KNOWLEDGE OF COMPLEX SYSTEMS

“Climate is an angry beast, and we are poking it with sticks.”
Wally Broecker (quoted inThomas Homer-Dixon’s “The Ingenuity Gap”).


Broekner is a scientist who has raised the question of the stability of the water cycle in the Atlantic Ocean. There is a huge northward flow of surface water in the Atlantic from the tropics toward the Arctic. As the water flows north, surface evaporation increases its salinity. As the cold air of the northern winter blows over the ocean, the temperature of the water drops. The cold, salty water in the vicinity of Iceland and Greenland is dense, and flows downward, creating a counter-flow toward the south. The deep ocean flow to the south eventually results in an upflow in the tropics, and thus there is a north south circulation in the Atlantic.

The heat and moisture dumped into the atmosphere by the north-flowing surface waters dramatically affect the climate of Europe. My ancestors from Devon and Cornwall in England and the west of Ireland were blessed with a relatively warm and rainy climate as a result of this current. But it affects all of Europe. Moreover, the downflow of water in the north Atlantic carries huge amounts of carbon dioxide into the deep ocean, sequestering it from the atmosphere. Since carbon dioxide is an important greenhouse gas, the effect is to reduce the rate of global warming.

In recent decades, relatively warm weather has resulted in melting of glaciers, and increased flows of fresh water into the northern Atlantic. If global warming continues as predicted, the effect will be increased. Moreover, as there is more heat energy in the atmosphere, more water should evaporate from the sea and rainfall should increase. The fresh water dilutes the sea water, reducing its density. Broekner suggests that eventually the density of the northern surface water might no longer be sufficient to drive it into the depth of the ocean, and the circulation of the ocean might stop. It appears that this has happened in the past. The result would be catastrophic climate change in Europe, and probably over most of the globe. (Or not, the theory is still controversial.)

The key issue that concerns Homer-Dixon is that the effect would be to switch from one quasi-stable state to a different one. We all know that the weather is variable. In the last generation scientists have learned that the El Niño/La Niña phenomenon and a few others affect climates. Weather is significantly different in El Niño years than in La Niña years over many areas of the globe. We are used to these short term fluctuations. But were the Atlantic ocean circulation to be cut off, there would be a much larger, more permanent change. That is an “angry beast” we are poking with the global warming “stick”.

Homer-Dixon is writing about this and a number of similar situations. There are lots of systems that fluctuate in known ranges, but that have the potential for sudden, larger fluctuations into unknown territory. We deal with known health problems, and then a pandemic arrives such as AIDS. We see stock market fluctuations from day to day, and then there comes a drop such as triggered the depression of the 1930’s or the more than 20% drop on one day in 1987. Economic development occurs, but then there is a financial crisis such as have occurred in Argentina, Mexico, and Asia in recent years. Relations between superpowers fluctuate, but then there comes a “Cuban Missile Crisis” that reaches the brink of thermo-nuclear war. The Soviet Union political and economic systems fluctuate within fairly limited grounds until communism falls abruptly.

We have evolved procedures to control and limit change within such systems, and we generally assume that those procedures work adequately. The sudden shift from one quasi-stable state to another invariably illuminates the limitations of such control procedures. Homer-Dixon points out that all the systems involved are very complex, and that while we may understand their operation adequately to affect behavior within a quasi-stable state, we seldom understand well enough to do much in the transition between such quasi-stable states.

I was especially struck by Homer-Dixon’s comment on watching the news on October 19, 1987 – the day of precipitous decline in the Wall Street and other stock markets. The façade cracked. The newscasters expressions showed that they did not understand what was happening, nor where it would lead. Indeed, it appeared that their confidence that someone, somewhere understood and could step in to stop the crisis was shaken; perhaps the economy was beyond our understanding and control.

It made me think about the difference between politicians and media pundits on the one hand, and scientists on the other. The former always seem to present a façade of perfect knowledge. There is always someone on the news to explain exactly why the Dow Jones average moved a fraction of a percent one way or the other yesterday. On the other hand, scientists, who have spent lifetimes studying specific phenomena, generally are quite modest about the understanding they have achieved, and their ability to predict. No wonder the public tends to have a comforting, and largely erroneous belief that someone in control really understands, since the pronouncements that reach the public are usually those of the media and the politician, not the scientist.