How Do We Know?:
In general I have tried to steer clear of the arguments about the reality of climate change that pervade, mostly now, the web. But I got a note this week from a reader that had as one part of the note “How do we know?” This question coupled with a number of events got me thinking. How do we know?
When I was at NASA I was involved in the assessment of the environmental impact of airplanes. Often we were investigating new types of airplanes, like commercial supersonic jets. These would fly higher than the current fleet, in the stratosphere, and their pollutants would stay in the atmosphere a long time. These studies were, of course, based on atmospheric transport and chemistry models. Over the years there were many numerical experiments and measurement campaigns. We developed a collection of knowledge, which included a catalog of what the models did well and what the models did poorly. With all of this knowledge we could state with some certainty what different fleets might or might not do to, say, the ozone layer. Occasionally we would get a request for what a VERY small fleet, say less than five, of very high flying airplanes might do. Based on our experience with both observations and models we could state, without further experiments, that this very small fleet would not (or would) have significant impact. Still though, the sponsor of the research would want us to do a numerical experiment to “prove it.” Without the experiment – how would we know?
Of course some would argue that a numerical experiment does not give us a definitive yes or no answer. In fact, there are those in the world who maintain that we never know until something happens, and we can experience it or measure it. There are those in the world who believe that the process of past experience, measurements, theory (remember theory is derived from testable hypotheses), and prediction tell us with high probability what will and will not happen. That knowledge is actionable.
This train of thought reminded me of the spring of 2005 when I was finishing up a sabbatical at the Lawrence Livermore National Laboratory
. I was in the barbershop on Main Street getting my last Livermore haircut, and there was a property appraiser in the chair next to me. The property appraiser was planning to quit his job because he had just been asked to reappraise a house to add $50,000 dollars to the price. He had gone out and said that a 100 square feet of tile in the entrance, which he had “overlooked,” was worth $50,000 dollars. He felt dishonest, used, and liable for lying. We talked about the way the housing market was working, and how the run up in prices did not sit on a foundation that even rose to the level of “house of cards.” It was a situation that was unsustainable and stunningly stupid. There was little we could do outside of “not participate.” (I never imagined, however, that this stunning stupidity could reach so far and so deep.)
How did we, this house appraiser and I, know about the housing market? Experience is one way. Some simple math is another way – the robustness of the housing market required exponential growth of wealth and that just doesn’t work for very long. (And exponential growth of waste in the environment will also not work for very long.) But in the end, we did not really know -- did we?
How do we know? Sometimes this question can be quite informed. How did Columbus and Magellan know that they would not fall off the edge of the world? (I limit the question to Columbus and Magellan and don’t include the Vikings and the Chinese and the Polynesians, because I know the European world had been indoctrinated that the world was flat. They drew maps.) There were writings and measurements that supported the idea that the Earth was round. There were, perhaps, even reports from other cultures of experiences in lands across the water. So the answer is that Columbus and Magellan did not know. They set out to find out. They set out, I assert, with some information.
When we set out for the Moon, did we really know that it was not the staring eye of monster?
How do we know? There are people who will never accept the prediction of global warming. They will not accept the evidence from the experiential base, nor will they accept the utility of models. They will not accept the process of evaluation of models, which documents both what we know well and what we know poorly. As long as there is any discrepancy in the knowledge base they will find a foundation on which to question and dismiss the conclusion that: carbon dioxide released by the industry of humans into the atmosphere will warm the Earth, cause sea level to rise, and the weather to change. How do we know? How do they know otherwise? Why do people believe what they believe?
I sit and write this (tardy) blog on an airplane. This is a mass of metal held up above the ground by air that I cannot see. This particular mass of metal was largely designed by model simulations based on observations and theory (remember theory is derived from testable hypotheses). (And based on this model-assisted design, some pilot sat in this mass of metal the first time it was built and accelerated to some speed that, in a crash, would crush her or his aorta. They sat in that new airplane with the reasonable expectation that they would have dinner when they got home in the evening.) This metal shell moves forward at more than 500 miles per hour towards Denver, with the Earth turning below it, and with some knowledge that what lies ahead is more invisible air that can hold the plane up. We fly with presumed knowledge of the density of the air, the temperature, the wind speed and that the air is not full of hard ice. Likely, this plane will land no more than a few inches from where it was planned to land when it started down the runway in Romulus. How do I know I will get there? I don’t. But I have reason to expect that I will. (And if you read this, I did.)
We are placing massive amounts of carbon dioxide, waste, into the atmosphere. We know that carbon dioxide in an atmosphere irradiated by the Sun heats up the atmosphere. The amount of carbon dioxide we emit is increasing exponentially. How do I know? How do we know?
Does smoking lead to lung cancer? Does two pounds of barbeque a day lead to obesity? Does obesity lead to heart disease? How do we know? (And yes, I can know that something is potentially bad for me, and I will still do it.)
It is true that some people get tired of hearing about global warming. At this point, I am tired of hearing about the collapsing economy. I am angry that because the stunning stupidity of wanting people has threatened my savings, my retirement, my future. I am upset because I am placed in a position where my experiential base does not tell me what to do, or how to figure out what to do … if there is anything that I can do. I am hopeful that the policies developed during the 1930s and 70 years of generation of economic knowledge offers strategies to keep us from another great depression. I am wary that economic theory and economic models are based on quantification of markets and the behavior of people. Yes, I am tired of hearing of the reality of the economic instability, but that makes it no less real. I can commiserate with those who are tired of hearing of global warming. Global warming – an important reality that is based in the principles of predictable classical physics and billions of observations. Global warming – an important reality that we can do something about.
We have knowledge, and the ability to make informed decisions about what will happen. We might not always “know” to the satisfaction of all people. We can view this knowledge as a blessing or a curse. I view the knowledge as a blessing, an opportunity, something to be thankful for.
rNEWS: The Sun Shows Signs of Life
Figure 1: New-cycle sunspot group 1007 emerges on Halloween and marches across the face of the sun over a four-day period in early November 2008. Credit: Solar and Heliospheric Observatory
The Solar and Heliospheric Observatory (SOHO). From Science at NASA
. (Thanks again to Judith Lean.)