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Post by socold on Apr 17, 2009 19:10:52 GMT
I disagree. The issue in question is the divergance problem. As per my point about the satellite records which diverge from the proxies too. So there was no medieval warm period or little ice age because the proxies say so...but it doesn't phase you one bit when the proxies suffer epic failure on the current warming. That depends on the cause of the divergance problem. I don't know enough about it to comment. No I don't Even under a world with strong positive feedbacks you still need strong forcings to cause signfiicant temperature change. Perhaps there have been some strong forcings in the past 1000 years, perhaps not. On the contrary if you don't ignore any of the physics then you do get significant warming from co2. Conversely in order to find a lack of warming from co2 requires ignoring part (or all) of the physics. A strong amplifying feedback in climate is based on both the physics and climate swings in the past. The interglacial-glacial swings in temperature are too high to be explained by the orbital forcing alone.
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wylie
Level 3 Rank
Posts: 129
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Post by wylie on Apr 17, 2009 19:23:28 GMT
Socold,
I have always wondered about the subject of your last statement. I.e. is CO2 the only reasonable forcing to explain the strong swing to warmer climate for the interglacial period?
Isn't the albedo change caused by the melting of the temperate ice-sheets (e.g. central US) coupled to the changes in ocean currents that might have occurred in response to the melting of all that fresh water ice enough to suggest an alternative to CO2? I (think I) know that Arctic and Antarctic ice sheets melting and becoming open ocean do not cause a huge albedo change at that high a latitude (water and ice at large Sun angles have similar albedos). However, I would expect (admittedly without enough data) that temperate ice-sheets would have rather different albedos as compared to either water or land. This would amplify the melting initially caused by orbital forcing.
Another possibility is that cloud cover might change as a result of a melting of the ice-sheets. Couldn't cloud cover (which we don't really understand well) changes account for a large enough shift to explain the amplification of the orbital forcing? Do we really know enough about all these factors to be reasonably certain that CO2 is the "positive feedback" that explains the amplification of the orbital forcing?
Appreciate your thoughts (and those of anyone else on this topic).
Ian
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Post by socold on Apr 18, 2009 1:49:08 GMT
Im not saying co2 explains it, only that a strong positive feedback in climate in general is needed to explain it. That's just going on discussions where someone has said noone can explain how the temperature can swing so much given the orbital forcing alone. I assume that factors in ice-albedo feedback and still it doesn't work.
Then again there are timing problems with the orbital forcing as the driver anyway so the feedbacks might be the least of the issue.
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Post by kiwistonewall on Apr 18, 2009 2:16:48 GMT
What we don't understand very well is timing. The Earth's climate is a very subtle engine. Some parts turn over rapidly, other parts are turning over very slowly. We have diurnal - 24 hour cycles - these we see and understand. We have monthly (moon) tidal variations which drive currents, but also in the times that large areas of intertidal zones are exposed to day or night. (Evaporation, Albedo etc) At low tide, shallow ocean areas warm up rapidly. There are subtle moon based climatic effects. (I'm not a believer in moon based weather forecasting!) We have the annual seasons, again, reasonably well understood. We have the ca. 11 year solar cycle, and other maybe longer solar cycles. Then we have the long cycles. These consist of the great ocean currents, the drift of glaciers carrying precipitation from many years ago to the sea, and the effect of slow changes in the astronomical situation - planets, precession of orbits etc. Add to this mix one off events (or rarely repeating events). Thus there are a whole lot of waves of forcings over time, effecting our climate in ways we do not yet comprehend. When several warming waves superimpose, we have warm times, and vice versa. Anyone pointing to a single "driver" as the main cause of a slow and subtle variation over time is a little presumptuous. I'm not saying we abandon the task of learning more about the climate. But it is sad that the only way some scientists can get funding is to panic the general population. I am reminded when teachers strike for better pay and conditions. Its ALWAYS for the sake of the children. Actually, if we did pay our teachers more, and insist they are A grade rather than C, maybe we wouldn't have raised a generation that can't think intelligently about the issues.
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Post by gettingchilly on Apr 18, 2009 22:09:56 GMT
"If a proxy can be shown to be invalid based on data today, then it can not be used as a proxy for earlier events."
That's sort of what I was saying. You can compare real data with proxy data but the real data is what matters. Proxy data is only useful in the absence of real data. You should never adjust real data to validate the proxy which is unfortunately the way things are panning out.
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jtom
Level 3 Rank
Posts: 248
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Post by jtom on Apr 19, 2009 3:03:34 GMT
And just to clarify what I implied: if real data today invalidates a proxy, then it invalidates all the past 'data' derived from that proxy, and that data must be discarded. Not only must you not fudge real data to suit the proxy (obviously), but you must go back and redo all the analysis already done that used the invalidated proxy. If a scientist does not do that, he is a poor scientist (and someone will do it, anyway). If the scientist continues to use the past proxy-derived data in future research knowing that the proxy has been falsified, he's unethical. If he uses that derived-data to get funding for research knowing that it is based on a falsified proxy, he is fraudulent. When a proxy is falsified it ripples throughout the research.
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