This post is from ScIU’s archives. It was originally published by Chris ChoGlueck in October 2017 and has been lightly edited to reflect current events.

Whether it’s the “alternative facts” from politicians or the “fake news” from the media, facts are at the fore. While they can’t agree on much else, politicians, pundits, and the public do agree (mostly) about facts: facts are separate from fictions, they are reliable and authoritative, and, most importantly, they have something to do with (good) science. But, what exactly is a scientific fact?

Let’s a take a contemporary example: it is a scientific fact that the earth’s atmosphere has warmed in an unequivocal, unprecedented manner. This is the first conclusion from the most recent assessment report (AR5) from the Intergovernmental Panel on Climate Change (IPCC) (for one representation of this fact, see figure 1). You should note that this fact describes a temperature trend around the planet.  It is not an explanation for the trend, such as, that humans are responsible for releasing heat-trapping emissions. (The IPCC AR5 states this as a fact as well, but we’ll start with the basics.)  

What makes this claim about global warming a scientific fact? To begin, the claim is an empirical one because it involves experience with the world, rather than reasoning with theory and logic. Thus, to evaluate whether the earth has warmed, we would need to go out and look. It would not be enough to sit and think about thermometers or climate patterns. Insofar as these are both experience-based, scientific facts are similar to our everyday facts, like the observation that it’s hot today.

However, not just any old experience from our senses will do. This fact about global warming, for instance, could not simply be observed or confirmed like an everyday fact. What would it even mean to say that someone observed a 0.8⁰C change in surface temperature over the past 150 years? For one, this observation requires extensive and consistent records. It also entails separating the signal of the trend from the noise, often accomplished with modelling and statistics. Otherwise, the trend might actually be picking up some variation other than climate change, such as, changes in the measuring instruments or local conditions. In these ways, scientists’ interactions with the world are more systematic because they involve procedures for planning, recording, and analyzing the data they collect.

As you can see, we’ve started to diverge from the everyday notion of facts as something simply observed by our senses. Scientific facts require additional direction and support from theory and logic, including the mathematics needed for measurement and computation. This systematic endeavor involves a complex system of theory and practice to secure the fact-finding process.

But something is still missing from this story. How can scientists make so many measurements? How will they know if they’ve made errors? Scientists don’t work in isolation but in communities, exchanging and critiquing each other’s findings and ideas. This fact about warming does not come from one set of observations, but from countless collections (some ranging back to 1850) from all over the world. They involve records of receding sea ice, earlier spring blooms, upward migrating tree-lines, changes in soil moisture, and many more.  his variety of observations provides scientists with robust grounds for this fact.

In addition to the many lines of evidence, there are many individuals and groups who have worked together to produce this knowledge. We often credit individuals with foundational achievements and discoveries, such as Joseph Fourier’s theory of the greenhouse effect and Charles David Keeling’s groundbreaking CO2 curves (figure 2). However, these individual merits were founded on a community of scientists, and it was their successors who really showed the validity of their ideas. Thus, bringing together our insights so far, scientific facts are the product of communal, systematic experience with the natural world.

So the empirical, procedural, and social aspects of science come together to produce factual knowledge. This might leave you wondering: I thought facts were simply given? But, if scientific facts rely not only the natural world but also the work and ideas of humans, are they just our fancies or inventions?

Scientific facts are not simply handed to us by the world “on a silver platter,” independent of our actions, but they are also not arbitrary conventions or constructions. They result from our interaction with the world, and scientists attempt to apply rigorous standards to ensure that they are reliable. Furthermore, controversial facts, such as this claim about global warming, undergo heavy critique from many different angles. The resilience of facts under pressure should give us peace of mind that we can trust them. Stay tuned for my next post, where I’ll talk more about these processes aimed at producing objective, reliable knowledge.

IPCC, 2014. “Climate Change 2014: Synthesis Report.” Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp.  Available online.

Edited by Karna Desai and Victoria Kohout