I recently made the mistake of starting a conversation about climate science on facebook by suggesting people watch a video of a speech by Leonardo DiCaprio at the recent UN Climate Summit. DiCaprio makes a very moving presentation, but as I watch it again, I realize the extent to which it is a political speech with assertions that are not supported by what I would regard as reliable science, by emotional appeals, and by recommendations of what the UN body should do to “combat climate change”. While I do believe it important that climate change become a major political issue, equally I think it fundamentally important that we first ground ourselves on the science of climate change, and in posting this video clip I confused the issues.
So let’s start by talking about what science is and what it is not. A standard definition of science runs something like, “Science is the intellectual and practical activity encompassing the systematic study of the structure and behavior of the physical and natural world through observation and experiment.” So science is an iterative process in which observations are made in the world; theories made to explain the observations and predict how similar systems will behave under different conditions; experiments performed on the system under those conditions; then more observations made and the theories reviewed for their success. The mainstream scientific community has established a system of open debate and peer review to reinforce this process: sure, it has flaws, but for the most part, and over the long run, I have been convinced it works and works well.
Most of the more emotive political issues of the day – such as gun control and women’s reproductive rights – can be viewed from within a statistical and sociological framework, but there is little that I see science being able to offer as informational and theoretical background and framework for these discussions.
Climate science, however, is different.
Climate science can provide large volumes of data and information about the history of global climate and about how the various systems of the earth – oceans, the water cycle, atmospheric absorption and radiation – respond to a variety of actual and hypothetical changes. Science has the ability and responsibility of making measurements, establishing correlations, developing theories, and testing those theories. But science also has the responsibility of being clear about what is known and what is not known, and about the limitations of the data and the theories. Scientists have a responsibility to stay true to their scientific mission, and when they move into the political or religious realms (as some do frequently and others rarely), to make it clear that they are no longer talking as scientists. One of the most powerful negative examples of a scientist not respecting those boundaries is Richard Dawkins, an evangelist among other matters of atheism and evolution going way beyond what I believe to be established by science.
In my own studies of climate science I have found a massive and growing preponderance of scientific evidence founded on 150 years of empirical measurements of temperature from thousands of weather stations around the globe and on an overwhelming body of evidence from elsewhere (e.g. ocean behaviors; the cryosphere; precipitation levels), that the average global temperature since the beginning of the 20th Century has risen gradually by approximately 1.5 degrees Fahrenheit and that this rise is unprecedented in historical terms over a period of thousands of years. I have found similar overwhelming evidence and consensus that atmospheric carbon dioxide concentrations have risen by roughly 30% to 0.04% over the same timeframe, and that burning fossil fuels is a significant contributor to this growth.
We can also look at the earth’s energy balance: you can Google the phrase and find out a lot more, but one picture, courtesy of the National Oceanic and Atmospheric Administration, is shown above. This energy flow is based on an scientific understanding of the physics and chemistry of clouds; gaseous absorption of and transparency to visible light and infrared; and the conversion of incoming visible light by Earth into outgoing infrared light. Much of the science, in modern terms, is surprisingly straightforward (for example based on considerations of the absorption spectra of atmospheric nitrogen, oxygen, water vapor and carbon dioxide). This is a good model that seems to serve us well today.
But moving from an understanding of how all this works today into the future is much more challenging. The earth is an incredibly complicated system. We don’t have a long enough history of changing the climate variables, or data over a sufficient range of climate variables, to permit us to develop models that can predict with high confidence how (for example) further changes in CO2 levels will affect climate in the future. In short, climate science can do a really good job of telling us what we know, which is where we are and how we got here; it can do a good job of describing the basic physical and chemical processes at work; but I find no evidence that there are reliable scientific models of what climate will become in the future. That said, the models are improving every day, and we should certainly look at them for valuable perspective.
And yet we politicize and radicalize the conversation. For example an article in the British newspaper, The Daily Mail, talks about what it describes as the “Myth of Arctic Meltdown“. It is an article designed to debunk what many activists (NOT climate scientists) see as a poster-child issue, but along the way it politicizes the matter and leaves the reader with the suggestion that climate science is poor. In this particular instance this is an unfounded conclusion. The article is based on two years of data and a handful of comments taken out of context. A good scientific viewpoint would be to look more closely at the data, for example looking over a longer time-frame and acknowledging both long term trends and short term volatility. The National Snow & Ice Data Center, (supported by NASA, NSF and other federal agencies) charts data which show considerable short-term volatility, but an average decline in ice volume of 10% per decade. That’s it: it offers no conclusions about what this means, about what will happen in the future, or about what we as a society should do. This is cold, clinical, unemotional. Perhaps part of the problem is that real science is boring!
There is a lot of similar commentary from both sides of the political debate, a recent example being from Earth Justice (an organization I happen to support): “Climate Change Laps At Our Doorstep“. This is also not science, but a call to action; it is one we are free to respond to or to ignore, but we should not allow ourselves to confuse this appeal (as the authors may have done) with scientific certainty of the future.
There are many bloggers on Climate Science (here’s a link to a posting that uses Technorati data to rank the ten most viewed). Many – but not all – of the bloggers have credible backgrounds and credentials, write intelligently, and offer challenging perspectives and viewpoints. But in the end any individual blogger (self included, of course!) is trapped in his or her own paradigm: active bloggers are passionate, and they bring that passion to bear! On top of the tendency for bloggers to lose sight of the woods for the trees, there is a more dangerous tendency for readers to focus on blogs that support their own viewpoints. It’s great to read blogs, but important when doing so to intentionally read widely, and to include not just those who support your own views.
My conclusion, then, is that any discussion of climate science should start with a clear understanding of what we mean by the science, and of where the line is between science and politics. It is clear to me, as it seems to be to the overwhelming majority of the scientific community, that average global temperatures and global atmospheric CO2 levels have risen significantly (by 1.5 degrees Farahnheit and 0.01% respectively) over the last 100 years, and that atmospheric CO2 absorbs infrared radiation from the earth and emits the majority of this back to the earth, warming the earth in the process (this is literally why the earth is not covered in ice!). I believe that holding political conversation to curb potentially escalating CO2 emissions is an urgent priority – but this last point is my belief and there is considerable scientific uncertainty in the evidence I use to support it.
I encourage you to read a recent article in the Wall Street Journal by Steven Koonin (a man with considerable scientific and political pedigrees), titled “Climate Science Is Not Settled“, in which he explores this same theme.
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