A call for EVIDENCE regarding human caused global warming

Yes, I understand the first accurate measurement of the solar magnetic field was recorded in the Domesday Book.
I believe they said “low, but rising.”

You are right, I was moving too fast, and I somehow ended up at the Santer et. al. Science paper and not the Soden et. al. Science paper. My apologies, mea culpa.

Regarding the Soden paper, whether or not the models can replicate one given part of the climate system is not the question. It’s whether they can replicate the whole climate. It is easy to tune a model to match one part of the climate or another, but to forecast climate, they have to match everything.

For example, in the same issue of Science, and commenting on the Soden paper, the editors pointed out here :

Of the 19 models listed, only 5 of them were within 25% of being correct on cloud forcing (CRF = cloud radiative forcing), and 5 of them were out by more than 100%. This is hardly a resounding vote of confidence in the models …

The point about theory is that any theory is unproven until it is supported by evidence. That’s why there is theoretical physics, and experimental physics. Experimental physics provides the evidence to prove or disprove the theories.

My point about the climate is that although it abounds with theories, evidence is very thin on the ground. I have asked for evidence, and have gotten theory …

The weather forecasts are often wrong. Should we not make them? No, but we should remember that as they look further ahead, their predictions get worse and worse. See, for example, the UK Met Office, which shows that for forecases 19-31 days out, they do scarcely better than chance. What does that mean about forecasts for next year, or decade, or century? You tell me …

Since you are a modeler, perhaps you can tell me what statistical tests you apply to the results of your model. For example, does it produce a similar standard deviation, skew, kurtosis, and IQR to the real world data?

Because I can assure you, the climate models don’t. Regardless of whether you think that models are reality (they aren’t, which is why physicists still do experiments), the climate models do not produce realistic, life-like results.

If you think they do, please point us to some citation for the fact that they do.

Of the 10,000 model results from the recent distributed computing climate model experiment, hundreds and hundreds of the results showed cooling.

Is this evidence the world will cool?

Of course not.

What would I consider evidence? Well, Mars seems to be coming out of an ice age and growing warmer. This, if confirmed, would be evidence that the inner planets are warming, and would support a natural explanation for the earth warming.

Recent studies of the effect of cosmic rays on the clouds are certainly evidence for a magnetic solar - earth weather connection, again supporting a natural source for the warming.

Evidence is what we garner from observation of the real world.

In the real world, the troposphere has not been warming (whether you take UAH or RSS data) as much as is predicted by the models. Which is evidence against the models.

In the real world, the South Pole is cooling. This again is evidence against the models.

The study I cited is not the only example of large scale swings in albedo. See Long-term global distribution of earth’s shortwave radiation budget at the top of atmosphere, N. Hatzianastassiou et. al., Atmos. Chem. Phys. Discuss., 4, 2671–2726, 2004 © European Geosciences Union 2004. This study shows a similar decline (they show 7 w/m2 vs 10 w/m2 in the earthshine study) over the same time period as the earthshine study.

The UAH data never showed long term cooling. It just didn’t warm as fast as the ground surface record … and still doesn’t. The corrections have all been minor, the last one only affecting the tropics. The disagreement with the surface record still exists.

Citing the realclimate web site as evidence is a tragic joke. I’ve tried a number of times to ask questions there, and they haven’t printed (or answered) my questions. They only answer the easy questions. Nor is this just my experience, it has happened to a number of people. Plus, they are apologists for Michael Manns behaviour.

Again, my call is for evidence. Anyone have some?



Originally Posted by intention

Since then, the solar magnetic field has strengthened, and at present is stronger than it has been in 1,000 years.

Bryan, thank you for posting. Your post inspired me to further research, which is a good thing.

I had said strongest in 1,000 years, based on the research by Solanki (The Head of the Max Planck Solar Institute) et. al. done in 2003 and published in Nature magazine. That research showed the current solar activity as being greater now than at any time in the last 1,000 years.

What I found was that the same research team has published again, extending the research out to 11,000 years ago. Their research shows that it has been 8,000 years since the the sun has as active as it is today.

There is a very comprehensive press release (I’m not a subscriber to “Nature”, no access to the paper) about this recent paper by Solanki et al available here. It contains illustrations and graphs from the paper. There is a solar hockeystick in the data … go figure. Take a look.

Again, my thanks for writing.


Ludovic, I appreciate your post.

I haven’t ever requested any “proof” as you seem to think. I’ve just asked for evidence. So far, there’s not been much evidence produced. I’ve read the cited references to the IPCC “Detection and Attribution” section … no evidence there, just computer models.


Sure, because weather is (as you noted) an extremely complicated turbulent non-linear system, and hence not very well understood theoretically.

However, we still have to make plans for future events that will be affected by the weather. So we take long-term weather forecasts into account when making those plans, even though we recognize that the forecasts aren’t reliable.

Similarly, we have to make decisions now about things that will affect our global climate in the future. Like it or not, we have to base those decisions partly on our current predictions about climate change, even though we recognize that those predictions don’t have the kind of certainty that we’d expect from predictions about, say, Newtonian mechanics.

What? Why would you assume that a warming trend for Mars, in addition to a warming trend for the earth, would necessarily constitute definite evidence that all the inner planets are warming? There could be lots of alternative explanations for seeing warming trends simultaneously on Mars and Earth.

You say you’re refusing to accept AGW (anthropogenic global warming, for any of our readers who’ve forgotten) interpretations of observational results unless the evidence is absolutely incontrovertibly solid in favor of them. In that case, you can’t go off half-cocked and just assume that a warming trend on Mars would necessarily imply a **non-**AGW interpretation, for which the models are also not very well understood.

As pointed out earlier, nobody has the kind of evidence that you’re demanding (unless your evidentiary standards are really as lax as they seem to be from your Mars example). You’re demanding from AGW climate models the same certainty and precision that we expect from other physical theories (like, say, Newtonian mechanics) that are far more clearly and fully understood than global climate. Climate is an extremely complicated turbulent non-linear system, and the current models aren’t good enough to give us certainty and precision on that scale.

But we don’t have the option of just shrugging and saying, as you seem to want to do, “Well, the evidence concerning the problem isn’t rock-solid, and therefore there’s no need for us to do anything about the problem.” From a scientific point of view, it’s irresponsible to pretend to certainty when we don’t have it; but from a policy point of view, it’s equally irresponsible to demand absolutely certain evidence on an incompletely-understood problem before attempting to do something about it.

By the way, just FYI, jshore has a doctorate in physics, so you don’t have to bother explaining to him the difference between theoretical and experimental physics or similarly basic concepts.

What, precisely, is the point of this thread? The OP at least talks as though he is considerably better read on this subject than the average member of this board. He certainly has access to scientific papers on the subject, therefore one presumes that if he really wanted to find evidence of human-caused global warming, he could have done so without resorting to asking for it on a general-interest message board. If he has not found such evidence in the peer-reviewed literature, why does he expect it to magically appear here?

I contend the OP already believes he knows the answer to his question, at least as he narrowly defines “evidence”. I do not believe he is actually looking for any real evidence of human-caused global warming, but that he is simply making a roundabout argument that in his view there is no such thing, and that therefore there is no justification for taking such steps as legislative action to curb carbon emissions.

So, seems more like a harangue, not really a debate. If what the OP really wants to argue is that there is no such thing as human-caused global warming, or that there is no reason to take any action that might reduce its effects, he should just go ahead and do so, without all the misdirection.

Well, maybe intention can explain his views on this basic evidence in favor of AGW, which is at least as good as the “evidence” for non-AGW that would be provided by a warming Mars.

  1. The earth is currently warming, and it has been warming especially rapidly in the last few decades.

  2. Human activity has drastically increased the concentration of CO2 in the atmosphere, particularly within the last few decades.

  3. Ice core observations extending back over half a million years show that Antarctic climate and greenhouse gases have been closely linked throughout this period.

This, to me, constitutes evidence that climate change is strongly dependent on atmospheric CO2 concentrations.

It’s not absolutely definitive evidence, and there are doubtless other possible explanations that could explain it. But it is evidence, at least by intention’s “warming Mars” standards.

However, the press release you link to acknowledges that there has been no increase in solar activity corresponding to the sharp rise in global temperature in the last 20 years or so:

Well, there are at least two possible explanations for a lack of response from a scientific commentary website. It could be that the respondents aren’t actually scrupulous and/or competent enough to answer the questions, or it could be that the questions aren’t intelligent and/or meaningful enough to be worth answering. At present, we don’t seem to have enough evidence about you or about www.realclimate.org to determine which explanation is the true one.

I note, however, that realclimate.org’s “about” page describes them as “a commentary site on climate science by working climate scientists” who aim “to provide a quick response to developing stories”. So there seems no reason to expect that they would “print questions” from correspondents who are’t working climate scientists, irrespective of the questions’ merit.

So let me get this straight; computer models are not acceptable (per the OP), but Norse Sagas are ok?

Where does it say that they “tuned” the model? My impression is they simply ran it in the mode where it is normally run. And, it is not like these models have oodles and oodles of free parameters (although they do have some parameters that are uncertain) so, no, it is not so easy to tune them to match many different aspects of climate.

Well, clouds are indeed a source of considerable uncertainty. However, it is worth noting that those different models that all have various degrees of correctness in how they model clouds still all predict considerable warming due to greenhouse gas emissions. So, it seems that the models are fairly robust in this regard.

One of the reasons why the models don’t have to be too perfect is that the simulations are generally run by running the models with and without the greenhouse gas forcing and then subtracting the difference, so you don’t have to do a particularly good job simulating everything as long as you don’t miss some sort of strong dependence on a change in greenhouse gas forcing.

That is why there is a whole field of study where the models are compared to past climate variations, checked against seasonal changes in climate, checked to see if their “noise” is similar to the “noise” in the real climate system, etc., etc. That is not to say it is a difficult problem when one has only one earth’s climate system to study. However, these same sort of difficulties are faced in other fields such as geology and biological evolution.

Okay…I’ll admit I brought up the weather analogy. However, I am sure that you are aware that there is a big difference between predicting weather and predicting climate. One means following a specific solution to a complicated set of PDEs whereas the other is just looking at average quantities. The forecasters now run ensembles with perturbed initial conditions in order to see how sensitive their solutions are to initial conditions. The same thing is often done in climate model simulations and although the solutions certainly differ in their wiggles, they tend to all predict similar results for the basic question of how much warming occurs with rise in greenhouse gases.

Well, the models are not perfect…but their results are realistic in a wide variety of ways. I’d recommend the IPCC report for references on this.

Because of the simplified coupling that they were using between the atmosphere and oceans (in order to run so many realizations), some of the runs (6 out of the 414 model versions) suffered from a known flaw in this and did lead to significant cooling but that these runs were clearly different easy to identify as physically unrealistic and eliminate. Once that is done, there are almost no models that show a sensitivity of less than 2 C for a doubling of CO2 and some show a sensitivity as high as 11 C. (Such a high sensitivity can probably be discounted on the basis of other evidence such as the glacial-interglacial cycles.) See here for the Nature article of their results.

Here is a piece on RealClimate (which, yes, I know you don’t like) discussing the supposed “global warming” on Mars. It concludes:

This whole thing also illustrates the very poor state of the science on the naysayer side of the global warming debate. Because, even if Mars were warming, given that its atmosphere is way way different than ours and that those who posit a sun-climate connection necessarily need to invoke some sort of exotic mechanism (like a dramatic effect on clouds) in order to have a prayer of making it work, it seems like it would be very unlikely that the same mechanism would work on Mars.

Give me a break! All we basically have on the sun-climate thing is people trying in vain to search for a correlation. When they find one, it tends to break down over the last 20-30 years and, plus, is often given without even an attempt to justify a mechanism. (See here.)

And then, they have to find a mechanism by which the known forcing due to greenhouse gases miraculously gets cancelled out once feedbacks are taken into account.

You seem to have two standards here:

If one is proposing that climate change is due to anthropogenic greenhouse gases, then it is not enough to show (e.g.) how the models can only reproduce the warming, the thermal structure of the oceans, etc. with currently understood estimates of forcings if one includes the greenhouse gas effects.

However, if one is proposing that climate change is due to natural causes, then you don’t have to show anything. You just come up with a few vague ideas or some correlation that seemed to at least hold until recently. You don’t have to model anything or show how the structure of the warming actually agrees with your mechanism.

I don’t think that is true. I believe the RSS data is pretty much right there with what the models predict for the lower troposphere warming relative to the surface warming. The UAH data is still a little off…but not much, particularly given the error bars in this. And, of course, the UAH data has been trending upward with time as it gets corrected.

Not really.

No…It did originally show cooling before they took the orbital decay of the satellites into account. And, the corrections have been significant and the remaining disagreement with the surface record is not that large…In fact, I think it is only very significant in the tropics and a recent assessment concluded that the remaining disagreement is most likely due to remaining errors in the reconstruction itself.

For a discussion on reconciling temperature trends in the lower atmosphere, see this draft report from the U.S. Climate Change Science Program. Note these conclusions iin the executive summary:

(bolding mine)

On the issue of Greenland’s Ice Cap:

The thickness of the center of a Continental Glacier is determined by the rate of deposition of new Ice. The total area and the thickness of the margins are determined by the rate of flow, and the rate of melt. A more energetic atmosphere (warmer earth) would, in all likelihood cause more snow to deposit in the colder central highlands of Greenland than would be deposited in a cooler atmosphere. The higher temperature would affect the overall plasticity and flow, and the rate of melt at near sea level.

On the beginnings of the warming period, and the role of human activity:

Deforestation begun in earnest in the northern hemisphere in the 1400’s would have a slow cumulative effect on the carbon cycle, including burning wood in the newly invented fireplaces and clearing forests for the newly planted fields. In addition, the gradual increase in root crops that were grown to adapt to the very cool spring and fall condition in the inhabited parts of Eurasia during the “little ice age” involve a far more thorough aeration of the soil, encouraging the formation of methane, and the release of soil gasses into the atmosphere. While trivial compared to fossil fuel use in the twentieth century, it represents an early beginning in continent wide, and even world wide anthropogenesis in the process of change in the atmosphere.

Hard data on the subject of temperature, and climate is just reaching its first century. That data deals almost exclusively with the northern hemisphere, and overwhelmingly with North America. (Family history buff, my grandfather installed the first recording systems in hundreds of locations for the US Weather Service, now the NOAA.) Prior to that, instrumentation was haphazard, where extant, which was pretty much none. Single source data for decades long periods simply did not exist until that collection system had had half a century to accumulate data. Even now, it is only a partial look at one century, which in climatology is single squint through a small peephole.

That said, the entire body of evidence does support the theory that climate is warming, and it is warming in the places that people inhabit more than in the places where there are no people. That first shot lands squarely in the target for anthropogenesis. It is of further note that there is no evidence that reducing greenhouse emissions would have no effect on climate. Even a warming trend with other causative factors would show some response to significant changes in the levels of the most important gasses. To posit that that change is more likely to have no effect, or cause more warming is ludicrous.


By the way, another source of information on some of the evidence for anthropogenic climate change is presented in this RealClimate posting (under the header To what extent is “Global Warming Theory” verified?). Note, for example, that the greenhouse gas mechanism can explain the observed simultaneous warming of the lower troposphere and cooling of the stratosphere, whereas I think that this is harder to do with a solar mechanism (certainly a direct one; I am not sure about one involving a cloud feedback).

Ummm … not really. I don’t really understand why people think the cosmic ray - solar magnetism - clouds relationship is unknown or unstudied. Additional known and studied mechanisms are solar UV changes affecting the atmosphere, as well as direct changes in the total solar irradiance. For examples of studies showing effects and mechanisms, see:

Marsh, N.D. and Svensmark, H. 2000. Low cloud properties influenced by cosmic rays. Physical Review Letters 85: 5004-5007.

G., N. Marsh, G.A. Kovaltsov, K. Mursula, and O.G. Gladysheva, Latitudinal dependence of low cloud amount on cosmic ray induced ionization, Geophys. Res. Lett.,

Marsh, N., and H. Svensmark, Galactic Cosmic ray and El Niño-Southern Oscillation trends in ISCCP-D2 low-cloud properties, J. Geophys. Res., 108(D6), AAC 6-1, doi:10.1029/2001JD001264, 2003.

Marsh, N., and H. Svensmark, Solar influence on earth’s climate, Space Sci. Rev., 107, 317-325, 2003.

Palle Bago, E. and Butler, C.J. 2000. The influence of cosmic rays on terrestrial clouds and global warming. Astronomy & Geophysics 41: 4.18-4.22.

Svensmark, H. and Friis-Christensen, E. 1997. Variation of cosmic ray flux and global cloud coverage - A missing link in solar-climate relationships. Journal of Atmospheric and Solar-Terrestrial Physics 59: 1225-1232.

Kniveton, D.R. and Todd, M.C. 2001. On the relationship of cosmic ray flux and precipitation. Geophysical Research Letters 28: 1527-1530.

Marsden, D. and Lingenfelter, R.E. 2003. Solar activity and cloud opacity variations: A modulated cosmic ray ionization model. Journal of the Atmospheric Sciences 60: 626-636.

Palle Bago, E. and Butler, C.J. 2000. The influence of cosmic rays on terrestrial clouds and global warming. Astronomy & Geophysics 41: 4.18-4.22.

Feynman, J. and Ruzmaikin, A. 1999. Modulation of cosmic ray precipitation related to climate. Geophysical Research Letters 26: 2057-2060.

Shaviv, N.J. and Veizer, J. 2003. Celestial driver of Phanerozoic climate? GSA Today 13 (7): 4-10.

Solanki, S.K., Schussler, M. and Fligge, M. 2000. Evolution of the sun’s large-scale magnetic field since the Maunder minimum. Nature 408: 445-447.

Svensmark, H. 1998. Influence of cosmic rays on Earth’s climate. Physical Review Letters 22: 5027-5030.

Marsden, D. and Lingenfelter, R.E. 2003. Solar activity and cloud opacity variations: A modulated cosmic ray ionization model. Journal of the Atmospheric Sciences 60: 626-636.

Pang, K.D. and Yau, K.K. 2002. Ancient observations link changes in sun’s brightness and earth’s climate. EOS, Transactions, American Geophysical Union 83: 481,489-490.

Hengyi Weng
Journal of Atmospheric and Solar-Terrestrial Physics. Volume 67, Issues 8-9 , May-June 2005, Pages 793-805 (Solar and Heliospheric Influences on the Earth’s Weather and Climate

Tourpali, K., Schuurmans, C.J.E., van Dorland, R., Steil, B. and Bruhl, C. 2003. Stratospheric and tropospheric response to enhanced solar UV radiation: A model study. Geophysical Research Letters 30: 10.1029/2002GL016650.

ZHEREBTSOV, G.A., V.A. Kovalenko and S.I. Molodykh, 2005. The physical mechanism of the solar variability influence on electrical and climatic characteristics of the troposphere. Advances in Space Research Vol. 35, No 8, pp. 1472-1479, August 2005

WANG, Yongjin et al., 2005. The Holocene Asian Monsoon: Links to Solar Changes and North Atlantic Climate. Science, Vol. 308, No 5723, pp. 854-857, May 6, 2005

TOURPALI, K., C. J. E. Schuurmans, R. van Dorland, B. Steil, C. Brühl, and E. Manzini, 2005. Solar cycle modulation of the Arctic Oscillation in a chemistry-climate model. Geophys. Res. Lett., 32, L17803, doi:10.1029/2005GL023509, September 3, 2005

You do realize that a volcanic erruptions also results in a lot of ash and debris scattered into the atmosphere and in the case of huge erruptions enough is sent into the atmosphere to block some sunlight.

Yes, there are a mish-mash of known and hypothesized mechanisms, some observed correlations over some time periods, etc. But, like I said, they haven’t come together to constitute any sort of quantitative explanation of how the current warming could be accounted by solar forcing.

The papers you link to illustrate that. Some of them don’t even try to address the issue of whether solar effects can account for the current warming. It is poor logic to claim that any paper that talks about solar forcing supports your idea that the current changes are due to that. Clearly, it is understood that the sun plays an important role in our climate…and it is also well-accepted, for example, that the ice age - interglacial oscillations over the last couple million years were triggered by various (Malinkovitch) oscillations in the earth’s orbit that affect solar insolation.

As another example, while “the jury is still out” on the proposed cosmic ray forcing mechanism of Svensmark, the observed trend in these cosmic rays doesn’t agree with the recently observed warming. (See here.) Here is another example of a widely-touted correlation between sunspot cycle and temperature which has broken down in the past ~25 years.

Also, while I think it is true that way back in time when there was much more volcanic activity, it could significantly effect the CO2 level, the contribution these days is very small…an average of <0.1 Gigatons of carbon per year as compared to 5.3 GT from fossil fuel burning. (I am not even sure you can see any signal in CO2 from the eruption of Mt. Pinatubo in 1991, for example…at least I can’t see it.) By contrast, it is well-understood and observed that such eruptions cause cooling because of their emission of aerosols, as you note. In fact, the response to this eruption has even been used to check on the climate sensitivity, specifically the climate models’ handling of the water vapor feedback.

Here are a couple of papers that critically analyze some of the claimed correlations between solar activity and climate:

P. Laut, Solar activity and terrestrial climate: an analysis of some purported correlations, J. Atmospheric and Solar-Terrestrial Physics 65, 801-812 (2003).

P. E. Damon and P. Laut, Pattern of Strange Errors Plagues Solar Activity and Terrestrial Climate Data, EOS 85, 370 (2004).

jshore, thanks for the references. The second one merely points out that one of the papers showing a climate/solar link contains errors in the post 1980 section.

The first one shows very good agreement between solar and climate until 1980, at which point the solar component disappears …

We have several choices regarding these papers. We can ascribe the change to:

  1. Solar influence on the planet abruptly disappearing in 1980 (extremely doubtful)

  2. CO2 having no influence until 1980, then suddenly dominating the solar influence. (extremely doubtful).

  3. Problems with the surface temperature record. (extremely probable, particularly given the widespread closing of rural temperature stations in the 1980s)

Regardless of the explanation of the post 1980 record, these papers support my argument that the sun has a huge influence on climate. Yes, they point out the post 1980 difference, but*** up until 1980, both papers show that 100% of the temperature changes can be explained by solar changes.***

However, none of this is particularly to the point of the thread, as it does not provide evidence for AGW. Instead, it shows that AGW is not necessary to explain climate changes up until 1980 at least …