A friend asked me how I was going to feel when I discovered that anthropogenic climate change (ACC) was not real, when science was proved wrong. ‘Wonderful,’ I said. I’m not happy about ACC, and if I’m wrong that would be fantastic. I don’t have any epistemic commitments to anthropogenic climate change. My commitments are to finding the facts about the world. That is why I became a scientist. I have strong commitments to truth-finding. I’m forced to accept ACC, not because I like the idea, or think this makes economic sense, or even because I’m getting the big bucks with my fellow coconspirators for promoting it. I argue for it because not to believe it would be irrational given the evidence. The sheer number of papers that support the view is staggering. Oh sure, the deniers can site a couple of papers that suggest the case is still open (like this hooter from a couple of civil engineers–why can’t they find climatologists saying things like this?), but they ignore a massively coherent story coming from climatologists, teams of geologists, ecologists, oceanographers, foresters, plant scientists . . . well name a field, the scientific literature is rich with supporting evidence.
The story of Earth’s climate is complex and much about it is not well understood, and there are copious debates within science about how that story of Earth’s atmosphere has unfolded. Scientists are in heated debates about he role of solar cycles, ocean absorption of CO2, the effect of climate change on weather patterns, on and on and on. A common ACC denier tactic is to take these attempts to sort things out, and understand things in greater nuance and clarity, as evidence that ACC is not a consensus. I can’t tell you how often denier sites put up abstracts from scientific papers on the web that explore the role of, say, solar cycles, or something, as evidence that ACC is not real. “See it’s caused by solar cycles.” However, if you read the paper more closely, the scientists doing the study are part of the consensus on climate change. They are trying to sort out a more complete story, to give better analyses, and to make better predictions. That’s what scientists do. That there are fights going on in science is a good thing. That’s how science works. But when you see deep agreement and consensus among scientists from multiple disciplines, its a sign you’d better pay attention, and if you’ve got money riding on the finding you’d best take that into account when making a wager. Take the germ theory of disease. Nowadays, when someone finds a new illness like SARS or Swine flu they immediately start looking for, and usually find, a causal organism. Sure you can find lots of Internet stuff by people, even scientists, who believe that the cases are caused by some imbalance of the humors, or a misalignment of Chi, and you can provide links to their internet sites by the thousands (the most famous case being the Nobel scientist who did not believe that AIDS was caused by HIV). But the germ theory of disease has a lot of science baking it up and if you are going to step out of it, you are stepping out of science. Just like in ACC.
But what I want to really talk about is global cooling. This is brought up so often it staggers the mind that the real story is not more widely known. The statements go something like this: “Thirty Years ago scientists were talking about global cooling, now it’s global warming. What will it be next year?” This pessimistic induction fails to understand science in two ways. First, science changes its mind. It’s not something that stays married to previous stories when those stories turn out not to stand up to new data, new analysis, or new explanatory apparatuses. For example, most scientists once believed the continents where stable and did not move. Now we know that they do, and we have mechanisms that explain how it works. There are boat loads of evidence for continental drift’s actually coming from better instrumentation, and from the ability to take deep ocean sediment cores, and from data that explains things better based on what we find in the Earth’s crust. This is what makes science strong. Changing to fit the facts is the best tool we have for understanding the physical laws of the universe. So, if thirty years ago scientists said that the Earth was cooling, and now they say it’s warming than pay attention. It means that more data has been gathered, better analyses have been conducted, supporting evidence has been reinterpreted. Scientists changing their minds is not a flaw in science. It’s its among its greatest strengths.
Second, scientists, as a group, never said the Earth was cooling. One scientist did. A scientist named Schneider in 1971 published a paper describing a model that showed the Earth’s atmosphere would cool. It got printed in Newsweek, and so was born the myth that science once taught the Earth was cooling. The modeler went back and realized the model had underestimated CO2, and overestimated aerosols from volcanic eruptions. Was cooling a scientific consensus? Were data coming in from freezing glaciers in alpine regions? Was arctic ice getting thicker? Were species from multiple taxa, everywhere you looked, redistributing because of a cooling planet? Were oceans becoming less acidic? Was there less CO2 and other greenhouse gasses being measured in the air? Were temperatures actually being measured as going down from multiple sources? Were multiple models, from multiple independent labs, located in multiple countries across the world, converging to the same story? No. No, to all of these. One guy. One inadequate model. One more weapon in deniers arsenal to put up a smoke screen to the scientific story unfolding on ACC.
The truth is that global warming as been talked about for 200 years. The mechanisms supporting ACC where proposed in the 19th Century and evidences for it has been accumulating for decades. The case for it has only has become strong in the late 80s (I’ve blogged about a conference on ACC I attended in the early 90s and the belief among scientists then was only 50/50–that’s changed to 1:1000), and scientifically it is on very solid footing today.
So for good reasons, the pessimistic induction that “because science changes its mind it can’t be trusted,” is just wrong. The case for ACC? There is much that needs to be sorted out. There are anomalies, complexities, and difficulties. But as the evidence pours in from multiple disciplines, better instrumentation (including satellites and ocean monitoring techniques and ice core data), more sophisticated and robust models, greater diversity of statistical analysis methods, the case for ACC is strong. Could science be wrong? You betcha. Disease might be caused by an imbalance in humors too. But that’s not the way to bet.