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How much does human activity contribute to climate change?

 
 
Reply Tue 11 Dec, 2007 04:42 pm
Forget about politics and political preference. I just want to understand the data.

We know the climate is changing. We can see from the graph below (and from other sources) that over the last 450k years global temperatures have a very strong and pronounced cycle. And since humans haven't been industrial for most of that cycle it's obvious that all preceding spikes are not due to human activity.

Here's my question: Relative to the natural pattern of warming which we are experiencing now, how much is human activity contributing to the warming? How is this relative contribution determined? And where is the data to back up any conclusions?

http://img355.imageshack.us/img355/6058/carbondioxidekz6.jpg

Thanks.
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spendius
 
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Reply Tue 11 Dec, 2007 07:01 pm
That's a print out of Molly's heart rhythm when I was giving her the business. I would recognise that pattern anywhere.
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TheCorrectResponse
 
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Reply Wed 12 Dec, 2007 08:03 am
This is not something that will be easily found in conversational level publications at the level of detail that I think you desire. I have seen this data in some Journal articles over time but was, as I mentioned in the other thread, more interested in the chemistry that it contained and spent my time on that tangent so I really can't recall a specific article that could help.

From responses so far I don't think anyone here is in the field of climatology so the chance that anyone can name a publication and article(s) off the top of their head is probably not high.

However I suggest you start here:
http://ams.allenpress.com/archive/1520-0477/72/4/pdf/i1520-0477-72-4-499.pdf

This article is at a general level, you can then use the Journal references at the end of the article to help you find the detailed information you seem to want. Hope this helps.
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fresco
 
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Reply Wed 12 Dec, 2007 09:21 am
bm
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rosborne979
 
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Reply Wed 12 Dec, 2007 03:06 pm
TheCorrectResponse wrote:


Thanks for the link.

That document was released in 1991. It makes statements that indicate the climate change (warming) is a result of greenhouse emissions, yet it doesn't offer any data to back up that claim, other than to mention "Supercomputer Models" (the same thing I read in another article earlier today).

The 1991 article also doesn't seem to differentiate between known natural warming and human induced warming. It goes to a lot of trouble to argue that warming is happening (even though in 2007 we already know that warming is happening), but it doesn't really break down the relative causes (which is what I'm trying to find out).
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TheCorrectResponse
 
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Reply Wed 12 Dec, 2007 05:12 pm
From 2007, Notable source (Procedings of the National Academy of Sciences). Let me know if this is the type of informatioon you are looking for.

Go here:
http://www.pnas.org/cgi/content/full/104/47/18866?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=1&author1=J.+Canadell&andorexacttitle=and&andorexacttitleabs=and&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=relevance&fdate=10/1/2007&resourcetype=HWCIT

you can choose to view it online or as PDF. Hope this helps.
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spendius
 
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Reply Wed 12 Dec, 2007 06:58 pm
Hope springs eternal.
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Vengoropatubus
 
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Reply Wed 12 Dec, 2007 10:19 pm
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rosborne979
 
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Reply Thu 13 Dec, 2007 09:27 am
TheCorrectResponse wrote:
From 2007, Notable source (Procedings of the National Academy of Sciences). Let me know if this is the type of informatioon you are looking for.

Go here:
http://www.pnas.org/cgi/content/full/104/47/18866?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=1&author1=J.+Canadell&andorexacttitle=and&andorexacttitleabs=and&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=relevance&fdate=10/1/2007&resourcetype=HWCIT

you can choose to view it online or as PDF. Hope this helps.

Thanks TCR. That's close, but it's not exactly what I was looking for. Let me explain...

That document starts with the following:
Abstract:
"The growth rate of atmospheric carbon dioxide (CO2), the largest human contributor to human-induced climate change, is increasing rapidly."

This tells me that CO2 is the largest contributor to "Human-induced" climate change. But it doesn't tell me if "Human-Induced" climate change is the largest contributor to climate change in general (which is really what I'm asking for). And it doesn't address the relative relationship between natural climate change and human-induced climate change. And that's what I'm looking for. I know it's a subtle distinction, but I think it's important (since this is the piece of the puzzle which polarizes the two positions in the debate).

The rest of the document proceeds to back up it's initial claim. But since I don't disagree with its initial claim, the backup isn't necessary (at least for me).
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rosborne979
 
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Reply Thu 13 Dec, 2007 09:29 am
Vengoropatubus wrote:
The EIA cites global energy consumption at 421 quadrillion Btu in 2003.

Hi Vengo, since my math skills are pretty much limited to adding 2+2, could you please translate that into english. Thanks. Smile
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TheCorrectResponse
 
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Reply Thu 13 Dec, 2007 10:17 am
I think VENS numbers above are what you are asking for. Is that right? Are the numbers sufficient or do you need them from an authoritative source (no offense intended VEN).

I would also point out this is just in terms of energy consumption, it does not include any added amounts of CO2 because of the loss of CO2 to the atmosphere due to deforestation (cutting down trees releases their CO2 content), nor does it take into account the amount of CO2 absorbtion lost due to this same deforestation (less trees left to absorb CO2).

There is also a high level of probability that human actions are changing the pH of the oceans and degrading their effect as a CO2 absorbtion mechanism.

There are also other chemicals such as methane that human actions add to the atmosphere. In terms of total amount vs CO2 they are small but are more problematic per molecule, a methane molecule for example is about 100 times as efficient in blocking radiation from escaping into space as is CO2. Which is where I think the EIA'a prediction at the high end i.e. 6+ degree K is from.
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rosborne979
 
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Reply Thu 13 Dec, 2007 08:47 pm
TheCorrectResponse wrote:
I think VENS numbers above are what you are asking for. Is that right?

Unfortunately no. Apparently I'm not asking this question precisely enough.

Here, let me try again (and I appreciate your indulgence): "What is the relative proportion of human-induced warming within the naturally occurring warming trend? (assume we average the natural trend over the last 20k years)"

I'm looking for an answer should be in the form of a proportion, like 1/5th of the warming trend is attributable to human activity, or 9/10'ths or 1/100'th. Something like that. And I'm not looking for precise numbers, I'm interested in ballpark numbers.

Once I get that answer, then I'm going to ask how that answer is determined, but at the moment I would be happy with just the first part.

(Here's the original question from the top of the thread: Relative to the natural pattern of warming which we are experiencing now, how much is human activity contributing to the warming? How is this relative contribution determined? And where is the data to back up any conclusions?)

I hope that helps.
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fresco
 
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Reply Fri 14 Dec, 2007 01:38 am
I have the same question as Rosborne.

It seems to me that even if in the short term humans contribute to the acceleration of "natural" climate trends, in the long run these "interferences" will be assimilated by" the earth" even if that results in reducing the human population. Cosmologically that would appear to be of little importance.

Lets face it, WW2 resulted in 20 million deaths over a decade which might be a much higher figure than any projected climate related disaster. So what exactly is the philosophical and psychological status of our anxieties ? Is it merely that we believe that we can actually control our "climate change" behaviour as opposed to our "belligerency" ? Some hopes !
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Chumly
 
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Reply Fri 14 Dec, 2007 01:50 am
Rosborne979's claim of a "natural pattern of warming" can be argued as false if used as predictive, unless one can show empirical causation.

Otherwise all we have is historical data which appears to be cyclical.
Quote:
A random process consisting of a sequence of discrete steps of fixed length. The random thermal perturbations in a liquid are responsible for a random walk phenomenon known as Brownian motion, and the collisions of molecules in a gas are a random walk responsible for diffusion. Random walks have interesting mathematical properties that vary greatly depending on the dimension in which the walk occurs and whether it is confined to a lattice.


http://mathworld.wolfram.com/RandomWalk.html

It's my understanding that there is nothing necessarily stopping a random walk from giving a cyclical appearance at some point, in fact statistically if at some point a random walk did not give a cyclical appearance given enough time, that may well be reason to investigate causation.

Further even if empirical causation as to a "natural pattern of warming" can be argued, that does not necessarily mean that "the natural pattern of warming which we are experiencing now" will be of similar magnitudes as in the past.
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rosborne979
 
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Reply Fri 14 Dec, 2007 07:18 am
Chumly wrote:
Rosborne979's claim of a "natural pattern of warming" can be argued as false if used as predictive, unless one can show empirical causation.

See Graph at top of thread. That seems like a VERY strong pattern to me.

Based on the last 450k years, do you have any doubt that we are about to hit the top of the most recent spike, and then slide rapidly down into another cold patch? Unless someone can show that the data in the graph (and others like it) are false, then I doubt there's any amount of warming humans can induce which will prevent a repeat of the pattern. I suspect that global forces are far more powerful than human forces, but that is why I asked the question.

The other reason I asked the question is to point out why the political push for acceptance of human-induced global warming is having such a hard time getting traction. If nobody (and no public scientific material available on the web) can answer a simple question like the one I asked, then there will never be consensus on how we should respond (especially when a response will have an affect on economic systems).
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Vengoropatubus
 
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Reply Fri 14 Dec, 2007 07:29 am
As rough as my numbers are, they seem to suggest to me that human activity(energy consumption, not CO2 release) is more than just a factor, but the tipping factor that has put our environment into a warming cycle.

If I'm not mistaken, I did convert 421 quadrillion Btus into Joules Smile
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rosborne979
 
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Reply Fri 14 Dec, 2007 08:28 am
Vengoropatubus wrote:
As rough as my numbers are, they seem to suggest to me that human activity(energy consumption, not CO2 release) is more than just a factor, but the tipping factor that has put our environment into a warming cycle.

We were already in a warming trend.

We've been in a warming trend for the last 25k years. And it's the same climate change cycle that's been happening for the last 450k years. Unless you disagree with the data shown of course. Do you disagree with the ice core data?

Clearly these large scale trends are not caused by humans. So how do you know what proportion of the trend over the last 500 years is caused by humans versus natural causes.

(sheesh, I'm running out of ways to ask this question. Why is it so hard to get such a simple answer?)
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Chumly
 
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Reply Fri 14 Dec, 2007 03:48 pm
rosborne979 wrote:
Chumly wrote:
Rosborne979's claim of a "natural pattern of warming" can be argued as false if used as predictive, unless one can show empirical causation.

See Graph at top of thread. That seems like a VERY strong pattern to me.

Based on the last 450k years, do you have any doubt that we are about to hit the top of the most recent spike, and then slide rapidly down into another cold patch? Unless someone can show that the data in the graph (and others like it) are false, then I doubt there's any amount of warming humans can induce which will prevent a repeat of the pattern. I suspect that global forces are far more powerful than human forces, but that is why I asked the question.

The other reason I asked the question is to point out why the political push for acceptance of human-induced global warming is having such a hard time getting traction. If nobody (and no public scientific material available on the web) can answer a simple question like the one I asked, then there will never be consensus on how we should respond (especially when a response will have an affect on economic systems).
I am not inherently arguing against your views, but for fun I will on some points, if you don't mind.

I will start with one question: Are you familiar with the expert coin tossing scenario?

1) Take oh-say 200 people and put them in a room.

2) Have them all repeatedly flip coins until one "beats" all others in terms of "consistency".

3) VoilĂ  not only have you a "predictive expert', you have a "definitive pattern".

Actually nope; not unless you can show empirical causation, and the predictive mechanisms for future tossing.
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rosborne979
 
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Reply Fri 14 Dec, 2007 11:13 pm
Chumly wrote:
I am not inherently arguing against your views, but for fun I will on some points, if you don't mind.

Fun is fun, but I really wish someone could answer the question.

Scientists are winning nobel prizes over global warming issues and ex-politicians are winning film awards for urging humanity to stop our disastrous activities, yet nobody can even offer a ballpark idea as to what percentage of global warming is due to human activity? Isn't that one of the most basic things we should know?
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Chumly
 
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Reply Fri 14 Dec, 2007 11:21 pm
To me global warming is a metaphor for stupid environmental risk so I am not too bothered if the global warming claim itself is lame-ass or right-on-the-money or somewhere in between.

Carbon dioxide (being a byproduct of combustion) is not the worst yardstick I can think of.

Definitive population reduction would be one of the best yardsticks I can think of in the most general terms of saving ourselves from ourselves.

I guess that does not help your perspective much sorry to say.
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