Figure 2 in last week’s blog demonstrated our most important tool for determining how we identify human contributions to climate change on both a local and global scale. The figure, taken from the NASA site, describes simulated 20th century global mean temperatures (with and without human influences), as compared to observed temperatures. This important comparison determines the validity of the simulation and its conclusion regarding the driving forces behind a particular event:
Computer simulations reproduce the behavior of a system using a mathematical model. Computer simulations have become a useful tool for the mathematical modeling of many natural systems in physics (computational physics), astrophysics, climatology, chemistry and biology, human systems in economics, psychology, social science, and engineering. Simulation of a system is represented as the running of the system’s model. It can be used to explore and gain new insights into new technology and to estimate the performance of systems too complex for analytical solutions.
In other words, this tool is used everywhere in science, to such an extent that it is unimaginable that any branch of science – including social sciences – could survive today without it. These mathematical models are designed to reproduce the behavior of real systems. How good the model is depends on how well it incorporates actual measured results into the assumed driving forces within the simulated system. This works especially well for simulating a complex system with many individual components and driving forces. As such, it is perfectly suited to simulate climate change. Figure 3 in last week’s blog showed an example of the framework of the forces assumed to drive climate and weather.
Per definition, mathematical models are products of human efforts, which means that they are subjective: they can be skewed by the unscrupulous to agree with preconceived opinions and mispresented as “real science.” Climate change is obviously a fertile ground for this kind of misbehavior, especially because the consensus among the scientific community implies real consequences for all of our futures. Cases of intentional cheating in science are not confined to climate change; in most cases those creating the false information do so while seeking career advancement, promotion or fame. The general public is not usually privy to these shameful activities and usually lacks the prerequisites to understand either what is being done or why it matters. Climate change is different because it affects all of us – the public needs to understand both.
Some scientists object to other scientists’ attempts to warn us about the consequences of climate change. They claim that predicting consequences equates to predicting the future, a field outside the mandate of science (May 7, 2012 blog):
The letter was signed by 49 former NASA employees that included seven Apollo astronauts and two former directors of NASA’s Johnson Space Center calling NASA to move away from climate model predictions and to limit its stance to what can be “empirically proven.” The letter specifically targets James Hansen – Director of NASA Goddard Institute (GISS) (Hansen and the GISS have been acting as the “the canary in the coal mine,” warning, for years, about the consequences of relying on fossil fuels as our main source of energy.) The letter states that, “We believe the claims by NASA and GISS, that man-made carbon dioxide is having a catastrophic impact on global climate change are not substantiated.” The reason for the doubt includes that.”NASA is relying too heavily on complex climate models that have proven scientifically inadequate in predicting climate only one or two decades in advance” and that “There’s a concern that if it turns out that CO2 is not a major cause of climate change, NASA will have put the reputation of NASA, NASA’s current and former employees, and even the very reputation of science itself at risk of public ridicule and distrust.” This is backwards; it’s the letter that should be held up to public ridicule.
If the senior NASA employees had had their way, Figure 2 probably wouldn’t exist and I would have had a much harder time demonstrating how we can show the degree to which we are responsible for weather events and what we can do to modify our collective behavior. NASA’s fear of looking bad in the case that some of its predictions turn out somewhat differently than expected should not take precedence over our chances to decrease the odds of local disasters.
Not long after I started this blog (December 10, 2012), I described a situation in which I gave a talk to another campus’ physics department and got embroiled in a useless argument about whether or not trying to measure human contributions to climate change counted as “real” science – as compared to investigating the physical properties of a specific semiconducting material. At the end of this chat I was asked if I had heard Freeman Dyson’s take on the topic. I have.
Freeman Dyson is one of the most distinguished and recognized physicists, with many major accomplishments in a wide range of topics:
Freeman Dyson FRS is an English-born American theoretical physicist and mathematician. He is known for his work in quantum electrodynamics, solid-state physics, astronomy and nuclear engineering. Born: December 15, 1923 (age 94), Crowthorne, United Kingdom. Awards: Templeton Prize, Wolf Prize in Physics, Hughes Medal, MORE
Education: Bates College, University of Cambridge, Cornell University, Winchester College
In 2009 David Biello published an interview with him in the Scientific American blog. Biello’s take on Dyson’s points prompted the rather unsubtle title, “Freeman Dyson and the irresistible urge to be contrary about climate change”:
At the luncheon put on by the Cato Institute, when the talk turned to climate change Dyson started out sounding as if the whole thing was overblown, noting that the prospect of global warming is a problem that should be taken seriously. But he also said that no one should be alarmed about it yet.
Then he outlined his main criticism: Too much of the science of climate change relies on computer models, he argued, and those models are crude mathematical approximations of the real world. After all, a simple cloud—small in scale, big in climate effects, the product of evaporation and condensation, all of which it is difficult to create equations for—eludes the most sophisticated climate models.
So climate modelers turn to what they call parameters or, as Dyson likes to call them: “fudge factors.” These are approximations, such as the average cloudiness of a particular spot at a particular time, that are then applied globally. With the help of about 100 of these parameters, models can now closely match the world’s present day climate, Dyson says. These models then, like the one developed at Princeton University where Dyson is a professor emeritus, are “useful for understanding climate but not for predicting climate.”
That’s too much of a temptation for scientists working on the problem, however. “If you live with models for 10 to 20 years, you start to believe in them,” Dyson said, witness the implosion of the financial markets after over-reliance on quantitative models. He characterized this over-reliance as a disease infecting everything from physics to biology: “A model is such a fascinating toy that you fall in love with your creation.”
Ultimately, “every model has to be compared to the real world and, if you can’t do that, then don’t believe the model.” And he noted that the real world has been through some significant climate changes before: witness a lush Sahara Desert thousands of years ago or the forests that once covered Greenland.
Of course, models have been tested against the real world (both today’s and eons ago’s) and many of Dyson’s other objections have been rebutted elsewhere. He also did not address the real world impacts already observed: ice melt, sea level rise, ocean acidification and more. His main concern seems to be that worrying about climate change distracts from more important problems such as poverty and infectious disease. Many might note that poverty (the inundation of Bangladesh) and infectious disease (improved conditions for transmission) are also problems exacerbated by climate change.
But Dyson’s purpose seems to be to throw out “heretical” ideas that can then spur further debate. (As even he would admit, his heresies are a little more grounded in the real world when he’s talking about nuclear weapons. Before discussing climate change, he told a roomful of people who probably want to put former President Ronald Reagan on Mount Rushmore that the Great Communicator blew a real chance to rid the world of nuclear weapons in 1986 because he was too attached to the “Star Wars” missile defense program.) As he said: “I know a lot about nuclear weapons and nothing about climate change.”
“I like to express heretical opinions,” Dyson said, with an impish gleam in his eye. “They might even happen to be true.”
I am sure that Dyson himself has used extensive computer modeling of various sorts, opening him up to the same kind of possible abuses that he describes. He is also more than familiar with the ways in which scientists work to minimize the impact of such manipulations.
I will let you draw your own conclusions.