WUWT readers, Figure 4 is noteworthy, because it points out the trend of 20th century warming in context with other periods of warming derived from the ice core record. I suggest you bookmark this post and that graph, as it tells a simple but indisputable story. – Anthony
Guest post by Frank Lansner
In a recent article:
http://wattsupwiththat.com/2010/09/08/working-925-what-a-way-to-make-a-livin-at-agw/
I estimated the total raw CO2 warming to be around 9,25 times the warming effect of one CO2-doubling:
Fig 1
Heat from one CO2-doubling (the “CO2-sensitivity”) has been estimated by IPCC and J. Hansen to be 3K or even 6K, including feedbacks. The 9,25 CO2 “doublings” cannot all have such a huge effect including feedbacks, so present day conditions on Earth must be extraordinarily heat sensitive (at least according to the IPCC).
Claim: Just a tiny temperature increase under present day conditions (like raw effect of one single CO2 doubling) should result in temperature jumps of up to 3 – 6 K.
Is this claim supported by evidence?
Fig 2
I have examined high quality Vostok temperature ice core data from the interglacial periods of the last half million years. These warm periods are the best evidence we have from Earth to examine the dynamics of present day climate on Earth.
We are looking for other huge temperature rises of 3K – 6 K that should result from just minor temperature rises.
Below I have identified all temperature rises of the Vostok data fulfilling the following criterion: “Temperature at the beginning of temperature rise must be at most 1 K below today’s temperatures indicated by -1K anomaly in the Vostok data. Next, the examined periods must be at most 300 years in length (we want to focus on the warming effect of one century time intervals) and finally, the initial temperature increase from glacial to interglacial is not included”:
Fig 3
96% of all temperature increases are between approx 0 and 1,4 K, only in one situation (approx 1 %) we find an interglacial temperature increase of almost 3 K.
That is: Under present day like conditions, temperature rises of 3K are very rare indeed, while smaller temperature rises of around 1 K are abundant and normal.
The interglacial periods shows no temperature peaks of the size interval larger than 3K. If in theory a minor warming of 0,5 – 1 K should lead to a 4-5-6 K warming including feedbacks, why are there no such peaks in the previous interglacial periods? There are plenty of 1K warming peaks (resulting of from all kinds of natural mechanisms) to induce the massive positive feedbacks that IPCC and Hansen expects.
Fig 4
The average interglacial temperature rise (from these data criteria) shows a warming of 0,65 K and lasts 113 years. In average they begin at –0,17K and end at +0,48K. (These averages are only to some degree dependent of my definition of interglacial periods – unless my definition of interglacial periods are totally wrong.)
The average temperature increase for these data of 0,65 K over 113 years – does not exactly make the modern temperature increase 1900 – 2010 of around 0,6-0,7K appear that special, does it?
Fig 5
The data tell us more: When the time intervals exceed around 100 years, the average magnitude of the recorded temperature increase does not increase. This is interesting and surprising because a longer interval should give time for a larger temperature increase. But on average the time intervals in data longer than around 100 years shows smaller net temperature rises indicating – unless this is a coincidence – that temperature peaks of the interglacial periods in average lasts around roughly 100 years.
Via Joanne Nova, I got a feedback to this result from George White:
“The analysis is consistent with long term averages changing more slowly than short term averages. The correlation drop at 100 years is because of a periodic effect of about 180 years. After 90-100 years, the direction of the temperature change reverses and the deltaT drops. If the analysis is continued, a second peak should appear between 250 and 300 years as a result of the second cycle of this period showing up with a minimum centered between the peaks. ”
Interesting, and thanks to George White.
When nature has warmed the planet over 100 years, this warming seems to END rather systematically. If positive feedbacks were strong why do temperature rises end so systematically? At least this warming-turn-off suggest that:
Natural forces or perhaps negative feedbacks are stronger than positive feedbacks after just a limited warming over 100 years
In addition, we see very few small temperature increases (of the order of 0 – 0,15K) for time intervals less than 150 years. On the other hand, the longer time intervals shows several of these tiny temperature increases. This indicates – unless it’s a coincidence – that if at first, temperature is on the rise, it often continues to rise until a significant temperature rise is reached. In other words: Temperature variability is the norm and constant temperature seems unusual.
Conclusion
Nature has provided us with data telling a simple story: For periods on earth comparable with today, we see many examples of temperature increases in the magnitude of 1 K for all kinds of natural reasons. Very rarely does any temperature rise (via supposed positive feedbacks) reach 3 K within 100 years.
It is thus surprising that IPCC and others with big confidence can claim large temperature rises of up to 3 – 6 K as most likely result from just a minor temperature increase, for example induced by CO2 warming.
More, it appears (fig 4.) that the temperature rise of 0,7K from 1900 to 2010 is as normal as can be when comparing with other temperature rises during other warm periods.
***
Comments
1) I have defined “interglacial temperature rises beginning at -1K compared to modern temperatures, no lower. On this definition I found that the temperature increase 1900-2010 was normal. If I had defined interglacial periods as starting at -2K, then there would have been a few more temperature increases in the area 1-2K which would make the present temperature rise appear smaller in comparison. However, the limit -1K for interglacial periods mostly is in compliance with the nature of the interglacial periods. When first we have interglacial period its not often we find temperature in the area under – 1K. Therefore I found -1K to be the best choice to limit interglacial tendencies. Also, temperatures should resemble today’s temperature range as close as possible.
2) I have used 0,7K for the temperature increase 1900-2010. This is obviously highly questionable due to significant UHI measuring problems and adjustment issue that is likely to have exaggerated the temperature increase 1900-2010. On the other hand, temperature variations at Vostok are likely to be larger than global temperature changes, so perhaps a qualitative compare is somewhat fair after all. At least, if you claim that the present temperature increase is extraordinarily large, I think one should show data that supports it. And, as I showed, Vostok data does not really support the claim.
3) By Joanne Nova: “In the past natural temperature rises we should also see the positive feedbacks at work. But it is very difficult to isolate the exact amount of warming due to the natural forces vs that due to the natural feedbacks. Where does one stop and the other start? In any 3 degree rise, how much was due to the forcing, and how much to the feedback? If positive feedback was strong we would expect to see examples of it occurring in the past ice cores.”
Frank: This is very true and makes this topic a little fluffy to deal with. However, the absence of 3K – 6K temperature rises in the interglacial periods means that there should not have been any natural warming excl feedbacks of just 0,5 K or so (matching the raw CO2-sensitivity warming). And we still can see that the temperature rise 1900 – 2010 is just a normal interglacial variation.
4) Hereafter it could be interesting to do analysis using Dome C core temperature data that has twice a many data points for temperatures which may refine the results to some degree.
Source used for Vostok data:
http://www.ncdc.noaa.gov/paleo/icecore/antarctica/vostok/vostok_data.html
See also:
http://joannenova.com.au/2010/08/ice-core-evidence-no-endorsement-of-carbons-major-effect/
http://hidethedecline.eu/pages/posts/925—a-factor-that-could-close-the-global-warming-debate-193.php
http://wattsupwiththat.com/2009/01/30/co2-temperatures-and-ice-ages/
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Joel Shore says:
December 9, 2010 at 2:19 pm
The point is that all because chickens produce eggs does not imply that eggs can’t also produce chickens. The close correlation of CO2 and temperatures over a variety of timescales is suggestive of the correlation going both ways. While the change in temperatures seems to start first in the glacial – interglacial case because those transitions are understood to be initiated by changes in the earth’s orbit around the sun (and axis of rotation), the changes in greenhouse gases follow along soon enough that there is still plenty of room for the change in greenhouse gas levels to amplify the warming or cooling once it has begun.
So, let me see if I understand you, Joel. Those extra CO2 molecules dance around and avoid the photons for 800 years and then they get so tired they give up and start absorbing them. Is that about it?
Baa Humbug says:
Your example assumes that the positive feedbacks are sufficiently strong to produce instability. Nobody (or essentially nobody) believes that to be the case. Rather, we are in the regime where the feedbacks amplify the warming … Mathematically, it is the difference between a diverging and converging series.
For example, if a 1.0 deg C warming due to CO2 increases water vapor causing an additional 0.5 deg C of warming, then the additional feedback on that 0.5 deg C of warming will be an additional 0.25 deg C of warming, and so on. In this example, what you get is the geometric series 1 + 1/2 + 1/4 + 1/8 + … which converges to a value of 2, i.e., the feedback ends up doubling the warming.
Not really. First of all, as you note, the Vostok data is expected to have about double the variability of the global average for the glacial – interglacial transitions. I assume it is similar (or maybe more) for fluctuations on shorter timescales. The UHI and warming adjustments, I think is, by contrast, mainly a fictional complaint.
Second of all, I think you need to talk to someone very knowledgeable about this data to find out how reliable such temperature proxies are expected to be for the sort of timescales and variations that you are looking at. I.e., I could imagine there might be a level of noise in the proxies.
Basically, everyone serious agrees that the “raw CO2 effect” is about 3.7 to 4 W/m^2 and that this translates to around 1.0 – 1.2 C warming…Lindzen agrees with this (albeit he thinks the feedbacks are negative and thus reduce it) as does Spencer, as far as I know. If you want to argue about this, you are really headed way out into the weeds.
And, what significant forcings do you propose there were during the interglacials? The reason there haven’t been dramatic warmings is because there haven’t been very significant forcings. Even the total forcing from the glacial to interglacial conditions is only estimated to be about 8 W/m^2 or thereabouts.
If you can come up with compelling evidence of significant forcings during interglacial times (and small temperature responses to those forcings), then you have something. Just arguing that the temperature doesn’t vary that much during the interglacials without any attempt to figure out what the forcings are doesn’t give you anything useful.
Richard M:
Perhaps reading comprehension is not your strong point?
Steve Mosher and Joel Shore:
This is how one would calculate the climate sensitivity of CO2/GHGs based on the ice age data:
Fill in this table: the question marks are where one shouldn’t really know what the value is:
http://img641.imageshack.us/img641/4003/iceageforcingmath.png
Now suppose I told you the Ice and Vegetation Albedo forcing was really -12.0 watts/m2 (based on the actual climat ice age maps and cloud changes forcing information). Then one can see how cherry-picking values can result in the fake climate sensivities that Hansen’s climate science have indoctrined people with.
The Real table looks like this which then produces a real climate sensitivity of just +1.27C per doubling of CO2/GHGs.
http://img683.imageshack.us/img683/4827/iceageforcingreal.png
As Joel says, it is all about the forcing. 3.7 W/m2 for doubling CO2 is exceptional to a degree that is not seemingly realized enough. The LIA and MWP correspond to solar forcing possibly only in the range of 0.5 W/m2, but are generally considered to be significant events. We are at the tail of a growing warming that only will become more obvious with time, especially within the next decade or two. The 0.7 C so far is not much above the noise, but is already comparable with the LIA and MWP, and we have a lot further to go this time. Only the ice ages themselves are comparable, not the little wiggles between that the original post examines.
Joel Shore, You ave some correct points ere and there, but my “stomack” feeling is that your not unbiased – i may be wrong.
You just start out claiming that UHI has no impact (!???!?!?!?!?) and then you just go ahead as if you where not on thin ice.
-and you must be claiming the about warming adjustments (!) for your logic to make som sence.
And: The temperature difference between average interglacial and average glacial is around 8K, and there are souces that suggests that globally its more like 6K. Ok lets say that the difference is 50% then. But the truth is, the availability of real global temperature data for a period like the last ½ mio years is not that impressive, so we are guessing a little here.
But you just claim 100% without a blink, “it is expected” you say.
But what really interesting then is that you do not use this “info” in both ways, only in the direction that supports critic of my point. You forgot something, Joel: If you where correct, then all temperature rises in fig 3-5 should be half size when conparing to global. This means, that the IPCC “CONFIDENT” expectations to future temperature rise on fig 3 is not corresponding to 3K but 6K…… and only then can we say with REAL confidence that the IPCC expectations of temperature rise is EXTEMELY UNLIKELY!!!
Do you undersatnd this? If you are correct in your opninion “global-temperatures-should-be-multiplied-with-2-to-compare-with-Antarctic-temperatures” then the “best estimate” from IPCC is 6 K as reponse to one single CO2 doubling temperature.
So suddenly IPCC is 4 times higer in their expectations than the normal upper limit of around 1,5 K for these temperature rises.
And then back to your “fresh” “No-UHI” claim (!)I think a good place to start is the biggest and the best investigation ever, and its done by Thomas Karl. The force of his study is, that he used mostly UNadjusted data, so the issue of how city vs. rural temperatures are alligned are not excisting. UNadjusted because the resaerch took place in the mid 1980´ies.
More, he used ALL relevant US city-rural pairs yielding around 4-500 compares. US has more long temperature series than rest of the world in GHCN, so a full US resaerch like this is very relevant. Here are his raw results:
http://hidethedecline.eu/media/UHIworldtour/USAKarl.jpg
These values are just for the period 1900-1983 so you have to multiply with around 1,3 or so to get nearer the true 1900-2010 values. So very vey fast we will have a UHI signal that covers perhaps 20-50% of the mostly city-measured supposed global warming temperature signal of around 0,65-0,7 K.
Even Phil Jones later China research show an AVERAGE UHI false warming of 0,5K ! (And you think other developing countries like India, Mexico, Brasil, do not have massively growing cities to yiels a similar result perhaps?)
And temperature corrections: Alone for the USA, it is directly black on white knowledge that cant be denied: Adjustmet are more than 0,4K ! I can document.
But you, Joel, just say: NO UHI! NO adjustments! 100% more signal in Antarctic data without using this info as it should: It makes IPCC claims of temperature rise 100% more in dissagreement with previous temperature rises sown on the figures.
etcetcetc.
And then if you have time: Can you in any way argue against that we actually have around 9,25 doublings for CO2 ?
And after you hopefully has explained the above problems, Lindzens 0,5K for CO2-sensitivity (and many others with low feedback expectations): You are missing the point of the article.
The article baically show ten thousands of years with shorter temperature rises that seems not that large and also timelimited, that is, natural mechanisms normaly make an end to temperature rises. The small earlier temperature rises does not support IPCC in their belief that smaller temperature rises for “sure” will lead to much larger temperature peaks.
this is the point
THEN we start explaining WHY that is. WHY are the old temperature peaks small?
and in this context, it is not important if the small temperature rises in the past are caused by
1) a small raw CO2 signal of 0,2K + positive feedback of 0,3K
or
2) a raw CO2 signal of 1K – negative feedback of 0,5K
In either way, we end up with a small temperature rise in the past that simply does NOT make IPCC “confident” predictions of large temperature rises now supported in data. So if Lindzens idea is, that is estimation of CO2 is a low 0,5 K due to large negative feedbacks this IS a sound explanation as to why we dont see many IPCC-like large temperature rises in the past.
I am not religious about WHY the IPCC “confident” large claims are not that well supported by low temperature variability in the past, I just pinpoint the problem.
((And finally as a 100% less important side remark: As a real skeptic, yes, I use logic and not “who believes what”. Never mind who says waht, I do NOT find it likely that CO2 should be responsible for one third of the Earths greenhouse effect – 9,25 * 1,1 = on third of greenhouse effect. AND I do NOT find it likely that all heating due to an atmosphere should be caused by greenhouse gasses, and thus i find the Earths combined greenhouse effect of 30 K to be exxagerated. Saturn has hardly any greenhouse gasses in the atmosphere but shows no difference in isolating effect when doing a simple compare. Titan orange-red armophere is STUFFED with greenhouse gasses but may have the very poorest isolating atmosphere in the solar system… But this is another conversation! ))
K.R. Frank
stephen mosher says:
“Anthony, willis, lindzen,monckton, christy, spencer all accept the basic science
and the radiative properties of C02.”
Your answer perplexed me, as I have not denied “the radiative properties of CO2”. I have a problem with people who use man made CO2 as the reason for a future modeled catastrophe for which the politicians must take money out of our pockets and implement draconian restrictive policies that ultimately impede eventual understanding of climate. Smokey @5:55 AM says it better than I do:
“Carbon” is only a cover story for the UN’s true [and thoroughly immoral] motive: extracting the wealth of the West based on a completely unproven scare story, and handing our national wealth over to corrupt regimes – after first taking its own hefty cut. That is the fraud which we must fight.
It turns out that I made an ass of myself. Completely misunderstood your response @10:52 AM, and proceeded to rant on. When I read your reply, I did some back reading on WUWT and your site. If I could take it back, I would.
My apologies 🙁
Bill Illis says:
So basically, you are saying that you have calculated the forcings due to albedo changes between the LGM (last glacial maximum) and now, gotten an answer significantly different (by about a factor of 2) from what scientists have determined, and we are supposed to blindly believe your results?
And, just as a side note, even if you were correct, your calculation concludes that doubling CO2 produces a warming that is one quarter the size of the difference between the ice age and now. Quadrupling CO2 (which we apparently have enough coal to do quite easily) would produce a warming half the size of the warming between the LGM and now. Those sorts of changes are still nothing to sneeze at.
Of course, the reality is that scientists have estimated the albedo forcing to be lower than you claim. Furthermore, as Hansen has pointed out, this whole way of estimating the climate sensitivity takes the change in albedo due to ice sheet and vegetation changes to be a forcing, not a feedback. In the present case, such effects will be feedbacks, further increasing the warming due to the change in greenhouse gas levels. (Hansen estimates this doubles the climate sensitivity from ~3 K to 6 K over the long run…although other scientists have noted that the effect will probably not be that great in going from the current state to a warmer state because there is less ice sheets to melt than there were in going from the LGM to the current state.)
Bill Illis posted this data earlier in the thread, which is important and deserves attention:
http://img801.imageshack.us/img801/289/logwarmingpaleoclimate.png
The Occam’s razor simplest interpretation of this data is that, rather than 85 or 40% of a greenhouse effect, CO2 is in fact responsible for zero percent of a non-existent greenhouse effect.
Apart from the very low CO2 end of the graph, where limitation to plant growth may play a role in temperatures, there is no correlation – the only justifiable regression is a null horizontal line. The overlaid colored curves bear no relation to reality.
In fact, above about 400 ppm CO2, a small downward slope of temp with CO2 is even suggested.
Of course, the AGW interpretation of this is no doubt to apply special pleading to EVERY SINGLE ONE of these data points, reeling of pages of argument about why – each for its own distinct reason – not one of these data points is valid without a sophisticated adjustment, such as the dim sun argument (not significant from the Phanerozoic onward).
Every single data point is thus somehow the exception that proves the rule.
The rule (CAGW) which is supported by no data.
BTW the only way that the “greenhouse” is a useful metaphor relates to the practice of horticulturalists to add CO2 to greenhouses to boost plant growth.
“Joel Shore says:
December 11, 2010 at 8:02 am
Bill Illis says:
So basically, you are saying that you have calculated the forcings due to albedo changes between the LGM (last glacial maximum) and now, gotten an answer significantly different (by about a factor of 2) from what scientists have determined, and we are supposed to blindly believe your results?”
Hansen’s “tuned” ice and vegetation Albedo estimate is 0.307 (versus today’s global Albedo of 0.298).
Well, all that additional ice and desert and grassland and tundra in the ice ages certainly changed the Albedo by more than that.
This is how Hansen’s estimate plays out by latitude. It is effectively impossible to get a number that low. It is tuned so that he gets a temp C change per watt/m2 of 0.75C/w/m2 so that his 3.0C per doubling still works.
http://img251.imageshack.us/img251/2764/albedobylatitude.png
And here is a paper from researchers at NCAR that says the ice-vegetation Albedo forcing in just the northern hemisphere alone was -11.7 watts/m2 at the Last Glacial Maximum. (Throw in a little less for the southern hemisphere and a reduction in cloudiness of 10% or so and you have a number which even greater than the one I used).
It was not published however (I assume the team got involved). It is the ONLY paper I have found in mega-searching that actually addresses how it should be calculated rather than just throwing a number out.
http://kiwi.atmos.colostate.edu/pubs/Burt_Randall_Otto-Bliesner_submitted.pdf
Bill Illis
Dec 11, 4:54 pm
It was not published however (I assume the team got involved).
Business as usual for the (climate) science community.
Human nature is even more difficult to regulate than CO2 emission.
Bill,
It is hard to argue with someone whose worldview is predicated on conspiracy theories (Hansen “tuned” his albedo estimate, the “team” prevented the paper from being published, etc., etc.) with no evidence whatsoever to back up these wild charges.
There is in fact something about that paper that doesn’t add up or that we are misunderstanding. Their temperature change of 4.9 C is not compatible with such large forcings given the equilibrium climate sensitivity of the climate model that they are using (which the IPCC AR4 lists as 2.7 C). Now, you may doubt that the real-world sensitivity is that high, but I don’t think you would dispute that this is the sensitivity of the model and so their forcings and temperature change should be roughly compatible with that; as you understand their forcings (and I can’t say where I see that you are wrong), it is not even close. Maybe that is why the paper was never published…that there was some error in what they did that either they or the referees discovered?
REPLY: Joel, I’m calling BS on your comment, see this email from Phil Jones to Mike Mann
Thu Jul 8 16:30:16 2004
“I can’t see either of these papers being in the next IPCC report. Kevin and I will keep
them out somehow – even if we have to redefine what the peer-review literature is !
Cheers
Phil
source: http://www.eastangliaemails.com/emails.php?eid=419
Mikey is a member of Hansen’s RC “team”.
You are delusional if you think this group of scientists is above such behavior after reading statements like that. – Anthony
Anthony –
(1) Were the papers that he referred to actually kept out of the IPCC report in the end?
(2) Was he objecting to the papers because he didn’t like the conclusions or because he thought they were garbage?
(3) Even if one could find a situation where a paper was rejected by a referee for questionable reasons, does that we mean that we are entitled to assume that any such paper we find a preprint of that hasn’t appeared in print falls into that category? I have had a paper of mine rejected for reasons that I did not think are justified but I don’t think that justifies me to assume that any time any paper by me gets rejected it must be for unjustified reasons.
REPLY: Nice spin buddy, your comment is still BS. On #2 I can’t be in the mind of Phil Jones or Mikey, or Jim or any of those. #3 is hypothetically irrelevant. I can only go by what was written. What is written is that Phil Jones said he and Trenberth would work to keep papers out. The central question is: can the team be trusted? The answer that keeps coming back by words and deeds is “no”. Just like in Wikileaks, there’s lots more that we have not seen I’m sure. – Anthony
Sorry for getting you into this Anthony.
My main point is that there is no way Hansen could have calculated such a low Albedo number for the ice ages.
If you go region by region – 2km high ice sheet by 2 km high ice sheet, desert by desert, snow covered tundra for 10 months of the year by snow covered tundra, loss of tropical rainforest by loss of tropical rainforest, you are only at a higher number.
Anyone who argues against the rush-to-judgement of global warming science should recognize that the 0.75C or 0.81C/W/m2 response sensitivity assumed (including all the feedbacks) has to be lower. It is lower to date, it was lower in the ice ages, it was lower in the Pinatubo eruption, it is always lower. It has to be protected by the science at all costs or the +3.7 W/m2 of doubled GHG forcing does not result in +3.0C.
Bill,
It is not just Jim Hansen who has made these estimates and it is not like Hansen’s are out-of-line with others. Here is a paper from close to 10 years ago: https://e-reports-ext.llnl.gov/pdf/240137.pdf (which just happens to be the first scientific paper that came up when I typed “estimates for albedo at lgm” into google). They conclude that “the climate sensitivity is about 1 K W” m2 with a range of +10%. This would imply a global warming in response to a doubling of CO2 in the range of about 3.1 to 3.7 K”. So, their estimate of the sensitivity is slightly on the high side of Hansen’s.
Joel Shore says:
December 12, 2010 at 6:50 pm
Nice discussion of some climate model results that have tuned parametres.
Bill and Joel,
I also looked at that paper and noted a couple of things. First of all 11 W/m2 is very high, and requires a substantial ice albedo equivalent to perfectly whitening everything beyond both arctic and antarctic circle from black before (or the NH alone down to 60 N). Even, if the LGM did that, examining what they mean by that number, it seems to be the surface albedo change only, and would therefore be overestimated by not considering cloud-cover before or after the change which would surely reduce the difference by the pre-existing cloud albedo. I don’t know the average arctic daytime cloud-cover, but I expect it is quite high.
Let’s just take one small 10 degree latitude band – 50N to 60N.
Right now the average total Albedo (including cloudiness) in this latitude band is 0.41 ranging from 0.37 to 0.56. The lowest amount is in the Pacific and the highest amount is in Hudson Bay and Central Asia.
At the last glacial maximum, North America is covered in 1 to 2 km high glaciers from 50N to 60N. The Albedo of glaciers this thick and at this latitude is about 0.65 versus the current Albedo of about 0.45 today. The Atlantic is mostly sea-ice covered with some melting in the summer – Albedo in the ice ages about 0.55 versus today of 0.40.
Europe is covered in 1 km high glaciers – Albedo of 0.65 versus today of 0.42. As we move into Russia and Siberia, there is less glacier and more desert, tundra and grassland. The snow melts in the summer for at least 2 months since the mammoths were eating something. Albedo in these conditions is 0.54 versus 0.46 today. As we move into the Pacific, sea ice covers most of the region for 10 months of the year; Albedo 0.5 versus today of 0.37.
Put that all together and you have this latitude band changing from 0.41 today to 0.54 in the ice ages (the number I have) versus Hansen’s of around 0.42.
Given the solar irradiance in this small 10 degree latitude band, the change of Albedo above changes the global solar forcing by -1.7 watts/m2 by itself.
Now do the same process over the whole globe and you should see what I mean.
Bill,
Do you calculate albedo from the point of view of the sun? This diminishes the effective values at high latitudes significantly. For example above 60 N is less than 3% of the earth’s disk as viewed from infinity but over the equator, but you should check my geometry, and also I am not sure if this is the relevant value to use.
Jim D says:
December 12, 2010 at 9:24 pm
50N to 60N is 5.0% of the global surface area and receives 3.85% of the total global solar irradiance. So, yes, all that was taken into account using the proper solar incidence angle etc.
This makes even a 3% albedo increase very difficult. Wouldn’t you agree? Their glaciers only got to 50 N over some of the continents. Also when considering winter, sea-ice would seem to be a positive feedback compared to water, by radiating less energy to space, and I don’t think that was accounted for.
Jim D says:
December 13, 2010 at 6:09 pm
I encourage everyone to calculate things for themselves so that they will have greater understanding.
See what you can come up with for the ice ages with the model below. Investigate the last glacial maximum maps of ice coverage and vegetation changes. Build in about a 10% reduction in cloudiness. Find out how Albedo changes in those changing conditions.
You will find that is indeed hard to change to Earth’s Albedo, but it changes rapidly as the ice moves toward the equator as in the last glacial maximum when it got to 40N in North America and seasonal sea ice got down to 40N on the North American Atlantic coast.
Then try Snowball Earth when ice extended to the Tropics.
[Warning – it will be scary when you try to use Hansen’s 0.75C/Watt/m2 for the solar forcing reduction you will calculate].
http://img706.imageshack.us/img706/2697/albedomodel.png
At least for the land ice, what happened in (eastern) North America appears to be the exception rather than the rule:
http://en.wikipedia.org/wiki/File:Iceage_north-intergl_glac_hg.png
Bill,
I would say until you make some serious calculations and publish them in the peer-reviewed literature, I am not sure why you expect people (other than those predisposed to believe anything along these lines) will take your claims seriously.