As a prelude to a new book, Nigel Calder (who was the editor of New Scientist for four years in the 1960s) has written an op-ed for the Times (UK) basically recapitulating the hype over the Svensmark cosmic ray/climate experiments we reported on a couple of month ago (see Taking Cosmic Rays for a spin). At the time we pointed out that while the experiments were potentially of interest, they are a long way from actually demonstrating an influence of cosmic rays on the real world climate, and in no way justify the hyperbole that Svensmark and colleagues put into their press releases and more ‘popular’ pieces. Even if the evidence for solar forcing were legitimate, any bizarre calculus that takes evidence for solar forcing of climate as evidence against greenhouse gases for current climate change is simply wrong. Whether cosmic rays are correlated with climate or not, they have been regularly measured by the neutron monitor at Climax Station (Colorado) since 1953 and show no long term trend. No trend = no explanation for current changes.
Jon, whoever told you that “AGW theorists think that greenhouse gases are the only actor” was setting up a straw man. Search this site regarding attribution and you’ll see that ol’ Sol is considered. Finally, the IPCC states with >90% certainty that global warming is due to anthropogenic greenhouse gases. They haven’t closed their minds to other possibilities.
Re: #150
You’ve been seriously misinformed! Mainstream thinking on global warming is not that it depends only on retention of heat by greenhouse gases; rather it includes the effect of reflective aerosols (both volcanic and anthropogenic), the aerosol indirect effect, black carbon soot, albedo change due to changing snow and ice patterns, land use changes, and — yes indeed — changes in solar output, as well as others. Without taking all the factors into account, calculations don’t match observation; when all factors are taken into account, the match is superb.
When we look at the data, one of the factors is much larger than the others, and that’s greenhouse gas forcing. Since 1950, it is indeed the only forcing that’s had a potent warming effect. That is not an assumption of “global warming theory,” it’s based on actually measuring the strength of the various forcings.
It’s like investigating why someone is suddenly gaining weight rapidly. This involves a large number of factors including diet, exercise, hormonal balance, etc., all entering into an extremely complex system. But if we have measurements of diet, exercise, kidney function, hormonal balance, etc., and only one of those factors has changed enough to affect weight, we can identify that as the cause. This doesn’t mean that the other factors aren’t important, and especially doesn’t mean that they haven’t been taken into account. But when all the other suspects have an ironclad alibi …
In #126, John Tillman wrote: “The peer review process for many relevant journals has become part of the problem in the AGW discussion. Many skeptics are retired, so no longer subject to retaliation for heretical departures from AGW orthodoxy. Thus I’m not sure that regularly publishing need be a criterion, if they’ve done so with distinction in the past…”
This raises a point that has concerned me for some time. Without naming names, I have noticed that some of the most distinguished “skeptics” are retired, older scientists who, I would suggest, formed rigid opinions years ago and simply stick with them, even though they have not really kept up with the science. This is indicated by their heavy use of personal scientific judgement, without bothering to address the data. If they are going to challenge the conclusions of their younger peers, they should follow the rules of the game. They seem to like the attention and recognition they can get without the pesky need of publishing peer reviewed papers. It is sad, but I am of an age where I can see how easy it would be to fall into this trap. In a totally different kind of setting, I sometimes find it necessary to simply bite my tongue and avoid the ramblings of an old fool riding a wave of the past.
In Reply to “I’ll start to take the idea seriously. I’m still waiting to see trends in anything related to GCR that could even have a prayer of giving the recent temperature pattern, and I’m still waiting to see a first-principles derivation of the magnitude and distribution of radiative forcing purportedly due to GCR. ]”
A) Trends in GCR vs Gobal Temperature
As noted in my comment 120, modulation of GCR is not the only means in which changes in the sun, can affect cloud cover. In comment 120 there is a link to Palle’s paper that provides satellite data that shows overall planetary cloud cover decreased at 0.0165%/yr from 1993 to 2001. How can you explain the reduction in clouds that Palle notes in that paper? Palle notes the reduction in clouds is consistent with Tinsley’s electroscavenging process (A link to Tinsley’s paper is attached in my comment 120). As noted in Palle’s paper there is a 99.5% correllation between variations to GCR and variations to cloud cover up until 1993. Starting in 1993, ions are removed by the electroscavenging process, thereby blocking the GCR process.
The increases to the electroscavenging process, is caused by an increase in global electric current. (See Tinsley and Yu’s paper which is attached in comment 120 for a diagram of the Global Electric Curcuit and a detailed explanation of the electroscavenging process.) The increase in the Global Electric Current is due the Solar south pole coronal hole moving towards the solar equator, at the end of each solar cycle. For example, the sun is currently spotless but the solar wind is high due to the coronal hole CH257. (I also included a link to the daily Solar Terrestrial report in my comment 120.)
Attached below is a link to a second Palle paper that provides data from observing the shine of the earth on the moon, to measure planetary albedo. The earthshine data, confirms cloud cover was reduced in the 1993 to 2001 period, which supports the satellite data. Palle converts the reduction in cloud cover to a warming of 7.5 W/m3 +/- 2.4 as compared to the estimate for CO2 warming of 2.5 W/m2.
http://solar.njit.edu/preprints/palle1266.pdf
The proxy climatic record provides evidence of a multitude of global warmings followed by global coolings. Electroscavenging appears to be the warming mechanism. When the solar forcing function that is increasing the Global Electric Current is complete, a Maunder like minimum follows. The solar sunspot cycle is then interrupted, which causes an increase in GCR which causes an increase in cloud cover. An increase in GCR also changes cloud macroproperties. An increase in GCR increases cloud albedo.
[Response: You’re still going around in circles, and not listening to the argument. GCR is supposed to be the forcing function, but there’s no demonstrated trend in that. Even if the earthshine analysis proves correct (there are many questions about that), at most it would have shown there is a possible correlation of cloudiness (high clouds? Low clouds? you don’t know) to solar cycle. You still wouldn’t know if this is GCR, or simply a response of cloudiness to the known effect of the short term solar cycle on temperature. You still wouldn’t have the physically demontrated quantified link between GCR and cloudiness. And you still have no trend. If, in another hundred years, all the gaps are filled, at best you’d have a theory for GCR modulating solar cycle surface temperature fluctuations. Not a theory of global warming. And besides that, it’s just alchemy to think you can throw out physics that is known and established, like the effect of CO2 on the radiation budget. That’s just not in dispute, and if you want to spin some wheels about water vapor feedback you’ve got to explain why a stabilizing water vapor feedback fails to stabilize your precious GCR idea. Gavin is a very charitable man. He thinks maybe the GCR crowd are at the point that Tyndall was at with CO2 a bit over a century ago. Sometimes I think the GCR people are more like Paracelsus groping for the philosophers’ stone — and not because they’re dumb but because, for some reason, they’re wasting their time trying to disprove global warming rather than doing the really interesting things they could do to test their theory. –raypierre]
I find one claim of the blog to be quite disturbing:
“Even if the evidence for solar forcing were legitimate, any bizarre calculus that takes evidence for solar forcing of climate as evidence against greenhouse gases for current climate change is simply wrong.”
According to James Hansen the climate sensitivity employed by the models (0.5-1.0 C/W/m2) derives its claim to empirical legitimacy from the ice ages. This entire argument rests on the assumption on the notion that the sun does not vary in forcing over the course of the ice ages, neither directly nor indirectly through the svensmark effect. However, there is now empirical evidence that the sun itself does indeed vary and correlate strongly with the ice ages. This completely undermines the primary empirical evidence supporting a high climate sensitivity.
It’s quite simple: if there is a hitherto unknown forcing causing the ice ages, it follows quite obviously that greenhouse gases account for less of the warming than previously assumed. This argument seems quite straightforward. Please tell me why it is “simply wrong.”
[Response: It isn’t ‘simply wrong’. If there was an additional forcing that just happened to be correlated with precessional, obliquity and eccentricity cycles (all of them, mind you) that was quantifiable and significant, that would lead to a re-evaluation of the ice age evidence for climate sensitivity – (while other lines of evidence would still be valid), though not of the attribution of current changes to GHGs. However, there is a significant hurdle to demonstrating that such a forcing exists – principally you would have to show that there was no way that the causation was the other way around. That is, if you found a solar proxy that was correlated to the ice ages, you’d need to demonstrate that that the recording of that proxy was indpendent of climate itself. That is clearly not the case for any exisiting solar proxy, and the extremely low probability that solar variability would be correlated with the Earth’s orbital features (why? how?) makes it pretty clear that this is a very long shot indeed. But, in science, it is difficult to ever rule anything out completely and so the possibilty exists. But as we’ve said before, for the current changes the largest forcing is from greenhouse gases – so whatever the sensitivity, the attribution for today doesn’t change. – gavin]
Dear Gavin,
The link you give in 147 doesn’t work for me.
[fixed. – gavin]
Dear John A (148),
Why does ‘your side’ dump many hours and dollars into PR rather than into experiments that would address your questions?
Hi chaps,
I just had to put the cosmic ray data from the Colorado Climax station into an spreadsheet. The resultant pdf graph is year versus the monthly mean and can be found here:-
http://putstuff.putfile.com/49019/4869140
Hope the link works – first time I’ve done this.
And as can be seen there’s no upward trend. Maybe a bit of a cycle. 11 year solar? I think the Times and the Telegraph owe us each a retraction, an apology and $10,000 plus expenses.
As my mate said anything is linear if you use a log-log scale and a thick marker pen!
Keep up the good work.
I have just noticed that in the extension of the Willson and Mordinov (ACRIM-) composite data set of TSI the previously reported trend of minima has vanished. While there has been reported a trend of +0.037% between minimas of cycle 21 and 22, the trend between minimas of cycles 21 to 23 is now a tiny 0.004%, and we have still not passed the minimum of cycle 23. See http://www.acrim.com/ACRIM%20Composite%20Graphics.htm
Thus there is no data set anymore showing any significant trend of TSI over the last three decades. One more argument for solar induced warming over the last decades gone to Nirwana…
I’m sorry but I’ll have to submit Gavin’s usual misdirections to examination:
[Response: Actually, we are all sorry. ]
Not an answer. Does your reality include a feedback that precedes the cause by several centuries every time? Mine doesn’t. The concept of feedback still requires in climate terms THAT CARBON DIOXIDE RISE SHOULD PRECEDE TEMPERATURE RISE. Except that it doesn’t. Furthermore the witness of the icecores shows that carbon dioxide continues to rise for several centuries AFTER temperatures have begun to fall. What kind of feedback is that?
[Response: Let me spell it out slowly. M i l a n k ov i t c h f or c i n g s lead to changes in temperature and circulation which affect CO2 and CH4 which then helps make it colder. It’s really not that complicated. But you are trying to insinuate that CO2 rises now are not anthropogenic – they are, and no amount of your posturing changes that. ]
[edit]
Svensmark has experimental evidence. A direct experiment showing how cosmic rays seed clouds in all depths of the atmosphere. A reproducible experiment which will shortly be reproduced. And the Greenhouse hypothesis has?
[Response: What part of the above sentence is unclear to you? Possibly you should try reading Tyndall’s paper. Laboratory experiments showing that CO2 is a greenhouse gas have been reproduced thousands of times and are clearly documented the HITRAN database. To deny this is blindness of the highest order.]
Here we come back to the bizarre calculus of greenhouse modelling: A prediction is supposed to explain a FUTURE event, whereas greenhouse modelling predicts what has already happened.
So we’ll take those “evidences” in turn:
“Stratospheric cooling”: so does the solar hypothesis
“surface and troposphere warming”: so does the solar hypothesis
“Arctic polar amplification”: There isn’t any. See Polyakov et al, 2004 – so Greenhouse Warming produces a failed prediction. The Arctic is warming well within the natural variation
“water vapour increases”: so does the solar hypothesis
“increased precipitation intensity, more positive phases of the annular modes, decreased TOA flux at CO2 absorption lines, increased ocean heat content etc. etc” so does the solar hypothesis.
Greenhouse warming also predicts polar amplification in the Antarctic, except that the Antarctic is cooling (rather severely in places like the Dry Valleys) and not warming at all except in the area most exposed to ocean currents with attendant collapses in floating ice sheets that are downstream of an active undersea volcano. It predicts that the Southern Hemisphere should be warming (nope). It predicts (after the fact) that hurricane seasons will have more storms being forced by the increasing greenhouse gases – except that the distribution of hurricanes follows a Poisson distribution indicating that there is no trend: its a random process. It even managed to predict a slowdown in the North Atlantic Drift, whose apparent confirmation by a single measurement was rather shortlived when much longer measurements showed the natural variation of that oceanic phenomenon – no slowdown of the Gulf Stream at all.
Greenhouse hypothesis predicts (in the sense of “explains after the fact”) many things including warming, cooling, less precipitation, more precipitation, less storminess, more storminess and so on. It “predicts” everything which means that it isn’t a scientific theory in the sense of any prediction that can be falsified.
As I said, Greenhouse Theory appears to be unable to predict (as in the future) any phenomenon in any reasonable timeframe. It can’t even predict the next El Nino, but it does appear to be the perfect explanation after the fact. Such a flexible theory cannot be falsified. It has failed to predict any phenomenon uniquely compared to other hypotheses but it has made predictions which have failed to come about.
[Response: Errr… where to start? Well, let’s take stratospheric cooling. Not only was this predicted as a function of greenhouse gas increases in the 1960s (Manabe and Weatherald, 1967) (years before it was observed), but all solar forcing increases would lead to a warmer stratosphere (through increased absorption by ozone). Your claims otherwise are without foundation. The rest of your claims for the ‘solar hypothesis’ fail at every turn because there is no trend in current solar forcing and thus no prediction or hindcast to show anything. And since that line of attack is worthless, you then bring up a bunch of other items that are equally bizarre – Antarctic peninsula is warming because of an undersea volcano? CO2 isn’t a forcing because it doesn’t predict El Nino? Because hurricanes follow a statistical distribution they can’t have a trend? This is nonsense (as you well know).
To paraphrase Eric Idle – arguments should be a series of statements designed to support a contrary statement, not the automatic gainsay of anything anyone else says. To which you’ll no doubt reply ‘No it isn’t’. If instead you were a serious person, you’d move on from these tired talking points and discuss more interesting uncertainties – I won’t hold my breath. I only have 5 minutes for this, not the full half hour. -gavin]
With regard to GCR theories (#154). Assume that they are correct and significant. Since cloud nucleation increases, this moves water from the vapor phase into aerosols and increases the rate of precipitation which decreases relative humidity. Unobserved.
[Response:Far be it for me to support our reality-challenged friends, but I doubt this would be a noticeable effect. Changes in cloud nucleation can have very different effects on precipitation depending on exactly what happens – more nuclei can reduce average droplet size and make it harder for raindrops to form for instance. Also, the amount of water in vapour compared to condensate is so large that it is very difficult to make a change large enough to effect realtive humidity. I think a better line would be the prediction of increased cloud in areas of low natural aerosol content where you would expect such an effect to be more important. Also not observed. -gavin]
I have just attended a seminar by Mike Lockwood from the Rutherford labs in the UK. He specialises in Solar activity and links to Earth. He set out the ways in which the variations in Solar activity can influence our climate, via increases in radiance and in modulation of GCR.
He then showed analysis of variation in solar activity, this rose to a maximum in around 1985, then declined. Overlaying this on the constant rise in Earth global mean temperature, his conclusions where that whilst there are now fairly good paleo records correlated with Solar activity, there is no correlation between current warming and solar activity. In fact taking solar activity into account in climate models ( I think he reffered t the HADCM3 model) increased the sensitivity of the models to anthropogenic forcing.
[pointless verbiage deleted]
[Response: Sorry to be abrupt, but the endless recycling of strawmen arguments, fake ‘predictions’ and complete inability to apply a little logic to your thinking makes any dialogue almost impossible. There are ways to be sceptical and to engage constructively (Charles Muller, Ferdinand Englebeen are two good examples) and people learn from those exchanges. But it requires a certain detachment and a willingness to refrain from questioning the motives and credibility of your interlocutors. Leave the conspiracy theories at home – We’re just not interested. gavin]
Re: 161 and “influence the earth”
Is there a estimated amount of influence that’s being bandied about? There’s a calculation of so much W/m^-2 for CO2, for methane, for soot, for aerosols, etc. If there isn’t an actual multiplier associated with GCR, shouldn’t its adherents have a bit of wit and hold their fire until they come up with one?
Re #155
Gavin,
first of all, your argument about correlation/causality applies equally well to greenhouse gases and the ice ages. We know for a fact, that 1) warming causes oceans to degas, thereby causing a strong correlation between temperature and CO2, and 2) greenhouse gases lag temperature by 4-800 years thereby relegating them at most to an intensifier of existing climate change. In an unbiased science greenhouse gas correlations and solar correlations would be on an equal footing.
[Response: Of course. If the only evidence was the correlation that would not be sufficient. It’s the fact that the physical properties of ice sheets, greenhouse gases and vegetation changes do a good job at explaining the temperature and climate changes over the ice age cycles. -gavin]
Second, the work by Mukul Sharma (2002) makes a strong case through spectral analysis that the correlation is not spurious.
[Response: Not a strong case at all. Read Bard and Franks, EPSL, 2006. Sharma’s records are almost certainly contaminated by climate changes (read Field et al, 2006, JGR) to see how that might happen. -gavin]
Third, Milankovitch theory is debunked. There is the 100 ky problem, the 400 ky problem, the unsplit peak problem, the stage 5 problem, the causality problem and the transition problem, all mounting to a thorough rejection of the theory as the driver of ice ages. Notice that the unsplit peak problem indeed shows that the eccentricity cycle is spurious. Spectral analysis of the o18 temperature proxy shows one single very sharp peak at 100 ky. This 1) is evidence against eccentricity which has TWO peaks at 95 and 120 ky respectively, and 2) is evidence for another forcing of astronomical origin. Only an external forcing could possibly create a clockwork clean peak 100 ky temperature cycle, and it’s not the weak eccentricity cycle(s).
[Response:Milankovitch is not debunked. It’s not perfect (nor complete), but the predictions from these forcings are so well correlated with observed changes, that it is inconceivable that they are not linked – see Roe (2007) for instance. -gavin]
[Response:The idea that the 100 kyr glacial oscillations represents a simple linear response to Milankovitch forcing is a ‘straw man’ that was discarded long ago. It is well known (e.g. the work of Saltzman and many others over the past 20 years) that a proper explanation requires, at a minimum, the model of a non-linear dynamical system that can exhibit free oscillations, but which is paced by weak Milankovitch external forcing. I myself would not point you to the specialist literature, but instead would refer you to the intro textbooks (e.g. Ruddiman’s “Earth’s Climate: Past and Future) for a basic discussion that will bring you a bit more up to speed on this. -mike]
Fourth, why on earth couldn’t the Milankovitch cycles be correlated with solar cycles? We know for a fact that the 11-year sunspot cycle is strongly correlated with the planetary motions, strongly suggesting some kind of interplanetary resonance/synchronization effect. We know that two grandfather clocks that are placed in proximity will tend to become synchronized if the pendulum motion is sufficiently similar in frequency. Why not something similar with planetary motions wobbling the sun?
[Response:If the dominant solar variability was going to be affected by planetary motions (for which no evidence exists), they would not be those of the Earth. If that were the case, climate on Earth would respond to the orbital parameters for Jupiter. They don’t. -gavin]
Fifth, as it happens renowned astrophysicist Robert Erlich has modelled variations in the sun showing the existence of oscillations that could explain both the 100 ky and 41 ky solar cycle.
http://pressesc.com/01169672696_
[Response: He has (potentially) shown that those frequencies may exist in solar osciallations – that is not the same as showing that they exist or that they are correlated to known orbital or climatic changes. -gavin]
Re #154
Raypierre,
you’re throwing the baby out with the bathwater here. It is perfectly possible for the observed climate change since 1940 to have been caused by something other than the sun. One possibility is increased greenhouse gases. (and another intriguing possibility is bad surface temperature reconstruction creating spurious warming) Now, as Richard Lindzen has shown, even if all the warming since 1950 is caused by increased greenhouse gases this does not in any way validate high climate sensitivities. In fact, it is perfectly consistent with a low climate sensitivity of only 0.5 C per doubling.
In other words, if cosmic rays/the sun has caused 50% of the warming in the 20. century then *obviously* climate sensitivity for greenhouse gases must be lower.
# Gavin, 159 comment
“Well, let’s take stratospheric cooling. Not only was this predicted as a function of greenhouse gas increases in the 1960s (Manabe and Weatherald, 1967) (years before it was observed), but all solar forcing increases would lead to a warmer stratosphere (through increased absorption by ozone).”
Sorry to insist, but if you look at HadAT2 and MSU T4 (RSS or UAH) graphs for lower stratosphere, you observe : a sustained cooling from 1979 to 1995 (except El Chichon and Pinatubo), no trend from 1995 to 2006.
How do you explain the later point from model prediction ? IPCC SPM explained us that GHGs forcing rose by 20% during the last decade, we can reasonably think that water vapour feeback also happened in this warmest decade of instrumental records (Soden 2005)… so, for what physical reason should we expect this 11 or 12 years pause in place of a more pronounced slope toward cooler stratosphere ?
[Response:The lower stratosphere trends from the MSU4 are mostly related to ozone depletion, not greenhouse gases. GHG related cooling occurs higher up (see https://www.realclimate.org/index.php/archives/2006/11/the-sky-is-falling/ and references there, also http://www.atmos.colostate.edu/ao/ThompsonPapers/ThompsonSolomon.pdf ). -gavin]
In Reply to [Response: You make a good point, different timescales must be treated differently, and then you blow it by suggesting that correlations over the hundred million year timescale have relevance to the last few decades (even assuming that their analysis was valid, which I would not- see http://pubs.giss.nasa.gov/abstracts/2004/Rahmstorf_etal.html ).
It is only fair to include Shaviv’s and Veizer’s response and defence of their paper, “Cosmic Rays, Carbon Dioxide, and Climate” to Rahmstorf’s attack.
http://arxiv.org/pdf/physics/0409123
From Shaviv’s and Veizer’s above response to Rahmstorf’s attack”
“The estimated 1.4 +/- 0.4 W/m2 of warming attributable to the increased solar luminosity and reduced galactic ray flux since 1990 should therefore have contributed about 0.32 +/- 0.11C or roughly half of the observed global warming. …(My comment: Shaviv does not include the significant reduction in cloud levels from 1993 to 2001, which would further increase the portion of 20th century warming that is attributable to solar changes.)… The low sensitivity obtained over different time scales is clearly below the large range obtained in the Global Circulation Models (GCM). This implies that a) Earth has shown us that the GCMs do not predicted sensitivity accurately (This is most likely because of our poor understanding of cloud feedback (Cess et al 1989)
It seems they have a scientific response to each of Rahmstorf’s questions.
[Response: I’m puzzled as to how this article constitutes a response to the Rahmstorf et al (2004) article when it doesn’t even reference it. It certainly does not address the main criticisms raised by Rahmstorf et al. – mike]
In reply to “Response: I’m puzzled as to how this article constitutes a response to the Rahmstorf et al (2004) article when it doesn’t even reference it. It certainly does not address the main criticisms raised by Rahmstorf et al.”
Sorry the above was a link to the paper, Rahmstorf is criticising. The following is Shaviv and Veizer�s detailed response to Rahmstorf et al criticism.
http://www.phys.huji.ac.il/~shaviv/ClimateDebate/RahmstorfDebate.pdf
[Response: This link is just a self-published thing on Shaviv’s web site, and has not been subjected to any kind of peer review. It would be fairer to refer to the arguments that actually made it into EOS. But leaving that aside, readers should be properly skeptical of just deciding an issue based on who had the last word. Editors always allow a comment/response format that allows both sides to get their two cents in, with some basic screening for respectability of the arguments. Just as on RealClimate, the lack of a further response does not mean the other side has caved in. You have to read the articles and responses, understand the arguments, and draw your conclusions. I’m sure Mr. Astley will can do this and declare that Shaviv has “won,” but among all climate scientists I know who have a publication record and have real accomplishments, those who have looked over Rahmstorf (or Damon and Laut) and the responses are of the mind that the criticisms of the GCR idea as applied by its main proponents are devastating and fatal. There are really only two alternatives to forming an opinion on something like this. Either you have to read the arguments to the point where you can understand them yourself, or you have to know who to trust. –raypierre]
Re #164,
Gavin & Mike,
it requires a stretch of the wildest imagination to make the 95,120,400 ky behave like a sharp 100 ky cycle. See Muller and MacDonald for a refutation:
http://muller.lbl.gov/papers/nature.html
Appealing to nonlinear dynamics is the classic modelling trump card again. Essentially you are claiming that the climate is behaving like a filter that removes the 400 ky variation and dramatically amplifies the 95/120 into a sharp 100 ky cycle. That’s a neat story but where is the evidence for it? All you have is a model reconstruction tweaked in such a way as to behave like a filter that gives exactly this outcome. As the world’s best and foremost modellers (the statistical modellers in economics) can tell you, it’s extremely easy to overfit a model to fit the data with surprisingly few degrees of freedom. This truth of stock markets is most certainly also true in climate.
I do however agree that there can be no question about the *link* between the climate and the milankovitch cycles (particularly the precession and obliquity cycles). The clockwork regularity of the ice ages means that there *must* be an external forcing of astronomical origin causing them. It is just unclear at the moment what this link is and what the causal factors involved are. Muller and MacDonald have shown that for some weird reason the 100.000 year cycle perfectly matches the orbital *inclination* cycle of the Earth, both in terms of phase and frequency. That’s also another freaky coincidence. The only problem is that the orbital inclination does not in any way influence the insolation of the sun. If this cycle is the culprit then it is likely related to the grandfather clock effect: what is causing the Earths inclination to wobble at 100 ky is also causing the sun to do the same.
Also, you say that the sun does not respond to Jupiter’s planetary motions, but that is simply wrong. In fact, Jupiter’s orbit is 11,86 years, very close to the 11 year solar cycle. The sun’s most prominent cycle is highly correlated to the motions of the planets, including Jupiter. It is worth noting though, that the influence of the planets are nontrivial. The influence appears to be related to the frequency of syzygies, i.e. planetary *alignments* towards the sun. During these alignments the gravitational forces of the planets synergize in a way that may modulate the sun. Traditionally this line of reasoning has been discarded because it is believed that the modulation factor is far too small to have any real impact on the sun. But the primary finding in Erlich’s paper is the identification of feedbacks that are capable of dramatically amplifying internal variations and causing oscillations in the sun’s activity level. Well, what do you get if you hit the resonance frequency of a naturally oscillating system? You get a standing wave. As bridge constructors have experienced so bitterly the tiny forces of the wind is sufficient to break the bridge at just the right speed. The fact that the sun is so cyclic combined with the strong correlations with planetary motions is more than a strong suggestion that the sun varies at longer time scales via similar mechanisms.
Onar,
Muller and MacDonald have an interesting theory; it might even be correct, but I doubt it. For one thing, the paleoclimate response at 100,000 years does not match the inclination cycle as well as they suggest. They base their results on sediment core data from ODP 607 and the SPECMAP stack. But other records don’t show anywhere near such straightforward response. They select their data based on the incorrect statement that other records are “tuned” to the eccentricity cycle, when in fact, orbital tuning is usually done to obliquity or precession cycles, or the 65N insolation, which is not significantly affected by eccentricity.
More important, the inclination theory of M&M doesn’t match the evolution of the instantaneous period of glaciations over the late Pleistocene. Wavelet analysis shows clearly that the period of this “cycle” has increased over the last 600,000 years, in a manner which matches extremely well the changing period of the eccentricity cycle, but does not match the inclination cycle.
You don’t even seem to understand Muller & MacDonald’s theory very well. They don’t attribute its impact to the “grandfather clock effect” causing the sun to change, their primary suggested mechanism is an increase in interplanetary dust accumulation due to longer time spent near the solar system’s invariable plane.
You also seem to be under the misapprehension that paleoclimate scientists attribute large-scale glacial changes since the mid-Pleistocene transition to eccentricity forcing. This hasn’t been true for some time now, which is why nonlinear phase locking, stochastic response, “cycle skipping” of obliquity forcing, and freshwater-induced deep-water overturning (the subject of the post) are current ideas for the cause of glacial terminations. New developments might actually put eccentricity back on the map, but at the moment, you’re trying to dispel what is not part of the concensus view.
As for your offhand dismissal of nonlinear dynamics, do you really believe that glacial response to astronomical forcing is linear? If so, you are the only one. Nonlinear response is not “the classic modelling trump card,” it’s what is indicated both by the complexity of ice sheet dynamics and by the data. Appealing to the “grandfather clock effect” to argue for cyclic solar variations in response to earth’s orbital configuration — now that is some serious hand-waving.
Re #169: Onar — If you actually look at the data, the just completed ice age lasted for about 120,000 years. Similarly for the one before that. But the one just previous seems to have only lasted for 80,000 years…
Re #171, #170
David,
take a look at this correlation. Clearly there is a 100.000 year period in the ice age data:
http://muller.lbl.gov/papers/scicorr.htm
Tamino,
I understand Muller and MacDonald’s theory quite well, thank you. Their preferred explanation for the correlation was dust in the interplanetary plane, causing cloud formation and therefore cooling. This explanation failed, though, but this does not rule out a grandfather clock effect, which is a different mechanism entirely.
The grandfather clock effect is not hand-waving. Correlations between planetary motions and solar activity has been well-established for years. It is also well-established that the sun varies at many different time scales, well-documented and undisputed up to at least the millenial time scale. Why is it such a stretch of the imagination to assume 1) that these cycles are quasi-modulated by the planets and 2) that there are solar cycles at larger time scales as well? This is no more handwaving than the claim that the feedbacks in climate must be strongly positive due to the strong fluctuations of the ice ages. We could equally well argue that there must be strong positive feedbacks in the sun amplifying the weak gravitational (and/or electromagnetic) modulation of the planets.
Re #172: I don’t recall hearing about any bump (up or down) in the solar data in association with the very well-observed planetary alignment of 20 or 30 years ago. I think the grandfather clock idea is toast in the face of that.
FYI, Muller abandoned the M&M hypothesis some years back.
Hmm:
“GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L04701, doi:10.1029/2006GL028083, 2007
“Arguments against a physical long-term trend in global ISCCP cloud amounts
“Amato T. Evan, Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin-Madison, Madison, Wisconsin, USA
“Andrew K. Heidinger, Office of Research and Applications, National Environmental Satellite, Data, and Information Service, NOAA, Madison, Wisconsin, USA
“Daniel J. Vimont, Department of Atmospheric Science, University of Wisconsin-Madison, Madison, Wisconsin, USA
“Abstract: The International Satellite Cloud Climatology Project (ISCCP) multi-decadal record of cloudiness exhibits a well-known global decrease in cloud amounts. This downward trend has recently been used to suggest widespread increases in surface solar heating, decreases in planetary albedo, and deficiencies in global climate models. Here we show that trends observed in the ISCCP data are satellite viewing geometry artifacts and are not related to physical changes in the atmosphere. Our results suggest that in its current form, the ISCCP data may not be appropriate for certain long-term global studies, especially those focused on trends.
“Received 11 September 2006; accepted 23 January 2007; published 17 February 2007.”
Gavin, I’d be very, very curious to know what the folks downstairs think about this.
[Response: I doubt they’ll be surprised. They’ve been poo-pooing the idea of significant trends in the ISCCP data for years. -gavin]
Re: #172
Not that I’ve ever heard of. What correlations are those? References, please.
[[even if all the warming since 1950 is caused by increased greenhouse gases this does not in any way validate high climate sensitivities. In fact, it is perfectly consistent with a low climate sensitivity of only 0.5 C per doubling.]]
No it isn’t. Show your work. Lindzen’s papers have been demolished by later papers. Climate sensitivity is around 3 K per CO2 doubling, 0.5 K isn’t even in the running.
[[In other words, if cosmic rays/the sun has caused 50% of the warming in the 20. century then *obviously* climate sensitivity for greenhouse gases must be lower. ]]
No, it’s not *obvious* at all. Climate forcings are independent and additive. There are positive forcings and negative forcings and they don’t generally influence one another. You’ve got a mental picture of the only effect of forcings being the 0.6 K rise since 1880. It’s more like a 1.2 K rise + a 1.5 K rise + a 0.3 K rise – a 1.2 K fall – a 1.2 K fall.
Re #175
Tamino,
a list of work done on planetary tides can be seen here:
http://perso.orange.fr/jpdesm/sunspots/sun2.html
Desmoulins himself have identified excellent correlations between Venus-Earth-Jupiter syzygies and the solar cycle:
http://perso.orange.fr/jpdesm/sunspots/sun_fig3.gif
The green curve is the amplitude of the VeEaJu Syzygies, whereas the red curve is the signed Wolf numbers. As you can see the correlation is good.
Everyone agrees that the influence by the planets on the sun is small, and this has normally been used to dismiss the correlations as spurious. But hey, if climate scientists can get away with appealing to nonlinear dynamics and amplifying, positive feedbacks, why not also in solar physics? The sun seems like a pretty likely candidate for funky nonlinear physics.
[[it requires a stretch of the wildest imagination to make the 95,120,400 ky behave like a sharp 100 ky cycle.]]
Get a graphing calculator, or write a graphing routine that can handle multiple functions at once. Create some random sine-wave functions and map them all. Then sum them and see what you get. You might be surprised.
Re: #177
Onar,
To quote Eric Cartman, “Weak. Totally weak.”
As the last entry in the list you referred to states:
In fact the evidence you reference to support your statement that “Correlations between planetary motions and solar activity has been well-established for years,” is so pathetic, it’s actually embarrassing.
Your claim has no more scientific credibility than alien abduction. Here’s my theory: you will accept uncritically any and all ideas, even those backed by the most flimsy evidence, or none at all, so long as it allows you to persist in your disbelief of global warming. But you refuse to accept the reality of nonlinear dynamics and amplifying feedbacks in the climate system. I can no longer take you seriously.
Tamino, allow me to put in a semi=good word for Onar. When he was posting on sci.environment, he was one of the few antis that engaged in rational discourse. Of course he was most often wrong, but what the heck
Onar, Perso’s page says “written in 1989, revised in 1990” and “making such simulations on a PC XT computer without floating point operator is not the ideal situation for making efficient and reliable program” — this is quite old work. Has anything more recent been published that confirms or extends this notion?
We’ve had a handful of spacecraft that should have detected an effect, if an alignment of planets allows say the magnetotail of Earth to reach as far as and somehow boost that of Mars, or whatever effect is supposed possible.
Not saying it isn’t so, but did this ever reach the level of publication and replication?
Re: Timeframes, GCR, and solar influence
The beryllium-10 downward trend over the 100-150 years clearly shows that the Sun has been more active than the previous centuries. I don’t see why there is any need to invoke GCR at all as mechanism to explain anything. Isn’t the simplest explanation simply that the solar constant has not been constant and that more radiation has been coming from the Sun in the last century than the previous centuries.
http://en.wikipedia.org/wiki/Image:Solar_Activity_Proxies.png
It is true that this trend levels off in the graph beginning in about 1950 in the above linked graph. This is completely in line with neutron counts and other satellite observations that have shown no significant change in solar output.
If we add together the warming effects of increased solar output with the GHG contribution and subtract the cooling effects of global dimming, wouldn’t we end up with warming in the early part of the twentieth century, followed by pauses in the warming, followed again by dramatic warming in the last decade or so as global dimming has reversed.
I find the position of some RC posters to discount the possibility of solar variation about as bad as the denialists who discount the influence of GHG.
We know the Sun’s output changes over an 11 year cycle. There is good reason to suspect a 1500 year cycle. Ehrich’s paper suggests a theoretical basis for a longer term 100K year cycle.
http://arxiv.org/abs/astro-ph/0701117
Of course, there are other influences too – the Milankovitch cycles and the CO2 feedback mechanisms – but it would seem to me to be narrow-minded to reject out of hand any possibility of solar cycles being involved in the ice ages.
Re #172: Onar — Sorry, but there is only a 100 ky band in the power spectral density, or cross-correlation. There is only about 2.5 My of data total, with the 100 ky band only appearing in the records for the last 0.9 My. So there is not enough data to resolve this band into more refined portions.
If there were, it is possible the band would resolve into an 80 ky band and a 120 ky band. There is at least one paper suggesting why this might be so.
one thing, how does weathering of rocks decreace carbon in the atmosphere?
[Response: In the presence of water, carbon dioxide reacts with minerals containing silicon (“silicates”) to form carbonates (loosely, “limestone”). The carbon goes from the air into the rocks. In the normal course of events, the rate of removal by this reaction is balanced by the rate at which CO2 is cooked out of limestone in the hot, deeper earth. There’s a good elementary description of this in Kump, Kasting and Crane’s textbook, “The Earth System,” available on Amazon. You can also have a look at David Archer’s new global warming textbook. –raypierre]
[[I find the position of some RC posters to discount the possibility of solar variation about as bad as the denialists who discount the influence of GHG. ]]
Of course Solar output varies. But it hasn’t varied significantly in the past 50 years or so, so it can’t be driving the sharp warming now. We’ve been measuring the Solar constant from satellites for decades now.
Is the argument that somewhere in the geological record are hidden the sort of very fast increase in CO2 and temperature we’re seeing right now? And that this is typical each time there’s a very tiny variation in the solar ‘constant’ like the one over the past few hundred years? So people are arguing that it’s that tiny change in the sun’s output, that has caused events like we’re experiencing now to happen, but then they’re not in the ice or sediment core record because they happened so-o-o-o briefly somehow, or were s-o-o-o quickly reversed by some other mysterious forcing? Just a blip in the layer of mud or snow but too bad, they didn’t find them so they _must_ be very temporary, wait another 30 years and it’ll cool off naturally?
It’s like assembling a jigsaw puzzle in which most of the pieces are hypothetical and the rest are improbable, eh?
The following is a new paper by Svensmark. What are your thoughts concerning the attached paper?
The Antarctic Climate Anomaly and GCR Svensmark�s 2006 Dec Paper
http://arxiv.org/pdf/physics/0612145
Svensmark’s paper concerns the Antarctic anomaly, which is also called the Polar see-saw. The Polar see-saw is the term used to describe the phenomena where when the Atlantic region warms the Antarctic cools and vice versa. While other hypothesis (such as ocean currents) have been proposed to explain the polar see-saw, they cannot explain why the change is simultaneous. (i.e. If the effect has due to ocean currents one would expect a delay from hemisphere to hemisphere, as the ocean currents take time to change) Svensmark’s paper provides data (bore hole temperatures, figure 1, and satellite data figure 2) and equations (paper (1)) to support his hypothesis that changes in global cloudiness is causing the polar see-saw.
[rest edited out]
[Response: Yet once again, we are faced with an exotic, highly speculative and frankly quite dubious solar mechanism to explain an observed phenomenon which already has a very plausible, physically proven mechanistic explanation (see our previous article “Antarctic Cooling, global warming?”). As we find many of the points about solar mechanisms continuing to be recycled even after we have responded to them many times, we’re going to be screening such comments out unless they introduce something that is truly new, to increase the “signal to noise” ratio of our discussion threads. -mike]
Re #186: I don’t see how that argument could hold water. In order for there to be some sort of blip in CO2 of magnitude anywhere comparable to the current increase, there’d first have to be someplace for the CO2 to come from, then there’d have to be a sink that would quickly remove the CO2 so that it doesn’t hang around for many thousands of years.
I don’t think there is any such source. The only possibilities I can think of that would even come remotely close are a super-Yellowstone scale volcanic eruption, or a large asteroid strike causing significant ocean heating & fires. Either of those would have left unmistakable evidence of its presence. And unless the real climate scientists have been hiding something, there’s nothing at all that would meet the requirement for a sink.
Re #179
“In fact the evidence you reference to support your statement that “Correlations between planetary motions and solar activity has been well-established for years,” is so pathetic, it’s actually embarrassing.”
But this is true. The *correlations* are well-established in peer reviewed literature. Identifying anything that resembles a plausible physical explanation has proved annoyingly elusive, however. Hence, the problems of constructing predictive schemes. We just don’t understand the sun very well, and the way the planets influence the sun — if they do — is non-trivial at best. I think it is quite likely that this matter will not be thoroughly resolved until a) we understand stellar physics better, and/or b) we have sufficient observational data from extrasolar planetary systems. We know that there are stars out there that vary considerably in strength and that some of them have orbiting planets. The more of these orbits and variations we map, the greater the chance is for finding a common denominator that eludes us when merely studying the sun.
[Response: Incorrect. Vague numerical coincidences have been reported in the literature. For instance, Jupiter’s annual cycle of 11.86 years is not in a constant phase relation to the quasi-11 year signal in sunspots – it is therefore much more likely to be a coincidence rather than fundamental. -gavin]
Notice that I completely agree with you that the evidence for a grandfather clock effect is flimsy at best. The reason I still emphasize this line of research is because I regard the evidence for strong positive feedbacks in climate equally flimsy. I have not seen any plausible explanation by any climate scientist why the current climate sensitivity should be 5-10 times greater than the *average* climate sensitivity. (i.e. total greenhouse warming divided by the total greenhouse effect) I would love to see one. Indeed, it would be great if any of the skilled climatologists here at RC could explain this.
[Response:It’s because you are not comparing like with like, I might do a post on this at some point but surface fluxes divided by surface temperature changes are not appropriate metrics. – gavin]
Until then a much more plausible explanation for me is that the empirically measured climate sensitivity of the ice ages are anomalously high, reflecting hitherto unidentified climate forcings that bring the ice age estimate down to all the other empirical estimates. One very obvious candidate for doing this is the sun. There ARE well-established and irrefutable correlations between the sun and the ice ages, and even though the direction of causality is currently disputed any reasonable, unbiased scientist *must* consider the strong possibility that the sun resolves the high climate sensitivity paradox.
[Response: There are not ‘well-established and irrefutable correlations’ between the iceages and solar activity. There have been reports of such correlations, but there are also significant problems with them (Bard and Frank, 2006). If you wish your arguments to be taken seriously, don’t spin the literature. -gavin]
I’d like to point to Nir Shaviv’s reasoning on climate sensitivity here:
http://www.sciencebits.com/OnClimateSensitivity
(see figure at the bottom)
Without a solar/cosmic ray effect the average climate sensitivity derived from a variety of independent data sets and time scales is 2+-0.5 C. (which interestingly enough is consistent with the lower end scale of the IPCC estimate) Notice, however, how the sensitivity varies wildly with temperature. Also notice how adding cosmic rays dramatically reduces the range of variation in the estimates. If cosmic rays were just any random signal added, we would have expected the variation in the estimates to *increase*. The fact that it significantly *decreases* strongly suggests that cosmic rays are non-random, i.e. that the correlation is not spurious.
[Response: Well, I would agree that Shaviv’s adjustments to the sensitivity calculations are non random. However, his estimates both for the radiative forcing due to GCR and the evidence of GCR changes are completely subjective and do not stand up to scrutiny. In particular his calcuations for the LGM are simply in error. Climate sensitivity from every properly done analysis gives a best estimate of near 3 deg C for a doubling. -gavin]
Re: 182. Jim, I’m afraid I may not understand your argument. Are you arguing for a direct solar forcing? The problem here is that this is easily measured–even with a black rock in placed in the sun. The change in insolation is simply not large enough to explain the observed effects. Moreover, it is not clear to me why a solar mechanism would not give larger effects at the tropics and smaller effects at the poles–the opposite of what we see. The rejection of insolation is based on empirical observation.
#166
Thanks for the answer and links, Gavin.
Thompson and Solomon 2005 find a strong tropical stratospheric cooling they consider as “…not evident in the simulated response to observed trends in ozone and well-mixed greenhouse gases at levels below 10 hPa. Additionally, increased concentrations of carbon dioxide favor relatively weak cooling in the tropical lower stratosphere, since increased emissivity acts on relatively low climatological mean temperatures there… ” So, they suggest in conclusion an adiabatic cooling by enhanced upwelling in the tropical stratosphere, but acknowledge themselves the speculative nature of their hypothesis.
For the first link (RC page and ESPERE page), trends are most often estimated for 1979-2000, where there’s a clear cooling, but not for the past decade or (1995-2006), the object of my question. Concerning the level of stratosphere where most cooling is expected because of GHGs specifically, it’s still hard for me to understand.
– GHGs absorb IR and trap heat in troposphere, and this first effect is maximum for GHGs trace in higher tropo and lower strato (where there’s not a lot of cooling in past 12 years)
– It’s unclear for me why the GHGs second effect mentioned on ESPERE (net loss of heat) should apply to 30-50 km level rather than 20-30 km level.
– In their recent report, Ramaswamy et al. 2006 analyzed the human/natural influence on lower stratosphere 12-22 km, not particularly trends in higher levels.
V. Ramaswamy et al. (2006), Anthropogenic and Natural Influences in the Evolution of Lower Stratospheric Cooling, Science, 311, 1138 – 1141.
http:// http://www.sciencemag.org/cgi/content/abstract/311/5764/1138
Svensmark’s theory seems to be taken seriously enough by CERN. They are conducting their own CLOUD experiments to find if there is a link between cosmic rays and cloud formation. First results are expected in the summer of 2007.
It will be interesting to see if Svensmark’s experiment will be replicated.
Press release:
http://press.web.cern.ch/press/PressReleases/Releases2006/PR14.06E.html
Re #189
Gavin,
As I have said previously the correlations are non-trivial. Jupiter is not the only planet in the solar system and it seems fairly obvious that if there is a real gravitational/electromagnetic planetary modulation effect then it involves ALL the planets, not just Jupiter. The orbital interactions of these planets are, to put it mildly, VERY complex. It is, however, worth noting that all the Milankovitch cycles are caused by precisely these planetary oscillations. According to Wikipedia:
“The Earth’s eccentricity varies primarily due to interactions with the gravitational fields of Jupiter and Saturn.”
Thus, if there indeed is a grandfather clock effect of gravitational/electromagnetic tides on the sun then there is every reason to expect this effect to be highly correlated with the Milankovitch cycles. Disentangling the solar and the orbital variations could therefore prove a highly complex task. The transition problem, the causality problem and the split peak problem are precisely the kind of effects we would expect if the Milankovitch cycles are merely secondary correlations to solar variations.
Now, of course, I’m not claiming massive evidence for this, but the strong climatic correlations to the Milankovitch cycles are not evidence *against* this theory due to the above mentioned possibility of strongly entangled orbital and solar correlations.
Think a moment what the implications of such a theory, should it prove right, really is: it means that our present understanding about climate change needs to be thoroughly revised. These implications are far too important for an objective scientist to ignore.
I am looking forward to an article refuting the low sensitivity calculations. A nice summary of the low sensitivity view is over at Junkscience:
http://www.junkscience.com/Greenhouse/What_Watt.htm
Addressing these would be nice. On Shaviv’s LGM figure I cannot comment. I don’t know exactly how he arrives at the figure, but I register that his estimate varies significantly from Hansen’s. Definitely worth scrutinizing.
Re #193: Onar, eccentricity is *one* of the Milankovitch cycles. The other two are obliquity and precession, which between them certainly dominate eccentricity and have little if any relationship to the motions of other planets. If there was a significant long-term irradiance signal of some kind thrown into the mix it would be hard to miss. Also, to repeat a point you didn’t answer above, a planetary effect on irradiance would have to be convoluted indeed for there to have been no noticable effect during the recent closely-observed planetary alignment.
Re #185
Barton did you actually read all of my post?
The fact that the solar output hasn’t changed in the last 50 years is in agreement with the Be-10 proxy. It is this same proxy that shows a sharp increase from the late nineteenth to mid-twentieth century and that shows solar activity at much higher (though flat) level of activity for the last 50 years than the previous several centuries.
[[Barton did you actually read all of my post?
The fact that the solar output hasn’t changed in the last 50 years is in agreement with the Be-10 proxy. It is this same proxy that shows a sharp increase from the late nineteenth to mid-twentieth century and that shows solar activity at much higher (though flat) level of activity for the last 50 years than the previous several centuries. ]]
Right, but you don’t seem to be seeing the implications. If Solar output was flat for the last 50 years, it can’t account for the exponential curve of temperature over the past 30 years.
Re #194
As I understand it the obliquity/precession is also influenced by gravitational tides. The moon certainly influences and stabilizes it.
As I also said previously, the planetary tides have very small effects on the sun, even during planetary alignments. Thus, if the grandfather clock is real, there is much more likely a subtle cumulative effect over several syzygies — a positive feedback of some kind that greatly amplifies the effect. I gave an example of such a correlation previously:
http://perso.orange.fr/jpdesm/sunspots/sun_fig3.gif
Notice here how there are typically around 6-7 syzygies during one solar cycle. One single planetary alignment doesn’t have much zap in it, but combined the cumulative effect og several in succession could modulate the oscillation of the sun.
Re #196
Why do expect that solar output has to increase to cause warming to increase? If you put a flame under a tea kettle, you don’t have to keep increasing the flame to cause the water to boil eventually. And where were the CO2 increases and decreases to explain the Medieval Warming or the Little Ice Age. CO2 changes do not explain the Medieval Warming or the Little Ice Age but these events do correlate well with solar output changes.
My point is that there are lag times and that also that global dimming moderated the solar influence. And I am not a single cause proponent. I think modern warming is caused by solar output increases and CO2 increases. With global dimming diminishing, both causes are now reasserting themselves.
Is it a coincidence that the warmest year in recent history was 1998 near the peak of the solar cycle? I would bet that the next 5-6 years leading to the next peak will be extremely warm and break previous records. However, I would also bet that the cycle following in the approximate 2015-2025 time period will be cooler than 2000-2010.
Re #198: “If you put a flame under a tea kettle, you don’t have to keep increasing the flame to cause the water to boil eventually.”
Think of the way that happens: if you turn on the heat, the kettle warms at a constant rate, not an increasing one. Likewise, if the sun’s output had increased prior to the start of satellite observations, then stayed constant since (as we know it has), we’d have seen a sharp temperature rise in the first half of the century, followed by a gradual tapering off as the new equilibrium was approached. Instead, we see just the opposite: warming that started slowly, but which keeps increasing.
“CO2 changes do not explain the Medieval Warming or the Little Ice Age…”
Of course. Try to understand this one simple idea: the present increase in CO2 due to humans doesn’t explain anything that has happened in the past, because it is something that has never happened before.
Re #198: “However, I would also bet that the cycle following in the approximate 2015-2025 time period will be cooler than 2000-2010.” Really? Then James Annan and Brian Schmidt would really like to hear from you! I’ll look forward to seeing the bets placed.