Urban 'heat island' effect is a small part of global warming; white roofs don't reduce it

Oct 19, 2011

Cities release more heat to the atmosphere than the rural vegetated areas around them, but how much influence these urban "heat islands" have on global warming has been a matter of debate. Now a study by Stanford researchers has quantified the contribution of the heat islands for the first time, showing that it is modest compared with what greenhouse gases contribute to global warming.

"Between 2 and 4 percent of the gross global warming since the may be due to islands," said Mark Z. Jacobson, a professor of civil and environmental engineering who led the study. He and graduate student John Ten Hoeve compare this with the contribution to gross warming of about 79 percent and the black carbon contribution of about 18 percent.

Black carbon is a component of the created by and biofuels and is highly efficient at absorbing sunlight, which heats the atmosphere.

Gross global warming is the total amount of warming that has taken place from all sources, mainly , black and heat islands. Net global warming is gross global warming minus the cooling effect of light-colored that reflect sunlight back into space, which offsets about half of global warming to date. Net, or observed, global warming is what is typically reported in the media.

Responding to skeptics

Jacobson and Ten Hoeve are authors of a paper describing the research that will be published in Journal of Climate. The paper is available online now. The study modeled climate response from 2005 to 2025.

Some global warming skeptics have claimed that the effect is so strong that it has been skewing temperature measurements that show that global warming is happening. They have argued that urban areas are a larger contributor to global warming than the greenhouse gases produced by human activity, and thus drastic measures to reduce greenhouse gases are not needed.

"This study shows that the urban heat island effect is a relatively minor contributor to warming, contrary to what climate skeptics have claimed," Jacobson said. "Greenhouse gases and particulate black carbon cause far more warming."

Prior to Jacobson's study, claims about the importance of heat island to global warming could not be addressed directly. The few previous modeling studies by other researchers that had examined the effect of urban heat islands on regional scales did not calculate global impacts.

Jacobson's high-resolution study was the first study of the impact of urban heat islands on global sea-surface temperatures, sea ice, atmospheric stability, aerosol concentrations, gas concentrations, clouds and precipitation. He characterized urban surfaces around the world at a resolution of one kilometer, making his simulation both extremely detailed and globally comprehensive.

"This study accounted not only for local impacts of the heat island effect, but also feedbacks of the effect to the global scale," he said.

Although his study showed that urban heat islands are not major contributors to global warming, Jacobson said reducing the effect of heat islands is still important for slowing the rise of global temperatures.

The urban is caused mostly by replacing soil and vegetation with paved roads, sidewalks and buildings. Paving prevents evaporation of water from the soil and plant leaves. Since evaporation is a cooling process, reducing evaporation warms cities. Additionally, the darker colors of some roads and buildings absorb more sunlight, heating a city further.

One "geoengineering" proposal for reducing the impact of urban heat islands is to paint roofs worldwide a reflective white. Jacobson's computer modeling concluded that white roofs did indeed cool urban surfaces. However, they caused a net global warming, largely because they reduced cloudiness slightly by increasing the stability of the air, thereby reducing the vertical transport of moisture and energy to clouds. In Jacobson's modeling, the reduction in cloudiness allowed more sunlight to reach the surface.

The increased sunlight reflected back into the atmosphere by white roofs in turn increased absorption of light by dark pollutants such as , which further increased heating of the atmosphere.

Jacobson's study did not examine one potential benefit of white roofs – a reduced demand for electricity to run air conditioning in hot weather. But a recent study done at the National Center for Atmospheric Research showed that the decrease in air conditioning use, which occurs mostly in the summer, might be more than offset by increases in heating during winter months.

"There does not seem to be a benefit from investing in white roofs," said Jacobson. "The most important thing is to reduce emissions of the pollutants that contribute to global warming."

Photovoltaic panels helpful

One way to reduce emissions while simultaneously reducing summer air conditioning demand is to install photovoltaic panels on roofs. Such panels not only generate electricity, reducing emissions of fossil fuels from electricity-producing power plants, but they also reduce sunlight absorbed by buildings because they convert sunlight to electricity. Because photovoltaic panels do not reflect the sunlight back to the air, unlike white roofs, reflected light is not available to be absorbed again by pollutants in the air, creating heat.

"Cooling your house with at the expense of warming the planet is not a very desirable trade-off," Jacobson said. "A warmer planet will melt the sea ice and glaciers faster, triggering feedbacks that will lead to even greater overall warming. There are more effective methods of reducing ."

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tpb
3 / 5 (16) Oct 19, 2011
"This study shows that the urban heat island effect is a relatively minor contributor to warming, contrary to what climate skeptics have claimed,"

This is willful distortion of the facts, no one says that the urban heat island effect is significant in heating the planet, what they are saying is that the temperature readings from the urban heat islands are significantly distorting the "global temperature readings", since most of the readings used to calculate global temperature come from stations in the urban settings.
Shootist
1.8 / 5 (19) Oct 19, 2011
algore charged with faking climate experiment. http://wattsupwit...re-49446

I wonder from whom he learned to do that?
Shootist
2.3 / 5 (19) Oct 19, 2011
"This study shows that the urban heat island effect is a relatively minor contributor to warming, contrary to what climate skeptics have claimed,"

This is willful distortion of the facts, no one says that the urban heat island effect is significant in heating the planet, what they are saying is that the temperature readings from the urban heat islands are significantly distorting the "global temperature readings", since most of the readings used to calculate global temperature come from stations in the urban settings.


You're correct, this astroturf 'science' is getting old. You can point to NOAA weather stations that were originally in rural settings that are now surrounded by concrete and tarmac. Of course their readings are higher now than earlier, of course these readings impact the measured data.

It is so simple only a moron, or an ax grinder, could miss the connection.
ryggesogn2
1.7 / 5 (11) Oct 19, 2011
A white roof helps keeps the house cool in a Tucson summer!

Reflected sunlight has a much shorter IR wavelengths than the IR emitted concrete, tar and shingles that absorbed the solar energy during the day.

Snow covered ground keeps the ambient temperatures cooler as most solar energy is reflected.

This 'study', or the reporting of it seems incomplete.
runrig
4.5 / 5 (8) Oct 19, 2011
"It is so simple only a moron, or an ax grinder, could miss the connection. "

precisely ... which is why they haven't.
bewertow
5 / 5 (7) Oct 19, 2011
I always wonder why people with no scientific background come here to troll climate/warming topics...
ryggesogn2
1.4 / 5 (11) Oct 19, 2011
Why do so many who claim to have a scientific background fail to understand emergence and the limits to the models that attempt to model that emergent system?
lairdwilcox
2 / 5 (12) Oct 20, 2011
Oh, No! Here I spent $16,000 and took off a perfectly good roof to put on bright white shingles, the neighbors are threatening me, the homes association is suing, my girlfriend left and birds are dropping blinded on my lawn. I trusted these AGW scientists and experts and they said white roofs would cool the planet and save the environment and now youre telling me they didnt know what they were talking about? This is terrible and I feel betrayed. I was hoping that everybody would love me for my social conscience, environmental awareness and self-sacrifice. Now they're calling me an enviro-nut. Wait until the deniers and corporate fascists hear about this! Its enough to make you lose your faith in AGW and join another cult.

NameIsNotNick
4 / 5 (9) Oct 20, 2011
I always wonder why people with no scientific background come here to troll climate/warming topics...

Because the typical anti-AGW troll belongs to that segment of society that believes scientists are members of a academic leftist elite and are motivated my Machiavellian schemes to make money, proving they not only have no scientific knowledge, but they have probably never even met a living, breathing scientist.
ryggesogn2
1.7 / 5 (17) Oct 20, 2011
Scientists are motivated by money. They resent free markets because the product of their academic work is ususally not in high economic demand.
A few decades ago, mathemeticians decided they were not going to value research the was practical. So phycis and engineering departments had to ramp up their own math classes for their engineering students who did want to do somenthing practical and had value.
And I have met Anderson, Lindzen and many others. Anderson from Harvard was quite a wild eyed AGW prophet.
Hayek had a pretty good theory too as to why so many 'intellecutals' support socialism. Govt subsidizes their universities and reseach so the 'intellectual' supplies the propganada to support the socialism.
Why is the ONLY solution for the AGW zealot MORE govt control of society? Assuming the AGW zealot has a hard science background why not propose hard science solutions instead increasing the size and power of the state?
antialias_physorg
4.7 / 5 (13) Oct 20, 2011
Scientists are motivated by money.

No. If we were motivated by money we'd go into business as consultants, freelance developers or simply join an R&D department of a company. The pay in any of these capacities is WAY above what a normal researchers at a university or state run facility makes.

You do science because you love it (and have an aptitude for it). I have yet to meet one scientist at any conference that is in it for the money.

(note also how scientists unanimously fail to own large mansions, expensive cars, trophy wives, ... )
NameIsNotNick
5 / 5 (2) Oct 20, 2011
If by "trophy" spouses.... if you mean really smart people, maybe a few ;-) Different standards...
antialias_physorg
5 / 5 (2) Oct 20, 2011
If by "trophy" spouses.... if you mean really smart people, maybe a few ;-) Different standards...

Well, you don't own a smart partner. I chose the word 'own' very carefully in the post above ;-)
NameIsNotNick
5 / 5 (3) Oct 20, 2011
It just didn't occur to me to associate the word "own" with "wife". I could get in a lot of trouble for that...
ryggesogn2
1.8 / 5 (15) Oct 20, 2011
You do science because you love it

Do you do it for free?
Bottom line is that you need money, which I suspect is quite frustrating for you. What are you willing to do and to whom to get funding for your projects?
Who are you more likely to convince for funding, private enterprise or the govt?
antialias_physorg
5 / 5 (6) Oct 20, 2011
Do you do it for free?

I would if I didn't have to eat/pay rent.

But yes: I do a little science in my spare time.
And while I was employed as a scientist I often spent the nights and wekeends at work (and it was not unusual to meet others there ... at my last science job it was actually more likely to meet all coworkers on the weekends than at any other time in the lab...with the notable exception of the project manager).

And no: we don't get paid by the hour and there is no such thing as overtime (or weekend pay)

Who are you more likely to convince for funding, private enterprise or the govt?

All projects I have been involved in were a mix of both. Getting funding isn't easy. Writing proposals that fly is hard work (since there are inevitably several groups applying for the same grant)

What are you willing to do and to whom to get funding for your projects?

You go look at what types of funding are available for the projects you want to do
ryggesogn2
1 / 5 (9) Oct 20, 2011
Yoe go look at what types of funding are available for the projects you want to do

Who is most likely to have available funding?
antialias_physorg
5 / 5 (4) Oct 20, 2011
Depends entirely on the type of research you're into.

As a very rough guideline I'd say the more theoretical your work is the more likely you're going to look for what kinds of government or international grants are available (note that the grant money is always available BEFORE anyone applies for it. It's not like scientists ask the government for money that needs to be diverted from somewhere else)
ryggesogn2
1.3 / 5 (13) Oct 20, 2011
(note that the grant money is always available BEFORE anyone applies for it. It's not like scientists ask the government for money that needs to be diverted from somewhere else

The grant (tax payers) money has already been diverted from more productive enterprises.
antialias_physorg
5 / 5 (6) Oct 21, 2011
The grant (tax payers) money has already been diverted from more productive enterprises.
Like? More weapons perhaps?
Remember that the research of today (no matter how theoretical it may seem) is the product of tomorrow. Don't do any research and history will pass you by in a hurry.

(Example: Baghdad was the center of research for many centuries, until they stopped in about the 14th century because they turned from a diverse, multi-ethnic and multi-religious society into a purely mono-religious one where enquiring minds were not welcome. The fall of the Arab empire was not long after that and they haven't recovered since.)

Governments set up framework programs every few years with emphasis on certain subjects (micromachines, meteorology, cloud computing, whatever...) because they see the need to get information on some subject or envision it to be crucial in order to remain competitive.

ryggesogn2
1.3 / 5 (14) Oct 21, 2011
Like?

Anything people do with THEIR money is BETTER and more productive than what YOU will do with THEIR money.

emphasis on certain subjects

And some private investor create new products and services the govt did not consider.
purely mono-religious

It is called Islam.

MA has a long legacy of trying to pick the next hot research area and subsidizing it with taxpayers money, and failing.
antialias_physorg
4.5 / 5 (8) Oct 21, 2011
It is called Islam.

Well I was trying to make it obvious that this is what is happening in the US right now. The nation is turning its back on science and going fo their mono-religion (it's called christianity) and starting to cut funding fo research.
Same result.
It seems that learning from history is not one of humanity's strong points.

Anything people do with THEIR money is BETTER and more productive than what YOU will do with THEIR money.

Unfortunately you would never find anyone who would have invested in research into quantum mechanics, superconductivity or the hole in the ozone layer, etc.
Some stuff is so fundamental (or big) that you don't know what will come of it - but that we have benefitted immensely from such fundamental research is pretty much indisputable.

You only get companies on board once the commercialization is imminent. But without the fundamentals we'd never have gotten there in many areas.
ryggesogn2
1.6 / 5 (14) Oct 21, 2011
The nation is turning its back on science

No, people are not trusting scientists who lie or promote a social agenda.
you would never find anyone who would have invested in research into quantum mechanics,

"Bohr was successful in creating a centre that attracted top young physicists from around the world, who (thanks to funding from the makers of Carlsberg Beer) were able to each spend a year or more being mentored by Bohr."http://qedinsight...necdote/
Vendicar_Decarian
3 / 5 (6) Oct 22, 2011
"algore charged with faking climate experiment." - Shootist

This kid is smarter than all of you denialists put together.

http://www.youtub...IaCKPlH4
Vendicar_Decarian
3.3 / 5 (7) Oct 22, 2011
"You're correct, this astroturf 'science' is getting old. You can point to NOAA weather stations that were originally in rural settings that are now surrounded by concrete and tarmac." - Shootist

And when they are removed from the temperature dataset, the temperature trend remains the same.

Not even Anthony Whatts could lie enough to make the trend to higher temperatures go away.

Why have you forgotten that Tard Boy?

Too Inconvenient a truth for you?
Vendicar_Decarian
3 / 5 (6) Oct 22, 2011
"No, people are not trusting scientists who lie or promote a social agenda." - RyggTard

You mean like Libertarians like you who have been repeatedly caught lying to promote your agenda?

Isn't id odd that whenever your side has accused scientists of lying, they have been investigated - often repeatedly - and it has been found that in reality it was the your side - the denialist side - which was actually the party guilty of lying?

Poor Libertarian. You are on the dishonest side of every issue.

Vendicar_Decarian
2 / 5 (4) Oct 22, 2011
Isn't socialism wonderful?

"It may not be inappropriate to mention here that the Royal Danish Academy of Science draws it's main financial support from the Carlsberg Brewery, which produces the best beer in the world. Many years ago, the founder of the brewery willed the income from it to the Academy to be used for the development of science, and it was specified in his will tha tthe palatial mansion which the old Carlsberg built for himself right in the middle of his brewery property was to be used as the residence of the most famous living Danish scientist. When Bohr came to his fame and the previous occupant of the Carlsberg Mansion died in the early thirties, Bohr and his family moved into it."

You see the same thing all over the Socialist world. For example in Canada there is RIMM funding the Perimeter Institute of theoretical physics.

Wonderful stuff this social contract.

Vendicar_Decarian
3.7 / 5 (9) Oct 22, 2011
"Anything people do with THEIR money is BETTER and more productive than what YOU will do with THEIR money." - RyggTard

Does that include finding a cure for Small pox? Chicken pox? Diphtheria? Invasive H. Flu? Malaria? Measles? Pertussis? Pneumococcal Disease? Polio? Tetanus? Yellow Fever? and Typhoid Fever?

Seriously RyggTard.. You can't be as stupid as you make yourself sound.

Are you actually intelligent enough to feed yourself?
Vendicar_Decarian
3.3 / 5 (7) Oct 22, 2011
"Scientists are motivated by money." - RyggTard

Scientists are trapped in a system in which money is needed to eat and purchase equipment. Outside of that motivation, money is typically very, very low on their priority list.

"They resent free markets..." - RyggTard

Unlike you we are smart enough to realize that "free markets" are PURE POISON.

You poor Tard you.
Vendicar_Decarian
3.4 / 5 (5) Oct 22, 2011
"Why is the ONLY solution for the AGW zealot MORE govt control of society?" - RyggTard

Why are you so mentally corrupt that you do not recognize that global problems require global solutions and global solutions require global organization.

Global Organization = Global Governance.
Vendicar_Decarian
3.7 / 5 (6) Oct 22, 2011
"Why do so many who claim to have a scientific background fail to understand emergence..." - RyggTard

Without positive feedback there would be no emergence. And you are in deep denial of positive feedback of Co2 enhanced warming.

Once again Tard Boy, you position yourself on the dishonest side of an issue.

How delightfully Libertarian of you.
Vendicar_Decarian
3.7 / 5 (6) Oct 22, 2011
"It is so simple only a moron, or an ax grinder, could miss the connection." - ShooTard

How did a moron like you miss this?

Greenhouse effect (in a bottle) explained
http://www.youtub...=related

And how did you miss that in your Whatts link, that the thermometers that your denialist friends used weren't placed in the same location in each cookie jar?

Don't you think that moving the thermometer closer to the side of the CO2 filled container will cause it's temperature to rise more slowly?

Oh well. We already knew that you were a dishonest fool.
Vendicar_Decarian
3.3 / 5 (7) Oct 22, 2011
"what they are saying is that the temperature readings from the urban heat islands are significantly distorting the "global temperature readings" - TBPTard

And when those urban heat islands are removed from the data set the trend is nearly identical.

You do know don't you that ocean temperatures show a similar warming trend, as do air temperatures over the ocean.

No heat islands there? Or are you going to blame aliens or men from Atlantis for that?

And of course satellites that measure the IR temperature of the earth's atmosphere show consistent warming trends in the lower atmosphere and cooling trends in the upper atmosphere that mesh with model results.

You poor Tard you. Were you born as stupid as you are now?

Could that even be possible?
antialias_physorg
5 / 5 (2) Oct 22, 2011
No, people are not trusting scientists who lie or promote a social agenda.

Funny how there are no scientist organizations that have anything about a social agenda in their charters. Must be one of those massive, global, hidden, secret, so-obvious-that-only-you-see-it-at-first-glance conspiracies.

Scientists have better things to do than play in sandboxes and throw poo at each other (i.e. engage in politics)
ryggesogn2
1.5 / 5 (8) Oct 22, 2011
Scientists have better things to do than play in sandboxes and throw poo at each other (i.e. engage in politics)

That's a laugh:
"Scientists must leave the ivory tower and become advocates, or civilization is endangered, says Stanford biologist"
http://www.physor...red.html
http://mahb.stanford.edu/
"UCS combines independent scientific research and citizen action to develop innovative, practical solutions and to secure responsible changes in government policy, corporate practices, and consumer choices. "
http://www.ucsusa.org/about/
antialias_physorg
5 / 5 (2) Oct 22, 2011
That someone has to make the point that scientists should get engaged all the more corroborates the fact that they curently aren't.

Certainly not on the global scale you seem to imagine. (Climate science isn't a US pet project, you know?)
antialias_physorg
4 / 5 (4) Oct 22, 2011
And you will be glad to hear that the following study received funds from:
"sources that back organisations lobbying against action on climate change."

including

"charitable foundations maintained by the Koch brothers, the billionaire US industrialists, who have also donated large sums to organisations lobbying against acceptance of man-made global warming."

http://www.bbc.co...15373071

And it is in remarkable agreement with all the previous studies done.
ryggesogn2
1 / 5 (6) Oct 22, 2011
Climate science isn't a US pet project, you know?

It is for many US govt agencies.
It required a congressional committee to force the NAS to even look at Mann's Hockey stick and were forced to slap him back.
It was Al Gore, now a multimillionaire from 'green' investments, who as a senator, launched the AGW panic.
Also, the IPCC is a POLITICAL organization, not a scientific one and it is the IPCC reports that are 'gospel' for climate scientists.
Don't forget how Ken Lay and Enron were pushing for Kyoto during the Clinton admin.
Shakescene21
2 / 5 (2) Oct 22, 2011
I'm skeptical about the statement that white roofs don't help slow global warming. At a bare minimum, the model doesn't seem to allow for the difference between white roofs in Houston and white roofs in Boston.
ryggesogn2
1 / 5 (5) Oct 22, 2011
I'm skeptical

Careful, you will be called a 'denier'.
Skepticism is not permitted in climate science. The American Physical Society won't allow it.
antialias_physorg
5 / 5 (1) Oct 22, 2011
It is for many US govt agencies.

So how do you account for the fact that they (with their supposedly secret agenda) come up with the same numbers as everyone else?
ryggesogn2
1 / 5 (5) Oct 22, 2011
What secret agenda?
The agenda of increasing their power is no secret.
What is interesting it the the UK and the US are proposing traceable on orbit radiometers to accurately measure the radiance of the earth.
Why would they want to do this IF the science is settled?
antialias_physorg
3 / 5 (2) Oct 22, 2011
If you go to the link I provided then you might notice that they already included such data (such sattelites are alraedy in orbit)

And: what power? What power do scientists have? what power do they excercise over the non-scientists?

I think you really need to take off that tinfoil hat. Talking to conspiracy theorists is no fun.
satanfornoreason
5 / 5 (1) Oct 22, 2011
Vendicar_Decarian

I totally agree with the points that you are making. Try not to take the bait when people try to distract you away from talking about the science - which is the issue - and start talking about politics. Don't address the politics, because you can't win: logic and reason play no part there, so you'll just end up frustrated, and you've gone down a path away from the subject.

Also, like I said, you make very good points and I agree with them, but I did report several of your comments because you're calling people names, which is another tactic commonly used by the people that you're arguing with.

Just like a few bad apple scientists can cause unnecessary doubt about the great majority of accurate scientific research and theory (for example, by manipulating data, being dishonest, etc.), calling people Tard is what kids do when they argue. Name-calling casts doubt on your other statements, and reduces the credibility of others who share your ideas.
ryggesogn2
1 / 5 (5) Oct 22, 2011
If you go to the link I provided then you might notice that they already included such data (such sattelites are alraedy in orbit)

"The Earth's climate is undoubtedly changing, but how fast and what the implications will be are unclear. Our most reliable models rely on data acquired through a range of complex measurements."
"Firstly, we have to detect small changes in the levels of radiation or reflection from a background fluctuating as a result of natural variability. "
"Secondly, satellites, particularly optical usually lose their calibration during the launch, and this drifts further over time.

The result is varying model forecasts. "
"TRUTHS will be the first satellite to have high accuracy traceability to SI units established in orbit. "
http://www.npl.co...Doc/4823
The science is settled. Why waste the money?
Skepticus_Rex
1 / 5 (4) Oct 22, 2011
No real controls, the rheostat closer to the CO2 jar than to the so-called control jar (which can alter the result if the CO2 jar absorbed and transmitted IR emitted from the rheostat), and no record of ppmv of CO2. Some experiment that was! He also did not come up with this experiment. It is actually a rather old experiment that has been done in Earth Science and Physics classes for decades. The average version of this experiment uses 1000s ppmv of CO2, which is not realistic.

And did the kid say, "My hypothesis OR gas..."? Since when did an hypothesis become a gas or vice versa? The kid also seems to have little to no real idea of either the composition of solar radiation or of the source of the IR that is trapped in the atmosphere by the so-called greenhouse effect.

Yeah, he exactly is the epitome of AGW/AGCC religionists. :)

By the way, for the record I sit on the fence waiting for either side to produce something more convincing than the other without tainting the data.
djr
not rated yet Oct 23, 2011
"congressional committee to force the NAS to even look at Mann's Hockey stick and were forced to slap him back."
Can you give us a source on this rygge? I found this report from the NAS that validates the Mann hockey stick. http://www.nap.ed...p;page=1 "This conclusion has subsequently been supported by an array of evidence" P.3
Why do you keep bringing up the hockey stick? - something according to the NAS (group that you quoted) is very much validated. It seems you are on a mission to skew perspectives - but evidence would suggest you just want to spread disinformation.
Skepticus_Rex
1 / 5 (3) Oct 23, 2011
The following warnings, taken from chapter 9 of the document you linked, would seem to be applicable:

The standard proxy reconstructions based on linear regression are generally reasonable statistical methods for estimating past temperatures but may be associated with substantial uncertainty.

There is a need for more rigorous statistical error characterization for proxy reconstructions of temperature that includes accounting for temporal correlation and the choice of principal components.

The variability of proxy reconstructed temperatures will be less than the variability of the actual temperatures and may not reproduce the actual temperature pattern at particular timescales.

To be continued...
Skepticus_Rex
1 / 5 (3) Oct 23, 2011
...continued.

Examining the prediction of the reconstruction in a validation period is important, but the length of this period sets limits on a statistical appraisal of the uncertainty in the reconstruction. Most critically, the relatively short instrumental temperature record provides very few degrees of freedom for verifying the low-frequency content of a reconstruction.

The differences among a collection of proxy reconstructions that have not been deliberately created as a representative statistical sample may not reveal the full uncertainty in any one of them.

Source: http://www.nap.ed...;page=83

Skepticus_Rex
1 / 5 (3) Oct 23, 2011
Continued...

Differences and variations between the models are discussed on page 106 of the same document, including the following problems:

None of the long transient simulations have included wave-length-dependent changes in solar irradiance, although this effect has been investigated with shorter sensitivity simulations and has been shown to impact regional surface climate (Shindell et al. 2001). Volcanic reconstructions used in the various climate model simulations show similar timing of major volcanic eruptions and temporal clusters of eruptions. The models differ in the conversion of volcanic sulfate loading into optical depth and in the seasonally dependent horizontal and vertical dispersion of the aerosol cloud. The models also vary with respect to the specifics of the radiative transfer calculations included for volcanic aerosols.
Skepticus_Rex
1 / 5 (3) Oct 23, 2011
Continued...

On the same page we also see the following cautionary statement regarding differences between the known climate models as to climate forcing and climate sensitivity at the time of the writing of said document:

Differences between the various model simulations can also be related to differences in the sensitivity of the models (Goosse et al. 2005). Two of the models, CSM and GKSS, are full three-dimensional climate models and have equilibrium climate sensitivities of 2°C and 3.2°C, respectively, for doubling of atmospheric CO2. Some simpler models have an adjustable climate sensitivity (i.e., the Gerber 1.5 × CO2 and 2.5 × CO2 simulations). Different models also exhibit different sensitivities to different external forcings.
djr
5 / 5 (1) Oct 23, 2011
What's your point Skepticus? The scientists compiling this report recognize that there are uncertainties when trying to reconstruct historical data - and they discuss these uncertainties - as you point out. However - they conclude that the basic premise of the hockey stick is valid. I qoute - "The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators. You guys keep beating a dead horse. You have a political point you are trying to make. You do not understand the science.
Skepticus_Rex
1 / 5 (3) Oct 23, 2011
And, you don't have a political point you are trying to make? I actually don't. I am a fence-sitter and proud of it. :)

Mann et al. had too short a timeline with considerable uncertainty in the proxy data that they used. Have you noted the height of the upper uncertainty in the datasets they used and wherein they lined up with or even exceeded the modern warming at points? Check the raw data (where available) for yourself.

And, because there is variability in the underlying assumptions in the models they are problematic at best. All agreed as to warming but none agreed as to amount of warming, degree of sensitivity of forcings, climate sensitivity, or precise methodology.

Until they agree there still is too much uncertainty to be precise enough to determine cause and effect that match with real-life observations. It's hard to admit, I know. :)
Skepticus_Rex
1 / 5 (3) Oct 23, 2011
The substantial uncertainties currently present in the quantitative assessment of large-scale surface temperature changes prior to about A.D. 1600 lower our confidence in this conclusion compared to the high level of confidence we place in the Little Ice Age cooling and 20th century warming. Even less confidence can be placed in the original conclusions by Mann et al. (1999) that the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods, and because not all of the available proxies record temperature information on such short timescales.


http://www.nap.ed...page=115

Yeah, that certainly is a ringing endorsement of and inspires unwavering confidence in the Mann 'hockey-stick' graph, alright. :)
djr
not rated yet Oct 23, 2011
No - not a political point - a point about science - which is basically to let the scientists who are doing the research be the ones to draw the conclusions. I provide you with a report that cites studies indicating 95% or more of climate scientists accept that premise that earth is warming, and the most likely driver is human activity. http://www.skepti...iate.htm This report lists all the scientific organizations supporting the consensus on global warming. Please show me your list of organizations that disagree! I won't hold my breath. I will leave you with a quote "As the level of active research and specialization in climate science increases, so does agreement that humans are significantly changing global temperatures." So my question was "why do you keep beating a dead horse, and raising the issue of the hockey stick?" It is clearly you who have a political agenda - I am on the side of science.
Skepticus_Rex
1 / 5 (3) Oct 23, 2011
So, what do you think about the fact that the paper you cited did not support your view on the subject? Something about too much uncertainty or some such... :)

And, so far as "consensus" goes, I would rather side with Bertrand Russell, who wrote in his Skeptical Essays: "Even when the experts all agree they may well be mistaken." That has been demonstrated time and again across the entire spectrum of all fields of science and religion. I have always been skeptical. That is why I chose science, after all.

Nothing either is sacred or is status quo, and everything potentially is falsifiable. If you don't have such a mindset, you apparently are not well enough acquainted with science as you might think. :)
djr
not rated yet Oct 23, 2011
So, what do you think about the fact that the paper you cited did not support your view on the subject?

That is flat out false - you are wrong - I repost my quote above from the summary of the paper.

"The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators
djr
not rated yet Oct 23, 2011
Interesting that this whole discussion started with asking for a source that substantiated the claim the the NAS was forced slap Mann back for his hockey stick curve. I am not holding my breath.
djr
not rated yet Oct 23, 2011
And, so far as "consensus" goes, I would rather side with Bertrand Russell, who wrote in his Skeptical Essays:

God you seem thick to me. If 99% of the doctors believe that vaccinations protect your children, and 1% tell you not to - because it causes autism - do you quote Bertrand Russell, and not have them vaccinated?
ryggesogn2
1 / 5 (3) Oct 23, 2011
Interesting that this whole discussion started with asking for a source that substantiated the claim the the NAS was forced slap Mann back for his hockey stick curve. I am not holding my breath.

Ever hear of Google?

"In response to a request from Congress, Surface Temperature Reconstructions for the Last 2,000 Years assesses the state of scientific efforts to reconstruct surface temperature records for Earth during approximately the last 2,000 years and the implications of these efforts for our understanding of global climate change. Because widespread, reliable temperature records are available only for the last 150 years,"
http://www.nap.ed...cription
ryggesogn2
1 / 5 (3) Oct 23, 2011
99% of the doctors believe..

Doctors used to believe bleeding helped, they also did not believe bacteria caused ulcers they didn't believe in sterilizing instruments for surgery, they....
Consensus kills.
djr
not rated yet Oct 23, 2011
rygg - your quote in no way supports the assertion that the NAS was forced to slap Mann back for his hockey stick curve. I am not holding my breath. Also your point about the doctors in no way answers the question about listening to doctors on current scientific consensus. Do you have your children vaccinated, or quote Bertrand Russell? It is a simple question. I go with the consensus. Future science may change our understanding - but we go with current best data. Works for me. I sense you prefer to make up your own data. Your privilege! - it just bothers me that you guys want to plaster web sites with your disinformation....
djr
not rated yet Oct 23, 2011
"Because widespread, reliable temperature records are available only for the last 150 years,"

From the very same report - "Large-scale surface temperature reconstructions yield a generally consistent picture of temperature trends during the preceding millennium," P.2

Cherry pick away - it does not change the science.....
ryggesogn2
1 / 5 (4) Oct 23, 2011
Congress demanded NAS address the issue after refusing previous requests.
dir, read the report. Any data prior to 400 years ago, based upon Mann's proxy's are highly uncertain.
ryggesogn2
1 / 5 (3) Oct 23, 2011
"This plot (hockey stick)purports to show that we are now experiencing the warmest climate in a millennium, and that the earth, after remaining cool for centuries during the medieval era, suddenly began to heat up about 100 years ago--just at the time that the burning of coal and oil led to an increase in atmospheric levels of carbon dioxide."
"But now a shock: Canadian scientists Stephen McIntyre and Ross McKitrick have uncovered a fundamental mathematical flaw in the computer program that was used to produce the hockey stick."
http://www.techno...y/13830/
If not for the Congressional hearing, McIntyre and McKitrick's critique would not have been allowed by the AGW press.
Skepticus_Rex
1 / 5 (3) Oct 24, 2011
So, djr, I take it that you have only read the summary, then. Did you forget about this from page 115:

"The substantial uncertainties currently present in the quantitative assessment of large-scale surface temperature changes prior to about A.D. 1600 lower our confidence in this conclusion compared to the high level of confidence we place in the Little Ice Age cooling and 20th century warming. Even less confidence can be placed in the original conclusions by Mann et al. (1999) that the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods, and because not all of the available proxies record temperature information on such short timescales."

That does not give room for pause of thought? Mann's 1999 material addressed by this quote is the original source material for the hockey-stick graph. :)
Skepticus_Rex
1 / 5 (3) Oct 24, 2011
And, what of the fact that it hasn't really warmed in ten years? If we accepted infilled data it looks like we heated up by less than a tenth of a degree in a decade. It should have been 1.5 degrees C higher than it is by now if IPCC model-based predictions had held out.

If we, on the other hand, reject the infilled data and accept only the real data it actually has cooled very slightly instead of getting warmer. In either case we have been sitting on a statistical plateau for the last decade.

Thoughts about that? :)
Skepticus_Rex
1 / 5 (4) Oct 25, 2011
For those interested in how badly the IPCC models did in comparison with real life (they missed their temperature prediction target because of failing to take other climate elements into consideration), visit the following site.

http://journals.a...LI3461.1

That is the abstract. You will have to pay to view the actual content if you don't have a subscription.