A firestorm is raging across the Internet after The New York Times ran an op-ed piece by University of California Berkeley scientist Richard Muller. In it, he explains why he turned from climate-change skeptic to accepting the central role that humans play in warming the planet.
Muller claims that a careful reanalysis of the data collected from temperature stations led him to conclude that the average global temperature "has risen by two and a half degrees over the past 250 years, including an increase of one and a half degrees over the most recent 50 years. Moreover, it appears likely that essentially all of this increase results from the human emission of greenhouse gases."
So, Muller is saying that we are the culprits.
Muller goes on to explain why this is the case. To do this, a scientist must isolate all possible causes of an effect (in this case, the rising global temperature) and analyze one by one to establish their impact (or not) on the quantity of interest.
The results are posted in five papers available at the Berkeley Earth Surface Temperature project (BEST). Muller claims that his group's findings are even stronger than those of the International Panel on Climate Change, which correlates the temperature to humans only during the past fifty years. Muller claims they go all the way back to when they can study correlations, 250 years.
Of course, when a team member defects, his/her ex-teammates shoot back quickly. A day after Muller's op-ed piece, Anthony Watts from the privately-owned IntelliWeather, posted a piece in his blog Watts Up With That, where he claims that the data of U.S. temperature trends shows a spurious doubling due to station measurement issues.
Predictably, the whole debate went viral and virulent. One of the main criticisms is that Muller's claim is based on fitting the increasing global temperature to the increasing release of CO2 into the atmosphere and that this is not good enough evidence.
Of course, Muller and co-workers would strongly disagree, as would most climate scientists. The danger of turning what is first and foremost a scientific issue into a political one is that very quickly the science gets distorted.
When it comes to such a complex endeavor as the prediction of how the climate of a whole planet will behave in the future, many factors come into play. At best, we can make statistical inferences. This conflicts with people's desire to have yes or no answers that are clear and final. Unfortunately, all that can be done here is to improve the data collection, the computational modeling, and the statistical analysis so as to match as best as possible the observed trends.
As Muller notes, it's naïve to claim that a given hurricane or a warmer summer is evidence of global warming. Many factors come into play, and they interact nonlinearly with each other, causing effects that are hard to predict.
It has been said that all models are wrong, but some are useful. There is much truth in this saying. The measure of a good model is its ability to explain data and, in the best cases, predict new phenomena, yet unseen. Here, Muller is focusing more on data collection and analysis than on modeling, a good thing.
There is no end in sight for the climate change dispute. However, in the meantime, it may be useful to keep reminding ourselves of an undeniable fact: the Earth is a finite environment and any artificial forcing away from its equilibrium may lead, due to nonlinear effects, to undesirable circumstances. A finite system can cope with only so much forcing before changes occur. (For example, the water you boil in a pan.) Surely, it is possible that global warming is not man-made or that a new technology will control it. However, given the possible negative outcomes, why not take a few steps toward improving our relation with the planet, moving from a parasitic to a mutually advantageous one. Earth couldn't care less about us. But we can't exist without it.