Q: Could you rank the things that have the most significant impact and where would you put carbon dioxide on the list?
A: Well let me give you one fact first. In the first 30 feet of the atmosphere, on the average, outward radiation from the Earth, which is what CO2 is supposed to affect, how much [of the reflected energy] is absorbed by water vapor? In the first 30 feet, 80 percent, okay?
Q: Eighty percent of the heat radiated back from the surface is absorbed in the first 30 feet by water vapor…
A: And how much is absorbed by carbon dioxide? Eight hundredths of one percent. One one-thousandth as important as water vapor. You can go outside and spit and have the same effect as doubling carbon dioxide.
And about prior climate changes:
“All this argument is the temperature going up or not, it’s absurd,” Bryson continues. “Of course it’s going up. It has gone up since the early 1800s, before the Industrial Revolution, because we’re coming out of the Little Ice Age, not because we’re putting more carbon dioxide into the air.”
Little Ice Age? That’s what chased the Vikings out of Greenland after they’d farmed there for a few hundred years during the Mediaeval Warm Period, an earlier run of a few centuries when the planet was very likely warmer than it is now, without any help from industrial activity in making it that way. What’s called “proxy evidence”—assorted clues extrapolated from marine sediment cores, pollen specimens, and tree-ring data—helps reconstruct the climate in those times before instrumental temperature records existed.
We ask about that evidence, but Bryson says it’s second-tier stuff. “Don’t talk about proxies,” he says. “We have written evidence, eyeball evidence. When Eric the Red went to Greenland, how did he get there? It’s all written down.”
Bryson describes the navigational instructions provided for Norse mariners making their way from Europe to their settlements in Greenland. The place was named for a reason: The Norse farmed there from the 10th century to the 13th, a somewhat longer period than the United States has existed. But around 1200 the mariners’ instructions changed in a big way. Ice became a major navigational reference. Today, old Viking farmsteads are covered by glaciers.
Bryson mentions the retreat of Alpine glaciers, common grist for current headlines. “What do they find when the ice sheets retreat, in the Alps?”
We recall the two-year-old report saying a mature forest and agricultural water-management structures had been discovered emerging from the ice, seeing sunlight for the first time in thousands of years. Bryson interrupts excitedly.
“A silver mine! The guys had stacked up their tools because they were going to be back the next spring to mine more silver, only the snow never went,” he says. “There used to be less ice than now. It’s just getting back to normal.”
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