Greenhouse Effect Experimental Designs

[CraigD]

Repeated, random capture or release of CO₂ will [math]\text{\sout{cancel}}[/math] minimize extraneous variables. All things being equal over time, the only significant change will be the quantity of CO₂ emitted or captured.

...

Randomization may not be a well known element of experimental testing. I provide the following:

 

Randomized experiment - Wikipedia, the free encyclopedia

 

"Randomization reduces bias by equalising other factors that have not been explicitly accounted for in the experimental design (according to the law of large numbers). "

...

Thanks for the explanation and links, Brian. However, what leads you to conclude that a randomized design for the experiment you propose in this thread – releasing and capturing [ce]CO2[/ce] into the Earth’s atmosphere while taking temperature readings, where the release of [ce]CO2[/ce] – presumably the amount, possibly other factors, such as the locations and duration of the releases and captures – is randomized, but the “member of the treatment group” (taking the phrase from the linked wikipedia article) – where, in this case, the “treatment group” consists of planets nearly identical, so randomizing it would consist of choosing which Earth-like planet has [ce]CO2[/ce] added or removed from its atmosphere– is not, is an good, or even a required, design? Have you encountered writing where someone expert in climate science agrees with this suggestion?

 

The obvious problem with this approach is that, unlike with a drug trail, where hundreds or thousands of animal or volunteer humans are available from which to chose, we don’t have a large physical population of Earth-like planets from which to randomly choose – unless, rather than choosing actual physical planets, we choose from different climate-modeling computer programs, and different program parameter.

 

In, for example, in a clinical drug trial, all the factors affecting the efficacy and safety of the drug that vary among the human population are not understood. Therefore, rather than selecting special test subjects, such as people theory suggest will be most effectively treated by the trialed drug, or all people who volunteer for the trial, a random population is selected, and divided into a group who receives the prescribed dose of the drug – the experiment group – and a group that doesn’t – the control group. From this, the researchers are able to predict the efficacy and safety of the drug is used by the much larger population of prospective patients.

 

With Earth, one is all we have. You can’t randomly choose from a population of one, so this statistical technique isn’t usable for your proposed experiment.

 

Statistical methods are certainly used extensively in climate and other physical sciences – average global temperature is inherently a statistically inferred quantity, as we can’t measure the speed of every atom in the Earth’s atmosphere to calculate it’s exact average temperature, so must rely on the few that interact with thermometers. However, not all statistical methods are appropriate to all experiments.

 

The selection of the treatment groups, not the drug dose or, is what’s random in a randomized drug trial. Thus, if these statistical methods were to be applied to planet climates in the way you propose, the selection of planets, not the amount, rate of release, or other factors involving [ce]CO2[/ce], is what would be randomized.

[BrianG]

...With Earth, one is all we have. You can’t randomly choose from a population of one, so this statistical technique isn’t usable for your proposed experiment...

 

This is true, it was discussed back on post 21:

 

http://hypography.com/forums/environmental-studies/21736-greenhouse-effect-experimental-designs-2.html#post287714

 

We may discuss it further, as needed. Since we have only one subject, we need to rely on one subject experimental designs. Fortunately these are well tested, here's the basics from Wikipedia:

 

There are experimental designs for testing a single subject: Single-subject research - Wikipedia, the free encyclopedia

 

"Single-subject research is a group of research methods that are used extensively in the experimental analysis of behavior and applied behavior analysis with both human and non-human participants. Four principal methods in this type of research are: changing criterion, reversal ("ABA"), alternating treatments, and multiple baseline. In verbal behavior research the multipleprobe research design is popular.

These methods form the heart of the data collection and analytic code of behavior analysis. Behavior analysis is data driven, inductive, and disinclined to hypothetico-deductive methods. Statistical methods, from The Behavior of Organisms (Skinner 1938) until now, have been largely ignored.

 

The AB design is the simplest version of this design in which a baseline ("A") is tracked, and then some treatment ("B") is implemented. If there is a change then the treatment is said to have had an effect. However, it is subject to many possible competing hypotheses, making it a very weak research design. The other variants essentially introduce ways to control for the competing hypotheses.

 

In a changing-criterion research design a criterion for reinforcement is changed across the experiment to demonstrate the functional relationship between the reinforcement and the behavior. See Mark Dixon's work with a participant using a short video clip to generate a preference for a progressively delayed variable reinforcement over a fixed shorter delay reinforcement in physical therapy.

 

The reversal design is the most powerful of the single-subject research designs showing a strong reversal from baseline ("A") to treatment ("B") and back again. However, many interventions cannot be reversed, some for ethical reasons (e.g., involving self-injurious behavior, smoking) and some for practical reasons (they cannot be unlearned, like a skill.

 

The alternating-treatment design is used in order to ascertain the comparative effect of two treatments. Two treatments are alternated in rapid succession and correlated changes are plotted on a graph to facilitate comparison."

 

Further information from: Single-subject design - Wikipedia, the free encyclopedia

 

"Single-subject design or single-case research design is a research design most often used in applied fields of psychology, education, and human behavior in which the subject serves as his/her own control, rather than using another individual/group. Researchers use single-subject design because these designs are sensitive to individual organism differences vs group designs which are sensitive to averages of groups. Often there will be large numbers of subjects in a research study using single-subject design, however--because the subject serves as their own control, this is still a single-subject design. These designs are used primarily to evaluate the effect of a variety of interventions in applied research.

 

 

The following are requirements of single-subject designs:

 

Continuous assessment: The behavior of the individual is observed repeatedly over the course of the intervention. This insures that any treatment effects are observed long enough to convince the scientist that the treatment produces a lasting effect.

 

Baseline assessment: Before the treatment is implemented, researcher to look for behavioral trends. If a treatment reverses a baseline trend (e.g., things were getting worse as time went on in baseline but the treatment reversed this trend) then this is powerful evidence suggesting (though not proving) a treatment effect.

 

Variability in data: Because behavior is assessed repeatedly, the single-subject design allows the researcher to see how consistently the treatment changes behavior from day-to-day. Large-group statistical designs do not typically provide this information because repeated assessments are not usually not taken and the behavior of individuals in the groups are not scrutinized; instead, group means are reported.

 

Phases within single-subject design

 

Baseline: this phase is one in which the researcher collects data on the dependent variable without any intervention in place.

 

Intervention: this phase is one in which the researcher introduces an independent variable (the intervention) and then collects data on the dependent variable.

 

Reversal: this phase is one in which the researcher removes the independent variable (reversal) and then collects data on the dependent variable.

It is important that the data are stable (steady trend and low variability) before the researcher moves to the next phase. Single-subject designs produce or approximate three levels of knowledge: (1) descriptive, (2) correlational, and (3) causal

 

Flexibility of the design

Single-subject designs are preferred because they are highly flexible and highlight individual differences in response to intervention effects. In general, single-subject designs have been shown to reduce interpretation bias for counselors when doing therapy.

 

Interpretation of data

In order to determine the effect of the independent variable on the dependent variable, the researcher will graph the data collected and visually inspect the differences between phases. If there is a clear distinction between baseline and intervention, and then the data returns to the same trends/level during reversal, a functional relation between the variables is inferred. Sometimes, visual inspection of the data demonstrates results that statistical tests fail to find.

 

Researchers utilizing single-subject design begin with Graphic analysis. During the baseline, data are repeatedly collected and then graphed on the behavior of interest. This provides a visual representation of the subject’s behavior before application of the intervention. It is critical that several (three to five is often recommended) data points are collected during baseline to allow the researcher to describe the effects on the target behavior during intervention.

 

In interpreting, the general strategy of all single-subject research is to use the subject as their own control. Experimental logic argues that the subjects baseline behavior would match its behavior in the intervention phase unless the intervention does something to change it. This logic then holds to rule out confound, one needs to replicate. It is the within subject replication and allows for the determination of functional relationships. Thus the goal is:

 

Prediction

Verification

Replication

 

Meta-analysis of single-subject research

Currently, several efforts exist to combine single-subject effects to determine the effect size of well researched interventions. Meta-analysis, like all research, has the ability to change a profession. For example, Gresham and colleagues (2004) in a meta-analytic review of JABA articles found that functional analysis did not produce greater effect sizes compared to simplecontingency management programs. Currently, researchers are debating the most effective and accurate way of doing a meta-analysis of single-subject designs. The two choices being debated are the percentage nonoverlapping data(PND) vs. data points exceeding the median(PEM) method. Noorgate and colleagues have argued that meta-analyses that analyze all linear trends in data don’t work since they don’t distinguish between effects on level and slope.

 

Limitations of single-subject design

Research designs are traditionally preplanned so that most of the details about to whom and when the intervention will be introduced are decided prior to the beginning of the study. However, in single-subject designs, these decisions are often made as the data are collected. In addition, there are no widely agreed upon rules for altering phases, so – this could lead to conflicting ideas as to how a research experiment should be conducted in single-subject design.

 

The major criticism of single-subject designs are:

 

Carry-over effects: results from the previous phase carry-over into the next phase,

Order effects: the ordering (sequence) of the intervention or treatment affects what results

Irreversability: in some withdrawal designs, once a change in the independent variable occurs, the dependent variable is effected this cannot be undone by simply removing the independent variable.

Ethical problems: Withdrawal of treatment in the withdrawal design can at times present ethical and feasibility problems."

 

Peer reviewed studies of single case experimental designs can be found here:

 

Multiple baseline designs: the use of a single-case experimental design in literacy research | Reading Improvement | Find Articles at BNET

 

Just because we have a limited (but finite) pool of experimental subject, doesn't mean we should give up on experimental science. Experimental science is the scalpel of technology and practical scientific advancement, we don't want to rely on faith, superstition or coincidence, when we can do the very best science possible. We understand, one Earth, it's a limitation to selecting subjects, we can't randomly assign planets to experimental groups.

 

Randomizing the variables we can manipulate, the emission or capture of [ce]CO2[/ce], quantity, duration, where and when will bring us closer to an experimental, empirical understanding of causality. Abandoning experiments in climate research is IMHO, not a good indication of reliable science.

[BrianG]

Repeated, random capture or release of CO₂ will [math]\text{\sout{cancel}}[/math] minimize extraneous variables. All things being equal over time, the only significant change will be the quantity of CO₂ emitted or captured. If you can repeatedly and randomly emit a known quantity of CO₂, or capture a known quantity and subsequently measure a temperature increase or decrease, then you know how much carbon dioxide causes how much warming. This will help us test computer climate models, determine the climate benefits of CO₂ emission restrictions and teach good science.

 

You guys give too many points, for infractions. I should have half as many, this is inflation. You’re wrong to think you can't do experimental tests on one subject, a planet. You can debate if it's ethical, you can argue however you like.

 

There's a technique, experimental testing, that shows a probability of change. Go ahead and ignore science, insist on a sacred duty to care for the world. Right and wrong can be judged. Let's just see, science isn't about hiding information, truth always wins out, over time.

 

“You can fool some people some of the time and most people most of the time but you can't fool all of the people, all of the time.” And I can’t post that in quotes, why is that? These things seem to become obvious. And two points per infraction, for improvable infractions, is too many. I should have three points reduced because too many were taken.

 

Sure, repeated, random experimental tests can't reduce uncertainty to zero, it can't cancel all error, but that's the goal of experimental testing. It's different from faith and theory in a quantitative way. That's why it works. A single Earth, that's all we've got. We owe it to Earth, to do the best science, to get experimental measurements. Eject or capture a greenhouse gas, on a large scale. Make a climate measurement, find correlation. The more trials, the more the observed results correlate with the capture or emission, the better the experimental science works. Not canceling errors, minimizing them.

[Zythryn]

Brian, you keep equating criticism of your 'single variable' experimental method with 'abondoning experimental science'.

Far from it, much experimental science is used in the GW studies.

We already do release tons of CO2 into the air and we do measure the effects.

The problems with direct experiments with this are:

A) Takiing CO2 out of the atmosphere is not fesible right now, so you can't reverse the test.

:) The results take years to see, and the other variables are not minimized easily, which would required the test to be run more times than is feasible. In other words, using your method alone, I don't think you would be able to draw a conclusion without running the test 1000's of times, at a minimum.

Isolating the variable and determining the physical properties of CO2 in the lab is the best way to start. Sure, run tests on the atmosphere as a whole as well, but why stop other experiments?

[BrianG]

Plants take CO₂ out of the air, they are cheap and plentiful. If we need to run an experiment a thousand times, we can do it, it's been done before. The lab experiments cited in the first post for this thread show a very weak greenhouse effect from doubling CO₂, about [math]0.5\celsius[/math], far lower than the IPCC's projection from the preindustrial ideal of 280ppmv, to our current approx 390ppmv.

 

Are there other lab experiments that show a stronger greenhouse effect? Do larger vessels, longer exposure or brighter IR light sources influence the effect?

[CraigD]

Plants take CO₂ out of the air, they are cheap and plentiful.

This is true. Plants essentially convert [ce]CO_2[/ce] + [ce]H_2O[/ce], carbon dioxide and water, into [ce](C_6H_{10}O_5)_n[/ce] + [ce]O_2[/ce], cellulose and other polysaccharides and oxygen. The solid polysaccharides – plant tissue – are removed from the atmosphere.

 

Ecologically, however, this transformation is not the end. Plant tissue is ingested by animals small and large, so much of the [ce](C_6H_{10}O_5)_n[/ce], is returned to the atmosphere as [ce]CO_2[/ce], [ce]CH_4[/ce] (methane), and other gasses, many of them strong greenhouse gasses. Some is burned, releasing mainly [ce]CO_2[/ce].

 

So, for plants to be used to remove carbon from the atmosphere, they must not only convert [ce]CO_2[/ce] + [ce]H_2O[/ce] into [ce](C_6H_{10}O_5)_n[/ce], the polysaccharides must be kept from burning and consumption by animals. For this to happen, it must form sediments, and these sediments be buried and compressed.

 

Because sedimentation occurs more reliable in water than on land, some of the more promising carbon sequestrations schemes involve a technique known as iron fertilization. The ocean contains much potential plant-like metabolism the form of phytoplankton, which are primarily algae. Their metabolism is restricted by the lack of nutrients uncommon in water, primarily iron. Thus, adding iron, such as in the form of [ce]FeSO_4[/ce] (iron sulfate), “starved” phytoplankton can be “turned on” to sequester carbon in the form of ocean and lake floor sediments.

 

Although an as yet only slightly explored technique, and much a more controversial approach than the more straightforward reduction of artificial greenhouse gas emissions, some estimate that, done on a large scale, iron fertilization could remove about 1 GtC/y, about 1/6th of that currently added by fossil fuel burning and cement production.

 

Land plants remove much more carbon from the atmosphere, about 122 GtC/y, but return it at about the same rate. Thus, a smaller sink that deposits most of its carbon in sediments can be more effective than a large sink that doesn’t.

 

(atmospheric carbon fluxes from the wikipedia article “carbon cycle”

If we need to run an experiment a thousand times, we can do it, it's been done before.

Obviously, an experiment that takes many years to run once, that can’t be run many times simultaneously, takes may thousands of years to run a thousand times. The experiment Brian proposes in this thread – burning huge amounts of coal to increase atmospheric [ce]CO_2[/ce] concentration at a much greater rate than the current burning of coal and other fuels – would, I expect, like the unintentional increased release of [ce]CO_2[/ce] from burning fuel for practical purposes, require many years to produce a detectable affect.

 

We – humankind – have not done this – an experiment that takes many thousands of years to repeat a thousand times – before.

The lab experiments cited in the first post for this thread show a very weak greenhouse effect from doubling CO₂, about [math]0.5\celsius[/math], far lower than the IPCC's projection from the preindustrial ideal of 280ppmv, to our current approx 390ppmv.

 

Are there other lab experiments that show a stronger greenhouse effect? Do larger vessels, longer exposure or brighter IR light sources influence the effect?

:Exclamati Here, Brian, I believe you misunderstand the fundamental science of the experiments you mention, and are misquoting their results.

 

Experiment - The Greenhouse Effect gives the results of 20 minutes of lighting of a glass vessel containing 0.037% (normal atmospheric) compared to 100% (pure) [ce]CO_2[/ce]. The normal air vessel increases from 22 to 44 C. The pure [ce]CO_2[/ce] vessel increased from 22 to 50.

 

Pico Technology Experiment: Global Warming gives the results of 20 minutes of lighting of a normal air vessel compared to one of unknown but higher than normal air [ce]CO_2[/ce]. The normal air increases from 22 to 25 C in 20 min, the other, from 22 to 30

 

Is the Earth Warming? gives instructions for an experiment in which a vessel of normal air is compared to one with twice the normal [ce]CO_2[/ce] concentration. Unlike the previous 2 experiments, this one measures the decrease in temperature over time in the 2 vessels after the light source is removed. It doesn’t provide results.

 

Though the last experiment compares a vessel of air to one with double the [ce]CO_2[/ce] concentration, none of them describe a 0.5 C difference in temperature.

 

None of these experiments is a “earth in miniature” experiment, intended to simulate Earth’s greenhouse effect. They’re intended simply to demonstrate to students how to experimentally demonstrate that increased [ce]CO_2[/ce] results in an increased greenhouse effect.

 

Earth is more complicated, storing heat not just in its atmosphere, but in its waters and solids.

 

Because it’s not possible to scale down important physical laws, such as gravity and fluid dynamics, I don’t believe its possible to conduct a table-top “earth in miniature” experiment that can accurately model the effect of the greenhouse effect on its climate.

[BrianG]

...

 

:Exclamati Here, Brian, I believe you misunderstand the fundamental science of the experiments you mention, and are misquoting their results.

 

Experiment - The Greenhouse Effect gives the results of 20 minutes of lighting of a glass vessel containing 0.037% (normal atmospheric) compared to 100% (pure) [ce]CO_2[/ce]. The normal air vessel increases from 22 to 44 C. The pure [ce]CO_2[/ce] vessel increased from 22 to 50.

 

Pico Technology Experiment: Global Warming gives the results of 20 minutes of lighting of a normal air vessel compared to one of unknown but higher than normal air [ce]CO_2[/ce]. The normal air increases from 22 to 25 C in 20 min, the other, from 22 to 30

 

Is the Earth Warming? gives instructions for an experiment in which a vessel of normal air is compared to one with twice the normal [ce]CO_2[/ce] concentration. Unlike the previous 2 experiments, this one measures the decrease in temperature over time in the 2 vessels after the light source is removed. It doesn’t provide results.

 

Though the last experiment compares a vessel of air to one with double the [ce]CO_2[/ce] concentration, none of them describe a 0.5 C difference in temperature.

...

 

Perhaps so, Svante Arrhenius proposed that the relationshp of CO2 and temperature, as CO2 increases geometrically, temperature increases arithmetically.

 

The first two experimental show a 6C difference between presumably 100% CO2, and air, if the CO2 in air were doubled 12 times, we'd see the 6 C increase, an increase of 0.5 C each time CO2 is doubled. Do you get different results? Are there other experimental results that show different temperature increase from increased CO2 concentration?

[CraigD]

:Exclamati Here, Brian, I believe you misunderstand the fundamental science of the experiments you mention, and are misquoting their results. ...

Perhaps so

Understanding the fundamental science of an experiments is too important, I think, to dismiss with a mere “perhaps so” admission of misunderstanding it, and needs further discussion.

 

The three experiments described in the links above are not meant to be models of the Earth. The temperatures they measure are not intended to be representative of temperatures on Earth.

 

Fundamentally, these experiments are intended to represent the effect of radiation from the Earth into space on its atmosphere when the atmosphere has different concentrations of [ce]CO_2[/ce]. This is why the glass vessels holding the gases hold only gas, not a partially reflective, partially light absorbing and reradiating target representing the Earth’s surface. They show, in an imprecise way of limited value to model more representative and predictive of Earth’s air temperatures and other climate factors, that, for the same radiation input, air with more [ce]CO_2[/ce] in it gets hotter than air with less.

 

To go further with experiments like these that can be inexpensively performed by students and hobbyists, I recommend adding spectroscopy and photometry to precisely measure how changing [ce]CO_2[/ce] and other gas concentrations affects the power passing through the vessel of gases. Spectrometers are easy to build and their output easy to record and analyize. With this and some fundamental physics, one can precisely measure the power scattered by different gas samples.

 

Svante Arrhenius proposed that the relationshp of CO2 and temperature, as CO2 increases geometrically, temperature increases arithmetically.

This is true, and an interesting bit of science history to which you’ve just now introduced me – thanks. :thumbs_up

 

According to his wikipedia article Arrhenius 1896 paper "On the Influence of Carbonic Acid in the Air Upon the Temperature of the Ground" (Arrhenius’s “carbonic acid in the air” refers to [ce]CO_2[/ce] gas, not to [ce]H_2CO_3[/ce] vapor as a modern reader might at first glance expect) gave is essence the simple radiative forcing equation still used to this day to predict the effect of atmospheric [ce]CO_2[/ce] on surface temperatures:

 

[math]\Delta F = \alpha \ln\left( \frac{C}{C_0}\right)[/math],

where [math]\Delta F[/math] is the change in power from radiation per unit of the Earth’s surface,

[math]C_0[/math] and [math]C[/math] are the before and after concentration of a greenhouse causing the change, and [math]\alpha[/math] is a constant that must be complicatedly calculated.

 

This equation yields power/area, not temperature, but another,

[math]\Delta T_s = \lambda \Delta F [/math],

where [math]\lambda[/math] is another complicatedly calculated constant, does.

 

Taking typical present results for [math]\alpha[/math] and [math]\lambda[/math], [imath]3.35 \,\mbox{W/m}^2[/imath] and [imath]0.8 \,\mbox{K}/\left(\mbox{W/m}^2\right)[/imath], a doubling of [ce]CO_2[/ce] concentration results in a 3 C rise in temperature.

 

Arrhenius’s 1896 paper suggested [math]\alpha \lambda = 8.6[/math], for a 6 C increase per doubling. By 1906 he’d reduced it to 2.3, for a 1.6 C increase. 2007 IPCC calculations place it between 2.9 and 6.6, for a 2 to 4.6 C increase.

The first two experimental show a 6C difference between presumably 100% CO2, and air ...

Experiment - The Greenhouse Effect uses 100% [ce]CO_2[/ce].

 

Pico Technology Experiment: Global Warming specifies filling a bottle with [ce]CO_2[/ce] from a “soda stream”. I assume this means vented from a carbonated soft drink. The webpage doesn’t state, and I can’t guess, what [ce]CO_2[/ce] concentration this would produce. :shrug:

... if the CO2 in air were doubled 12 times, we'd see the 6 C increase, an increase of 0.5 C each time CO2 is doubled. Do you get different results?

Per the above, doubling the [ce]CO_2[/ce] in air 12 times ([imath]2^{12}= 4096[/imath] times) would result in a 24 to 55 C increase. This is an inappropriate use of the forcing equation, however, and an impossible condition, as increasing [ce]CO_2[/ce] concentration from its present day 0.037% by a factor of 4096 gives a concentration of 152% - that is, you’d have to have a pure [ce]CO_2[/ce] atmosphere with and/or greater density than the current one – in which case breathing would, I suspect, be of greater concern than temperature. ;)

 

:QuestionM What’s your source for doubling [ce]CO_2[/ce] concentration forcing a 0.5 C temperature increase, Brian? This is a much smaller constant than any I’ve seen.

Are there other experimental results that show different temperature increase from increased CO2 concentration?

If I’ve been even slightly successful with this post, you now understand that a single tabletop experiment directly measuring temperature isn’t a good predictor of Earth’s surface temperature. You’ve got to break the effects to be measured down, experimentally measure them, and then combine the results per a climate model. To be able to do this, or even read with good comprehension the work of people who have, requires a modicum of basic and specialized education beyond what I currently have – but, given time and effort, have hope of acquiring.

 

Acquiring new modicums (modica? :)) of basic and specialized science education is a large part of why I spend so much time at hypography.

[BrianG]

Understanding the fundamental science of an experiments is too important, I think, to dismiss with a mere “perhaps so” admission of misunderstanding it, and needs further discussion.

 

I've given you my interpretation of the experiments, thanks for sharing yours.

 

The three experiments described in the links above are not meant to be models of the Earth. The temperatures they measure are not intended to be representative of temperatures on Earth.

 

Those are the only quantitative experiments I've found to describe CO2's greenhouse effect on temperature. If you could find more, I'd love to see them.

 

...

This equation yields power/area, not temperature, but another,

[math]\Delta T_s = \lambda \Delta F [/math],

where \lambda is another complicatedly calculated constant, does.

 

Taking typical present results for [math]\alpha[/math] and [math]\lambda[/math], [imath]3.35 \,\mbox{W/m}^2[/imath] and [imath]0.8 \,\mbox{K}/\left(\mbox{W/m}^2\right)[/imath], a doubling of [ce]CO_2[/ce] concentration results in a 3 C rise in temperature.

 

Arrhenius’s 1896 paper suggested [math]\alpha \lambda = 8.6[/math], for a 6 C increase per doubling. By 1906 he’d reduced it to 2.3, for a 1.6 C increase. 2007 IPCC calculations place it between 2.9 and 6.6, for a 2 to 4.6 C increase.

 

That's a real range of possible values, why can't we pin it down? The Gravitational Constant is 6.67428 +/- 0.00067 X 10^11m^3 kg^-1 s^-2, that's far more precise. The IPCC's larger estimate is over 100% larger than there smaller estimate. Can we find a more precise value with experimental tests?

 

 

Experiment - The Greenhouse Effect uses 100% [ce]CO_2[/ce].

...

 

Per the above, doubling the [ce]CO_2[/ce] in air 12 times ([imath]2^{12}= 4096[/imath] times) would result in a 24 to 55 C increase. This is an inappropriate use of the forcing equation, however, and an impossible condition, as increasing [ce]CO_2[/ce] concentration from its present day 0.037% by a factor of 4096 gives a concentration of 152% - that is, you’d have to have a pure [ce]CO_2[/ce] atmosphere with and/or greater density than the current one – in which case breathing would, I suspect, be of greater concern than temperature. ;)

 

:QuestionM What’s your source for doubling [ce]CO_2[/ce] concentration forcing a 0.5 C temperature increase, Brian? This is a much smaller constant than any I’ve seen.

 

Thanks for your help, I should have used the value 11, the amount of CO2 has been doubled more than eleven times and yields a temperature change of 6C, or 6/11C per doubling, about 0.545 C per doubling. Is this the best experimental test we can find to experimentally verify CO2's greenhouse effect? Have you ever seen an experimental test that shows a greater value for CO2's greenhouse effect on temperature?

[modest]

Continued from Re: Climategate

Assuming the tube has roughly 100% humidity and roughly 100% CO2 like Venus, why does it warm less than Venus and even less than earth?

I don't understand the difference and I'm trying to learn. I didn't assume the tube had 100% humidity, only compressed CO2.

The difference is explained in this post,

Re: Greenhouse Effect Experimental Designs

There are several reasons that this,

Lab experiments are good only for measuring the greenhouse effect. The experiments I've linked produce about a [math]5\celsius[/math] temperature change from 370ppmv [ce]CO2[/ce] to 100% [ce]CO2[/ce], or you could say the [ce]CO2[/ce] concentration doubles 12 times to get a [math]5\celsius[/math] temperature change. This is far, far lower than the IPCC predicts and better experiments will help quantify the greenhouse effect.

is not correct.

 

If I may use an analogy, it's very much like saying that a child throwing a lead toy at a wall will have the same effect on the wall as a naval cannon shooting a lead projectile at the wall. They are both 100% lead after all—clearly the child with the lead toy demonstrates that the cannonball will have no significant effect on the wall.

 

I have no problem explaining why the above paragraph is kinematically, or dynamically, wrong. But, if a person wanted to shoot the wall with a cannonball and insisted that the damage assessment was wrong based on such an obvious misconception, and would not amend their position when shown otherwise, then I have a problem. Your quoted claim above has been refuted, at least twice, while you continue to make it.

 

So, rather than us chasing that ball Eclipse Now was talking about, let's have you answer my question:

Assuming the tube has roughly 100% humidity and roughly 100% CO2 like Venus, why does it warm less than Venus and even less than earth?

In other words, Venus is warmed from 230 K (-43 °C) to 760 K (487 °C) average surface temperature by the greenhouse effect. It is warmed from below the freezing point of water to above the melting point of lead and aluminum.

 

My question, if you filled up a small transparent box with the same composition of gases as Venus' atmosphere and pointed a light at it (as in the experiment in the OP) it clearly would not heat the box to 487 °C—so, why is that? I'm asking you why. I'm asking you why the claim you keep making,

Two vessels, one with 100% [CE]CO2[/CE] and the other with 0.037% [CE]CO2[/CE] are exposed to IR and it looks like a [math]5\celsius[/math] is caused by the greenhouse effect. If you were to double the concentration by volume of the 0.037% [CE]CO2[/CE] a little more than 12 times, you would get 100% [CE]CO2[/CE]. Twelve doubling’s of [CE]CO2[/CE] produces [math]5\celsius[/math] warming, or each doubling of atmospheric [CE]CO2[/CE] produces about [math]0.42\celsius[/math] atmospheric warming. This greenhouse effect is significantly less than the IPCC’s forecasts for doubling the preindustrial atmosphere at 280ppmv CO2 to 560ppmv, yet it’s the best experimental test I’ve ever seen. Why is there such a large discrepancy?

The experiments I've linked produce about a [math]5\celsius[/math] temperature change from 370ppmv [ce]CO2[/ce] to 100% [ce]CO2[/ce], or you could say the [ce]CO2[/ce] concentration doubles 12 times to get a [math]5\celsius[/math] temperature change. This is far, far lower than the IPCC predicts and better experiments will help quantify the greenhouse effect.

The lab experiments cited in the first post for this thread show a very weak greenhouse effect from doubling CO

₂

, about [math]0.5\celsius[/math], far lower than the IPCC's projection from the preindustrial ideal of 280ppmv, to our current approx 390ppmv.

is not correct.

 

The answer is here,

Re: Greenhouse Effect Experimental Designs

and again, here,

Re: The GW denialists are winning

I'd like to hear your understanding of it.

 

~modest

[BrianG]

Continued from Re: Climategate...

In other words, Venus is warmed from 230 K (-43 °C) to 760 K (487 °C) average surface temperature by the greenhouse effect. It is warmed from below the freezing point of water to above the melting point of lead and aluminum...

 

My question, if you filled up a small transparent box with the same composition of gases as Venus' atmosphere and pointed a light at it (as in the experiment in the OP) it clearly would not heat the box to 487 °C—so, why is that? I'm asking you why. I'm asking you why the claim you keep making,

 

I've never made any claim about Venus, I'm interested in experimental tests, not interpretation of observations. I understand the heat source is important, that's why I'm looking for tests that show a maximum temperature effect from CO2's greenhouse effect. I've never claimed a lamp is a sun or a container is an atmosphere. I'm just looking for experimental, quantifiable tests.

 

 

Continued from is not correct.

 

The answer is here,

Re: Greenhouse Effect Experimental Designs

and again, here,

Re: The GW denialists are winning

I'd like to hear your understanding of it.

 

~modest

 

Your two posts discuss path lengths, the path lengths in the cited experiments appear equal, that's why I didn't respond to those posts. Do you know of any experiments that show different temperature changes for varying path lengths? Once the temperature effect of different GHG concentrations are demonstrated, and please note that my previous post corrects the 0.5C increase per doubling to 0.545C per doubling, then we would want to show how that effect will work through the height of our atmosphere.

 

I'm interested in quantifying CO2's ability to show a temperature change at different concentrations in our atmosphere. Since the consensus is, we can't change the airs CO2 content at will, we will have to work from lab experiments. We want to find a maximum effect, short of lasing the CO2.

 

When a child throws a lead toy at the wall, we'll measure the velocity and mass of the toy, and see the effect on the wall. Then we can measure the velocity and mass of a cannonball fired from a gun and theorize it's effect. One way or another, we have to do some experimental tests, to demonstrate the effect.

[modest]

When a child throws a lead toy at the wall, we'll measure the velocity and mass of the toy, and see the effect on the wall. Then we can measure the velocity and mass of a cannonball fired from a gun and theorize it's effect. One way or another, we have to do some experimental tests, to demonstrate the effect.

You understand, then, that the composition of the projectile is not directly related to the damage done to the wall. The composition is related to density and hardness which are then two variables in many that can tell you the expected damage.

 

You can apply that same reasoning ability to something which is less familiar to you,

 

Once the temperature effect of different GHG concentrations are demonstrated, and please note that my previous post corrects the 0.5C increase per doubling to 0.545C per doubling, then we would want to show how that effect will work through the height of our atmosphere.

 

That paragraph doesn't make sense. You are assuming that temperature is directly related to greenhouse gas concentration, saying "temperature effect of different GHG concentrations". The concentration of a gas is directly (and linearly) related to absorbance. The absorbance is then one factor in many, many, many others which are needed to tell you the temperature of a system.

 

The composition of the projectile is not directly related to the damage done to the wall. Yet, a person can know exactly how much the composition affects hardness and density and exactly how much those factors affect the damage to the wall when combined with other factors like velocity, wall thickness, projectile volume, shape, mass, etc.

 

A sensible question would be: do we know how much CO₂ absorbs different wavelengths of light under different conditions? The answer is yes. Gas absorption spectroscopy is a matured science. Theory, observation, and experiment all show the absorption characteristics of the greenhouse gases at varying pressure, temperature, and wavelength. This was not always the case,

 

The complacent view that CO2 from human activity could never become a problem was overturned during the 1950s by a series of costly observations. This was a consequence of the Second World War and the Cold War, which brought a new urgency to many fields of research. American scientists enjoyed massively increased government funding, notably from military agencies. The officials were not aiming to answer academic questions about future climates, but to provide for pressing military needs. Almost anything that happened in the atmosphere and oceans could be important for national security. Among the first products were new data for the absorption of infrared radiation, a topic of more interest to weapons engineers than meteorologists.(23)

 

The early experiments that sent radiation through gases in a tube, measuring bands of the spectrum at sea-level pressure and temperature, had been misleading. The bands seen at sea level were actually made up of overlapping spectral lines, which in the primitive early instruments had been smeared out into broad bands. Improved physics theory and precise laboratory measurements in the 1940s and after encouraged a new way of looking at the absorption. Scientists were especially struck to find that at low pressure and temperature, each band resolved into a cluster of sharply defined lines...

The Carbon Dioxide Greenhouse Effect

 

Can you explain, in your own words, what the greenhouse effect is?

 

~modest

[TheBigDog]

I have been conducting a highly .... uh uhhh... test about temperature. I drank some tequila, then I walked barefoot in the snow. It was colder in the snow in the back yard than the snow in the front yard. This may have been influenced by the fact that I walked in the back yard after walking in the front yard, and i did not let me feet warm up. I think this is hard evidence that I am not qualified to test global temperature stuff.

 

Cordully

 

Bill

 

HAPPY NEW YEAR!!!

 

WEEEEEEE!!!!!

[Michaelangelica]

I've never made any claim about Venus, I'm interested in experimental tests, not interpretation of observations. .

Please give us the benefit of your profound wisdom and design such a test/experiment for us.

 

Does it follow that you don't believe in Darwin and Natural Selection because it is based on

"interpretation of observations"

[BrianG]

...

Can you explain, in your own words, what the greenhouse effect is?

 

~modest

 

When you face the sun when it's high overhead, you can feel the heat, when you face the sun when it's lower on the horizon, you feel less heat. The greenhouse effect helps explain what happens to some of the heat in the air.

 

Can you explain in your own words, why this effect has over a 100% error margin, I noted in a reply to CraigD's earlier post? Do you think experimental tests could reduce the error margin?

[TheBigDog]

Greenhouse gases

Main article: Greenhouse gas

 

In order of volume, Earth's most abundant greenhouse gases are:

 

* water vapor

* carbon dioxide

* methane

* nitrous oxide

* ozone

* CFCs

 

By their percentage contribution to the greenhouse effect[12][13] the four major gases are:

 

* water vapor, 36–70%

* carbon dioxide, 9–26%

* methane, 4–9%

* ozone, 3–7%

 

The major non-gas contributor to the Earth's greenhouse effect, clouds, also absorb and emit infrared radiation and thus have an effect on radiative properties of the atmosphere.[13]

Look at those ranges of "Contribution to the greenhouse effect". Look at that chart that tells the same story. Do you think it is as simple as adding the hots and subtracting the colds? Cmon!!! There is cloud cover that changes the albedo of the planet and filters the frequencies of radiation that even reach the lower levels of the atmosphere to heat it. On some sites they show contrails as having a cooling effect for that reason, but on this chart contrails are shown as having a heating effect for their aerosol content. IT IS COMPLICATED!!!!

 

You cannot turn the CO2 dial and say it has this outcome or that outcome. We know that individually CO2 has a predictable affect, but in interaction it becomes too difficult to state the specific contribution of CO2 in any particular time frame or region. That does not change the fact that CO2 acts as a heating mechanism as its content increases.

 

Sweat and piss have similar chemical content, but you don't want everyone pissing in the swimming pool even if you let them jump in sweaty. It is prudent to take steps to limit our CO2 output, but the cost of such measures needs to be weighed against the indicated impact of that CO2 output. That is difficult to specify. We cannot be led by the extremists on either side of the debate. As we learn more we will take the appropriate steps. What are the appropriate steps TODAY will be a point of debate until forever. We need to keep that debate informed and civil.

 

Bill

[modest]

Good deal, now our task is to see a maximum effect from experiments that show CO2 absorbs heat energy...

 

The amount of energy that can be absorbed by carbon dioxide is limited by the C=O bond strength in the molecule. Being a double bond it is relatively strong. At normal earth pressure carbon dioxide decomposes at around 3,200 - 4,600 Kelvin. This energy can be attained via infrared radiation in which case the upper limit would be called multiple photon photodissociation.

 

What do you propose such an upper limit to the maximum heat absorption of carbon dioxide tell us about Earth's climate?

 

When the amount of carbon dioxide in the air doubles, the temperature will increase a finite amount. I want to see that measurement verified with experimental tests.

 

The temperature increase is a function of many things other than just the amount of infrared radiation that CO₂ absorbs—the height of the atmosphere, the concentration of different gases at different layers, the amount of water vapor at different layers, the albedo of earth's surface, the albedo of clouds at different wavelengths, the sun's spectrum and intensity, the changing spectrum and intensity of earth's IR, the solar orbital insulation, feedback effects, etc. You are looking for something which makes no logical sense. You are looking for a correlation between,

1. The temp / concentration dependence in a small experiment
   
2. The temp / concentration dependence of the earth
   

Such a correlation (between 1 and 2) should not exist. No one would propose such an experimental result—it would be nonsensical. Unless you have another earth identical to this one except for CO₂ concentration as an experiment then the temperature / concentration dependence between the experiment and the earth that you are looking for simply does not exist.

 

You should either explain exactly how such an experiment would be performed and exactly what the results would mean or you should stop insisting that the results of the 'experiment' are needed.

 

 

...

Can you explain, in your own words, what the greenhouse effect is?

 

When you face the sun when it's high overhead, you can feel the heat, when you face the sun when it's lower on the horizon, you feel less heat. The greenhouse effect helps explain what happens to some of the heat in the air.

 

Ok... I want to be honest and straightforward, but I don't want to be rude...

 

You don't seem to know what the greenhouse effect is, and it would certainly benefit your ability to criticize climatologists if you were to find out. The description you give is the opposite of the conceptual idea that is the greenhouse effect. It is not the heat (i.e. visible light) radiated by the sun that is blocked by the atmosphere, but rather the heat (i.e. infrared light) that is radiated by the earth.

 

I seriously need to get some sleep, so I won't go on and on describing, but maybe somebody will pick up where I left off, or maybe you could check out the wikipedia page, because... you just can't hope to debate much less criticize the science without a basic understanding of the concept.... I really am sorry to say.

 

~modest