....
Geologic time is such a vast concept that it¡¯s helpful to convert it to something more pedestrian just to get oriented. I like rainfall. [usgs geologic-time-spiral infographic]
* The total precipitation that falls on the world in one year is about one meter of rain, the height of a golden retriever.
* The total amount of rain that has fallen on the world since the industrial revolution began is about 200 meters, the height of Hoover Dam.
* The amount of rain that has fallen on the world since the time of Moses is enough to fill up all the oceans.
* The amount of rain that has fallen on the world since the Ice Age ended is enough to fill up all the oceans four times.
* The amount of rain that has fallen on the world since the dinosaurs died is enough to fill up all the oceans 20,000 times¡ªor the entire volume of the earth three times.
* The amount of rain that has fallen on the world since coal formed is enough to fill up the earth 15 times.
* The amount of rain that has fallen on the world since oxygen formed is enough to fill the earth 100 times.
....
The experiments that assign specific numbers of years to geologic layers are almost as simple as this science-fair project, although not quite, and they are just as reliable. Not everyone agrees with this assessment, of course. Geologic time does contravene certain religious beliefs, a notorious difficulty with the subject that is very regrettable, since it doesn¡¯t contravene the religious beliefs that count. But it¡¯s probably more significant that the experiments, simple though they may be, involve obscure facts about rocks, a knowledge of physical law, and the assumption that this law was the same in the ancient past as it is now. None of this is obvious, much less interesting, to the average person. If you go to the supermarket and engage the checkout clerk in a conversation about the Paleozoic Era, radioactivity, or the disappearance of the megafauna, you¡¯ll be met with a smile, whereupon you¡¯ll probably be escorted from the building as a lunatic. However, the time scales do come from something concrete that can be explained simply.
The geologic record suggests that climate ought not to concern us too much when we¡¯re gazing into the energy future, not because it¡¯s unimportant, but because it¡¯s beyond our power to control.i wondered what kind of formative experiences might have led to his conclusion.
By a stroke of fortune, the entire country is a complete stack of the world¡¯s sedimentary layers tipped gently downward to the northwest and then planed level at the top. The plentiful fossils in the ground, which are different in different layers, thus form narrow tracks that run roughly parallel to the coast of France. When people first discovered these tracks, they had no way to date the rocks in question, so they just assigned names. The easternmost track became Cretaceous, after the Greek word creta for chalk. The next one became Jurassic, after the Jura mountains in Switzerland. The next one became Triassic after a characteristic three-level sedimentation pattern (the Tria) found commonly in Germany. The next one became Permian, after the region of Perm in Russia. And so on and so forth. But the subsequent invention of radiodating later enabled actual ages to be assigned to these names, albeit with the precision difficulties encountered on my beach. The white cliffs of Dover are 70 million years old. The clay under Oxford is 150 million years old. The rocks under Stratford-upon-Avon are 200 million years old. The coal under Stoke-on-Trent is 300 million years old. The Lake District is 400 million years old. The Isle of Man is 500 million years old. The Highlands of Scotland are 600 million years old¡ªand more.posted by LobsterMitten at 2:03 PM on June 27, 2010
These actions simply spread the pain over a few centuries, the bat of an eyelash as far as the earth is concerned, and leave the end result exactly the same: all the fossil fuel that used to be in the ground is now in the air, and none is left to burn. The earth plans to dissolve the bulk of this carbon dioxide into its oceans in about a millennium, leaving the concentration in the atmosphere slightly higher than today¡¯s. Over tens of millennia after that, or perhaps hundreds, it will then slowly transfer the excess carbon dioxide into its rocks, eventually returning levels in the sea and air to what they were before humans arrived on the scene. The process will take an eternity from the human perspective, but it will be only a brief instant of geologic time.Exactly. Climate change is a concern because it affects human beings, not because it affects the planet. "The last time carbon dioxide levels were apparently as high as they are today--and were sustained at those levels--global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland."
From a geologic point of view, carbon dioxide is irrelevant to climate. This is because the CO2 will simply accelerate silicate weathering, drawing it out of the atmosphere and eventually precipitating it as carbonate.posted by russilwvong at 5:24 PM on June 27, 2010 [3 favorites]
While there may be transient effects, the timescale of those effects is too fine to resolve geologically, so they aren¡¯t worth worrying about.
As for the effects of climate on the biota, that too is irrelevant. Species go extinct all the time, and when they do, something else radiates into their niche.
So from the planetary perspective, this whole CO2 thing is just another blip like the PETM. In a few million years, it will be nothing but a curiosity. Narrow-minded activists interested in the survival of particular subgroups such as ice-dwelling pinnipeds or bipedal primates might complain, but to what end? We¡¯re all headed for the fossil record eventually, so changing the extinction time of a particular group by a few tens of kiloyears isn¡¯t going to be detectable in the long run.
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posted by fshgrl at 12:04 PM on June 27, 2010