Let me play the Devil's Advocate for a moment: If we have problems with long-term persistence in noise in ocean temperature data (and thereby attributing warming to rising GHGs), can we avoid this difficulty by focusing on attribution rising land temperature to rising GHG's? (To a first approximation, climate change is mostly a problem of rising temperature over land.
However, I remember that climate models have been forced with rising SSTs, rather than rising GHGs*. Use of historic SST's has some ability to reproduce the weather than is observed over land (including precipitation), but I don't remember how good this is. This reasoning suggests that noise in precipitation data and land temperature data are forced to have long-term persistence as ocean temperature data?
My understanding is that the oceans, having such large thermal mass, have *less* noise, long-term or otherwise. Long-term changes in ocean temperatures are less likely to be driven by "noise" than land temperatures are, and simpler, understandable physical processes dominate.
Ben: Because the ocean has such a large thermal mass, it takes more power and/or a longer time for chaotic fluid flow to produce chaotic change (or noise). Today we talk about radiative imbalance at the TOA of about 1 W/m2 (0.3% of the incoming 390 W/m2), which is enough to raise the temperature of the mixed layer of the ocean (the top 50 m) at an initial rate of 0.2 degC/yr. Local seasonal changes in irradiation can be hundreds of W/m2 for several months. Of course, the entire ocean has (IIRC) 40 times the heat capacity of the mixed layer, but it takes roughly a millennia for the entire ocean to "overturn" from top to bottom. From this information, you may or may not conclude there is plenty of power to make the ocean noisy.
Normally, cold water upwells in the Eastern Equatorial Pacific, get swept across the Central Pacific by trade winds while warming, and subsides in the Western Pacific Warm Pool. An El Nino - oversimplified - is a chaotic interruption in these fluid flows that makes the surface of the Eastern Equatorial Pacific much warmer than usual. That warmth rises into the atmosphere and is carried around the world. In the 1997/8 El Nino the temperature rose about 0.35 degC in nine months and fell 0.30 degC in the follow (as upwelling of South America returned to normal). These values are based on temperature data smoothed over 13 months. Using raw month data, the change was even larger (0.5 degC). In in months we experienced twice the warming in less than a year than rising GHGs (allegedly) are producing in a decade
Ice cores from polar ice caps may be some of our longest climate records and they cover both temperature and amount of precipitation, Has the nature of the noise in these records been studied, say during the Holocene?
In Greenland Ice Cores we apparently have three Warm Periods, the Medieval, Roman and Minoan. I don't remember whether these were linked to proxies for solar output. Should these Warm Periods really be treated as noise if they are large and have a hypothetical mechanism? (I don't think they are seen in Antarctic Ice Cores, so maybe they don't have a solar mechanism. Which leads me to problem. We can add whatever noise we want to real or simulated data, but in the real world, noise originates from some physical phenomena (though it may be chaotic, like ENSO). If you look at noise in Greenland ice cores during the last Ice Age, presumably you will find huge (10 degC), sudden oscillations in temperature associated with Dansgaard-Oeschger events. If I remember your posts on the Ice Ages correctly, there was some sort of see-saw in the Atlantic that moved warmth from one hemisphere to the other. I'm not sure I want to treat such events as noise rather than signal.
(Neither of these comments require an answer if you don't have one readily available.)
Let me play the Devil's Advocate for a moment: If we have problems with long-term persistence in noise in ocean temperature data (and thereby attributing warming to rising GHGs), can we avoid this difficulty by focusing on attribution rising land temperature to rising GHG's? (To a first approximation, climate change is mostly a problem of rising temperature over land.
However, I remember that climate models have been forced with rising SSTs, rather than rising GHGs*. Use of historic SST's has some ability to reproduce the weather than is observed over land (including precipitation), but I don't remember how good this is. This reasoning suggests that noise in precipitation data and land temperature data are forced to have long-term persistence as ocean temperature data?
My understanding is that the oceans, having such large thermal mass, have *less* noise, long-term or otherwise. Long-term changes in ocean temperatures are less likely to be driven by "noise" than land temperatures are, and simpler, understandable physical processes dominate.
Ben: Because the ocean has such a large thermal mass, it takes more power and/or a longer time for chaotic fluid flow to produce chaotic change (or noise). Today we talk about radiative imbalance at the TOA of about 1 W/m2 (0.3% of the incoming 390 W/m2), which is enough to raise the temperature of the mixed layer of the ocean (the top 50 m) at an initial rate of 0.2 degC/yr. Local seasonal changes in irradiation can be hundreds of W/m2 for several months. Of course, the entire ocean has (IIRC) 40 times the heat capacity of the mixed layer, but it takes roughly a millennia for the entire ocean to "overturn" from top to bottom. From this information, you may or may not conclude there is plenty of power to make the ocean noisy.
Normally, cold water upwells in the Eastern Equatorial Pacific, get swept across the Central Pacific by trade winds while warming, and subsides in the Western Pacific Warm Pool. An El Nino - oversimplified - is a chaotic interruption in these fluid flows that makes the surface of the Eastern Equatorial Pacific much warmer than usual. That warmth rises into the atmosphere and is carried around the world. In the 1997/8 El Nino the temperature rose about 0.35 degC in nine months and fell 0.30 degC in the follow (as upwelling of South America returned to normal). These values are based on temperature data smoothed over 13 months. Using raw month data, the change was even larger (0.5 degC). In in months we experienced twice the warming in less than a year than rising GHGs (allegedly) are producing in a decade
Ice cores from polar ice caps may be some of our longest climate records and they cover both temperature and amount of precipitation, Has the nature of the noise in these records been studied, say during the Holocene?
In Greenland Ice Cores we apparently have three Warm Periods, the Medieval, Roman and Minoan. I don't remember whether these were linked to proxies for solar output. Should these Warm Periods really be treated as noise if they are large and have a hypothetical mechanism? (I don't think they are seen in Antarctic Ice Cores, so maybe they don't have a solar mechanism. Which leads me to problem. We can add whatever noise we want to real or simulated data, but in the real world, noise originates from some physical phenomena (though it may be chaotic, like ENSO). If you look at noise in Greenland ice cores during the last Ice Age, presumably you will find huge (10 degC), sudden oscillations in temperature associated with Dansgaard-Oeschger events. If I remember your posts on the Ice Ages correctly, there was some sort of see-saw in the Atlantic that moved warmth from one hemisphere to the other. I'm not sure I want to treat such events as noise rather than signal.
(Neither of these comments require an answer if you don't have one readily available.)