(From The New Yorker, 17^th August 2016, by the late former astronaut Dr Piers Sellers)

Excerpt from “Space, climate change, and the real meaning of theory”:

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The facts of climate change are straightforward: there’s been a warming surge over the past hundred years, with a dramatic uptick in this new century. We are seeing the effects in the shrinking of the summer Arctic sea ice and the melting of the Greenland glaciers. That melt, in turn, has been partly responsible for the three-inch rise in sea levels since 1992. The Earth is warming, the ice is melting, and sea level is rising. These are observed facts.

Are we humans the cause of these changes? The answer is an emphatic yes. Many climate-research groups around the world have calculated the various contributions to climate change, including those not related to humans, like volcanic ash. It has been shown repeatedly that it is just not possible to explain the recent warming without factoring in the rise in anthropogenic greenhouse gases. If you left the increase in carbon dioxide out of your calculations, you would see a wobbly but, on average, level temperature trend from the eighteen-nineties to today. But the record—the reality—shows a steeply rising temperature curve which closely matches the observed rise in carbon dioxide. The global community of climate scientists, endorsed by their respective National Academies of Science or equivalents, is solid in attributing the warming to fossil-fuel emissions. Humans are the cause of the accelerating warming. You can bet your life—or, more accurately, your descendants’ lives—on it.
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Newton’s ideas, and those of his successors, are all-pervasive in our modern culture. When you walk down a street, the buildings you see are concrete and steel molded to match theory; the same is true of bridges and machines. We don’t build different designs of buildings, wait to see if they fall down, and then try another design anymore. Engineering theory, based on Newton’s work, is so accepted and reliable that we can get it right the first time, almost every time. The theory of aerodynamics is another perfect example: the Boeing 747 jumbo-jet prototype flew the first time it took to the air—that’s confidence for you. So every time you get on a commercial aircraft, you are entrusting your life to a set of equations, albeit supported by a lot of experimental observations. A jetliner is just aluminum wrapped around a theory.

Climate models are made out of theory. They are huge assemblies of equations that describe how sunlight warms the Earth, and how that absorbed energy influences the motion of the winds and oceans, the formation and dissipation of clouds, the melting of ice sheets, and many other things besides. These equations are all turned into computer code, linked to one another, and loaded into a supercomputer, where they calculate the time-evolution of the Earth system, typically in time steps of a few minutes. On time scales of a few days, we use these models for weather prediction (which works very well these days), and, on longer time scales, we can explore how the climate of the next few decades will develop depending on how much carbon dioxide we release into the atmosphere. There are three items of good news about this modelling enterprise: one, we can check on how well the models perform against the historical record, including the satellite data archive; two, we can calculate the uncertainty into the predictions; and three, there are more than twenty of these models worldwide, so we can use them as checks on one another. The conclusions drawn from a careful study of thousands of model runs are clear: the Earth is rapidly warming, and fossil-fuel burning is the principal driver.

But theories are abstract, after all, so it’s easy for people to get tricked into thinking that because something is based on theory, it could very likely be wrong or is debatable in the same way that a social issue is debatable. This is incorrect. Almost all the accepted theories that we use in the physical and biological sciences are not open to different interpretations depending on someone’s opinion, internal beliefs, gut feelings, or lobbying. In the science world, two and two make four. To change or modify a theory, as Einstein’s theories modified Newton’s, takes tremendous effort and a huge weight of experimental evidence.
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Dr Piers Sellers space flight experience.

Dr Piers Sellers in Greenland:

We need more knowledge in and of Space and Earth, not more force.