"If we look back over 1000 years, we find there have been bigger extremes by far – but not randomly distributed," it was observed in 1979. "The period 1000 years ago was a very cold period in the Northern Hemisphere. Lots of ice around Iceland, and the forests bordering Canada retreated southward again and northern Europe was cold, the winters severe. In (the 20th) century, this seemed to reverse. So, we have more nearly the kind of weather extremes now that were common back in the period from 1550 to 1900 – and not the nice, stable, unusual kind of thing that we think of as normal." 

In general, "...The world has been cooling off. On an average, it’s cooled down by something like one degree Fahrenheit or half a degree Celsius – and that cooling began around World War II. I would put my money on the idea that the cooling the world has been in for the 40 years (1939-79) is just one of these temporary swings of climate. And rather soon we will see the climate changing again into a new warming trend." 

It was argued, "…The climate will change as it has in the last few hundred years. There’ll be extreme periods of drought and wet, and warm and dry. But the overall global climate will drift up and down, a degree or 2 over a period of centuries to thousand of years – unless humans do something that makes it change more rapidly." 

To help explain weather (snow, rain, sleet, hail, winds, floods, dust storms), "Nature puts energy into our system, primarily energy from the sun. The energy from the sun is absorbed all around the earth, most of it in the tropics because they sit squarely in the sun’s rays; less at the poles. The temperature difference makes air rise in the tropics and sink at the poles; warm air moves toward the poles and the cold air at the poles flows back under it. The earth is also spinning. That deflects these wind currents into the complex pattern of what we call atmospheric circulation...It’s the balance of these energy flows, with some other factors like earth radiation, that creates wind currents, ocean currents, precipitation patterns, deserts, forests and so on." 

"Take the state of the art, with the processes we do understand. Admit we could be underestimating or overestimating the real effect. That still leaves the question, 'When do human effects become comparable to nature, on a global scale?' The answer is that some time by the end of (the 20th) century, the carbon dioxide effect, for example, should produce a warming of the earth by roughly one degree Celsius, which is about as large as any natural fluctuation in warming over the past few thousand years. After that, we become the major actor in changing long term climate. While there’s still uncertainty, we have to recognize that we may be insulting our environment faster than we’re understanding it." 

In conclusion, "Climate sets the limits within which we can grow food, store water, have houses. And we have a lot of leeway within those limits because of our technology. What we have to learn is to look at the climate’s extremes, not the averages. We’re quite capable of dealing with the averages, but it’s the bad winter, the dry summer that we have to be prepared for. I’ve called it a ‘genesis strategy’ after Joseph’s advice to the pharaoh to store up the grain in the good years against the inevitability of the bad years. Well, there are bad years now and it’s not just storing grain. It’s storing natural gas, so you don’t have half of Ohio unemployed in a bad winter. It’s storing water so that California and Colorado don’t go dry all year. And it’s storing food, not just in the United States but in Africa and Asia, the places where already half a billion people are malnourished and where any bad stress on food production from bad weather increases famine and starvation."

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