Redux: Arrogance, Models, Responsibility

By: Dr. Ricky Rood , 2:31 PM GMT on June 07, 2007

Redux: Arrogance, Models, Responsibility

I am motivated by the remarks to my last blog about the use of models that cannot predict next month's temperature to develop policy. The basic idea was that if the model cannot predict next month's temperature, then why should we give it any credibility predicting next century's temperature? This is a comment or criticism that is often stated in the climate change discourse.

Give this a run: Imagine that you live in a place with reliable rain. At the beginning of each year, you have some confidence that it will rain over the course of the year. You do not know in advance exactly which days it will rain, but you are confident that the rain will come. Suppose further, that you have a very good weather service, which can predict rain 2 days in advance. You decide to build a cistern, or a pond. I like the cistern better, because we can imagine closing it so that we don't have to worry about the loss from evaporation. If on New Year's you wanted to predict the filling of your cistern, then you would find yourself in the following situation. In any two day period you could predict with high accuracy that water would accumulate in the cistern; you have excellent 2 day weather forecasts. Over the course of the year, you can expect your cistern to fill up; you have reliable rain over the course of a year. In between two days and a year, your forecasts are not so good; you do not know beyond 2 days exactly when it will rain.

Therefore, you have a model with good short-term forecasts, reliable long-term forecasts, and that in the intermediate time an exact prediction is not so good. Still this is a useful model, and a model that has been used by farmers for thousands of years.

From a scientific point of view, this brings forward the notion of separation of scales. We often are able to know with some precision about the short-term and the long-term. In the short term, we have deterministic predictability. In the long term we know the nature of the balance that must be maintained from the fundamental physics--in the case of climate, the conservation of energy. In between, we are more reliant on probabilistic forecasts, and it takes some skill to know how to handle the errors in a probabilistic forecast.

It is equally as interesting to me how people use deterministic and probabilistic knowledge in decision making. There are many situations where knowledge does not rise to the top of the decision making process. An example that is often used is buying a lottery ticket--by a vast probability you are not going to win the lottery; you are giving your money away. This example can be dismissed as low-risk/high-reward or as simple entertainment. But people make decisions all the time based on their belief system or what they want to happen. I was recently introduced to the literature of how people make decisions by one of my students. (There is a literature on everything! (Perhaps too many academics in the world? Arrogant academics?)) One book this student referenced was, Dawes, R. M. (1988), Rational choice in an uncertain world (Fort Worth, Harcourt Brace College Publishers). Dawes discusses irrational decision making, and why we do it. If you Google search on the title you can find whole worlds of critical decision making.

It is my evaluation that the information from climate models is reliable enough that we need to limit our emissions of carbon dioxide. I think that the long-term costs will be much less if we act today. On the other hand, I recognize that the environmental impact of reducing carbon dioxide emissions will not be immediately realized. That does not lead me to the decision that nothing should be done. It leads me to the decision that there are a set of problems that exist in the near term, that require our attention. This is a separation of scales. If you choose to focus on only the short-term or the long-term, then you are faced with a set of seeming contradictions. These can be used to justify inaction; they can be used to discredit the other camp. As I said in the last blog ... inaction, seems to me (belief system here), as avoiding our responsibility. We have knowledge.

ricky

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43. atmoexp
2:23 PM GMT on June 18, 2007
Your references to a portion of Michigan are interesting no doubt - that is why it is called GLOBAL warming see this website provided by Ricky Rood some time ago: http://www.aip.org/history/exhibits/climate/index.html
The website above reviews much of the scientific history of global warming as well as an excellent synopsis of the science pertaning to these troublesome general cirulation models.
I used to be a global warming skeptic myself until I saw the data now I'm of the opinion of Spencer Weart, PhD (the author of whose website I've referenced above) - "The few who contest these facts are either ignorant, or so committed to their viewpoint that they will seize on any excuse to deny the danger."
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42. ZRR
10:06 PM GMT on June 17, 2007
Someone mentioned the dip in Global Average Temperatures in the 60's and 70's was from decreased solar output. Why isn't a bigger deal being made about this, as it may be a much more powerful force than an increase in a trace atmospheric gass. What forcing caused the Little Ice Age, well I think the most popular theory is solar output varations, but some have said it was more of a North American and Europian phenomena than Global, well through 1300 AD, to 1800AD I wonder how many observations we have outside of North America and Europe compaired to with in it. Most of the Earths Land masses and populations centers are in the northern Hemisphere.

Also..back to the models...Past GCM's failed to see the stratuspheric cooling that is taking place, as well as decreasing antartic surface termperatures.

Anyone with the patients or the pasion for weather research, should get access to there nearest recording stations records. Preferably one that is has records over at least a 100 year period in and has remaned un-urbanized. I've learned alot of interesting things about past Michigan Climate and when I hear people crying about how the last few summers were so bad and how something is wrong, when you look at the facts you see people perceptions and memories are often way way off reality.

Heres an intersting tid bit: these are the number of 90 degree days recorded at Iron River, MI for the summers 2006-1996.....22
for the summers 1930-1939.....88\

At two nearby stations rural stations with 100 year records a vast majority of the daily June record HI's were set before 1960.
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41. howarjo1943
1:54 PM GMT on June 17, 2007
One mans attempt to disprove GW. Sorry for the OSU Buckeyes reference in the beginning. I challenge you to watch the whole presentation because it is LOOOOONG, but it is very informative.

http://youtube.com/watch?v=mHjczyA75jU

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40. LowerCal
9:14 PM GMT on June 16, 2007
Posted By: hcubed at 11:15 AM PDT on June 14, 2007.

First, predicting the PAST is so easy, even a caveman can do it.
...
4. If the temps took a dip, who's to say that it won't dip again? Have the models been run farther than shown (red area prediction past 2005?)


That illustration is not "predicting the PAST". It is showing how well the models perform compared to the best documented climate behavior.

Yes, the models have been run further than 2005 ... those results are the basis of concern.
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39. ricderr
8:41 PM GMT on June 16, 2007
Limitations of Climate Models as Predictors of Climate Change
Brief Analysis

No. 396

Friday, May 16, 2002 Download this page in PDF format

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by David R. Legates

World leaders are making critical decisions based upon predictions of General Circulation Models or Global Climate Models (GCMs) that humans are causing global climate change or global warming. Global climate models attempt to describe the earth's climate and are used in a variety of applications. These include the investigation of the possible causes of climate change and the simulation of past and future climates. But these models are limited in important ways, including:

an incomplete understanding of the climate system,
an imperfect ability to transform our knowledge into accurate mathematical equations,
the limited power of computers,
the models' inability to reproduce important atmospheric phenomena, and
inaccurate representations of the complex natural interconnections.
These weaknesses combine to make GCM-based predictions too uncertain to be used as the bases for public policy responses related to future climate changes.

The Limits of Human Knowledge
The world's best scientists have only an incomplete understanding of how the various atmospheric, land surface, oceanic and ice components interact. Even if their understanding of the climate system were perfect, scientists would still face challenges. Consider that while scientists do have a general idea of the complex interrelationships of the atmosphere and the oceans, expressing this knowledge mathematically is very difficult.

The Limits of Computing Power
GCMs are limited in important ways. Global climate is produced through a variety of processes and interactions that operate on a wide range of scales, including molecular, regional, continental and global. Changes in climate occur from physical interactions that take place on any or all of these scales. The changes, and the resulting weather patterns, can occur nearly instantaneously or they can take decades or millenia to develop. Unfortunately, the computers and programs that run the GCMs are limited to gross representations of the geographic, geologic and atmospheric details that they use to run climate simulations. Thus, many small-scale features, such as a temporary but significant shift in the prevailing winds or unusually dry surface conditions due to increased evaporation from forest fires and high winds cannot be represented, even though they may significantly impact the local, regional, or even global climate.

Indeed, GCMs can at best represent only a thumbnail sketch of the real world, with spatial resolutions no finer than regional areas a thousand miles square. Many topographical, geological, atmospheric and biological variations can occur within any contiguous thousand square miles. For instance, GCMs might average rainfall amounts and wind velocity over large diverse land surfaces which could include arid mountain plateaus, low-land deserts and temperate coastal rainforests. But, even modest topographic changes - for instance, a new housing development that paves over farmland and drains a wetland area - could render a model of land-surface interactions inaccurate.

Resulting Model Breakdowns
Given the limitations noted, GCMs simply cannot reliably reproduce climate systems. Commonplace events like precipitation and the passage of typical weather fronts are difficult enough to depict; truly complex phenomena, such as hurricanes, thunderstorms and tornadoes, may be represented so poorly that they simply cannot be relied upon. El Niño, La Niña and the Pacific Decadal Oscillation are examples of complex climate patterns that are inadequately reproduced or completely absent in GCMs.

In addition, global average temperature is measured by three different instruments - ground-based thermometers, weather balloons and global satellite observations - with each system covering a slightly different range of the earth's atmosphere. The data they provide is conflicting. Whereas both the global satellite network and weather balloon observations show a modest cooling trend during the past 25 years, the ground-based thermometers show a modest warming of approximately 0.13 degrees Celsius per decade.

The GCMs display two flaws related to measured global temperatures. First, they show global temperatures rising across all levels of the atmosphere, a finding not reflected in reality. [see figure] Second, the lowest predicted global temperature measurement of the GCMs is nearly three times more than the temperature rise measured by ground-based thermometers. Thus, the GCMs do not reflect the temperature differences or the direction of temperature change within various levels of the atmosphere, nor do they show the actual amount of temperature change.

Finally, GCMs ignore the interconnected nature of climate processes and how an inaccurate simulation of one introduces errors into every other related process. A simple model for precipitation involves scores of variables. But a single error, say in representing atmospheric moisture or deciding what mechanism is causing precipitation, will make the simulation "wrong." For example, precipitation requires moisture in the atmosphere and a mechanism to force it to condense (i.e., by forcing the air to rise over mountains, by surface heating, as a result of weather fronts or by cyclonic rotation). Any errors in representing either the atmospheric moisture content or the precipitation-causing mechanisms will produce an erroneous simulation. Thus, GCM simulations of precipitation will be affected by limitations in the representation and simulation of topography.

Inaccuracies in simulating precipitation will, in turn, adversely affect the simulation of virtually every other climate variable. Condensation releases heat to the atmosphere and forms clouds, which reflect energy from the sun and trap heat from the earth's surface - and both sources of heat affect air temperature. This in turn affects winds, atmospheric pressure and atmospheric circulation. Since winds drive the upper currents of the ocean, the simulation of ocean circulation also is adversely affected. Additionally, inadequate simulations of precipitation lead to inaccurate assessments of soil moisture. Since vegetation also responds to precipitation, the entire representation of the biosphere becomes open to question. This is not to say that climate scientists lack skill or dedication; it is to reiterate the extraordinary difficulty of producing accurate climate models.

More than just long-term average and seasonal variations go into estimating the extent of climate change. Climate change is likely to manifest itself in small regional fluctuations. Moreover, year-to-year variability is important. Much of the character of the earth's climate is in how it varies over time. GCMs that simulate essentially the same conditions year after year, as virtually all climate models do, miss an important aspect of the earth's climate. Thus GCMs' predictive powers must be evaluated in light of each model's ability to represent the global climate's holistic and variable nature.

Although GCMs are not weather prediction models, climate is nevertheless an ensemble of weather events. The utility of a climate model is not in predicting whether it will rain in northern Florida on a certain afternoon. What is of interest is to determine the long-term probability that future precipitation will be significantly different - in frequency and/or intensity - from what it is today. Will the winter of 2048 be warmer or colder, wetter or drier than present conditions, and if so, by how much? If climate models cannot simulate processes known to drive daily weather patterns, to what degree can their climate predictions be believed?

Conclusion
Climate is to some degree a representation of the average of weather events that occur. If the frequency and locations of weather events are simulated inaccurately or not at all, the reliability of climate change prognostications is undermined. While GCMs cannot be expected to simulate future weather, they should be able to accurately depict the earth's present climate and vitality. Since they cannot, GCM predictions of climate change are statistical exercises with little bearing on reality.

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38. Snowfire
7:50 PM GMT on June 16, 2007

Posted By: hcubed at 6:15 PM GMT on June 14, 2007.

1. What explains the OVERALL dip in observed temperatures (as shown in several model charts?) It was this "dip" that scientists were using in the 70's to "predict" global cooling.




-A slight decline in solar output during this period.


4. If the temps took a dip, who's to say that it won't dip again?


Irrelevant nit-picking. Of course, a change in forcing factors (e.g. a VEI >6 volcanic eruption) could cause such an excursion. But that is not a long-term event, and is outside the scope of this discussion. Would you bet the farm on the likelihood of mankind's fortuitously being "rescued" by such events? Is that prudent?

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37. NOLAinNC
4:03 PM GMT on June 15, 2007
That's a great link.
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36. StSimonsIslandGAGuy
3:41 AM GMT on June 15, 2007
This is interesting Link
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35. hcubed
6:15 PM GMT on June 14, 2007
First, predicting the PAST is so easy, even a caveman can do it.

From the RealClimate article:

"If the analysis uses earlier data i.e. 1959, it will be affected by the 'cold start' problem -i.e. the model is starting with a radiative balance that real world was not in."

Either that, or using older data didn't give the drastic rise in predictive temps that was needed to convice the masses.

A few things about the model results that I can see:

1. What explains the OVERALL dip in observed temperatures (as shown in several model charts?) It was this "dip" that scientists were using in the 70's to "predict" global cooling.

2. On several of the charts, there is an EXTREMELY large swing in the "error limits" followed by narrower swings. What caused this?

3. On the global and global ocean temp charts, one area of the observed area goes ABOVE the projections. Couldn't the models have "predicted" the past better than that?

4. If the temps took a dip, who's to say that it won't dip again? Have the models been run farther than shown (red area prediction past 2005?)

How many times will Hansen et al have to "revisit" this paper to continually "prove" his theory?
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34. atmoexp
3:22 PM GMT on June 14, 2007
Great link LowerCal - thanks.
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33. Fshhead
6:25 AM GMT on June 14, 2007
Cal, they look pretty similar to me & yes I gotta AGREE on Heidi Cullen, rather annoying. Think they should have found someone a little better in my opinion!
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32. LowerCal
10:41 PM GMT on June 13, 2007
...
The validity of models can be tested against climate history. If they can predict the past (which the best models are pretty good at) they are probably on the right track for predicting the future – and indeed have successfully done so.
...


black - actual
red - models with greenhouse gas forcing
blue - models without greenhouse gas forcing


Credit: Climate myths: We can't trust computer models - climate-change - 16 May 2007 - New Scientist Environment
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31. crucilandia
7:52 PM GMT on June 13, 2007
If some skill could be demostrated on a seasonal and maybe an anual bassis then maybe I'd take the Global Warming projections a little more seriously.

I aggree


I heard that rather annoying Hiedi Cullen

strongly aggree
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30. NRAamy
7:49 PM GMT on June 13, 2007
"Objects may appear closer than they are"
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29. hcubed
7:47 PM GMT on June 13, 2007
Posted by: RickyRood, 10:31 AM EDT on June 07, 2007

It is my evaluation that the information from climate models is reliable enough that we need to limit our emissions of carbon dioxide.


Posted By: ZRR at 11:05 PM GMT on June 12, 2007.

However anyone interested should look at NCEP's Climate Forcast Sytem Model, it has performed horribly for many months now. In february it was predicting a terribly cold March, that surely never happened, thats just one example. Its forcast have almost been oposite of what has verified. Also note its horrible performance on this last EL Nino, and even the transition to the neutral and week La Nina we are in Now. If some skill could be demostrated on a seasonal and maybe an anual bassis then maybe I'd take the Global Warming projections a little more seriously.


And the real problem is that the "experts" who created the models won't admit that it could be THEIR models that are wrong. Instead, they'll come up with some way to blame HUMANS for the error, instead of a lack of data or a NATURAL reason.

It's about like the disclaimer some investing companies have to post: Past results are no guarantee of future expectations.
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28. ZRR
11:05 PM GMT on June 12, 2007
Comparing Global Warming models to 1 or 2 week forcasting of specific weather conditions within a specific region might be a bit un-fare. Models such as NCEP's Global Forcast System, or the Europian Center for Medium Range Weather forcasting are great scientific achievments and aid forcasters tremendously in predicting of weather, but we all know how wrong they can go with each passing forcasting hour. But those are not really climate models.
However anyone interested should look at NCEP's Climate Forcast Sytem Model, it has performed horribly for many months now. In february it was predicting a terribly cold March, that surely never happened, thats just one example. Its forcast have almost been oposite of what has verified. Also note its horrible performance on this last EL Nino, and even the transition to the neutral and week La Nina we are in Now. If some skill could be demostrated on a seasonal and maybe an anual bassis then maybe I'd take the Global Warming projections a little more seriously.

I heard that rather annoying Hiedi Cullen, The Weather Channels global warming hero say, "what the computer models have done is creat a twin earth inside the computer". Gag me please.... What the models have done is create a version of what is going on, on a partial and parameterized basis, with many unkowns yet to be unput into the system, not anything like a twin earth.
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27. NOLAinNC
3:26 PM GMT on June 12, 2007
I just left New Orleans (again) for North Carolina, which is suffering a serious drought. This year, a freak late spring freeze killed tree buds and caused crop damage in my region. My family is still in New Orleans and they are living through record temperatures.

Let's operate on the assumption that we all want a cleaner, greener environment and move forward. I don't have a financial stake in believing that human generated CO2 is increasing global warming, I just DO believe this. I also believe that we are polluting our planet and destroying ecosystems worldwide.

In trying to simplify my life and reduce my impact on the earth, I also figured out that less stuff and less consumption made me and my family happier and healthier, so I like to share my personal experiences here. That's it in a nutshell - no plot or conspiracy, no political agenda.

-NOLA
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26. crucilandia
3:14 PM GMT on June 12, 2007
laughts, appreciate it desert.
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25. desertdisaster
2:21 PM GMT on June 12, 2007
Sullivan, the G8 made some declaration last week about Global Warming… they are working so your descendant, if you ever have any! can still harvest tomatoes in the future…

Here are three of them:

48. We take note of and are concerned about the recent UN Intergovernmental Panel on Climate Change (IPCC) reports. The most recent report concluded both, that global temperatures are rising, that this is caused largely by human activities and, in addition, that for increases in global average temperature, there are projected to be major changes in ecosystem structure and function with predominantly negative consequences for biodiversity and ecosystems, e.g. water and food supply.

50. As climate change is a global problem, the response to it needs to be international. We welcome the wide range of existing activities both in industrialised and developing countries. We share a long-term vision and agree on the need for frameworks that will accelerate action over the next decade. Complementary national, regional and global policy frameworks that co-ordinate rather than compete with each other will strengthen the effectiveness of the measures. Such frameworks must address not only climate change but also energy security, economic growth, and sustainable development objectives in an integrated approach. They will provide important orientation for the necessary future investment decisions.

53. To address the urgent challenge of climate change, it is vital that major economies that use the most energy and generate the majority of greenhouse gas emissions agree on a detailed contribution for a new global framework by the end of 2008, which would contribute to a global agreement under the UNFCCC by 2009. We therefore reiterate the need to engage major emitting economies on how best to address the challenge of climate change. We embrace efforts to work with these countries on long-term strategies. To this end, our representatives have already met with the representatives of Brazil, China, India, Mexico and South Africa in Berlin on 4 May 2007. We will continue to meet with high representatives of these and other major energy consuming and greenhouse gas emitting countries to consider the necessary components for successfully combating climate change. We welcome the offer of the United States to host such a meeting later this year. This major emitters’ process should include, inter alia, national, regional and international policies, targets and plans, in line with national circumstances, an ambitious work program within the UNFCCC, and the development and deployment of climate-friendly technology. This dialogue will support the UN climate process and report back to the UNFCCC.

So! Things are still moving even if it’s quiet in here! And no Cruc, we are not tired of you even if you can be a pain sometimes…
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24. Patrap
1:32 PM GMT on June 12, 2007
The Planet is the only ears and voice in all of this. It will go along as it has Without any care to listen. But it will respond to the insult on its Being. And that response is occurring.As in Lake Chad..Greenland..and other areas across the Globe. It dosent quiver at posts and debate. But we do..daily at her whims.
Hot as Hades here in Nola.Set records yesterday.Same as I year ago same date in 06. Hit 97F
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23. crucilandia
1:17 PM GMT on June 12, 2007
I think you guys are tired of me.
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22. LowerCal
8:15 AM GMT on June 12, 2007
Hmm, maybe "the global warming crowd" is wondering what to do in the face of irrational decision making.

Modified: This comment doesn't make much sense now that the preceding comment by sullivanweather about "the global warming crowd" has been removed.
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20. NRAamy
4:07 PM GMT on June 08, 2007
Just ducky....

;)
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19. crucilandia
4:03 PM GMT on June 08, 2007
pretty good and you?
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18. NRAamy
3:57 PM GMT on June 08, 2007
cruc! How you doin'?

:)
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17. crucilandia
1:39 PM GMT on June 08, 2007
I do my best too.
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16. atmoexp
1:43 AM GMT on June 08, 2007
Well said NOLAinNC, developing ones abilities so that one can selflessly give back to our society, love of family and friends and obligation to do one's best. The wonderful thing about the attributes of a well lived life is that most of them can be attained for free (thank goodness for public libraries, univerisities and schools - though we are taxed for their services just being citizens means we can access them). Sadly, as you stated many of us believe we must pay for some expensive gadget or gizmo to find contentment - this only makes the rich goobs who control things richer. Sorry this is getting politcal.
Ricky Rood could you go over radative transfer of greenhouse gases in the near future? Thanks.
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15. NOLAinNC
10:22 PM GMT on June 07, 2007
Well said, Patrap. I am committed to making changes every day that reduce my consumption. We are taught in our society that consumption=happiness, but that just ain't so.
-NOLA
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14. crucilandia
8:01 PM GMT on June 07, 2007
catastrophes happen, example is the mass extinctions in the PT and CT boundaries
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13. NRAamy
6:39 PM GMT on June 07, 2007
But, we have had disasters....Katrina for example.....which people, others than those who live there, seem to have conveniently forgotten....
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12. atmoexp
6:33 PM GMT on June 07, 2007
I agree Patrap but the problem is both individuals and societies treat the atmosphere/bioshpere as a sewer or a whore, in most cases both. The daunting problem is making all societies sustainable. Sadly, it will probably take a disaster to truely increase awareness.
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11. Patrap
6:21 PM GMT on June 07, 2007
The debate is a age old one now it seems.Good points on both sides the fence.But I believe we can come to a consensus that the change is occurring.The rate of which is greater in some areas,albeit..than others. We have the most wonderful tools available to seek the answers we need to make the crucil choices our future generations will have to deal with.We need to be responsible.As stewards of this grand oasis..we must.
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10. crucilandia
6:13 PM GMT on June 07, 2007
I understand that models are the only tool we have, but what upsets me is the use of it beyond its capacity and the use of the outcome as the ultimatum.
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9. atmoexp
5:25 PM GMT on June 07, 2007
These excerpts are from:
http://www.aip.org/history/exhibits/climate/chaos.htm#L_0103-
"The meteorological questions that had launched chaos theory remained among the hardest to answer. Some scientists now insisted that the climate system's intrinsic fluctuations would utterly defeat any attempt to calculate its changes. Thus the 1980 edition of one classic textbook said that predictions of greenhouse effect warming were dubious because of chaotic "autovariations." Lorenz and others argued that the recently observed global warming might be no evidence of a greenhouse effect or any other external influence, but only a chance excursion in the drunkard's random walk.(34)"
"Just about any decent computer model, run repeatedly with just about any plausible initial conditions plus a rise of greenhouse gases, predicted a global warming. As the world's average temperatures climbed, it seemed less and less likely that the match with the models was mere accident. However, different models got different results for the future climate in any particular region. And a given model for a given region might come up with a surprising shift of the weather pattern in the middle of a run.(35) Some regional fluctuations and seasonal variations might be fundamentally chaotic, although only within the limits set by the overall average global warming. In fact, it had become a test of a good model that it should show fluctuations and variations similar in size and timescale to the real climate."
"Yet there was no way to prove that the modelers had not all overlooked some subtle effect, something buried in the poorly known geophysics and biochemistry, that could magnify itself into a grave surprise. What was no longer in doubt was the most important insight produced by the half-century of computer experiments. Under some circumstances a fairly small change in conditions, perhaps even an increase of greenhouse gases, could nudge climate into a severely different state. The climate looked less like a simple predictable system than like a confused beast, which a dozen different forces were prodding in different directions. Most of the time it responded sluggishly. Yet there was always a chance that at some point it would take an unexpected leap."
Food for thought - off to the strange world of chaos theory.
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8. crucilandia
5:05 PM GMT on June 07, 2007
Thank you MisterPerfect.

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7. MisterPerfect
3:50 PM GMT on June 07, 2007
Very well explained Cruc...I have monitored your comments the past few weeks and appreciate your input.
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6. crucilandia
3:49 PM GMT on June 07, 2007
pretty good.
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5. NRAamy
3:47 PM GMT on June 07, 2007
"Nice to be here
Hope you agree
Lying in the sun

Lovely weather
let's climb a tree
the show has just begun..."

:)
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4. crucilandia
3:45 PM GMT on June 07, 2007
Morning NRAamy, how are you?
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3. crucilandia
3:40 PM GMT on June 07, 2007
predictions are marginal of validity

1/3 of warming predictions is derived from what 2x CO2 will due to cloud change. There are few studies on this and uncertainties are very high

1/3 of warming predictions is derived from what 2x CO2 will due to water vapor. Again we have no confidence to knwo what doubling CO2 will due to water vapor.

Conclusion
2/3 of modeling power stands on a very very weak base. And the model does not use CO2 forcing as its base.
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2. NRAamy
3:33 PM GMT on June 07, 2007
Mornin' cruc...

:)
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1. crucilandia
3:32 PM GMT on June 07, 2007
Indeed, one overlooked mystery is why temperatures are not already higher. Various models predict that a doubling of CO2 in the atmosphere will raise the world's average temperature by as little as 1.5 degrees Celsius or as much as 4.5 degrees. The important thing about doubled CO2 (or any other greenhouse gas) is its "forcing"—its contribution to warming. At present, the greenhouse forcing is already about three-quarters of what one would get from a doubling of CO2. But average temperatures rose only about 0.6 degrees since the beginning of the industrial era, and the change hasn't been uniform

Modelers claim to have simulated the warming and cooling that occurred before 1976 by choosing among various guesses as to what effect poorly observed volcanoes and unmeasured output from the sun have had. These factors, they claim, don't explain the warming of about 0.4 degrees C between 1976 and 1998. Climate modelers assume the cause must be greenhouse-gas emissions because they have no other explanation. This is a poor substitute for evidence, and simulation hardly constitutes explanation. Ten years ago climate modelers also couldn't account for the warming that occurred from about 1050 to 1300. They tried to expunge the medieval warm period from the observational record—an effort that is now generally discredited. The models have also severely underestimated short-term variability El Niño and the Intraseasonal Oscillation. Such phenomena illustrate the ability of the complex and turbulent climate system to vary significantly with no external cause whatever, and to do so over many years, even centuries.

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I'm a professor at U Michigan and lead a course on climate change problem solving. These articles often come from and contribute to the course.

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