Saturday, December 10, 2011

Yep, it's getting warmer


In a recent issue of Science a trio of scientists who are experts on climate modeling and interpretations of data related to global climate summarize the best available information on variation in Earth’s surface temperature over the past half century or so. Their work addresses a controversial subject that those resisting the idea of global warming love to talk about.
Doubts about the reality of 20th century warming have been fueled by a veritable blizzard of misinformation and outright denial by politicians such as Senator James Inhofe and talk show hosts such as Rush Limbaugh and Glenn Beck. The political winds from the extreme right have been blowing so mightily against the notion of global warming that the front-runners in the race for the Republican nomination in 2012 seem to be obliged to join in the denialist chant. The American people are being deluged with misinformation and outright lies on this topic. It is thus worth thinking about the significance of this recent work by Santer, Wigley and Taylor.
One of the most difficult challenges in the entire business of drawing conclusions about Earth’s surface temperature is that there really is no single literal measurement that gives us the temperature of the planet. I wrote about this in Chapter 9 of my 2003 book, Making Truth: Metaphor in Science. When we want to measure our own body temperature, we insert a measurement device such as a thermometer, or one of the fancier digital probes, under our tongue, in our ear or up our rectum, as the case may be. The temperature we record in this way we take to be representative of our body as a whole. This works because our bodies are designed to maintain, as closely as possible, a single temperature throughout. But planet Earth is not like that. As I write this in Estero Florida the temperature is about 80 degrees Farenheit. At the same time, my daughter living in mid-central Illinois reports that the temperature there is about 11 degrees Farenheit. It is far colder still in Antarctica. No single value represents the surface temperature of the planet . For this reason, when we talk about the surface temperature of the planet we are using metaphorical language and thought. We talk aboutEarth’s surface temperature as though the planet were a small, temperature-controlled thing like a human body or a refrigerator.
To get to something that resembles a single value for the surface temperature, scientists began with simply averaging the temperatures measured at as many places as possible at the same time, and averaging over time as well. Before the modern age of satellite measurements the estimates were pretty crude. Consider that something like 70 percent of Earth’s surface is covered with water. How do we get sufficient measurements of the vast and varied seas to produce reliable numbers? And what about remote places that are not readily accessible, or crowded urban areas where human activity generates a good deal of local heat? With satellite measurements it has become possible to collect data over a short period of time that reflects surface temperatures
over most of earth’s surface. By averaging these in a suitable way, one ends up with a single number that we call the surface temperature of the planet. It’s a metaphorical entity, not a real single temperature, but its value over time can serve as a reliable measure of the change at Earth’s surface. However, the interpretation of satellite data is not entirely straightforward. A group of scientists at the University of Alabama at Huntsville concluded in 2005 from satellite data that the planet’s surface temperature had declined since 1979. This unexpected result was used to cast doubt on the reality of surface warming.
One of the hallmarks of good science is that controversial results are subject to reevaluation and continued exploration. The satellite measurements were a new technology, and many factors needed to be taken into account in interpreting the data. Climate scientists at a California laboratory identified two serious errors made by the Huntsville group in their analyses. These were acknowledged by the Huntsville scientists, who redid their recalculations. The corrected results showed a warming trend over the entire period 1979 to present. The revised estimate, following from critical scrutiny by other scientists, represents another step forward in our ability to measure and understand the evolution of the global climate.
Modeling the terrifically complicated global climate system is difficult. The challenge is to find a model that reproduces the historical record as well as possible, considering all the uncertainties,and then to use that model to forecast the future course of climate change, assuming various scenarios regarding levels of greenhouse warming gases, energy consumption, population growth and so on. The media are filled with confident pronouncements, for the most part self-serving, about climate change from political, ideological and financial interests. When we hear what people like Rush Limbaugh, James Inhofe or Newt Gingrich are saying or are ready to get behind, we need to ask what motivates them and what is their competence to speak on the issue at hand. We should also do that with respect to scientists, whatever the issue might be. Citizens need to go behind the one-liners of politicians and talk show personalities to learn what scientists think and the evidence that supports their views. There is no scientific conspiracy to deceive the public into believing that global warming is real, and that it has the potential to cause a great deal of human suffering. Scientists are just doing their work, trying to learn more about the way the world is.
An incredible amount of research across many scientific disciplines leads to an unambiguous result: the planet is warming, mostly because of increased concentrations of so-called greenhouse gases in the atmosphere. Denying this may be politically or financially expedient, but global warming is underway and it will gain strength with each passing year. How much adverse change occurs over the next 50 years and beyond will depend on whether humanity collectively decides to do something about continued generation of greenhouse gases. There is little hope for significant action in the near future. The 2011 Climate Change Conference in Durban, South Africa, just concluded with essentially no progress in setting mandatory goals for reductions of greenhouse gases. This should not surprise anyone. We humans have evolved to possess a strong consciousness of the future, but we still live very much in the present. Our proclivity to discount the future, particularly one so distant that we will not be there to live in it, prompts us to choose present needs and desires over future consequences of our actions. That seems to be the way it is with respect to climate change. As Kurt Vonnegut was fond of saying, “So it goes…”.

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