non-experts to recognize scientific consensus as evidence that a claim has been broadly vetted. It remains possible for a scientific consensus to be wrong, of course. People sometimes point to historical cases of mistaken findings, or unscrupulous scientists, in order to question the certainty of consensus, or reliability of science on a given issue. These critics overlook the fact that such errors were finally revealed and surmounted because of the very same scientific process of vetting and arriving at consensus which their narratives are meant to challenge.
Ambiguities in language can lead people to talk past one another. When people are unaware of a term’s technical usage or fail to specify how they are using a term, it creates an atmosphere ripe for misunderstanding and equivocation. We see confusion similar to that concerning the term “consensus” in the claim that evolution is “merely a theory.” Theory as the term is used in science differs from one of its most common usages, which means something closer to speculation or opinion. In modern science, a theory reliably describes reality in a way that is sustained by a broad body of evidence considered so strong, and so verifiable, that it is unlikely ever to be overturned. Indeed, a theory does not exist independently of an overwhelming scientific consensus.
Science is epistemically powerful because it is self-correcting, as opposed to self-sealing. This is how scientific consensus carries intellectual and experimental weight, and why it is responsible for non-experts to trust claims endorsed by scientific consensus.
Confusion Two: There is no “proof” that human activity causes global warming
Proof is a term best left to mathematics and formal logic. Every undergraduate student who studies philosophy (not to mention statistics!) will have heard some version of the mantra “correlation does not entail causation.” This is true, but far from the end of the story. David Hume, writing in the 18th century, made it clear that causal connections are not matters of mathematical certainty . Simply put: for any possible causal relationship it remains logically possible for a different causal relationship, or none, to hold. The term “proof” is, and will remain, irrelevant to causal reasoning. The question regarding a scientific correlation isn’t one of proof, but rather, of statistically relevant patterns. Consequently, the Intergovernmental Panel on Climate Change (IPCC) translates the 95% confidence level that global warming is primarily caused by human activity as “extremely likely.” 
Understanding the limits of causal inference is equally useful in apprehending the relationship between climate change and extreme weather patterns. No one hurricane, blizzard, drought, or flood (and the list could go on) can be attributed directly and exclusively to global warming. But it nonetheless remains true that a warming earth exerts a discernible influence on patterns of extreme weather. To argue that no single weather event can be causally linked to global warming is like arguing that no specific criminal act can be causally linked to poverty. The red herring search for precise and irrefutable necessary connections is irrelevant to the larger pattern of statistical correlation and influence.
The relationship between CO2 production and global warming is as well established as the link between smoking and lung cancer . Upon being diagnosed with lung cancer it would be silly to insist, before giving up smoking and pursuing a treatment plan, that one’s physicians identify the specific cigarette (or carton, or even year spent smoking) that caused the disease. Certainty is an epistemic impossibility when it comes to any inductive inference, including scientific inferences. Following Hume, this epistemological limitation has long been acknowledged; indeed many would say it has been understood philosophically since Hellenistic skepticism. In both philosophy and modern science, the acknowledgment of fallibility is a constructive move, separating authentic discovery from dogma. Responsible reasoning does not justify the rhetorical exploitation of uncertainty; advancement of scientific understanding can be granted despite the acknowledgment of fallibility. As such, to stubbornly require a “proof” that global warming is the result of human activity and that climate change influences patterns of extreme weather — given the ready preponderance of real evidence — merely reduces to an argument from ignorance.
Confusion Three: The terms denialist and denialism are forms of ad hominem (or inappropriately personal) attack against climate skeptics and their work
The term denier is often associated with those who claim the Holocaust was a hoax. It is considered an insulting term, and since sincere conversations should avoid offense, the argument goes, we should avoid using such terms. Yet denialism is a phenomenon of real academic interest, following recognizable patterns, and, in order to avoid confusions, it should be discussed responsibly with its appropriate label .
Established science might be denied for a number of reasons. Some people deny an established scientific claim because they embrace a religious doctrine to which they find the claim inimical. Others may deny an established scientific claim because they hope to challenge the epistemic privilege of science on philosophical grounds. Still others are motivated to reject science for financial or political reasons, or a vaguer sense of group affiliation with a political or cultural faction. When those who lack the scientific expertise relevant to a claim they are making deny the established science on the issue, they evoke the language and authority of science by demanding to be described as skeptics. Skepticism is not mere disbelief motivated by pessimism, cynicism, or political ideology. Skepticism has always entailed a philosophical investigation into the constraints on human knowledge, either in general or in a given area. The intellectually cautious nature of science reflects this philosophical lineage.
Science works through its skeptical methodology; this is the motor of the vetting process that can ultimately lead to consensus. We do not expect scientists doing field research to share exact methodologies with scientists working in laboratory settings, but all fields of science involve (ideally) rigorous applications of methodological skepticism. Skepticism is an essential component of the scientific process. When one who lacks relevant expertise denies a scientific consensus, and attacks scientists who support it, that person does not behave as a skeptic. It is to play at being a skeptic while refusing to acknowledge the legitimate fruits of skepticism. This form of denialism is accurately described as pseudo-skepticism; it is a common if not essential feature of pseudoscience . Pseudo-skepticism and pseudoscience should both be properly understood as types of science denialism. Many an appropriate label can be used constructively or as ad hominem bludgeons; this alone is not a good reason to give up on appropriate labels.
The majority of people who are unsure of what to think about climate change are not denialists of climate science. But for committed denialists, skeptics is a misleading and inappropriate label . The term skepticism is ill-suited to describe the behavior of those who obstinately deny the evidence for anthropogenic climate change — the term pseudo-skepticism is more accurate. Moreover, it is more appropriate ethically to challenge, rather than to ignore, the broader phenomena of science denialism . Indeed, it is vital to clear this sort of rubbish, which muddles the public’s knowledge of scientific consensus on climate change. Doing so requires sustained clarity of concepts, the consistent use of language, and active rejection of the distractions staged by the loud minority of denialists. It is an effort well suited to both scientists and philosophers.
Lawrence Torcello is Assistant Professor of Philosophy at the Rochester Institute of Technology, NY. He specializes in social and political philosophy, moral theory, and applied ethics. His current research interests focus on democratic theory, liberalism, and issues of climate justice. Recent work explores the moral implications of climate change denialism and other forms of science denial.
 Locke J., (1689) An Essay Concerning Human Understanding, Edited by Peter Nidditch (1979), “The Epistle to the Reader,” pp. 9-10 Oxford University Press.
 Torcello, L., Mann M.E., (2014) “Limiting global warming to 2°C: the philosophy and the science,” The Conversation US, Published online, Oct. 21.
 Cook, J., et al., (2013) “Quantifying the consensus on anthropogenic global warming in the scientific literature,” Environmental Research Letters, Vol. 8, No, 024024, 7 pages.
 Hume, D., (1748) An Enquiry Concerning Human Understanding, edited by Peter Millican, (2008) Oxford University Press.
 IPCC AR5 (2013) Website.
 Fischer, D., (2014) “Climate Risks as Conclusive as Link between Smoking and Lung Cancer,” Scientific American, Published online: March, 19.
 Pigliucci, M., (2014) “The varieties of denialism,” Scientia Salon, Published online, Oct., 28.
 Torcello, L., (2012) “The Trouble with Pseudoskepticism,” Skeptical Inquirer, Vol. 36, No. 3, pp. 37-41.
 Deniers are not Skeptics, Skeptical Inquirer, 5 December 2014.
 Torcello, L., (2011) “The Ethics of Inquiry, Scientific Belief, and Public Discourse,” Public Affairs Quarterly, Vol. 25, No. 3, pp. 197-215.