Does climate sensitivity depend on the cause of the change?
Can a response to a forcing wait and then bounce up after a period of inertness?
Does the existence of an 11-year time-scale prove the existence of solar forcing?
Why does the amplitude of the secular response drop when a long-term trend is added?
These are perhaps some of the questions that we might hope to see discussed in the sequel to the sequel on solar forcing by Scafetta & West (S&W), a few of which have been discussed before here and here. (I still think those earlier studies were seriously flawed and showed a lack of scientific understanding, by the way).
This time S&W present a set of new arguments and a new set of results which are scattered all over the place. The impression from reading their paper is that the upper range (they call it ‘upper limit’) is probably more representative than the lower estimates for the solar contribution to the global mean temperature.
I think that many of their arguments, on which this impression is built, are shortsighted. For instance, they claim that certain climate reconstructions must be wrong because they give ‘unphysical’ answers. But there is another explanation too that they did not contemplate: their idealistic (one may also argue unphysical) model may also be wrong! Thus, they fail to exclude other explanations.
S&W attach the ACRIM Total Solar Irradiance (TSI) product (not the PMOD product, probably because that does not show any trend) to a TSI reconstruction (Lean 2000 TSI [see Lean, 2004], or Wang et al., 2005) in such a way that the average reconstructed TSI value over 1980-1991 corresponds with the ACRIM mean for the same period – never mind the discrepancies in trend and that such cavalier stitching of data series is one of the deadly sins in climatology (hint: the series is inhomogeneous).
One new aspect of this S&W study is the focus on ‘feedbacks’. They assume the TSI reconstruction is a proxy for the total solar influence and that CO2 is part of a solar ‘feedback’ (isotope ratios suggest the CO2 comes from deep underground reservoirs, but it’s not clear how the sun manages to dig up this carbon from deep below Earth’s surface).
S&W maintain that the climate response is greater for longer time scales (which is reasonable) as illustrated in their figure 4 (reproduced below), and assisted by the simple model illustrated in this figure, they argue that the present warming is a delayed response to past solar changes (presumably before the 1950s). But it is unclear why the temperature then flattened out and even dropped a little between 1940-1970 at the time when it really should have increased fastest. One could argue that something else also happened then, but for an unknown reason, this forcing then seemed to have a shorter relaxation time. Why such an interference would give a quicker response than a solar signal is unexplained (the response to volcanoes is fairly prompt, however).
The study by S&W has some suspicious results. When their simple ‘phenomenological thermodynamical model’ (PTM) is forced by a signal with shorter time scales (high-frequency response representing the ~11-year solar cycle), it produces weaker response than if the forcing has longer time scales (or lower frequency) – as expected. But if you add a long-term trend to the former, the amplitude of the high-frequency response diminishes further (their Figure 4, reproduced above): The amplitude of the higher frequency response in their upper panel (4mm measured in the print) had diminished by ~50% in the lower panel (2mm). This is probably because the relaxation time response has been increased between the two panels and is greater than 10 in the lower panel. The presence of a trend should not affect the amplitude of the higher frequency in such a simple linear system (see my reproduction above).
Their figure 5 (below) does not correspond with the discussion in their paper (see scanned part of the text). Again, their analysis is sloppy in the estimate of change, underestimating the observed temperature change (T(obs) in Fig 5a, the total warming is stated to be ~0.8K since 1900, but the figure suggests it is greater than 0.8K) and exaggerating the solar contribution T(sol). This way, the fraction T(sol)/T(obs) gives the impression of a more sensitive response to changes in the Sun. They then proceed to use the lower T(obs) estimate for Mann & Jones (2003) for the total temperature change (claiming 0.8K, although this is too low), but taking a solar contribution estimated from the Moberg et al. (2005) temperature with more pronounced variations (the right estimated warming should exceed 1.0K – not 0.8K as they claim). Hence the fraction of solar signal to total change T(sol)/T(obs) is spuriously inflated.
But what about GHGs if the sensitivity is so high and the relaxation time is so long? We know from laws of physics and lab measurements that the CO2 levels have been increasing and that CO2 absorb infra red radiation. In fact, the Mauna Loa observations done by infra-red gas analysers measure the absorbing properties of air samples – a pure GHG effect on a microscopic scale without feedback effects. The high climate sensitivity and long time delay suggested by S&W would be scary – imagine the GHG warming that is not yet materialised and would be in the pipeline! (Lindzen who doesn’t believe in the lagged response would indeed be surprised if this was the case!).
S&W propose two mechanisms which may amplify the response to solar variations: (i) GCR (here, here, here) or (ii) UV-radiation.
But S&W ignore the issue about the lack of trend in the GCR (Lockwood & Frohlich, 2007; Benestad, 2005), the fact that trends in the diurnal temperature suggest otherwise (IPCC, 2001, 2007), and that there is not a clear trend in the cloud cover. Thus, explanation (i) is not convincing.
The problem with the UV-explanation (ii) is that the stratosphere has been cooling – some of which is due to the ozone depletion. How could they have ignored that?
Finally, the paper oozes of vague but subjective and cherry-picked statements forming the impression that the climate and solar reconstructions of Mann & Jones (2003) and Lean (2000) (why not use more recent reconstructions, by the way?) respectively are less accurate than others. Apparently because these do not give the desired results.
The paper also offers some incorrect references (Kristjansson et al, 2004, do not support the notion that GCR affect the climate). Furthermore, their paper contains little physics, but is little more than a curve-fitting exercise with no cross-validation.
Thus, S&W make a number of unjustified assumptions and sweeping statements which turns it into a mere speculation. In a way, the conclusions are already given when S&W assume that the sun is the predominant cause from the outset. S&W presumes a desired conclusion when arguing that if the TSI variations are small but the temperature variations are pronounced, then this suggests greater climate sensitivity and vice versa. No surprise, their conclusion is that the sensitivity to solar changes is high. Any other conclusion would then be surprising, wouldn’t it?
If they were my students, I’d have flunked their paper.
#146, 147 Timothy (and #148 Wayne)
Solar level of understanding : see AR4 IPPC, SPM, fig. 2, p. 4 (LOSU : low)
Solar “small forcing” : that is precisely the problem. TSI forcing has been progressively reduced as we better calibrate it from satellite measurement and solar models. If we take the mean climate sensitivity of 0,75 K/W/m2, and apply it to solar forcing of AR4 (0,12 W/m2), it would imply a solar contribution to modern warming of max. 0,09 K, probably less (we’re not at the equilibrium). But in this case, I guess the first warming of 1910-40 is hard to attribute (See Stott 2003, Ingram 2006 for detection-attribution problems with solar forcing). So, the less TSI amplitude is pronounced on decennal or centennal reconstructions, the more you need some “solar amplification” mechanisms to match the data (that is, numerous climatologies correlated with solar variations in paleoclimates or in minimum-to-maximum cycle evolution). There are presently two fields of research for such amplification mechanisms : UV effect on stratosphere and coupling with troposphere, solar flux effect on GCR and nebulosity.
Solar UV effect on stratosphere, and coupling with troposphere. As UV spectral variations are the most pronounced in total irradiance variations in a cycle (approx. 60%), researchers work on the influence of UV on stratosphere (chemical effect on ozone), its coupling with troposphere and general circulation (planteray waves, QBO, Brewer-Dobson circulation).
See this special issue of Space Science Reviews 2006, recently published as a book by Springer, Section IV, particularly Geller 2006, Labitzke 2006, Chanin 2006, Calisesi et Matthes 2006, Salby et Callaghan 2006, Brönnnimann et al 2006, Haigh et Blackburn 2006 :
http://www.springerlink.com/content/h70306173316/?p=3ffd16c15f8e45568f3b1decda1a0b45&pi=6
Or for an introduction, the Haigh et al. Hadley Technical Note n°62, 2005, pp. 40-47.
http://www.metoffice.gov.uk/research/hadleycentre/pubs/HCTN/index.html
See also IPCC AR4, section 2.7.1.3
GCR and nebulosity : the issue is still debated, see IPCC AR4 table 2.11, p. 202. The IPCC aggres that “some empirical evidence and some observations as well as microphysical models suggest link to clouds” but underscores a dependence on correlation and doublt/lack regarding physical mechanisms. On physical mechanisms, the CERN program CLOUD should give some results in the next few years. Anyway, IPCC attributes a very low LOSU. I’m still skeptic on a solar-GRC significative influence on nebulosity, but also skeptic on RC “dada” to dismiss systematically works on this field. I’m a layman, no reason to believe some specialits (Palle, Svensmark, Shaviv, Harrisson, etc.) are all wrong, some others (guys here) all right. So wait and see.
Forcing, sensitivity : see the recent paper of Kiehl 2007: models all reproduce the T slope of past 100 yrs, but models differ by a factor 2-3 in CS. How is it possible ? Because they also differ by a factor 2 in forcings they implement (with aerosols as the most uncertain). Models with the highest CS are also models with the lowest forcing ; and vice-versa. So, it’s not hard to understand that if we reevaluate solar effects on climate – on Ts trend for past 100 years-, models with their present CS would be unable to reproduce the observed trend. Problem is not with TOA forcing itself, but with forcing effect on climate, that is sensitivity. And contrary to your assumption, there’s still a lot of uncertainty in water vapour / coulds feedbacks, which are by far the most important positive feedbacks in 2000-2100 simulations. See for example AR4 statement chap 8, p 592 : “Important deficiencies remain in the simulation of clouds and tropical precipitation (with their important regional and global impacts).” So, here again, wait and see.
Kiehl :
http://www.agu.org/pubs/crossref/2007/2007GL031383.shtml
Charles Muller wrote: “So in my opinion, if S&W are OK, it would imply that modern climate has not the same sentivity to 1 W/m2 TSI forcing and to 1 W/m2 CO2 forcing.”
Now, hold on a wee minute here. Let’s not abandon conservation of energy just yet. I realize that you may be sugesting that there could be feedbacks to insolation (note spelling) that are not present for ghg forcing, but this is a proposition for which we have zero evidence–in fact we may have evidence against it, since all feedbacks seem to be mainly thermally activated (albedo effects being the only quasi-exception, and even here higher temperature plays an important role).
Here is a crucial section from one of the denialist pieces that are found only too frequently in our media.(Remember that New Zealand is home to an active group of denialists called the Climate Science Coalition, to whom the author of the following points is a “scientific advisor”).
It is from Dr Chris de Freitas, School of Geography, Geology and Environmental Science, University of Auckland. It was published in the New Zealand Herald, 27 November 2007 and I quote only the points emphasised by the author:
“There have been four periods of global warming in the last 1500 years.
Data clearly shows the Earth cooled during a recent 35-year period despite the continuing rise of carbon dioxide in the atmosphere.
In recent times, global temperature has been steady since 1998, despite the continuing rise of carbon dioxide in the atmosphere.
Average global sea level rise has shown no acceleration over the past 300 years.
And it is an uncontroversial fact that all climate models are unreliable, so their output is not evidence of anything. “
As a non-scientists who has been closely following the issue of climate change, my response to those statements would be:
What is the relevance/pertinence of the first point:?
What 35 year period is being referred to in the second point?, which I do not accept as valid anyway.
The third point is untrue (which is nicer than saying it is a lie).
I don’t know enough to comment on the fourth point.
The fifth point is a ridiculous over-simplification designed to confuse people who know nothing at all about science or about modelling.
But I’m not a scientist, so could you help me out on this because I’d like to be able to do quick response answers to such denialist dross when it appears in our press.
Re: #152 (Paul Harris)
About “four periods of global warming in the past 1500 years”: what’s the evidence of this? What temperature reconstruction is relied upon for this statement? If you want to know more about temperature reconstructions, read this.
About the “35-year cooling period”: I’ve discussed this before, there’s a period from about 1945 to 1975 when the planet was not warming. That’s not the same as cooling; genuine cooling seems to be limited to a very brief time span in the late 1940s. You can see a graph here. The cause of this mid-century non-warming is the large quantities of (man-made) aerosols in the atmosphere.
About global temperature being steady since 1998: such statements represent either sloppy research or outright lies. See this.
About global sea level over the last 300 years: What’s the evidence to support this claim? I hear a different story here.
About computer models: In the most celebrated of all computer model predictions, 1988 James Hansen testified in congress about the future of global average temperature based on — you guessed it — computer models. His prediction turned out to be right. You can also read this paper about comparison of model predictions and subsequent observations.
Minor Quibble re #140- “In Statistical Methods in Hydrology”,U.S. Army Corps of Engineers -1962, by Leo R. Beard, he uses a binomial distribution to solve several probability situations involving the recurrence interval of specified floods.
Re 154, Technically, I think that the Poisson distribution is the better to use, since we are talking about extreme events whose occurence fluctuates about a mean rate. That means the probability of occurrence in a given period (or trial for the binomial distribution) is small–precisely the conditions under which the binomial distribution reduces to the Poisson. So, while you can use either (the Binomial reducing to the Poisson for rare events), I think the Poisson distribution yields more insight.
In either case, I don’t mean to impute that the physics of extreme weather and magnetodynamos have anyting in common.
Ray Ladbury> Let’s not abandon conservation of energy just yet. I realize that you may be sugesting that there could be feedbacks to insolation (note spelling) that are not present for ghg forcing, but this is a proposition for which we have zero evidence…
Shouldn’t we expect different feedback effects from insolation changes (stronger water vapor feedback in the tropics) than from GHG feedback effects (less effect in the tropics, more effect on polar albedo)?
[Response: One might think this, but in fact the atmosphere turns out to be pretty good at redistributing heat, so that the pattern of temperature response to solar forcing and GHG (both normalized to have the same global mean) is quite similar. This shows up clearly in Caldeira’s GRL article on geoengineering, but there are other studies that point in the same direction. That equalization also equalizes most of the things that might lead one to expect different feedbacks. –raypierre]
Paul Harris, Tamino et al., One of the things people seem to get wrapped around the axle on is the whole idea of settled science in the face of model uncertainty. In modeling a complex system, it is common to start with the most important contributors and try to nail down their contribution, following with other contributors until we can actually say something about the physics. This, contributors such as TSI and forcing for the major ghgs. Eventually one reaches a state where the major contributors are constrained by several independent lines of evidence. They are unlikely to change, even though there may be considerable uncertainty among other factors. At this point the scienc regarding these factors/forcings can be considered “settled” even though uncertainty remains wrt the model as a whole.
In reply to Timothy Chase’s comment 120.
“Local abrupt climate change. Bipolar seasaw. Greenland suddenly warms (my comment cools.) by ten degrees Celsius or more within a matter of decades while Antarctica undergoes somewhat slower warming. Heinrich events. Can’t be explained by solar variability per se since it has effects which are in opposite directions in the two hemispheres. It would appear to be due to change in the modality of the ocean where ocean circulation flips between two modes.”
The following is an attempt to explain what is observed using a solar forcing hypothesis that drives the events, supplemented with the Milankovitch orbital variations, albedo effect of an increase in the ice sheets, and so forth.
A) Polar See-Saw
The following is a link to Svensmark’s paper where he presents a hypothesis that modulation of cloud cover is the cause of the polar see-saw. His hypothesis is: As the albedo of the Antarctic ice, is greater than clouds, and as clouds provide insulation during the night, the net effect of an increased in cloud cover in the Antarctic is warming not cooling. Following that hypothesis an increase in cloud cover, causes other regions of the planet to cool, while the Antarctic warms and visa versa if there is a reduction in planetary cloud cover.
http://arxiv.org/pdf/physics/0612145
[Response: This is very poorly argued. The same effect is true in the Arctic (not mentioned by Svensmark), the data record is actually solely due to one station (Orcadas) in the early part and there is no evidence (none) that clouds in Antarctica have changed in any way – let alone in the way predicted by Svensmark’s speculation. – gavin]
B) Global Synchronous Cooling?
The following is a new finding of synchronous global climatic change (Synchronous cooling, see links below), which if it is correct, seems to require a global climatic forcing function to explain the proxy data. This article notes researchers have found evidence of increased glaciation in the Andes which is concurrent with the North American glacial changes.
The authors (Singer and Kaplan) of the study believe their data and analysis:
“…address(es) a major debate in the scientific community, according to Singer and Kaplan, because they seem to undermine a widely held idea that global redistribution of heat through the oceans is the primary mechanism that drove major climate shifts of the past.
The implications of the new work, say the authors of the study, support a different hypothesis: that rapid cooling of the Earth’s atmosphere synchronized climate change around the globe during each of the last two glacial epochs. …”
http://www.sciencedaily.com/releases/2004/03/040319071426.htm
http://www.sciencedirect.com/science?_ob=GatewayURL&_method=citationSearch&_urlVersion=4&_origin=SDTOPTWOFIVE&_version=1&_piikey=S0033589404001644&md5=28f00741073e9a764288eab1487e626e
Timothy, when I look at the 20th century warming and if it was followed by abrupt cooling, the hypothesized solar mechanisms (Electroscavenging and reduction in GCR followed by an increase in GCR and reduction in TSI) would seem to produce what is inferred to occur during a Heinrich event, during the glacial cycle. To me that hypothesized mechanism would seem to fit the observations.
[Response: If you want a globally synchronising forcing, might I suggest… err… ummm….. well-mixed greenhouse gases? – gavin]
Steve, keep in mind that forcing due to H20 will be logarithmic in humidity, so I think a watt is still a watt to first order. And in any case, you’re talking about spatial distribution of the power, not different forcers.
Charles Muller (#150) wrote:
You are forgetting the fact that there are other greenhouse gases. Methane would be a big one. And while it increased rather dramatically in the earlier half of the century, it slowed in the latter half. And there are other forcings. Land use, ozone (a greenhouse gas), black carbon, reflective aerosols, etc..
Stratospheric water vapor (a positive forcing) was revised upward. Total direct aerosol is entirely new (a negative forcing), direct carbon aerosol was revised upward (towards zero – a negative forcing), the actual sign on direct biomass burning aerosol changed (from a negative forcing to a positive forcing), direct mineral dust aerosol was revised upward (towards zero – a negative forcing), etc. All of this is available on in Chapter 2 of AR4 on page 204.
More research has been done. Our understanding has improved. Our modeling of processes has improved. And we now have a better handle on a number of the forcings.
Now of course the numbers which are given on page 204 show final forcings relative to 1750, not year for year, but if you don’t mind seeing the forcings expressed relative to 1880, the data used in the calculations by NASA GISS are available:
http://data.giss.nasa.gov/modelforce/RadF.txt
The graph that results from this data can be found on the following page:
http://data.giss.nasa.gov/modelforce
Charles Muller (#150) wrote:
Nebulosity — clouds. Why didn’t you use the term clouds? It could have meant aerosols, aerosols plus clouds, some fifth force — who knows? The term is — nebulous.
UV. We take UV into account when we deal with ozone. Its a greenhouse gas. Operates primarily in the stratosphere. The coupling of the stratosphere with the troposphere? This too is taken into account by mainstream science.
Galactic cosmic rays? They have been flat for as long as we’ve been measuring them. No trend. What would you expect? They come from supernova throughout the universe in all directions. Cosmic background noise that typically averages out — assuming you don’t have a supernova go off all that close to you.
They are too small to form the nuclei that result in cloud formation. And we have more than enough nuclei of the right size to explain the formation of clouds.
Charles Muller (#150) wrote:
The “some empirical evidence” is a very small effect which is statistically significant — “detected” in Great Britain — but which does not show up in US data. What is still “debated” is whether there is any effect at all.
Charles Muller (#150) wrote:
You will notice that some of these authors are quite specifically proposing it as a mutually exclusive alternative to mainstream science. The geomagnetic field explains everything. There exists such-and-such a correlation. William Astley pointed us to just such a paper.
But then what happens to our knowledge of spectra? Spectral absorption? Satellite imaging of infrared emissions by greenhouse gases? Ability to image altitude by the optical thickness of carbon dioxide? The strong super greenhouse effect detected in the tropics? The ability to image the emissions of all the major greenhouse gases at a variety of altitudes using over two thousand different channels? Things for which we have a great deal of data?
Charles Muller (#150) wrote:
Climate sensitivity?
The best estimate has been around 3 K since the 1960s. 460,000 years of paleoclimate data says the same thing. The forcings? They give you the spreads. In some cases the forcings differ by as much as a factor of two, but generally these are small forcings.
Water vapor and clouds? Wouldn’t affect the paleoclimate data — it already takes them into account. Many of the uncertainties tend to cancel out. Clouds have both an albedo effect and a greenhouse effect.
And AR4 is generally several years out of date. It doesn’t take into account the most recent research, the fact that we have reduced many of the uncertainties. But where there are still problems with the modeling — its there in the mainstream literature. Jim Hansen is quite explicit about the deficiencies which still exist in the modeling by NASA GISS.
#159 Does this really happen?:
“As the albedo of the Antarctic ice, is greater than clouds, and as clouds provide insulation during the night, the net effect of an increased in cloud cover in the Antarctic is warming not cooling.”
Recent Arctic long nights had a more extraordinary effect, clear skies with way above average surface temperatures. Secondly and to complement this, the great ice melt of 2007 was done by a series of consecutive clear air Anticyclones. Clouds were not involved. GCR’s during a solar minima should be greater , by theory, more clouds….
#150 Thanks for the elaboration Charles, UV correlates well with the stratosphere, which has been
colder than warmer lately (past ten years), this has not affected the warming troposphere, or if it has this means that the 1977-2007 troposphere (along with a theoretical normal temperature stratosphere) should have been even warmer then present all time maximas. But you must consider TSI and UV anomalies were almost the same, which brings me back to my original argument, where’s the extra heat coming from? I leave out GHG’s (the greatest and now the only reason for warming), and let you find a suitable likely substitute, if there is one.
I responded Rasmus
look at #123 above
(I believe my reply was posted on this web site 2 days after I wrote it!
I could see it with the computer I wrote it, but not for another computer.
I do not know why.)
Thanks for the helpful replies to my earlier post.
William Astley (#159) wrote:
As others note, clouds would have a lower albedo in the northern hemisphere just as well as the southern. In the Arctic, Greenland and elsewhere.
Likewise, a hypothesis without so much as the suggestion of a means of testing it constitutes mere opinion. When it is used to rescue a theory without a means of independent verification, it is called an “ad hoc hypothesis.”
William Astley (#159) wrote:
What sort of quality controls were in place? Were others able to replicate their findings? And as Gavin notes, it is based upon just one location. I noticed the same thing myself.
Likewise, it would constitute only one thread-bare line of evidence even if it included a fair number of sites. It might easily be subject to a completely different interpretation — once other evidence comes in.
Earlier Ray Ladbury (#50) states:
This is a very important principle underlying empirical science. A conclusion which receives justification from multiple lines of evidence is generally justified to a far greater degree than it would be if it were to receive from only one line of evidence in isolation from the rest.
With the IPCC, we had roughly 2,500 scientists in relevant fields contributing. It would not be unusual for a given author to write several dozen papers in a single year. Typically a paper will reference several dozen other papers. A single chapter in AR4 referenced more than 200 papers. Not that unusual for a review nowadays.
William Astley (#159) wrote:
If it undermines a widely held idea (“… that global redistribution of heat through the oceans is the primary mechanism that drove major climate shifts of the past…”) then it would appear that there is no “major debate in the scientific community.” Echoes of the creationist “teach the controversy” when there is no actual controversy in the scientific community.
William Astley (#159) wrote:
Rapid cooling of the Earth’s atmosphere synchronized around the globe isn’t what we see in the paleoclimate record. Rapid cooling occurs only with bipolarity. The cooling of a global ice age is gradual.
As for the link — science by press release. It appears 4 months before the journal receives the article and nearly two years before online publication.
William Astley (#159) wrote:
If 20th century warming were followed by abrupt cooling, the cooling would not fit the pattern of Heinrich Events. All of the Heinrich events occured during glacial periods. Currently we are in an interglacial. As such, it does not fit observations. Likewise, if we were to suddenly see 20th century warming followed by abrupt cooling, this would not fit the description of a Heinrich event. Heinrich events are usually preceded by Dansgaard-Oescher events, not the reverse. During one of these events Greenland warms typically by 5 C in 30-40 years.
Nothing like this has occured in the Holocene Era. The warming that we have seen in the 20th Century doesn’t compare to this. But what we are seeing are quite possibly the highest temperatures in over a million years, perhaps longer. And the temperature is still rising.
*
Here are a few final thoughts…
Let us assume that somehow it was demonstrated that a cosmogenic theory similiar to the one the authors you’ve cited proposed turned out to be right. How would you explain why carbon dioxide does not have the effect that mainstream science holds it does?
We have HiTran — a database with data on over a million spectral lines for carbon dioxide and other molecules — obtained by precise measurements in labs. These spectral lines are virtually derivable from the first principles of quantum mechanics. We know that such gases do not simply absorb but emit the energy they receive. We can measure their emissions at ground level, from balloons, planes and by satellite. And in the case of the latter, they are taking measurements on approximately 2,500 different channels in the spectrum. Satellite images actually show carbon dioxide as it is drifting away from industrial centers.
Here are links to some of this:
Products – AIRS Carbon Dioxide
NASA AIRS Mid-Tropospheric (8km) Carbon Dioxide
http://www-airs.jpl.nasa.gov/Products/CarbonDioxide/
Multimedia Animations
http://airs.jpl.nasa.gov/Multimedia/Animations/
Visualization of the global distribution of greenhouse gases using satellite measurements, by Michael Buchwitz. The Encyclopedia of Earth. Posted July 31, 2007
http://www.eoearth.org/article/Visualization_of_the_global_distribution_of_greenhouse_gases_using_satellite_measurements
For more check out comment 555 to the Part II: What Ångström didn’t know post.
*
Likewise, we can measure the backradiation that we recieve from the atmosphere. We can measure altitude by means of the opacity of carbon dioxide to thermal radiation between that altitude and the surface. We can measure the drop in temperature of the stratosphere as carbon dioxide and water vapor reduce the amount of thermal radiation which reaches it. And we have paleoclimate evidence demonstrating the strong feedback relationship which exists between temperature and carbon dioxide levels.
*
What is your explanation for the paleoclimate evidence? How do you explain the cooling of the stratosphere? The ability to measure altitude by means of optical thickness? What is your alternate explanation for our spectral measurements? And where is your alternate theory for quantum mechanics?
In reply to Gavin’s comment (to my comment 159) concerning A) Svensmark’s paper on the polar see-saw:
“The same effect is true in the Arctic (not mentioned by Svensmark), the data record is actually solely due to one station (Orcadas) in the early part and there is no evidence (none) that clouds in Antarctica have changed in any way – let alone in the way predicted by Svensmark’s speculation.”
Svensmark’s paper does include satellite data that supports modulation of Antarctic cloud and I have a paper that shows Antarctic cloud cover is modulate by Forbush events. I thought the Antarctic climate was isolated, where as the Arctic climate is not.
Gavin is an expert in the completing polar see-saw hypothesis which is that ocean currents are hypothesized to cause the polar see-saw. The Arctic and Antarctic ice core temperature data that Svensmark provides in his paper shows a cyclic polar see-saw, which would be consistent with a solar forcing function.
The Antarctic and Arctic temperatures are varying 180 degrees out of phase throughout the period measured by the bore hole temperatures.
Gavin are you saving that Svensmark’s bore hole temperatures for that period are not correct or that ocean currents are responsible for the proxy data?
In reply to Gavin’s second comment:
[Response: If you want a globally synchronising forcing, might I suggest… err… ummm….. well-mixed greenhouse gases? – gavin]
Yes GWG is a global forcing function. Is the question: What is correct factor for GWG forcing as compared to solar forcing?
The second comment is in response to B) Kaplan and Singer’s finding of synchronous global cooling (see my comment 159) which can not be explained by the Milankovitch orbital variations as they are 180 degrees out of phase comparing Northern Hemisphere to Southern Hemisphere.
There is evidence that a solar forcing function affects climate and there is evidence of cyclic solar change. (See below for an example.) In this case GWG has not response for the change. It seems unlikely GWG could not be responsible for the abrupt climate changes.
“Solar modulation of Little Ice Age climate in the tropical Andes”
http://www.pnas.org/cgi/reprint/0603118103v1
“The underlying causes of late-Holocene climate variability in the tropics are incompletely understood. Here we report a 1,500-year reconstruction of climate history and glaciation in the Venezuelan Andes using lake sediments. Four glacial advances occurred between
anno Domini (A.D.) 1250 and 1810, coincident with solar activity minima. Temperature declines of approx 3.2 +/- 1.4°C and precipitation increases of approx. 20% are required to produce the observed glacial responses.”
[Response: A polar see-saw does not provide evidence of GCR-cloud interactions. Since clouds are a net positive forcing in the Arctic as well as the Antarctic, Svensmark’s theory would anticipate synchronous behaviour at the poles – not a see saw. That kind of behaviour is much more characteristic of ocean circulation changes. – gavin]
> I could see it with the computer I wrote it, but not
> for another computer.
I noted this a while back; I still have to refresh pages here fairly often to see the most recent postings; for one example when using the “Recent Comments” links, the page will open to a copy of that thread that’s some hours outdated — without the recent comment whose link I clicked on showing — but refreshing the page will show it and often several other comments. It may be that copies are being cached on the local computer and not updated. Just guessing.
Re # 59 (62) Dear Ray:
Ilya Usoskin responded to yr considerations as follows:
“Dr. Ladbury is right. No statistically significant conclusion can be drawn concerning the shape of the distribution of the Grand Minima shape. But the matter is that the division on Maunder-like and Spoerer-like minima has been done much earlier basing on only a few minima. Our present result is consistent with such a division, although a long-tail continuous distribution cannot be excluded. I also agree that hardly any direct implication for climate studies is apparent, and we were primarily interested in observational constraints for solar dynamo models.”
DEAR ALL:
When you are here dealing with CGR, too, please see the following new study by Ilya Usoskin, of which Ilya sent the following comment:
“….in our recent review we found an interesting relation (see Fig.4 and discussion in sect. 3.3).
Best regards,
Ilya”
The study is:
Usoskin, Ilya G., and Gennady A. Kovaltsov, 2007. Cosmic rays and climate of the Earth: possible connection. Comptes Rendus Geoscience, accepted October 30, 2007, in press, online http://cc.oulu.fi/~usoskin/personal/CRAS2A_2712.pdf
Abstract
“Despite much evidence relating climatic changes on Earth to solar variability, a physical mechanism responsible for this is still poorly known. A possible link connecting solar activity and climate variations is related to cosmic rays and the physical-chemical changes they produce in the atmosphere. Here we review experimental evidence and theoretical grounds for this relation. The cosmic ray – climate link seems to be a plausible climate driver which effectively operates on different time scales, but its exact mechanism and relative importance still remain open questions.”
Re 123, Nicola
a few questions:
What do you think about the composite of Dewitte et al. 2005 (IRMB)?
The difference between PMOD and ACRIM before 1980 causes a more positive trend in the PMOD composite and thus does not explain the difference between the two trends, does it?
According to your theory about solar cycle length, TSI during solar cycle 23 should be lower than during solar cycle 22 and 21, because solar cycle 23 is longer. Same thing for the length between the sunspot maxima (cycle 22-23 is considerably longer than cycle 21-22), TSI for 22-23 should be lower than for 21-22. Both contradicts the ACRIM composite but is in accordance with the PMOD. What’s your explanation?
Re # 158 Ray
Yr consideration reminded me what I wrote in 2003:
“In Natural Sciences, new ideas, hypothesis, theories, observations, studies, experiments, results, and conclusions replace old ones.
Although Climatology is a very young branch that has been widely studied for only about 20 years, this progress can be seen clearly. The progress is so swift – thanks to immense research funding – that many findings only two years old are outdated.
Another aspect is the huge advancements achieved, and the following fragmentation of research into more and more detailed and specific areas.
The progress and advancements make difficulty in mastering all the enormous amount of information. In “the good old days” one qualified scientist could master his/her branch. Not any more, and especially not in Climatology, a branch including so many sub- and adjoining branches.
Climatology contains all the branches of Science which have to do with climate and weather and the tools to master those; e.g. meteorology, geology, oceanography, and cryosphere, lithosphere and biosphere studies, ecology, biology, chemistry, physics, astrophysics, solar, planetary and galactic cosmic ray studies, history, mathematics, statistics, etc., etc., etc..
No one person can master all these subjects, and the adopted solution is co-operation.
This co-operation has three forms:
– a multiscientific approach: climatology is studied simultaneously by different branches, but the actual co-operation and especially integration remains feeble,
– an interscientific approach: this integration is most effective when research ideas, methods and views of various branches are utilised in a planned co-operative process.
– a cross-scientific approach: this provides an abstract conformity and finally a common theory for Climate.
It seems to me that Climatology has become a combination of multiscience and interscience. And it is certain that we have not yet achieved an all-inclusive theory of climate.”
Well, as far as I can see, this is the case also in foreseeable future.
But, honest scientists do admit they don’t even try to find the ‘Truth’ whatever it may be, they only try to find probabilities.
Timothy #161
I leave some aspects of our discussion OT here. Just some precisions.
nebulosity : sorry, it’s a gallicanism, we say nébulosité in French rather than cloud or cloud-cover (nuage, couverture nuageuse).
AR4 is generally several years out of date : not really true, it would be foolish to imagine there’ve been a mass of ground-breaking research or observations in 2006-2007. Climate is a slow process… as well as climate sciences.
More broadly, you repeat that GHGs is a very well known forcing. But I agree with that. You suggest in fine that climate sensitivity is a well constained domain: I strongly disagree with that – and I think there’s a consensus among scientists for recognizing WV and cloud feedbacks are still a major source of uncertainty for climate projections.
You tell me that coupling of stratosphere and troposphere is well taken into account. Do you have any reference ? AFAIK, the SPARC (Stratospheric Processes And their Role in Climate) project, from WCRP is still going on. We don’t know precisely the role of dynamical and radiative coupling with the stratosphere in determining long-term trends in tropospheric climate, or even the exact way by which the stratosphere and troposphere act as a coupled system. So, it would be very surprising the current generation of GCMs implements mechanisms whose physical understanding is still low. But maybe I’m out-of-date like a vulgar IPCC report, so references are wellcome (I mean precise references on the coupling strato-tropo and long term effects of that coupling in models).
Hi Timo, Thanks for the info from Usoskin. Also, again, I think his conservative wrt GCR/solar-cycle modulation is warranted. Certainly, it is plausible that GCR could have some effect. It is not plausible that it can explain the current warming trends, and in the absence of a physical mechanism, it is impossible to even guess how important such modulation might be. What is clear is that it is extremely unlikely to revolutionize our understanding of climate sufficiently to dislodge anthropogenic CO2 as the most plausible mechanism for the current warming, since CO2 forcing is constrained by multiple lines of evidence to its current range of values.
WRT, your post #170, with respect, I’d take issue with several of your contentions:
1)Climate science has been studied for >150 years, and climate modeling dates back to at least early in the last Century. To contend that the science is too young to be well established is simply incorrect. As I posted previously, there are uncertainties, but there are many aspects that it is fair to say we know–ghg forcing among them.
2)I also disagree that science has progressed to the point where no one can have a broad knowledge of it. I used to write for a physics trade magazine, and I found that in many fields, the same names kept recurring, regardless of whether the article–in geophysics for instance–was on deep-focus earthquakes, mantle hotspots or the geodynamo. John A. Wheeler (U of TX) is another example in physics–he’s said to be the guy Nobel Laureates turned to when they couldn’t solve a problem. It is true that such individuals are rare and that most of us find ourselves sucked into specialized fields of research. Still, they’re out there if you look, and while they may not be household names, their scope and judgement make them quite influential in science. And there are many of us in the rank and file of science who work hard to keep abreast of progress in a variety of fields. My day job is radiation effects in semiconductors. Yet I keep abreast of developments in geophysics, condensed matter physics, particle physics (my PhD subject), astrophysics and a variety of other subfields. As avocations I study history and philosophy of science, especially as they relate to prababilistic understanding.
3)It is a mistake to downplay the level of cooperation in climate science. These guys attend the same meetings, read many of the same journals and often attended the same schools, and good research is likely to spread via word of mouth. The fact that not every subfield is integrated reflects the complexity of the subject and the likely significance of the various subfields for the current goals of climate theory more than it does any balkanization of climate science.
4) Don’t downplay probabilistic and statistical argument. If properly executed, they provide us with the most reliable forms of knowledge. There is an old saw about a man with one watch always knowing what time it is and a man with two never being sure. However, a man with an ensemble of watches can not only hone in on the most probable estimate of the time, but also tell you how far he is off!
#150 Wayne
But you must consider TSI and UV anomalies were almost the same, which brings me back to my original argument, where’s the extra heat coming from? I leave out GHG’s (the greatest and now the only reason for warming), and let you find a suitable likely substitute, if there is one.
In fact, TSI and UV anomalies are not the same, either in cyclic amplitude (UV change accounts for 60% of total change in a cycle, athough 8% of the radiation is emitted at these wavelenghts) or in effects on our atmosphere (UV mainly interacts with O2 and O3). And you know that’s still poorly observed – there’s for example a gap in XUV/EUV range for 1980-97 period, even if MUV and FUV have a reasonably well coverage.
When you say “extra-heat”, I suppose you mean for 1977-2006 period – a 0,5 K warming in 30 yrs. Extra-heat from this period may come from GHGs, of course, but also mutlidecadal intrinsic variability, downward trend for aerosols in Northern Hemisphere except part of Asia, and… solar forcing we’re discussing. I focus on the later.
First, according to te recent post of N. Scafetta quoting Willson, there’s still a strong disagreement between ACRIM and PMOD so we cannot exclude ACRIM team is right (which would imply a slight upward trend for TSI in cycle 21-23)
Second, there’s still no conclusive argument in our debate for the timing of climate sensitivity to solar forcing. Even if you have no trend for recent cycles 21-23, it’s obvious for all TSI reconstructions show that solar activity is higher in 1951-2000 than in 1901-1950. Look at theses reconstructions : solar cycles minima of the second half-century appears as more active than solar cycles maxima of the first. So, more solar energy have penetrated climate system in the recent decades.
Third, if we just take into account the TSI itself, variations for 1951-2000, 1901-1000 or 1750-2000 are very weak according to Wang-Lean, Solanki-Krivova or Forster reconstructions – for the longest period, less than 5% of total positive anthropogenic forcing. You may conclude that anthropic factors caused 95% of the observed warming for 1750-2000. But Gavin in a comment above (#34) suggests that solar forcing accounts for “roughly 10%-20% of 20th Century warming”. Even in this conservative estimate, how a forcing accounting for 5% of TOA budget translates in a 10-20% warming trend on Ts ? I guess we should precise the famous “solar amplification mechanism(s)” in terrestrial climate. When we’ll get the right physical explanations, we will ensure more precisley its importance by implementing it in models.
I’m a layman, not a scientist. At this point, it would be nice if Rasmus, or Gavin or any RC contributor answers to this basic and direct question here : do you think there’s a solar amplification mechanism (even weak) in climate system, not fully understood now, or do you think on the contrary that models and observations reasonably exclude any mechanism of that sort, so that solar influence is strictly limited to TSI change in TOA budget?
[Response: In terms of effects that have been demonstrated to exist in obs and models, only the change of UV impact on ozone (both strat and trop) has been shown to be relevant. So yes, there is at least one factor that amplifies some responses (regional patterns mainly rather than global mean temperatures), but that neither implies nor precludes other factors. They simply have not been demonstrated to be relevant (as yet). – gavin]
Sorry if this is a bit off-topic, but some may find this interesting (or amusing, or frustrating).
Test your knowledge of global warming:
http://www.globalwarmingheartland.org/GWQuiz/Q1.html
William Astley (#166) wrote:
Actually what Henrik Svensmark’s “The Antarctic climate anomaly and galactic cosmic rays” contains are graphs. The graphs which have a description speaking of ERBE refer you to “ref.” If you look up “ref.” in the references, there is nothing that corresponds to it or which mentions ERBE.
As such, while there may be data for his graphs, he does not actually provide it or reference it in any recognizable fashion. Perhaps one of the “references” that his paper refers you to actually does contain the data — but there is no indication which of these references it might be.
With regard to the paper you mention above but do not name — perhaps we can try forcusing on Svensmark for a bit first. There is only so much time in a day, and while I probably have considerably more time than Gavin, it is still limited.
*
What ERBE would seem to refer to is the Earth Radiation Balance Experiment. Basically ERBE is designed for a kind of accounting, measuring radiation coming in and going out in both the shortwave and longwave. The data it provides would be essentially of the same nature as that which forms the basis for the images I linked to in 165 — and which show that when you increase the amount of carbon dioxide or other greenhouse gases, you reduce the amount of thermal radiation which is leaving the system, increase the amount of thermal radiation which reaches the surface.
Given the conservation of energy, the surface must heat up until it reaches a temperature at which it is emitting enough thermal radiation that it compensates for increased levels of greenhouse gases. This works for water vapor, carbon dioxide, nitrous oxide, CFCs and ozone — athough it is directly absorbing ultraviolet radiation from sunlight rather than relying upon the surface to convert sunlight into longwave. In terms of the principle, this will apply to all gases to the extent that they are able to absorb radiation in their environment. In any case, with ERBE he is relying upon the very same technology which demonstrates that the greenhouse effect must occur.
*
Oddly enough, if he is proposing this theory as some sort of alternative meant to explain bipolarity, it is not an alternative to an enhanced greenhouse effect, but an alternative to a bimodal theory of ocean circulation. Something which recieves no mention in his paper. As such, in contrasting his theory to the greenhouse effect, he is arguing against a strawman.
*
Now yes, of course the Antarctic climate is isolated — primarily by the Antarctic Circumpolar Current. When there was a land bridge between Antarctica and South America, Antarctica was subtropical. However, as the two continents moved apart, the circumpolar formed and became stronger, and given the location of the Antarctic continent, resulted in Antarctica being sent into a deep freeze. Mainstream science also relies upon this isolation to a degree to explain the behavior of Antarctica with current warming.
*
What his theory would at least seem to suggest in the context of global warming is “polar dampening.” Given the ice that exists at both poles, assuming that cloud-formation decreases with lower amounts of galactic cosmic rays, and relying upon a raising of albedo with lower amounts of clouds over Antarctica to result in lower temperatures per his bimodal theory, we would expect a reduction in clouds over the Arctic to result in cooling while the lower latitudes whereas the tropics will experience higher temperatures with diminished clouds.
But what we are seeing with respect to the Arctic is polar amplification. We are likewise seeing strong polar amplification along the West Antarctic Peninsula.
There is of course some cooling which is currently taking place in the interior of the Antactic continent, but there is much warming as well. The cooling itself would seem to be the result of the reduction ozone lowering the temperature of the stratosphere, resulting in an enhanced temperature differential between the troposphere and the stratosphere, strengthening the polar vortex. Air flow from the center of the continent has resulting in some cooling in other places.
*
Given polar amplification, the West Antarctic Peninsula has been warming quite considerably. In fact, the only place where we may currently be seeing more warming is over the Tibetan Plateau. The Larsen A Ice Shelf disintegrated in January of 1995 and the Larsen B Ice Shelf disintegrated in February of 2002. We have over a hundred glaciers which are picking up speed and heading to the ocean.
Likewise the mass balance of Antarctica as a whole has begun declining – this was detected by Grace in 2006. Snow is adding to the ice mass of Antarctica (not surprising given that it receives so little precipitation, and warming temperatures will actually increase this precipitation), but this increased precipitation is more than outweighed by the melting which is occuring.
And a large part of the continental interior of Antarctica experienced an unexpected melt only 310 miles from the South Pole back in 2005. Likewise, nearly all of the Southern Ocean has been warming — particularly along the coasts.
And we are seeing rapid warming of much of the troposphere during the winter.
Please see:
Significant Warming of the Antarctic Winter Troposphere
J. Turner, T. A. Lachlan-Cope, S. Colwell, G. J. Marshall, W. M. Connolley
SCIENCE, 31 MARCH 2006, VOL 311, 1914-17
… which is available at:
Science – Significant Warming of the Antarctic Winter Troposphere
Posted on: March 31, 2006 6:28 AM, by William M. Connolley
http://scienceblogs.com/stoat/2006/03/science_significant_warming_of.php
The exception which Svensmark believes “proves the rule” would seem not to be quite so much of an exception.
*
William Astley (#166) wrote:
Actually Gavin is an expert in climate and paleoclimate modeling. He does not specifically focus on bimodal theories of ocean circulation. But I suppose there might be some utility in thinking that he does.
*
The bore hole temperatures of mainstream science is correct. What they describe are Heinrich events and Dansgaard-Oescher events. But this does not correspond to the warming which we have seen in the 20th century — it corresponds to what we saw more than 10,000 years ago during the ice ages.
As I have stated earlier in 165:
Likewise, simply in terms of the warming which is occuring in much of Antarctica which I mentioned above, the evidence is inconsistent with the Dansgaard-Oescher events in the most basic fact that as Greenland warms, we should expect to see Antarctica cool dramatically — instead of cooling in some places and rather dramatic warming in others.
*
William Astley (#166) wrote:
By “correct factor for GWG forcing,” I assume you mean climate sensitivity to a forcing. Climate sensitivity isn’t built into the models. It is something which falls out of the models, although the exact value will depend upon the model. The models themselves are based upon primarly physics: radiation transfer theory, thermodynamics, fluid motion theory, etc.. But there is also a great deal of chemistry – particularly in the study of the atmosphere, ocean and carbon cycle — as well as some biology.
*
William Astley (#166) wrote:
You are thinking of the tilt of the axis which controls the seasons. What about the eccentricity of the orbit? This is what would control the amount of radiation the climate system receives in a year. The more eccentric the orbit, the faster the earth will be moving when it passes close to the sun and the more time it will spend at greater distances from the sun. Greater eccentricity will mean less radiation being received throughout the year. And changes in the eccentricity of the orbit are predictable — given the gravitational effects of Jupiter and Saturn upon the earth’s orbit.
*
William Astley (#166) wrote:
There is considerable evidence of either quasi-periodic or chaotic solar change. We wouldn’t claim that greenhouse gases are responsible for initiating the warming that takes place as the result of changes in solar insolation. We would however claim that it is responsible for amplifying those effects — as rising temperatures will result in lowering the capacity of the oceans to absorb additional carbon dioxide and retain carbon dioxide the carbon dioxide which they have already absorbed, leading to increased levels of carbon dioxide, and falling temperatures will result in the reverse.
Re: #166 (William Astley)
The earth’s axial tilt (obliquity) affects both hemispheres equally, i.e., in phase, greater tilt causing more solar insolation at extreme latitudes (both north and south) but less in the tropics. The precession parameter, the product of eccentricity and the sine of the angle between perihelion (closest approach to the sun) and the vernal equinox, affects the hemispheres oppositely, i.e., 180 degrees out of phase.
Re: #175 (Timothy Chase)
While greater eccentricity does indeed mean earth moves faster when closest to the sun and slower when furthest, the overall effect averaged throughout the year is that earth receives slighly more solar energy when eccentricity is highest.
I posted on these topics here and here.
Tamino (#176) wrote:
I appreciate the corrections — tilt vs. eccentricity in relation to the Milankovitch cycles was the one area that I felt uncomfortable with — although I had noticed the bit about the tilt causing more warming during a hemisphere’s summer near the corresponding pole for both hemispheres – without mentioning it. I should have followed that through further.
I presume a smaller tilt cools the poles and the albedo effect causes the ice to spread towards the equator with positive feedback – despite the increased insolation in the region of the equator of itself. But in any case, I probably should have either not “addressed” this issue or should have taken the time to look more up.
I will check out the links later today.
Quick Note: With regard to tilt and the Milankovitch cycles, I was wondering whether Singer et al. had made some sort of argument similar to what Ashley proposed in 166 and which tamino responded to in 176, and I found this:
In doesn’t out-and-out say what Ashley seems to think it did — but it seems designed to be interpretted in that fashion, namely that tilt can’t explain ice ages occuring in both hemispheres at the same time. And the references? Some appear to be to controversies long since resolved.
Re orbital parameters and climate, what do you think of Richard Muller’s theory of inclination driving ice ages?
A New Theory of Glacial Cycles
[Response: It’s not so new anymore, and as I understand it, the requisite increased dust fluxes called for in the sediments have not been found. Maybe someone from his group can enlighten us as to its current status? – gavin]
[Response: The “Muller and Macdonald” theory is all but dismissed now by serious researchers in the field. A nice, concise explanation of why is provided in this Science article by Clark et al (1999): Muller and MacDonald [ R. A. Muller and G. J. MacDonald, Science 277, 215 (1997)] argued that the origin of the 100-ky cycle involves non-Milankovitch changes in the Earth’s orbital inclination, which caused the Earth to periodically pass through a cloud of interplanetary dust. Sedimentary records and calculations of dust flux, however, do not show large changes in extraterrestrial dust accretion [F. Marcantonio, et al., Nature 383, 705 (1996); F. Marcantonio, et al., Earth Planet. Sci. Lett. 170, 157 (1999); S. J. Kortenkamp and S. F. Dermott, Science 280, 874 (1998)], whereas spectral analyses of the marine 18O record of global ice volume suggest that this mechanism is unnecessary [J. A. Rial, Science 285, 564 (1999); A. J. Ridgwell, A. J. Watson, M. E. Raymo, Paleoceanography 14, 437 (1999)]. Hardly a ringing endorsement. Muller’s “death star” hypothesis for explaining the major geological extinctions events including the K/T extinction, hasn’t fared much better. –mike]
Re: Ice Ages
It is no longer true that “For many decades it has been widely accepted that the 100 kyr cycle of the ice ages is caused by changes in the eccentricity of the Earth’s orbit.” The global climate forcing due to eccentricity is at most about 1.7 W/m^2, and that’s only when eccentricity gets as high as 0.06, which it very rarely does — the present value is more like 0.017, yet at present we’re solidly in an interglacial. Also, the timing of deglaciations doesn’t match the eccentricity cycle so well. These days, eccentricity forcing is generally considered just too weak to be a driver of glacial cycles.
The orbital-inclination theory of Muller and McDonald caused a stir for a short time, but is no longer considered a serious contender.
For over two million years, from about 3 million yr ago to about 750,000 yr ago, glacial cycles were overwhelmingly dominated by the 41,000-year obliquity cycle. This time period has even been called “The 41-kyr World” (Raymo and Nisancioglu 2003, Paleoceanography, 18, 1011). Only in the last 750,000 yr or so has a 100,000 year cycle been visible, and even that is not certainly a genuine cycle. Some researchers (I think Wunsch is one) propose that the recent changes are essentially stochastic, with the appearance of cyclicity an artifact of the very red noise character of the signal combined with a roughly 100,000-yr time scale (not period) in ice sheet dynamics. In any case, the 41,000-yr obliquity cycle and roughly 21,000-yr precession cycle are still clearly present in the Fourier spectrum of the last 750,000 years. Many theories have been proposed to explain what triggers deglaciation during the last 750,000 years, including synchronization of obliquity and precession cycles and the aforementioned stochastic behavior, and changes in the carbon cycle are implicated as well.
My own “pet” theory revives the influence of eccentricity, but only in combination with obliquity, thus: when obliquity increases, the poles are more exposed to sunlight and the equator less so. Since the poles are highly reflective, this actually increases earth’s albedo and can explain the slight cooling which is sometimes observed just before a deglaciation. There is also less sunlight falling on the world’s oceans, which can further cool the oceans and initiate drawdown of CO2, helping explain the pre-deglaciation cooling, and may retard warming sufficiently to defuse a deglaciation unless polar warming is sufficient to disintegrate ice sheets. Only when obliquity nears its peak and eccentricity is increasing, can the greater ice melt from combined obliquity & eccentricity be enough to trigger deglaciation.
Re #169
Ok Urs,
>>What do you think about the composite of Dewitte et al. 2005 (IRMB)?
IRMB alters some of the published data too, but in a way different from PMOD. ACRIM is the only composite that fits perfectly the published satellite data. PMOD fits the TSI proxy reconstruction by Lean, IRMB doesn’t.
>>>The difference between PMOD and ACRIM before 1980 causes a more positive trend in the PMOD composite and thus does not explain the difference between the two trends, does it?
No, Urs. What is important is not just the trend but the amount of TSI the Earth received for a given period. With ACRIM the earth received more irradiance because the maxima are higher.
>>about the solar cycle length.
It is not well understood how solar cycle length might relate to the TSI trend. That is why Lean and Solanki do not use it for their reconstructions.
#173
Gavin says: “So yes, there is at least one factor that amplifies some responses (regional patterns mainly rather than global mean temperatures), but that neither implies nor precludes other factors.”
very well said!!!!!
I suspect there are some other factors, but the model guys adopt a methodology that can only pick them up one by one and a little by little. That is why I thought an alternative method that tries to pick them all at once :)
[Response: … and then some. ;) – gavin]
[Response: Further, positing the existence of a yet-unidentified hypothetical amplifying mechanism which acts on solar forcing but not on GHG forcing does not justify neglecting the known radiative forcing due to GHG increases. (that’s the “and then some” business Gavin is referring to). To fail to treat this forcing on an equal and consistent physical footing with the unknown hypothetical forcing you are invoking is just bad science. –raypierre]
Solar forcing (direct and indirect modulation of clouds) drives abrupt climate changes?
There seems to be strong evidence to support a solar forcing function for abrupt climate change.
http://www.cosis.net/abstracts/EGU06/00841/EGU06-J-00841-3.pdf
“This periodicity, initially associated with the so-called Dansgaard-Oeschger oscillations,is also found in a great variety of studies through the Holocene. The 1500-year period seems to occur independently of the general glacial – interglacial climate changes. According to these results, the millennial-scale variability was attributed to the same forcing, ruling out any direct link with the ice-sheet oscillations.”
“Residual Delta14C time-series analyses confirm Bond’s hypothesis: solar forcing appears to be the dominant forcing during Holocene with two persistent periods of 2 500 and 1 000 years respectively.”
From Wikipedia:
“Gerard Bond suggests that changes in the flux of solar energy on a 1,500-year scale may be correlated to the Daansgard-Oeschger cycles, and in turn the Heinrich events; however the small magnitude of the change in energy makes such an exo-terrestrial factor unlikely to have the required large effects, at least without huge positive feedback processes acting within the Earth system.”
My comment: The cyclic warming and cooling is driven by the solar influence on clouds? Has anyone read Palle’s papers?
“Dansgaard-Oeschger events are closely related to Heinrich events. ….There is evidence to suggest Dansgaard-Oeschger events have been globally synchronous (Bond et al., 1999).”
Link to Bond’s Persistent Solar Influence North Atlantic in the Holecence.
http://www.deas.harvard.edu/climate/pdf/bond_2001.pdf
“A solar forcing mechanism therefore may underlie at least the Holocene segment of the North Atlantic”
N. Scafetta nicely gave me the file for TSI reconstruction of Wang et Lean 2005, on which IPCC AR4 best estimate is mainly based.
I’ve some problem with the TSI trend, the same problem I met with the Crowley 2000 reconstruction used by Mann 2005. In fact, I’m quite astonished by the values Wang et Lean obtain.
Fisrt point : if we take the 1910-40 trend (first signal of GW with 0,4 K trend), TSI variance from maximum to maximum is less than 0,2 W/m2, less from minimum to minimum. That is for TSI : the TOA forcing (Earth as a sphere and reflexivity) leads to a value of… 0,04 W /m2 maxi. Or other words : nothing or so. But if it is the case, we must say clearly that there’s NO solar influence at all for 1900-present T trend : 1910-40 warming is explained bu GHGs, less volcanism, intrinsic variability, without any significant solar forcing TOA. And if we suggest an influence (eg 10-20% of Gavin), we must explain how a 0,04 W/m2 TOA forcing would produce any significant effect on climate.
Second point, not with absolute value, but with trend : I think RC contributors disagree with Wang et Lean when they say (frequently) there’s no trend since 1960. Because in their TSI reconstruction, maxima of cycle 21 (1981) and 22 (1989) are the highest of the past century, at the same value that cycle 19 (50s) and not far from cycle 23 (2002). In contrast, cycle 20 (1970) is less pronounced, so in Wang et Lean :
a) there’s an increasing trend from the 1970s to the 1980s
b) values of the 1980-present period are the highest of the century, with no other similar period in the previous decades for 3 successive cycles.
Any way, this last point has no climatic sense when we consider the first, that is the extremely low absolute values of TSI change during the past 100 yrs.
So, I see at least three hypothesis :
– Wang et Lean (and other recent TSI rec. of the same magnitude) are wrong, and solar models miss an important point in proxies of past solar activity (before 1978 and satellite measur.) ;
– Wang et Lean are right, TSI>TOA forcing is the good factor for understanding solar influence, and there is nearly no solar influence on modern GW (not solely since 1950, but for 1850-1950 as well)
– Wang et Lean are right, TSI>TOA forcing is not the good factor for understanding solar influence, and we still miss the famous solar amplification mechanisms.
Any preference in these hypothesis… or any other hypothesis ?
Off topic but I’d really like to get your opinion regarding the recent paper by Roy Spencer (“Cloud and radiation budget changes associated with tropical intraseasonal oscillations”). It suggests that increased sea surface temperature in the tropics would result in reduced cirrus clouds and thus more infrared radiation leakage from Earth’s atmosphere which would be a negative feedback. My questions are as follows.
1) Are you aware of any published reactions to the Spencer paper?
2) Is it true that the circulation models assume that increased sea surface temperature would result in increased cirrus clouds which would have the effect of warming the sea surface further and thus there would be positive feedback? If so, can you point me to the main evidence supporting this assumption?
#173, Charles, not bad arguments for a lay person. UV is better understood than you might believe. Especially since Dobson and his spectrometer. As far as I can read
(and measure) UV has not changed that much, but stratospheric ozone did go for a wild concentration ride, for the better recently. Go back to 1997, it was a time when the Polar vortex was intense, at its center -80 C was reached, ozone concentrations dipped to its lowest values since measurements began. An excellent opportunity to study tropospheric warming by UV. Records show a small temperature increase for the Northern hemisphere in March 97, aside from that 1998, had double the temperature anomalies near +1 C, with lots more stratospheric ozone. I like the idea, of looking further, but I think that UVis not a significant temperature booster. Rather, as said many times here on RC, Antarctic ozone holes create substantial cooling. 1997 was the last cold Arctic winter spring I experienced, I know that many may enjoy -45 C for weeks on end, but the travel agencies kept it a secret then.
Today is a different world, may be RC readers should consider last few days of explosive Arctic warming, over an astounding huge Polar swat, warmer than +10 C above average. Starting from where the open water and thin ice is, between Alaska and Russia. The speed of this warming was simply astonishing.
http://www.cdc.noaa.gov/map/images/fnl/sfctmpmer_01a.fnl.anim.html
#185 Wayne, thanks for the precision, I’m currently reading on that topic, so I’ve no clear idea for the moment. When I mentioned a solar influence stratosphere-troposphere coupling, I did’nt think to a direct and global effect of solar on stratospheric T, and then a transfer on troposheric T. Rather an influence on general circulation maybe mediated by planetary waves (but as I just open up these questions and as they’re quite complex, I won’t go further for the moment).
I try to illustrate by an example : recently in J Clim, Lisan Yu analyzes oceanic evaporation (1958-2005, from Objectively Analyzed Air–Sea Fluxes OAFlux) and find a shift in 1977-78, with decrease before and increase after, and with 1990s as the most dramatic increase in Evp. (That’s perfectly coherent with the signature of 1977-2007 GW, by the way).
An EOF analysis shows that the first factor of variance in Evp since 1977 is wind speed (the greater, the faster water vapor is blown away and the air–sea humidity gradients restablished). So, that is a kind of indirect effect I’ve in mind : in this case, any factor that influences wind speed (regionnaly on Tropics or subtropics for example) would influence evaporation, so convective-radiative budget, so Ts and Ttropo.
Please, let’s be clear : I DO NOT say here that wind speed is influenced by solar variation!! I just give an illustration of the kind of an “amplification mechanism” we could imagine. But my example is clearly not adapted for the solar discussion (in fact, I don’t know if it is adapted to… anything, because in this case I don’t really understand why there would be decadal variations in wind speed and if there is, I suppose GHGs induced modification would be the first candidate). I’m going to read again and more carefully the paper Gavin, Mike on some others here wrote on regional response to Maunder minimum, in order to get a more realistic example of indirect mechanisms of solar influence.
Re #185: Wayne, that link is quite a teaser. What can you say about it from a meteorological standpoint? Also, that whole area is pretty much in 24-hour darkness just now, right?
#184, on question 2, for instance this (not sure this is what you’re looking for)?
On question 1, surprisingly no.
Having read the paper myself (but not being a climatologist) I saw one big problem, not with the paper itself, but with the implication that this would be relevant to climate change. The paper doesn’t overstate its case and makes the caveat, e.g., that the time scales of the natural experiment described (weeks to months) and global change (decades) are quite different. But this is only part of a larger limitation: the mechanisms involved are quite different. The climate change mechanism is well known involving CO2, the tropical warming described has some other mechanism inside the weather system. What they have in common is temperature increase, but “correlation doesn’t prove causation”.
The carbon dioxide is also relevant in another way. Without it increasing, what may happen as the troposphere heats up is that water will tend to condense out as liquid rather than ice. CO2 changes the vertical thermal structure of the troposphere, and the water may now condense out at a higher, colder level where ice again can form.
Against Lindzen’s ‘iris hypothesis’ argues also the absence of evidence for significant forcing of this kind during the ice ages/interglacials. But that’s admittedly a very different regime from today.
Real climatologists please correct me ;-)
Charles — sorry, I didn’t see your post until late.
Charles Muller (#171) wrote:
Perhaps a couple would be more accurate. In any case, here is some of the news I know about from the past two years. I have divided it into three parts: Cryosphere and Sea Level, Carbon Cycle, and Clouds. It is by no means exhaustive. With more time, the list would undoubtedly be much longer.
Cryosphere and Sea Level
Their projections for Arctic sea ice showed it lasting from 2050 to well into the next century, but the sea ice extent in this year alone is 25% less than the previous recorded minimum of 2005, and estimates have been within the range of 2020 to 2040 — with a simple linear estimation of the behavior suggesting 2020. Likewise we have seen dramatic developements in terms of the glaciers of the Tibetean Plateau — which is now projected to be glacier-free by the end of the century.
Currently we are seeing negative mass balance in both Greenland and Antarctica — with negative mass balance in Antarctica having occured only with the past few years and was discovered in 2006. Studies have shown that Greenland’s icemelt has increased by a factor of two and that icequakes have increased by a factor of three over the span of a decade. We have discovered a region within 310 miles of the South Pole that had melted for weeks in back in 2005 — but which was picked up through data analysis only much later.
Carbon Cycle
We are seeing positive feedback in terms of the carbon cycle – with several parts of the ocean in the Atlantic, Pacific and even Southern Ocean showing signs of becoming saturated. We are likewise seeing evidence of the weakening of the carbon sink provided by plants — at least during the warmer, drier years.
Only within the past couple of years have we found that large parts of the permafrost are thawing. We have discovered that yedoma – a deep, especially methane-rich form of permafrost is roughly a hundred times more common that previously thought. Meanwhile, Global Climate Models which incorporate the carbon cycle exist — and received some small mention in AR4 — although they were not generally involved in making the climate projections.
Clouds
Just this year we found that there is an invisible twilight zone that extends for kilometers beyond the edges of visible clouds — and with this discovery should be able to improve our modeling of clouds and their effects. We have discovered that while the Asian Brown Cloud results in cooling at the global level, within much of Asia it amplifies warming.
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Charles Muller (#171) wrote:
Water vapor and cloud feedback is still a major source of uncertainty, although it is my understanding that this has been reduced. But results regarding climate sensitivity can be obtained which are largely independent of our knowledge of these feedbacks.
There are two papers which combine the results from a great many studies to converge upon a high likelihood value of approximately of either 2.8 or 2.9. Now given the nature of climate sensitivity, a value which is considerably higher than the high likelihood is much more likely tha a value which is considerably lower. As such, the distributions which we are dealing with are highly asymmetric. Thus while the study based upon paleoclimate data cannot exclude considerably higher values, values which are substantially lower (e.g., 1.5) than the high likelihood value are effectively eliminated.
The following post deals with one of these two papers: “Using multiple observationally-based constraints to estimate climate sensitivity” (2006) by J.D. Annan and J. C. Hargreaves that by means of Bayesian logic is able to combine the results from a variety of studies employing different methods for the estimation of climate sensitivity where the range of uncertainty is relatively high to constrain the uncertainty, producing a much tighter range. Thus for example, if one simulates the eruptions of Agung, El Chichon and Pinatubo using a simple energy balance model that has a tunable climate sensitivity, one finds that while the plausible range for each is fairly wide (with a lower limit of 0.3 to 1.8 and an upper limit of 5.2-7.7), the high likelihood value has 2.8 with a lower bound of 1.8 and an upper bound of 4.4.
Of course this sort of approach simply as it applies to three eruptions may be somewhat biased. Nevertheless, by bringing in he results of numerous other studies using other methods and models provide similar ranges, and by a similar application of bayesian logic one is further able to constrain the range of uncertainty. The authors conclude that anything as high as 4.1 is highly unlikely, and the same would apply to values significantly below the high likelihood value of approximately 2.9 and a range from 2.6 to 4.1.
24 March 2006
Climate sensitivity: Plus ça change…
https://www.realclimate.org/index.php/archives/2006/03/climate-sensitivity-plus-a-change
There is a link to the actual paper in the article.
The authors of the following paper give us a similar high-likelihood value based upon paleoclimate evidence. Although they cannot entirely exclude high climate sensitivities, they effectively rule out anything below 1.5 K per doubling, and their best fit for the past 420 million years using data compiled from 47 different published studies employing five different methods was for 2.8 K per doubling.
Royer DL, Berner RA, Park J. 2007.
Climate sensitivity constrained by CO2 concentrations over the past 420 million years.
Nature, 446: 530-532.
Neither of these studies would appear to be dependent upon our knowledge of the feedbacks due to water vapor or clouds. In fact, the study involving paleoclimates would appear to be entirely independent of such knowledge. The same is obviously true of volcanoes. And as I stated, many of the uncertainties will tend to cancel each other out. For example, greater cloud-formation will mean increased albedo, but they will also produce their own greenhouse effect.
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Charles Muller (#171) wrote:
What I said was that the coupling is already taken into account — not that all of the details have been worked out in terms of the chemistry or the modeling of all of the processes. But just because we don’t know everything (“even the exact way by which the stratosphere and troposphere act as a coupled system” as you put it) does not mean that we know nothing and are only able to model as much.
The recent models include the stratosphere. The boundary which separates the stratosphere from the troposphere is called the tropopause. Models predicted that the tropopause would rise as the result of global warming. It has. They wouldn’t have been able to do this if they weren’t already incorporating the stratosphere. Likewise, I seriously doubt that they would have been able to model the Hadley cells to the point that they could be used to predict the expansion of the Hadley Cells — but all of the models in AR4 show it.
And now the most recent NASA GISS model is now modeling the lower layers of the mesosphere.
Please see:
It is only by incorporating the stratosphere and our physical understanding of it that we can begin to compare the behavior of the model with the real world and thereby discover what important physical processes have been left out so that they too may be incorporated into the models. Incidentally, the paper by Schmidt et al describes some of the progress which has been made in the modeling of clouds – although it indicates that there is still more progress to be made.
Wayne 185! Can you please help me understand that animation you pointed us to? It refers to surface temperatures. Is it really saying that over the last few days surface temperatures over the Arctic have moved up by 15 to 20C?!?!!? Really??! Are surface temperatures the air teperature at the surface or the temperature of the surface? Either way …!
Timothy Chase wrote:
[[The more eccentric the orbit, the faster the earth will be moving when it passes close to the sun and the more time it will spend at greater distances from the sun. Greater eccentricity will mean less radiation being received throughout the year.]]
Actually, it’s the opposite — because of the inverse square law, a more eccentric orbit actually gets a little more insolation than a perfectly circular one. The difference is very small, though. The ratio is equal to 1 / sqrt(1.0 – e^2) where e is the eccentricity. Earth’s eccentricity varies from about 0.00 to 0.05, so at maximum eccentricity Earth receives about 0.125% more insolation than at minimum.
Wayne@185. That’s stunning warming in the Arctic over the last week. What sort of weather system is driving that? It shows the pole warmer than -5, in the middle of the polar night.
Could it be an instrumental blip?
tamino@180: presumably the effect of eccentricity on forcing depends on the phase of the eccentricity with regard to the axial tilt. Not sure what the right terminology is here, but at the moment perihelion is close to the southern solstice, when albedo is high (highest?). I imagine that at other epochs perihelion might be close to the northern solstice, or close to an equinox. Because the earth’s albedo depends on this phase, the effect of eccentricity won’t be constant.
Re the Muller-MacDonald theory in 179, thanks to Mike and Gavin for the detailed replies.
Nigel, 185-190 — remember the projection. The huge expanse of ‘white’ at the top of that rectangle is actually a point (the North Pole). So when it changes from white to dark red, it does seem to indicate the North Pole warmed that much, that fast. But is there a data set we can check? a polar projection might be far more informative. Anyone know more?
I’ve got to encourage people who haven’t yet looked at the temperature anomaly animation linked to in 185 to do so. It’s like something out of a science fiction movie.
The recent big glop of cold temps in the central plains shows up clearly, but the anomaly to the north looks like something that Kurt Russell’s superiors would send him to investigate. Off the charts, I suspect, like the French heat wave of a few years back.
167-190-192… Its legit at least in my location, 74 43N 94 57W.
or in the Canadian sector of the Pole:
http://www.weatheroffice.gc.ca/data/analysis/jac06_100.gif
Its the warmest temperature boost measured in December here, beating 2005 and 2006, the latter being very warm winter. I am baffled by this speed, although I observed several Cyclones hitting towards the Pole over the last 12 days, mainly from the Pacific, some from the Atlantic It may be a cumulative effect of warming from above combined with warming from below, the thin ice multiple thousand extra leads open water. It can be something else. But the key is for sure the thin ice and open water. These are anomalies which are extraordinary. Another point, the coldest air is in the NWT-Yukon-Alaska region, prompting an antycylone which may pump further warm air towards the Arctic.
Re 185. Winds, probably. Thin ice breaks and waves mix the waters.
An Arctic sea ice area time series is found on page http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/sea.ice.anomaly.timeseries.jpg As the winds come and go, there are typically several dips in the ice area each winter. The long term trend is clearly diminishing.
Sea surface temp anomalies in polar projection can be found at
http://sharaku.eorc.jaxa.jp/cgi-bin/amsr/polar_sst/polar_sst.cgi
Barton Paul Levenson (#191) wrote:
Yep.
Tamino corrected me on this as well. But your explanation in addition to his will help. I can see how combined with Kepler’s second we could set this up as a differential equation then integrate. A slightly different angle of attack, but it should come up with the same results as what Tamino arrived at. And as I differential equation I believe I can see already why it should be slightly more.
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