Daniel1960, on 2012-July-24, 12:56, said:
Passedout,
While the 2C number is a good starting point, it is somewhat arbitrary. Temperatures have risen ~0.8C, but that is from the depth of the Little Ice Age, which was ~1.2C colder than the height of the Medieval Warm Period, which was at least 0.5C cooler than the Holocene maximum. Thus, a 2C increase from the end of the LIA puts at near the peak of the climate optimum. According to ice data, the recent climate optimum was a full degree colder then the previous interglacial high. Who is to say that if temperatures rise another 1.2C, and we reach a climate similar to the Holocene climate optimum, that that is the preferred climate.
Also, what is the catastrophy that is supposed to occur? Temperatures have risen and fallen multiple times in the past. Most "catastophies" have occurred when the temperatures have fallen. Historically, civilization has thrived during times of warmer climate; the Roman and Minoan warm periods saw the expanse of the so-named civilizations. Contrast that with periods of global cooling; the Little Ice Age, the Dark Ages, the Migration of Nations, etc.
Whilw I do not agree that a catastrophy will occur if global temperatures rise another 1.2C, I would prefer we do not find out. At the present rate (0.6C / century), we would exceed that number near the beginning of the 23rd century. Hopefully, by then we will have moved far beyond carbon-based fuels for energy.
On the timescale of millennia, ecologies are fluid, on the scale of decades they are not. This is the catastrophe. Look what the baking heat in the USA is doing to the price of corn. Sure, humans can probably move, but its not so easy to uproot a forest and move it a few hundred miles northwards.
Also, dumping iron into the ocean to feed algea to capture carbon seems like a terrible idea. We just have no idea what the likely effects will be. Perhaps it will just lead to lots more sperm whales eating all the algae. Messing with ecosystems in teh past has universally turned out badly. While there are plenty of people saying "this time we know more" and "this time will be different because we understand" I am almost entirely sceptical of those claims.
The physics is theoretical, but the fun is real. - Sheldon Cooper