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On May 1, 1967, Syukuro Manabe (真鍋淑郎) and Richard T. Wetherald published the landmark paper Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity (DOI: 10.1175/1520-0469(1967)024<0241:TEOTAW>2.0.CO;2) (URLs shortened because the odd characters in the URL seem to break the links), which was the first major attempt to model the earth's climate. Now, fifty years later, the science can be robustly evaluated, and they got almost everything exactly right. Ethan Siegel has an article (Javascript required) looking back at this first major attempt at global climate modelling and how well it has turned out:
The big advance of Manabe and Wetherald's work was to model not just the feedbacks but the interrelationships between the different components that contribute to the Earth's temperature. As the atmospheric contents change, so do both the absolute and relative humidity, which impacts cloud cover, water vapor content and cycling/convection of the atmosphere. What they found is that if you start with a stable initial state — roughly what Earth experienced for thousands of years prior to the start of the industrial revolution — you can tinker with one component (like CO2) and model how everything else evolves.
The title of their paper, Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity (full download for free here), describes their big advances: they were able to quantify the interrelationships between various contributing factors to the atmosphere, including temperature/humidity variations, and how that impacts the equilibrium temperature of Earth. Their major result, from 1967?
According to our estimate, a doubling of the CO2 content in the atmosphere has the effect of raising the temperature of the atmosphere (whose relative humidity is fixed) by about 2 °C.
What we've seen from the pre-industrial revolution until today matches that extremely well. We haven't doubled CO2, but we have increased it by about 50%. Temperatures, going back to the first measurements of accurate global temperatures in the 1880s, have increased by nearly (but not quite) 1 °C.
[Ed note: There seems to be an issue with the DOI link in that the URL itself contains both "<" and ">" characters. The actual URL is:
http://journals.ametsoc.org/doi/abs/10.1175/1520-0469%281967%29024%3C0241%3ATEOTAW%3E2.0.CO%3B2
If you are uncomfortable following the provided bitly link, just copy/paste this link into your browser. --martyb]
(Score: 2) by HiThere on Friday March 17 2017, @04:16PM (1 child)
FWIW, you should still expect a new glaciation. (Unless the current warming flips the climate into a really new region.) The problem is you don't understand the likely time frame. I believe that the current warming trend is required for the glaciation to happen, as that only happens after the oceans warm up sufficiently. Then some event like a major series of volcano eruptions will cool things down, while the oceans stay warm, so there will be lots of snow and little melt for a few years...which will then increase the albedo so when the atmosphere clears again you still won't get much melt, and since the oceans are still warm, you keep getting more snow.
The thing about the "2 degrees of warming" barrier that we are shortly breaking is that this is likely to move the climate into a new pattern were our current models are much less reliable, but which is likely to be warm enough that even a series of volcano eruptions won't cool things down enough to allow much snow. Did you know that there were once temperate forests on Antarctica? And that Antarctica seems to have been at the pole at that time? For some reasons the other continents move around a lot more (or is it faster) than Antarctica does. Well, that means that the other continents weren't in the same relation the last time Antarctica warmed up, so we can't predict the results in any detail. It does seem likely that many continental lowlands will turn into inland seas. And again, there's the problem of time frame. I'm not modeling this, but I'd be really surprised if it happened within a century, or even two.
FWIW, I think a new glaciation would be preferable.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 0) by Anonymous Coward on Friday March 17 2017, @04:39PM
You don't need any volcanoes. Increased moisture over the poles can trigger it:
http://cgge.aag.org/GlobalClimateChange1e/cfpart2/cfpart24.html [aag.org]
This matches well with the ice core data: https://en.wikipedia.org/wiki/Vostok_Station [wikipedia.org]