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Models(4) Iconic Figure:

By: Dr. Ricky Rood , 4:42 AM GMT on February 13, 2008

Models(4) Iconic Figure:

Of the figures that I consider the Iconic Figures of climate, there is one based totally on models. A recent version of this figure from the IPCC 2007 is given here.

Figure 1: Observations and simulation of the past century from the IPCC 2007 Technical Summary (Working Group 1) (largish PDF).

This is a figure of, approximately, the last century. In this figure there are three traces. One of traces, the black one, is of the observed, globally averaged surface temperature record. In the bottom figure is a blue curve, which is a model simulation that does not include anthropogenic (human-related) forcing. That is, it is “natural” forcing. In the top curve there is a red curve that is a model simulation that includes both natural and anthropogenic forcing. The point of this figure is that both natural and anthropogenic forcing is important, and that the recent warming requires the inclusion of anthropogenic forcing to simulate the recent observed temperature increase.

Forcing: For the purpose of this figure, “forcing” are those things that change the ability of the Earth to absorb or reflect radiative energy. Another “forcing” is the radiative energy that comes from the Sun. “Natural” forcing starts with the variability of the Sun. Of special importance in the realm of natural forcing is the impact of volcanic eruptions. Large volcanic eruptions put aerosols into the atmosphere. Aerosols above the Earth’s surface can reflect more solar radiation or they can absorb radiation in the atmosphere. These help cool the surface of the Earth. Aerosols also impact the infrared radiation; that is, the radiation emitted by the Earth back to space. Other natural forcings include water in the atmosphere, in all phases, and carbon dioxide. In general, these model experiments assume that the amount of carbon dioxide in the atmosphere prior to, about, 1850 is “natural.” Of course, the amount of solar radiation that is reflected by the surface is also included – ice and land.

In contrast to “natural” forcing is anthropogenic or human-related forcing. This is change in the forcing relative to the natural forcing. The most important of the anthropogenic forcings is due to carbon dioxide, which is calculated as the additional forcing due to the increased amount of carbon dioxide relative to the “pre-industrial” amount of carbon dioxide. Pre-industrial forcing is linked to about the year 1850. There are other greenhouse gases like methane, nitrous oxide, and the chlorofluorocarbons. Nitrous oxide increases are largely related to use of synthetic fertilizers. Other anthropogenic changes in the radiative balance of the Earth are related to changes in reflection at the surface due to how we use land.

The Plot: Here is my description of this plot. The dark red and the dark blue lines are averages from many model simulations. The light lines that surround the dark lines are all of the individual simulations. Prior to 1950 the natural and anthropogenic simulations are not much different from each other. After 1960 only the plot with anthropogenic forcing follows the temperature observations. Perhaps more importantly, the natural and anthropogenic curves diverge from each other as time goes along.

The light lines surrounding the dark lines give some idea of model variability. It is notable that, for the most part, this variability covers the range of variability in the observations. The models do not follow, point by point, the shorter scale variability in the observations, for example between 1920 and 1930. The models have variability, such as the El Nino – La Nina and North Atlantic Oscillation. The spread of the models suggests that the model variability covers this range of variability, but the models are not tracing this variability on an event-by-event basis. The comparable spread in the models and the observations also serve as a sanity check that the models represent variability in the same range as the Earth’s climate.

The simulations do show the impact of several large volcanic eruptions. The volcanoes do cause cooling of the globe. Volcanic eruptions, and especially the well observed Mount Pinatubo eruption in 1991, provide opportunities to evaluate processes in models.

It is also of interest to examine where the models and the observations do not agree. A most interesting period is from 1935-1940, a period when the planet was warm. (Thanks to crucilandia for pointing a reference to get me started.) A substantial literature is developing that examines this period. It seems to be associated with substantial Arctic warming. It is a period that demands more study. The cooling that all of the models calculate about 1915 is also interesting.

An important take away message from these simulations is that there are factors other than carbon dioxide that cause temperature variability. Hence, carbon dioxide and temperature are not necessarily correlated on shorter scales of variability. (This is a like my wave metaphor on this blog. )

Conclusions: This is a figure open to interpretation. Personally, I find this figure compelling. I know how difficult it has been to develop the models and to specify the forcing. There is also a huge depth of analysis at different levels of detail and averaging that support the conclusion that it is only with increasing carbon dioxide forcing that the recent temperature increase can be explained.

Others can look at this plot, and come to a different conclusion. One issue that many raise is what about the treatment of aerosols? This is a process in models which has substantial uncertainty in its quantification.

Looking forward to the comments.

Here are the previous blogs on models.
Uncertainty and Types of Models
Models (1) Assumptions
Models (2) Forgotten Layers
Models (3) Predictable Arguments

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

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89. sullivanweather
8:48 PM EST on February 15, 2008

Just didn't want to see you get fustrated when buster completely ignores your response

Member Since: December 31, 1969 Posts: Comments:
88. LowerCal
5:39 PM PST on February 15, 2008
Sully, Jer, no debate, just answering honest questions.
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87. quasigeostropic
8:26 PM EST on February 15, 2008
The sun is the only thing that makes sense...That would be the greatest culprit to warming the earth, since earth is heated directly from the sun to start with!!! Just because man-made GW theorists fail to make a graph that shows sun-spot activity as being the primary temp factor, doesn't mean you can rule it out.....It just means scientists still dont understand 99.999% of mother earth.
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86. quasigeostropic
8:18 PM EST on February 15, 2008
Mother nature is best when you stay out of influencing it(even though you cant really influence a huge earth/atmosphere system).....The biggest ecological problems are pollution, cutting down the rainforests, destroying animal's habitats, etc......This doesn't get as much air time as global warming because it would mean big industry would have to smarten up(ya ever think that most of all pollution is because of big industrial complexes?)...Then we have China and all those other countries over there that do nothing about reducing their emissions.....Al Gore spouts off about how bad we are creating GW while he goes around in his pollutant-ridden cars and planes....
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85. sebastianjer
8:14 PM EST on February 15, 2008
Before you engage yourself in a debate with buster I should warn you that you'll be getting no where.

Yeah you'll just dig yourself a tun,,, uh hole
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84. sullivanweather
8:10 PM EST on February 15, 2008

Before you engage yourself in a debate with buster I should warn you that you'll be getting no where.
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83. LowerCal
5:07 PM PST on February 15, 2008
#81) Photons (packets of electromagnetic energy) leave Earth for space taking their energy with them. The cooling does not require any loss of atoms or molecules.

#82) The energy generated by man's technologies ends up getting radiated into space also. However, the amount of that heat is insignificant compared to the energy delivered by the Sun every day to the entire Earth.
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80. crucilandia
10:06 PM GMT on February 15, 2008
Climate Anomalies Induced by the Arctic and Antarctic Oscillations: Glacial Maximum and Present-Day Perspectives

F. Justino and W. R. Peltier
Journal of Climate
Volume 21, Issue 3 (February 2008) pp. 459–475

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79. sullivanweather
5:01 PM EST on February 15, 2008
The last time the PDO shifted from positive to negative was in 1946 +/-2 years. The 1950 La Nina was fairly strong, but according to the MEI was a moderate strength event. It takes time for patterns to mature.

It would be my best guesstimation that as the PDO shifts and becomes sustained, La Nina strength on the MEI index would follow suit.
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78. LowerCal
2:05 PM PST on February 15, 2008
Buster, heat escapes into space as photons, specifically, electromagnetic radiation in the infrared band. The process is known as radiational cooling.
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77. crucilandia
9:52 PM GMT on February 15, 2008
Journal of Climate 18(21):4355–4373

Niklas Schneider and Bruce D. Cornuelle. The Forcing of the Pacific Decadal Oscillation

This study further clarifies the causes of the “impact” of the PDO on climate of the adjacent continental areas and teleconnection patterns from the Tropics. As found from modeling experiments by Pierce (2002), the PDO does not excite the climate modulation, but the PDO and these climate anomalies share the same forcing from the Tropics and from intrinsic variability of the Aleutian low. The impact of oceanic anomalies in the Kuroshio–Oyashio Extension complicates this picture at decadal time scales. The atmospheric response to these anomalies is likely small at best, and we do not expect a large trace of these in the climate over North America (Kushnir et al. 2002; Yulaeva et al. 2001). Furthermore, the relative roles of forcing are likely to be site dependent, and our results suggest, therefore, that the stratification of climate anomalies or teleconnection patterns be based on the underlying indices of ENSO and the NPI, rather than ENSO and the PDO.

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74. crucilandia
9:48 PM GMT on February 15, 2008
Yep. All the $$ is to "prove" that CO2 is to blame. Nobody studies in detail the natural fenomena in the oceans or atmophere.
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73. sullivanweather
4:40 PM EST on February 15, 2008

See what I mean??

Perhaps if more money was funded to understanding such processes that are natrual (as opposed to the tremendous amouts of money funded to research global warming) we'd know.

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72. crucilandia
9:40 PM GMT on February 15, 2008
yeah. I see the stars are saying something and the weather now is not following.
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70. crucilandia
9:28 PM GMT on February 15, 2008
The dynamics and the causative agents of PDO still poorly know. so

here is a good one

Latif, M. and T.P. Barnett, 1994: Causes of decadal climate variability over the North Pacific and North America.
Science 266, 634-637.
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68. sullivanweather
4:33 PM EST on February 15, 2008
Buster, the same way all heat escapes into space.
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66. sullivanweather
4:29 PM EST on February 15, 2008

There was no explaination.

I'm not 100% certain that it was the Milky Way, but they were looking to the stars for how they should plan for the weather. Certainly not the type of example that should have been used to explain how or why the climate is changing.
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63. crucilandia
9:26 PM GMT on February 15, 2008
so the milky way changed because of climate change? whatever. Even if looking to the milky way works for those guys to predict the weather, why is it no possible to do anymore?
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61. crucilandia
9:24 PM GMT on February 15, 2008
cyclone, sometimes I wonder if you are just saying things to bug us...

Think of what BTU means... is it a unit of particles/compounds?....
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60. sullivanweather
4:13 PM EST on February 15, 2008
After watching 'Six degrees can change the World' lsat night, I must say I am very disappointed in the program.

It seemed as though most of the program was based of legends and myths to explain that the climate is changing. For example, they used the example that natives in the Brazilian rain forest would looks towards the Milky Way to decipher upcoming weather patterns and that they could no longer do so because the climate has changed.

Sounds like a bunch of witch craft, to me.

There were a few other examples that I cannot remember right now that were very similar in approach to try and explain how the climate has changed that weren't science based. Oh well...


As for the paper I requested...

I would like to read a paper published in the last two years that goes to some length to explain PDO, how it changes, why it changes and what are it's effects in detail. If anyone could find such a paper I would greatly apppreciate it. This paper will also have to contain no reference to global warming induced climate change (there is no specific reason for me to look for a paper on PDO, I just want to see a paper that isn't full of global warming rhetoric). Remember, this paper should have been published within the previous two years (one would think such a paper would be easy to find since we are in the midst of a PDO regime shift, currently).
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58. hcubed
12:38 PM CST on February 15, 2008
Counters said:

"so that we can increase the accuracy of our fundamental assumptions"

Once again, must paraphrase:

"so that we can increase the accuracy of our fundamental statements that are assumed to be true for the sake of argument (assumptions)."

If, for your argument, they're already assumed to be true, how can you increase the accuracy of an assumption?
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57. crucilandia
2:13 PM GMT on February 15, 2008

what kind a paper are you looking for? atm oscillations, oceanic low frequency variability?
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56. crucilandia
2:12 PM GMT on February 15, 2008

how do you know they are lay? Do you think they would not understand a paper? You are an undergrad, so you are still pretty lay.
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55. sullivanweather
11:40 PM EST on February 14, 2008
I'd prefer a technical paper, but either or would suffice.

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54. counters
4:30 AM GMT on February 15, 2008
Re: #52

You want a technical paper or something written for the lay? I'm pretty busy between now and tuesday, but I might have some time to search for something related to your query.

However, I must protest your claim that there aren't papers written that don't "link everything imaginable to global warming induced climate change." I applaud your clear diction - you nail the correct phenomenon - but I believe the statement is disingenuous; there are precious few scientific papers that "link" things to global warming. What many researchers study, however, is how certain forcings may impact the overall effect. They run global climate models and tweak certain variables, or add new forcings, and see what overall effect that has. They're not "linking" anything; they're attempting to derive a better understanding of the climate system so that we can increase the accuracy of our fundamental assumptions and better determine what is going to happen to our climate.
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53. sullivanweather
10:56 PM EST on February 14, 2008
For those that missed 'Six degrees can change the world' on Sunday it is coming on in a few minutes.
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52. sullivanweather
6:44 PM EST on February 14, 2008
Hey Cal!

I'm really interested in seeing a scientific comparison of pre and post ~1970 variability though.

I'm with you on that one. However, I'm sure funding for that study will be hard to come by since most funding seems to be funneled into global warming err climate change research.

When was the last time you've seen a paper written about natrual variability of climate, or better yet, a paper written that doesn't link everything imaginable to global warming induced climate change.

If anyone out there knows of one, please, let me know!
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51. LowerCal
3:37 PM PST on February 14, 2008
#49 Global warming blamed for unusual cold spell

Another wonderful attention grabbing headline in the popular media. (That is their business-as-usual.)

Near the bottom of that article though,

Some experts have said the cold weather in China and Canada may be linked to La Nina, a sea-surface cooling pattern in the east Pacific, which leads to a warmer sea surface in the west Pacific near China and Asia.

"La Nina is causing warm moist air to move to the south of China," said Professor Yan Yuk- yee, who specializes in climatology at Hong Kong Baptist University. "When this meets the cold air of the monsoon, it causes freezing conditions."

It's surprising they included that but of course it was near the bottom. I predict with 95% certainty that "reporting" in the popular media will continue in this manner.

I'm really interested in seeing a scientific comparison of pre and post ~1970 variability though.
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50. sullivanweather
6:18 PM EST on February 14, 2008
Eh, I saw a similar story yesterday about the cold spell in Lebanon.

You know what they say...

You can't have your cake and eat it too.

I guess that applies here. Global warming is supossed to trigger warmer winters and warmer nights.

Last year when Tokyo had a snowless winter it was global warming, but then when someplace not accustomed to getting snow gets some it's also global warming.

In reality, what thy're getting is called weather.

Another good analogy that applies beautifully here...

"Climate is what you expect, weather is what you get" - Robert A. Heinlein
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49. sebastianjer
5:40 PM EST on February 14, 2008
Global warming blamed for unusual cold spell

Is this an oxymoron or just plain moronic.
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48. atmoexp
6:03 PM GMT on February 14, 2008
Visually the matches look good between observations and models but what correlation work has been done to statistically compare the data?
For example in the lab where I work we analyze the calibration curves by using correlation coefficents and linear estimates, the slope of the line, the y-intercept, etc - I'm sure there must be similar work done by climatologists after they run the models? Does anyone have any references (I'm pressed for time again)?
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47. hcubed
10:26 AM CST on February 14, 2008

Let's "re-define" a part of your statement:

"From the perspective of the scientific method, those statements that are assumed to be true for the sake of argument (assumptions) constitute a tentative explanation for a phenomenon, used as a basis for further investigation (hypothesis)."

To me, this means the results of the models are a STARTING point for future research. The results of models ARE NOT FACTS.
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46. hcubed
9:39 AM CST on February 14, 2008
30. counters said: 8:56 PM CST on February 13, 2008

"Re #26:

We make assumptions to simplify the models, and then run the models based on those assumptions. From the perspective of the scientific method, those assumptions constitute a hypothesis. Then, the models can illustrate what might happen to the climate system based on those assumptions."

So you input simplfied static values to start the climate model, and expect them to accurately illustrate what MIGHT happen to the dynamic, chaotic climate.

And if it doesn't match next year, you tweak it again. Hopefully, the changes you made to the input still match the past.
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45. sebastianjer
8:52 AM EST on February 14, 2008
Why worry about Global Warming perhaps will starve first

The Associated Press

Cereal stockpiles are expected to hit their lowest level in over two decades, contributing to keeping their prices high, a U.N. food agency said.

The low stocks combined with continuously strong demand - also driven by the growing biofuels industry - to keep prices elevated, the Food and Agriculture Organization said in a report on the global food situation, which was being released Wednesday.

By the close of the current season, stocks are expected to fall to 405 million tons - down 22 million tons, or 5 percent, from the start of the season, the Rome-based agency said. It would be the lowest level since 1982.

The food-and-supply demand remains tight, despite an increase in cereal production in 2007 and favorable prospects in 2008, the agency said.

"We do not anticipate a major downturn in prices even if production rises, because the increase would have to take into account the lower stocks," said Abdolreza Abbassian, an agency official who was part of a team working on the report.

The report said that "it may require significant increases in production of more than one season's cereal crop for markets to regain their stability and for prices to decline significantly below the recent highs."

In recent years, food prices have soared amid rising oil prices - which have increased food shipping prices - and growing demands for biofuels.

Biofuels, made from corn, palm oil, sugar cane and other agricultural products, are seen by many as a cleaner and cheaper way to meet the world's soaring energy needs compared to greenhouse gas-emitting fossil fuels.

It is estimated that some 100 million tons of cereals are currently used for the production of biofuels, making this sector a leading source of demand, the report said. Of this figure, maize accounts for 95 million tons, representing 12 percent of its total world utilization.

In 2007-08, the United States is expected to put at least 81 million tons of maize into the production of ethanol, which would be up 32 million tons, or 37 percent, from the previous season.

World cereal trade is expected to hit a new record in the current 2007-08 season, approaching 258 million tons, mainly due to a surge in imports in maize and other cereals by the European Union, the report said.


Well then again while we are starving the poorest people in the world and causing the world's economy unnecessary inflation, let's also make the perceived problem worse

Converting native ecosystems for production of biofuel feed stocks is worsening the greenhouse gas emissions they are intended to mitigate, reports a pair of studies published in the journal Science. The studies follow a series of reports that have linked ethanol and biodiesel production to increased carbon dioxide emissions, destruction of biodiverse forest and savanna habitats, and air and water pollution.

Analyzing the lifecycle emissions from biofuels, the first study found that carbon released by converting rainforests, peatlands, savannas, or grasslands often far outweighs the carbon savings from biofuels. Conversion of peatland rainforests for oil palm plantations for example, incurs a "carbon debt" of 423 years in Indonesia and Malaysia, while the carbon emission from clearing Amazon rainforest for soybeans takes 319 years of renewable soy biodiesel before the land can begin to lower greenhouse gas levels and mitigate global warming.


While a number of studies have shown that conversion of tropical ecosystems, including peat swamps in Southeast Asia and rainforests and grasslands in South America, for energy crops result in net emissions, the second study shows that when assessed at a global level, U.S. corn ethanol is also a major CO2 source — not a CO2 sink as usually claimed by the farm industry.

"Using a worldwide agricultural model to estimate emissions from land use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gasses for 167 years," write the authors.

Their assessment is based on the additional land that needs to be converted abroad as a result of increased corn acreage planted for ethanol production in the United States.

entire article

So let's get this straight. Not only are we driving up the price of food around the world, which hurts the poorest the worst, we are making it more profitable for people, both mega corporations and poor farmers in third world countries to destroy known carbon sinks to produce bio-fuel crops. In addition we are taking more food crops out of the supply line causing not only food shortages and increased food prices, but an increase in green house gas emissions.

All this and much more based upon projections of climate models. Is this what they mean when they say we don't have time to wait? We must do something now to stave off global disaster? Yes indeed let's shoot sulfur into the atmosphere while literally thousands are dieing of record cold weather. God forbid they should cut down a tree to burn to save their children's lives, it would increase their carbon footprint. ridiculous
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44. crucilandia
6:05 AM GMT on February 14, 2008
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43. crucilandia
5:49 AM GMT on February 14, 2008
ok no ad hominem you. just facts.

GW is a money machine, taxes for carbon go to other purposes.

Several countries in EU are taxing everything that makes CO2. So just wait, thanks to Al, we will be paying taxes per bag of coal etc.
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42. sullivanweather
12:16 AM EST on February 14, 2008
My girlfriend and I were talking about that earlier (the Clemens deal). I thought congress passed laws, not acted as prosecuters of the public? Who knows...

Indeed a waste of money and resources. Perhaps if that money was spent building a wind farm, improving the efficiency of solar panels or a methane capture system at a landfill etc...

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41. moonlightcowboy
4:58 AM GMT on February 14, 2008
Well said, Sully! And, you're absolutely right!

But, let's spend several million on geoengineering, while we're at it, too! Let's just see how much we can really screw up the environment! Hey, it doesn't matter that we've got emissions - no, we can just shoot some chemical up in the air and ignite it!

It doesn't matter that we've got people that need feeding. Let's just add something else to the budget that we can't pay for now anytime in the near future! Not to mention, how important is it that while all this is going on, we've actually got Congress questioning Clemens over drug use in baseball - talk about a waste of taxpayer dollars! Why don't they hold hearings on Congressional accountability instead - seems that would make much more sense(cents=trillions)!

Let's double or triple a budget for that geo experiment! Let's just leave science uninhibited to do as they wish while scaring the hell out of us at the same time!

Rant over!!!
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40. quasigeostropic
12:04 AM EST on February 14, 2008
oh and BTW, GW in itself is a chaotic system....
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39. quasigeostropic
12:00 AM EST on February 14, 2008
Washington is trying to pass legislation that would tax people over their fuel driven cars....as you might guess, it isn't popular so it will be hard to pass...but goes to show how they plan to profit off of man-made GW....
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Dr. Ricky Rood's Climate Change Blog

About RickyRood

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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