A call for EVIDENCE regarding human caused global warming

Great Debates
1

Everyone’s going on about “The Earth is warming! The Earth is warming!” … and it is, you know. Overall, it has been warming since the depth of the “Little Ice Age” in about 1700. During the Little Ice Age, the Thames River in London regularly froze, and glaciers expanded to unheard of sizes, a few even over-running long settled villages.

Since then, the globe has been slowly warming, with a gradually reducing ice mass and a gradually increasing temperature.

Now, it is very likely that human actions were not responsible for both the Earth going into the Little Ice Age, and the Earth coming out of the Little Ice Age, because we’d have to blow hot and cold to do that.

And it is probable that human actions were not responsible for much of either cooling or warming from 1700-1900, since it was decades before a significant rise in CO2. So a majority of this three century rise (and the fall before it) is not due to humans, but is a natural temperature variation. What is causing it, then?

Most scientists agree that it is not a coincidence that the Sun was in what’s called the “Maunder Minimum” in the years around 1700. This was a time when there were no sunspots for a number of years. This time of solar magnetic quietness is thought to be associated with the cold temperatures, by means of a curious intermediary. This is the fact that cosmic rays, by striking molecules in the atmosphere, encourage cloud formation. When the sun is magnetically quiet, the cosmic rays are free to stream into the atmosphere, making the clouds that cool the planet. More cosmic rays means more clouds. More clouds reflect more sun, and the earth cools …

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

This stronger magnetism deflects the cosmic rays from the earth, causing less clouds, and allowing the sun to heat the earth. Thus, over time, the changes in the suns magnetic field have gradually increased the Earth’s temperature.

Now a current theory, called “AGW” for Anthropogenic (human caused) Global Warming, holds that in addition to the solar-caused warming, the earth is also being warmed by the increase in atmospheric CO2. Accordingly, the following questions arise

a) is it true that the increasing CO2 level is affecting the global mean temperature?, and

b) if so, how much?

People have made lots of claims about this, claiming that yes, this human caused warming is happening, at different numbers up to 4°C per CO2 doubling. But to my eye, there has been a great dearth of evidence on both sides, as to whether this is actually happening or not happening.

So my question is … what is the evidence that this is, or is not, happening?

Some notes and requests, with the aim of keeping the discussion focused on scientific evidence:

  1. Please, no ad hominem attacks. I don’t care who paid for the grant, Greenpeace or Mobil, don’t go there. I don’t care if the scientist has made mistakes in the past. Scientific evidence must be either corroborated or contradicted by other scientific evidence, not by an attack on the scientist’s motives, previous work, or associations. AD HOMINEM ATTACKS ARE NOT EVIDENCE!

  2. No derogatory name calling, no “Mr. Oil”, no “Greensheep”. No “denialists”, no “warmers”. There are three camps here, which I will call Human GW, Natural GW, and Agnostic GW. Human GW means those people who believe human caused warming exists and is measurable at the present time. Natural GW means those people who think the variations are mostly natural, with human caused variations being minimal. Agnostic GW means those who think there is not enough evidence to decide. I invite people to identify their position in their posts – do you think the warming is human caused or natural warming, or are you agnostic? Me, I’m an agnostic regarding GW, because of the scarcity of evidence on either side, and the tiny size of the signal.

I have called the categories Human, Natural, and Agnostic GW to avoid insult, because these terms have little emotional baggage. Please use these terms rather than “sceptic”, “deniers”, “warmers”, “those brain-dead fools on the other side”, etc. NO NAME CALLING, PLEASE BE POLITE!

  1. The Earth’s climate is an externally driven, chaotic, buffered, multi-stable, tera-watt scale, fully developed constructal heat engine running at optimal turbulence. It has both known and unknown internal and external forcings, feedbacks, interactions, teleconnections, natural periodicities, and resonances. It has five major systems (ocean, atmosphere, lithosphere, cryosphere, and biosphere), each of which interacts with all of the other systems and with itself, at all scales, and each of which has its own internal subsystems. Current crude computer models of this maddeningly complex heat engine are very, very far from being evidence. All they can tell us are the beliefs of the programmers. CLIMATE COMPUTER MODEL RESULTS ARE NOT EVIDENCE! (Actually, computer models of any kind are not evidence, but that’s a subject for its own thread …)

  2. Because of the aforementioned complexity of the climate system, theoretical formulations are not evidence. Yes, Arrhenius calculated that CO2 will raise the temperature of a theoretical thermally quiescent earth with a theoretical stable amosphere by an amount logarithmically related to CO2 increase … but that means nothing about what might happen in response to such a forcing change in an optimally turbulent terawatt scale planetary heat engine with unknown feedbacks.

For example, moonshine studies have shown that from 1985 to 1997, the albedo increased significantly. As a result, the solar forcing (sunlinght hitting the earth) dropped about by ten watts/m2. Calculations using IPCC forcing numbers say that this should have caused a 5° - 10° temperature drop. Obviously, this didn’t occur, that’s a huge temperature drop, ice age size.

Why didn’t the temperature fall from the drop in forcing? That change in forcing is the absolute size of almost three doublings of CO2. Why didn’t the temperature drop radically?

Not to put too fine a point on it, we don’t know … but obviously, it’s something in my aforementioned “known and unknown internal and external forcings, feedbacks, interactions, teleconnections, natural periodicities, and resonances” that has counteracted this huge change in solar forcing. Simplistic linear theories don’t work to analyse a giant, chaotic, turbulent heat engine like the Earth. THEORY IS NOT EVIDENCE!

  1. There are three main global mean temperature calculations, done by different groups of scientists, called GHCN, GISS, and HadCRUT. Since there are only a certain number of meteorological ground stations in the world, or in any given country or area, these three global mean temperatures are calculated from the same raw data.

Unfortunately … the GHCN, GISS, and HacCRUT temperatures don’t agree with each other. They disagree on trend, mean, and year-to-year variation. Which one is closest to the real world? We don’t know.

In part, this scientific disagreement is based on the bad quality of the raw data. Temperature stations are often poorly sited, and get moved. Quality of equipment varies wildly, from a glass thermometer read three times a day most days, to digital constant recording thermometers. Times of observation change. Missing data is the rule and not the exception. Dust and spiderwebs clog up the louvres of the Stephenson Screens. Elevations are not consistent. Cities grow up around the ground stations. A paved parking lot goes in upwind, and temperatures soar. The new observer always rounds down and not up. Because of these and many other factors, the quality of the ground station temperature record is very spotty, and is subject to human-created “heat islands”.

These local heat islands add an upward bias to temperature measurements. The effect of these heat islands has been “adjusted for” in the GISS, GHCN, and perhaps slightly in the HadCRUT temperature measurements. Unfortunately, it has been adjusted for in different ways in each case, yielding different results, and there is no general agreement on the proper way to deal with the heat island problem.

Finally, on average there is only one thermometer for every 85,000 square kilometres on land, and less at sea. This leaves vast areas totally unsampled, and degrades the overall accuracy of the mean temperature calculation. The three different groups account for this in different ways, and thus give differing results.

A rigorous independent review of the surface record is clearly overdue.

IF YOU ARE USING SURFACE TEMPS, CITE WHICH ONE (GISS, GHCN, or HadCRUT), AND BEAR IN MIND THE DATA PROBLEMS.

  1. Evidence is scientific studies, measurements, and logical and mathematical analyses of the real world. It is not a study of a virtual world. It is not a press release about a study. It is not someone’s comment about a study. It is the study itself. Please cite the study, with a link if it is available online, and where possible provide the abstract. Explain briefly and clearly what the study means, and whether it supports Human or Natural GW. PLEASE CITE, QUOTE, AND EXPLAIN.

  2. Logical arguments which are based on evidence, while not evidence themselves, can explore the implications of the situation. To do so, they need to be firmly grounded in the evidence, and be evidently true. BE CLEAR ABOUT YOUR LOGIC.

  3. Avoid words like “could”, “might”, “may”, and the like wherever possible. Yes, we could see 11°C warming in the next century, and we might see a new ice age starting next week, and pigs may fly … if you wish to explore uncertainty, please provide numbers. Weather forecasts are a good example. Rather than saying “it could rain today”, which means very little, they’ll say “A 30% chance of showers”. PUT NUMBERS ON UNCERTAINTY, AND ERROR BARS ON NUMBERS, WHEREVER POSSIBLE.

Since I’m the OP, guess I’ll start.

An Example of Scientific Evidence

Science Magazine, 11 November 2005:
Vol. 310. no. 5750, pp. 1013 - 1016
DOI: 10.1126/science.1115356

*Recent Ice-Sheet Growth in the Interior of Greenland
*Ola M. Johannessen, Kirill Khvorostovsky, Martin W. Miles, Leonid P. Bobylev

Recent Ice-Sheet Growth in the Interior of Greenland (must be a subscriber to Science)

ABSTRACT

What This Study Means

After this study came out in November, another study of recent glacier surging around the coast of Greenland was reported last week. That other new study received a lot of hype, saying that it shows that the ice cap is melting, sea levels will soon be up around our ears, and the rest of the usual “the world is melting” nonsense.

That study, however, needs to be read in conjunction with this one I reference above, which shows that despite the surging, the Greenland Ice Cap has been getting thicker over the same period.

Regardless of surging, since the ice cap is getting thicker, the Greenland Ice Cap must be gaining ice overall, not losing ice. Of course, the usual caveat applies, this is only a short record. But it does indicate that during the time of the recent surging, the amount of ice was constantly increasing. We can cancel the sea level alert, because at the moment, with the snow piling up on top, Greenland is actually lowering the sea level.

Does this support Human or Natural GW? Neither, directly. It is in fact what we would expect in a warming world, because more heat brings more evaporation, and more evaporation brings more snow and rain. It does indicate, however, that there is no “runaway” heating going on, as the Greenland Ice Cap is increasing, not melting.

An Example of a Logical Argument

I argue that the maximum size of any possible human-caused change to the climate must be small, near the limit of resolution. The reason is that if the change were large, we would have already found it in the record. The fact that it has not been found, despite fifteen years of extensive searching, indicates that it must be small.

To review: I’m not looking for evidence of global warming. The globe has been warming for 300 years.

I’m looking for evidence that humans have caused some part of that warming.

w.

2

A study finding the greenland ice cap is getting thicker in the interior in no way implies it is getting larger, if it is also losing surface area at the edges.

3

Actually, there’s four camps, those who believe in natural causes, those who believe that humans have caused it, those who are agnostic and those, like me, who believe it’s both natural and human in nature.

4

Again, we only have about 120 years of reliable temperature measurements. As for the “Little Ice Age” (ca 1300-1700), this has been well documented: in Switzerland and France , villages and farms had to be abandoned ( due to the advance of the alpine glaciers). So these glaciers are now in retreat-does that prove humans are the culprits? or take the case of greenland and iceland: colonized by the Vikings (from about 900 AD- 1400 AD). The Norse sagas relate that Iceland was forested with birch trees in the beginning 9the trees were all chopped down by the settlers). Greenland was warm enough to farm-and the Norse colonies lasted until abouy 1450 AD, when the advancing glaciers and cold summers drove the settlers to leave. All of this took place before humans had any effect on the atmosphere. I think it likely that the solar activity is to blame-the siun’s output rises and falls in a cycle.
incidentally , for those who belive that human generated CO2 is to blame: erupting volcanos emit huge amounts of CO2 and sulphur dioxide. Do times of heavy volcanic activity coincide with warming or cooling? the last major eruption of Tambora (East indies) resulted in the famous 1806 “year without Summer”-it snowed in every month in New England, and the corn crop in Massachusetts failed (killing frosts in July).
So all this talk is speculation: we do not know.

5

This is a pointless thread.

The OP seems to disqualify just about every weather and climate reporting station in existence, along with every tool humanity has come up with to figure out what’s going on. At the very least he wants details that are far, far in excess of what is available to anyone other than a godlike being.

And he’s dragging moonlight albedo into the debate on global warming, along with references to Science papers. Gimme a break.

intention seems to have made up his mind already.

For those who might actually want to learn something, I’ll point you towards a science program I regularly listen to. Quirks & Quarks recently had a show focusing on global warming, and if you check the page I linked to, you find a bunch of articles concerning the topic, along with links to articles in the journals Science and Nature.

The one that fascinates me is the Antarctic ice drilling project showing that CO2 levels are the highest they’ve been in 650,000 years. Dr. Thomas Stocker is leading that project.

6

I don’t see how you can rule out theoretical formulations and computer model results. Why is this field of science subject to different treatment than all other fields of physical science where computer models and theoretical arguments are used? I agree that it is important to test the predictions of the theoretical arguments and computer models against reality, to test their sensitivity to parameters that are not well-characterized, etc. And, this is being done. For example, there is recent work testing whether the very important effects of water vapor are being correctly represented in the models (see here).

Can you show us plots so we can see how bad this disagreement is? My impression is that they are generally damn close. The major argument this year between these different temperature records seems to be whether 2005 was a tiny bit warmer or a tiny bit colder than the previous hottest year on record (the “El Nino of the Century” year of 1998 that was far hotter than any previous years at the time it occurred).

As for the general approach proposed by the OP, I don’t really see the point in throwing up a bunch of “dueling” scientific studies. The field of climate science sees hundreds if not thousands of papers published each year. In most areas of science, laypeople are willing to consider summaries of the peer-reviewed literature that are prepared by scientists in the field…and the expert opinions of these people in regards to the current state of the science. It is only when that science conflicts with strongly-held political, philosophical, or religious beliefs or economic interests that people seem to want to ask for higher standards of proof…i.e., to delve into the literature themselves. While there is nothing inherently wrong with delving into the literature…in fact I think it is a good thing…I do think it needs to be done with humility and a recognition that the best you can hope to do as an outsider is probably to get a bit of a feel for what is going on in the field, not to become enough of an expert to have an independent opinion.

In terms of such reviews, clearly the IPCC, which has all of its reports available online in various levels of detail (summary for policymakers, technical summary, full report) is the place to start. (Given your bias toward looking for direct experimental evidence of AGW, you probably want to look especially at the chapter on “detection and attribution”.) The National Academy of Sciences also has several reports related to climate change: NAS. The U.S. EPA website on climate change is another source of information.

Finally, there are some statements that summarize the views of the scientific community. Here is a recent joint statement issued by 11 National Academies of Science (including the U.S. NAS). Here is a statement by the council of the American Geophysical Union andhere is a statement by the council of the American Meteorological Association.

Even some (if not most) oil companies have come around to believe that anthropogenic climate change constitutes a real threat. Here is BP’s site on the subject and here is Shell’s.

An excellent source of information on climate scientist geared to the public is www.realclimate.org. That site, written by scientists in the field, covers lots of different topics.

7

It also seems to me that the “proof” requested is more along the lines of mathematical proof than scientific proof. While the evidence for AGW might not be “so persuasive as to make it foolish to not give tentative agreement,” like most scientific proof, it is dangerous to hold science to its usual high standard when debating policy.

What are the consequences of waiting until it is too late to change policy to counteract AGW? Too high to require a mathematically-rigorous proof. Which is not to say that we should enact crippling legislation on the flimsiest of proofs, only to say there has to be a balance weighed.

8

I think there are a number of problems with this claim:

(1) The climate system is complicated and the issue of determining attribution is not easy. However, the latest IPCC report in fact concluded that most of the warming of the last 50 years…which is most of the net warming over the last century…is likely anthropogenic. [A good analogy that has been made is to a loaded die. Suppose a die was loaded so that 6’s came up twice as often as by chance. This would have a very clear “policy implication” on how you should bet with this die and yet it would take quite a few rolls of the die to establish to a high degree of confidence that the die was in fact loaded and that the extra 6’s coming up were not just a statistical fluke.]

(2) One has to recognize that the time on which most of all influence on the climate system has occurred is relatively recent. As recently as 1970, the CO2 levels were only ~320 ppm, or 40 ppm above the pre-industrial baseline of ~280 ppm. Today, they are already approaching 380 ppm, or 100 ppm above the baseline. Furthermore, there is considerable inertia in the climate system due primarily to the oceans…so the earth is not in radiative balance (as recent studies of the warming in the oceans have shown), i.e., we have not yet equilibrated to the current amount of CO2 in the atmosphere.

(3) Not all of our climate influences have been in the same direction. In particular, some aerosol pollutants produce a cooling effect that has likely masked some of the human-induced warming. [Over time, as stricter air pollution standards go into effect, these pollutant levels will be dropping. Also, unlike CO2, the pollutants tend to wash out of the atmosphere fairly fast so they don’t have the same sort of long term cumulative effect as CO2. Thus, over the long haul, it is clear that the warming effects of the CO2 will dominate.]

Because of the uncertainties in the effect of aerosols and other uncertainties, the fact is that the current warming has not provided very strong bounds on what the future warming will be. (I.e., attempts to constrain the “climate sensitivity”, i.e., the temperature rise caused by a doubling of CO2, using data from the last 100 years has not put very tight bounds on it.) Better constraints are obtainable by other methods, such as looking at the glacial-interglacial cycles.

9

Barbarian, sorry, I was not clear on the source of the studies of moonlight as a measuring tool for the earth’s albedo. Here’s the break you requested above, it’s a scientific break:

Can Earth’s Albedo and Surface Temperatures Increase Together?
B Y E. PALLÉ, P. R. GOODE, P. MONTAÑÉS RODRIGUEZ, AND S. E. KOONIN
Eos, Vol. 87, No. 4, 24 January 2006

Measuring moonlight to determing the amount of earthshine (the amount of sunlight reflected by the earth back to illuminate the moon) is one of the more accurate means of measuring the albedo. This has been reported in, among other places, Science magazine …

The EOS study in turn references the appended studies, if you want more information on this way of studying the albedo, and the recent albedo changes. See, for example, Pallé, E., P. R. Goode, P. Montañés-Rodriguez, and S. E. Koonin (2004), Changes in the Earth’s reflectance over the past two decades, Science, 304, 1299–1301, if you want to read about moonlight and albedo in Science magazine …
All the best,

w.
Pallé, E., P. R. Goode,V.Yurchyshyn, J. Qiu, J. Hickey,
P. Montañés-Rodriguez, M.-C. Chu, E. Kolbe, C.T.
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the Earth’s albedo: 2. Observations and simulations
over 3 years, J. Geophys. Res., 108(D22), 4710,
doi:10.1029/2003JD003611.

Pallé, E., P. Montañés-Rodriguez, P. R. Goode, S. E. Koonin,
M.Wild, and S. Casadio (2005),A multi-data comparison
of shortwave climate forcing changes, Geophys.
Res. Lett., 32, L21702, doi:10.1029/2005GL023847.

Ramanathan,V., R. D. Cess, E. F. Harrison, P. Minnis,
B. R. Barkstrom, E.Ahmad, and D. Hartmann (1989),
Cloud-radiative forcing and climate: Results from
the Earth Radiation Budget Experiment, Science,
243, 57.

Stanhill, G., and S. Cohen (2001), Global dimming:A
review of the evidence for a widespread and significant
reduction in global radiation with discussion
of its probable causes and possible agricultural
consequences,Agric. For. Meteorol., 107, 255.

Wielicki, B.A., et al. (2002), Evidence for large
decadal variability in the tropical mean radiative
energy budget, Science, 295, 841.

Wielicki, B.A.,T.Wong, N. Loeb, P. Minnins, K. Priestley,
and R. Kandel (2005), Changes in Earth’s albedo
measured by satellite, Science, 308, 825.

Wild, M., H. Gilgen,A. Roesch,A. Ohmura, C. Long,
and E. G. Dutton (2005), From dimming to brightening:
Trends in solar radiation inferred from surface
observations, Science, 308, 847.

10

Interesting challenge.

I think overwhelming circumstantial evidence should count, but direct cause evidence is, of course, always better.

What pops to mind immediately are two things:

Uetsi (the “ice-man”) was found around 1990, exposed, but having been buried in ice for however many thousand years.

Icebergs breaking off of Antarctica contain very old (12,000 years+) ice.

If stuff was frozen for 12,000 years, and a whole lot of it (size of Antarctic ice sheet) melted in the last 30 years. It wasn’t gradual from 1700 until now - it took off about 30 years ago.

Also, in August of 2000, the north pole melted for the first time in 50 million years:
http://www.earthisland.org/eijournal/new_articles.cfm?articleID=73&journalID=43

11

I don’t know how you have derived the conclusion that you present here. It is true that one has to evaluate the mass balance carefully to figure out what is happening in net, but just because the center of the ice cap is gaining ice does not mean that the Greenland Ice Cap is necessarily gaining ice overall. And, in fact, the Perspectives article published in the same issue of Science as the Rignot and Kanagaratnam article on the surging of glaciers [J. A. Dowdeswell, Science 311, 963 (2006)] does not make the claim that you make (while it does cite and discuss the Johannessen et al. article). Rather, it concludes:

(bolding mine)

12

Here are graphs of the 3 temperature records that you speak of: This is the GISS record. This is the GHCN record (or perhaps more precisely, the record produced by NCDC “Smith and Reynolds Analysis” using SST anomalies combined with the land surface temperature anomalies from GHCN…see here.). This is the HadCRUT record. They all look to be pretty similar to me. Sure there are some small differences, perhaps the most notable in recent times being that 1998 is clearly warmer than 2005 in the HadCRUT record whereas 2005 is slightly warmer than 1998 (but well within error bars) for the NCDC analysis and also slightly warmer in the GISS analysis. However, this is a small point relative to the general overall trend…To focus on that is sort of to miss the forest through the trees.

13

jshore, thank you for your most interesting post.

First, let me thank you for your opening statement, “The climate system is complicated and the issue of determining attribution is not easy.” This is why I’m agnostic on the question.

Second, could I ask you for a citation for your statement about the IPCC?

Third, contrary to your claim, the planet warmed more in the first half of the century. I will use GISS figures. From the start of the century to 1945, the planet warmed by about 0.4°C. At that point, it cooled slightly, and did not regain the 1945 level until about 1980. Since then, it has warmed an additional 0.2°, for a total of about 0.6°. Two thirds of that 0.6° warming, however, had already occurred by 1945 …

What you say is true, but the effect is not proportional to 100ppm / 40ppm as you seem to think.

Because of the logarithmic relationship, the effect of CO2 is proportional to

log(ppm on a given date / ppm baseline)

log(2)

In 1970, the ppm was 325, so the increase is log(325/280)/log(2), and for the present time it is log(380/280)/log(2)

From the baseline to the 1970 level works out to about 20%. The change from there to 2000 is an additional 20% …

So no, because of the logarithmic relationship, the effect is not as concentrated in the recent years as you claim.

I’ve never understood this argument. It seems that the argument is that it takes a long time to heat up the part of the ocean that’s out of contact with the atmosphere. But since the part of the ocean that is in contact with the atmosphere heats up quickly, and since that surface layer is the only part that is affecting the atmosphere, why does that delay in heating the other part prevent current warming?

In other words, since the top layer of the ocean heats right away, seems to me we’ll see the effect right away.

Perhaps you could explain this argument is greater detail.

While aerosols have been claimed to produce a cooling effect, the hemispheric temperature anomalies make this very unlikely.

CO2 is well mixed and long lived in the atmosphere. Aerosols, on the other hand, are poorly mixed and short lived. In addition, the overwhelming majority of industry is in the northern hemisphere, and so the aerosols are heavily concentrated in the northern hemisphere, with very low levels in the southern hemisphere.

If aerosols had a cooling effect, you’d either expect to see the northern hemisphere warming less than the southern hemisphere, or at least you’d expect to see a aerosol-based cooling of the northern hemisphere temperatures that doesn’t show up in the southern hemisphere. I have looked for such a signal without success, and have not heard of it being found.

If we assume the warming from 1900-1945 was mostly natural as you say, we’ll have a hard time putting bounds on future temperatures at all, since they seem to depend on natural occurrences that are not predictable …

Many thanks for your posting, good scientific issues raised.

w.

14

Thank you, intention, for your response.

Here is a statement found in the technical summary of the Third Assessment Report issued in 2001 (similar statements can presumably be found elsewhere in the report):

The 4th assessment is due out next year I believe and it will presumably have even somewhat stronger wording since there are various studies that have strengthened this conclusion (such as the study of the warming of the oceans that I cite below and the clearing up of most if not all of the discrepancy between surface temperature observations and satellite observations of the lower troposphere).

Things depend on the exact dates that you consider. But my point that the warming seen in the last 50 years is equal to most of the net warming seen in the last century is true. For example, the GISS temperature record shows an increase of around 0.55 C between 1955 and 2005 which is most of the ~0.8 C seen between 1905 and 2005. [The statement becomes even stronger if one uses the dates of 1900, 1950, and 2000 because of the cooling between 1900 and 1910. Or, if you compare simply the total heights from minimum to maximum between the early 20th century warming and the late 20th century warming, you find the early warming was about 0.4 C (~1910-1940) while the late warming (~170-present) was about 0.55 C.]

Although the dependence is logarithmic, a logarithm is locally linear (as is basically any function except near special points where the derivative vanishes or diverges). Thus, while a simple linear prediction would be that a 100ppm rise gives 2.5X the forcing of a 40ppm rise, the logarithm just corrects that slightly to log(380/280)/log(320/280) ~ 2.3X.

The water mixes down…so heating ends up occurring down to hundreds of meters…and that makes for an enormous heat capacity. I saw a calculation by Hansen somewhere where he showed that the vast majority of the increase in heat content (like 95 or 98%?) has gone into heating the oceans with only a few percent going into heating the atmosphere. A good recent paper on the heating of the oceans is T. P. Barnett et al., Science 309, 284 (2005).

I believe there have been some studies of this and they have not concluded what you seem to have concluded here. I’ll try to dig them up if I get the chance.

The evidence is that the natural global excursions over the last couple thousand years have been pretty modest. The 20th century has been a period of transition between climate changes dominated by natural forcings and climate dominated by man. The climate changes of the 21st century will almost certainly be dominated by man (barring any unlikely major natural catastrophe like an asteroid hitting the earth).

15

By the way, this is a nice graph showing how it is necessary to include the best estimates of both natural and anthropogenic forcings in order to get reasonable agreement between climate model simulations and the observed temperature record between 1860 and 2000.

16

Thanks for that link.

17

Your URL shows a fascinating study. It compared the models to the data, and the conclusion was … the data is wrong. I have to confess, I was absolutely blown away by that conclusion, but these days, it’s a typical result. Some of the models showed results that had never been observed on the Earth in recorded history … but they were believed over the actual observational evidence … shockingly bad science.

Regarding why the models are not evidence in climate or any other area of science, consider another field of study, high energy particle physics. The theoretical understanding of particle physics is good, orders of magnitude better than our theoretical understanding of climate.

The computer models of particle physics are also good, orders of magnitude better than our crude climate models.

And yet particle physicists still spend billions of dollars to build powerful atom smashers, and conduct experiments. Why bother, if their computer models are so good?

The reason they do experiments, of course, is that computer models do not produce evidence. They merely reflect the beliefs and prejudices of the programmers. If you said “I’ve discovered a new elementary particle, and my proof is my computer model that shows it exists”, people would laugh at you. They’d say “You programmed the model, so no big surprise it shows your particle” …

And rightly so. The model results are not evidence. Models can produce anything. Only the real world can produce evidence.

The reason that theory is not evidence is slightly different, and unlike the computer model example, is particular to climate science. It relates to our very poor theoretical understanding of turbulent, chaotic phenomena. The climate is a optimally turbulent non-linear system. Applying linear theory to a turbulent non-linear system simply does not work. I gave an example of that, showing that a huge change in forcing didn’t change the temperature as predicted by simplistic linear theoretical models.

A theory based on constructal law might stand a chance, as that law explicitly covers these types of systems. However, while there has been one study along these lines, no such theory has arisen, and in fact, there is no general theory of climate in existence at all. This is an indication of our poor understanding of the subject.

w.

18

Hmmm…you must have read a different paper than the one I linked to. Either that, or you completely misunderstood the paper. In fact, the paper I linked to uses the observational data to test the models. It demonstrates that the model predictions are in very good agreement with the data but that in order to get this good agreement, it is necessary to include “upper tropospheric moistening”. When they artificially “turn off” this feature of the models, the results are indeed like nothing that is observed thus demonstrating the necessity of this feature in the models in order to reproduce experimental observations. Or, as they summarize it in their introduction:

If you want to claim this paper does what you say it does, you better start quoting from it to tell us where you get that idea.

As to your points about theoretical models and theory in general, what is the point of even producing theoretical arguments and models if you are going to decide that they are useless to predict anything and are going to refuse to believe anything they predict?? For example, in weather prediction, perhaps the meteorologists at the National Weather Service should just take observations so that they can tell us what the current weather is and what the past weather was. But, we shouldn’t allow them to predict the future weather because they have no evidence of what that future weather will be other than what their models tell them, which apparently doesn’t count.

I am a modeler by profession and I can tell you that when one models any physical system, one can come up with hundreds of things that are being left out of the model and that one might think would mean that the model will be useless. Nonetheless, it usually turns out that the models are in fact extremely valuable. Mind you, I am not arguing for having blind faith in models and theoretical predictions. It is very important to test the models as much as possible…and particularly to test specific physical mechanisms in the models…which is why the Soden et al. paper that I linked to is so important.

Also, I don’t even see how it is possible to try to find an attribution to the current warming without using theory or models. All we can say by looking at the temperature record is that they earth is warming. In order to answer the question of cause, we have to look at the predictions of models and theory with and without the best estimates of natural and anthropogenic forcings and compare them to what is observed. If, pray tell, you won’t allow us to do that, then exactly how do you propose that we should we try to determine whether the current warming is anthropogenic?!?!

Well, I wouldn’t say that. You gave an example of an experimental measurement that is not well-understood and seems to be in some contradiction with other measurements (see here for a discussion). And the fact is that sometimes experimental measurements can be wrong and if one abandoned one’s models everytime one got a measurement that didn’t seem explainable by them, you would again be restricting yourself to just observing the universe and never making predictions. For example, the UAH reconstruction of lower tropospheric temperatures from the MSU satellite measurements, which initially showed cooling in contradiction to both surface temperature measurements and model predictions, have turned out to be wrong…as subsequent corrections show.

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Sorry, but this can’t count: icebergs will contain very old ice anyway as they’ve been part of a glacier.

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So what, other than a model, would convince you of the reality of anthropogenic climate change? We can’t run an “experiment” on the global climate. Or, rather, we can, and are doing so – but by the time the results are in it would be too late to do anything about ti.