Previous posts on global warming (here, here at "Item 6," and here) have touched on reasons why panic might be premature. We don't know enough about how the Earth naturally stabilizes the climate.
When the earth grows too warm by way of increased emissions of the greenhouse gas carbon dioxide (as, it appears, has happened in the last few years) it seems the Earth has mechanisms to deal with it.
Increased carbon dioxide, the most common greenhouse gas, leads to a greening of the world - particularly in the northern latitudes. Plants require carbon dioxide and thrive in its presence. The secondary effect of a world "greening" is ultimately, a lowering of global temperature. Greater plant life absorbs more of the greenhouse gas carbon dioxide and releases oxygen.
This mechanism has limits. If the Earth's temperature rose too high or too quickly to cause the beneficial "greening" effect, you might see a scorched planet instead of a greener planet. The loss of rainforests is a significant blow to the earth's ability to handle carbon dioxide. And carbon dioxide isn't the only greenhouse gas we've been emitting.
Fortunately the earth has another mechanism for dealing with heat. Increased heat increases evaporation, which increases cloud cover. Clouds reflect more of the sun's heat and provide rain, which is of further benefit to the carbon-dioxide-absorbing plant life. Evidence that this mechanism is working came with the release last month of a study on earthshine. "Earthshine" (here's a picture) is the ghostly outline of light reflected from the Earth to the Moon and back again.
The new study, published in Science, was conducted by Enric Palle and colleagues at the Big Bear Solar Observatory in California and the California Institute of Technology in Pasadena. They report that the brightness of earthshine decreased steadily during the period 1984 to 2000, although that trend appears to have reversed since.The decline suggests fewer clouds, which reflect sunlight, and therefore that more sunlight has been making it into the lower atmosphere (troposphere). That change is "consistent with the large tropospheric warming that has occurred over the most recent decades", they write.
Beside offering another explanation for increased temperatures other than greenhouse gases, the best part of this news is that Earthshine has increased since 2000. This suggests that cloud cover is returning and that we are in for cooler, rainier weather.
We know more about how a warm Earth cools than how a cold Earth heats up. In his book A Short History of Nearly Everything Bill Bryson said (page 429):
If Earth did freeze over, then there is the very difficult question of how it ever got warm again. An icy planet should reflect so much heat that it would stay frozen forever.
Bryson suggests that we've been saved during previous ice ages by volcanoes pumping out heat and greenhouse gases.
UPDATE: This afternoon Reuters reports:
In an article in the science journal Nature, Norwegian researchers said they had found traces of thousands of hydrothermal vents in lava off Norway that could have been the source of a rise in greenhouse gases 55 million years ago.Until now, scientists have been at a loss to explain the trigger for a 5-10 Celsius (10-20F) global warming over about 10,000 years in the Eocene -- a blink in geological time.
"We think that magma heated sediments containing organic material and led to an explosive release of gases," said Henrik Svensen, a researcher at the University of Oslo and main author of the article.
The scientists said the annual rate of modern human emissions of greenhouse gases to the atmosphere in the 1990s -- from fossil fuels burned in cars, factories and power plants -- was 35-360 times as fast as the pace of the Eocene gas buildup…
"We can cause the same amount of global warming ourselves in a few hundred years at current rates," Svensen said.
I just can't work up too much panic over this. We can't say with any degree of certainty what fuels we will use 25 years from now, much less what our fossil fuel consumption patterns will be over the next "few hundred years."
It's amazing to see all the different tricks the climate uses to keep itself in check.
The notion that we might be "burning oil" for hundreds of years is interesting. Let's say that no viable alternatives are ever found for oil. We exhaust all the available reserves. We switch to oil sand then eventually shale and coal-derived fuels. At the rate of economic growth occuring worldwide, when would we run out?
Posted by: Phil at June 3, 2004 08:21 AMPhil:
With advances in technology for refining sewage and other biomass into crude, I'd say we'll live to see the day when oil is a renewable resource.
Good news for our energy requirements (and our strategic defense), but bad news for the environment.
My hope is that advances in our ability to strip hydrogen from water will make hydrogen fuel cells competitive with petroleum.
Posted by: Stephen Gordon at June 3, 2004 10:14 AMEnvironmentalism seems more about politics than science. It takes on faith that the environment is getting worse and that extreme remedies are necessary. It ignores the method by which man improves things-- reason and technology.
Every organism fouls its nest, but only man has the brains to clean up after himself. And he does this only when he sees that there is a problem. He can get caught up in old ways of doing things. Often, a problem must get rather bad-- and people must be injured-- before a solution is attempted.
But, the Environmentalists have not helped here; they have acted as Cassandra's who only had one solution: more government control. But, governmental control often has bad side effects. What do you do when Government regulations are the problem, not the solution? When yesterday's solution becomes tomorrow's problem? And new methods are thwarted by environmental dogma? Despite this the environment is getting cleaner than it was in the 1960's just when the Environmentalists refuse to recognize this and step over the line into becoming a religion.
How do you know when they have become a religion.? When they have rejected reason and science and become fanatics. When they manufacture evidence to support impossible conclusions. When they stop having reasonable doubts.
Mankind is a part of the environment; his activities can help or hinder it. Poor people are the worse polluters; they must be to survive. As Mankind's standard of living improves his impact on the environment lessens. Rich people can afford parks and wilderness areas; poor people can't. Rich people can afford the science and technology to lower their environmental impact; poor people can't. That is why the most polluted place on earth is Eastern Europe. Poverty and repressive government combined there to produce what Environmentalists have feared most. Unfortunately, Eastern Europe is the Environmentalist's political ideal.
Posted by: Louis Wheeler at June 5, 2004 06:25 PMA few last comments.
The world is still colder than it was in 1000 AD-- by about a degree and a half.
The satellites in orbit taking readings off the top of clouds haven't seen a substantial change in 22 years.
The world has been growing warmer, but most of the temperature change (.5 out of .7 degrees) was before 1945 and most of the increase of CO2 in the atmosphere was after that. If we use the Environmentalist's logic then the temperature increase caused the CO2 increase. But, I don't think so.
Is there room for reasonable doubt here? Yes.
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