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Post by oloflind on Apr 9, 2009 18:34:35 GMT
Steve, the Greenland ice cover area is a bit over 1 800 000 squarekm and the average ice thickness is somewhat more than 1,5 km (Swedish National Encyclopedia). Thus the volume of Greenland ice is about 2 800 000 cubic kilometres. Look at an ice pillar, 1500 m high and having a cross-sector area of 1 squaremeter. It contains about 0,9 x 1500 tons of ice, i e 13,5 x 10 exp9 grams of ice. To melt it down, there is a need of 333 x 13,5 x 10exp9 Ws = 450 x 10 exp9 Ws. To get this energy in 1000 years or 1000 x 365 x 24 x 3600 = 31,54 x 10 exp9 seconds, a power of 14,3 W/sqmetre is needed, i e ten times more than you stated. ;D
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Post by icefisher on Apr 9, 2009 21:05:00 GMT
Steve, the Greenland ice cover area is a bit over 1 800 000 squarekm and the average ice thickness is somewhat more than 1,5 km (Swedish National Encyclopedia). Thus the volume of Greenland ice is about 2 800 000 cubic kilometres. Look at an ice pillar, 1500 m high and having a cross-sector area of 1 squaremeter. It contains about 0,9 x 1500 tons of ice, i e 13,5 x 10 exp9 grams of ice. To melt it down, there is a need of 333 x 13,5 x 10exp9 Ws = 450 x 10 exp9 Ws. To get this energy in 1000 years or 1000 x 365 x 24 x 3600 = 31,54 x 10 exp9 seconds, a power of 14,3 W/sqmetre is needed, i e ten times more than you stated. ;D Sounds like Steve was putting in his order for rubber boots a bit prematurely. 10,000 years huh? By then our ancestors will be talking about this age wrapped up with the stone age and will probably call it the periodic table era. ;D
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Post by gettingchilly on Apr 9, 2009 21:17:34 GMT
"Personally, I don't think the models are based off of bad physics. I just think they are not able to take all factors into account...because the data/knowledge just isn't there yet."
There is one model that works just fine. Unfortunately it requires such a huge amount of processing power that it's output is only 1 second of output per second of modeling. The good side to this is that mother nature gives you the results in real time.
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Post by steve on Apr 10, 2009 12:10:44 GMT
Steve, the Greenland ice cover area is a bit over 1 800 000 squarekm and the average ice thickness is somewhat more than 1,5 km (Swedish National Encyclopedia). Thus the volume of Greenland ice is about 2 800 000 cubic kilometres. Look at an ice pillar, 1500 m high and having a cross-sector area of 1 squaremeter. It contains about 0,9 x 1500 tons of ice, i e 13,5 x 10 exp9 grams of ice. To melt it down, there is a need of 333 x 13,5 x 10exp9 Ws = 450 x 10 exp9 Ws. To get this energy in 1000 years or 1000 x 365 x 24 x 3600 = 31,54 x 10 exp9 seconds, a power of 14,3 W/sqmetre is needed, i e ten times more than you stated. ;D I agree with your calculation, but we are calculating different things. You are calculating the power required to melt a single column of ice in 1000 years. I am calculating the power required to melt the whole of Greenland in 1000 years, and then comparing it with the power of the "greenhouse" effect. So I am averaging the power requirements over the area of the earth and comparing it against the 3.7W/m^2 expected from doubling CO2. Please note I am *not* saying that Greenland will melt in 1000 years! The question posed was whether the observed melting of ice should be cancelling out the greenhouse warming in the same way that the ice in a drink keeps it at a constant few degrees C in a warm room.
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Post by steve on Apr 10, 2009 12:31:41 GMT
Models *are* real evidence. Steve, I'm happy to stipulate that the above statement may have been an oversimplification, but I still feel a need to address it and some of your later posts. A model, by itself, is evidence of nothing and proof of nothing. A model that correlates closely with observed behavior is limited evidence but falls well short of proof. Now again, you are correct that policy makers would be negligent if they ignored the long-term model forecasts. However risk analysis demands that they consider the probability of a problem as well as the effects of that problem when determining how much effort to put into mitigation. If a fist-sized meteor hits the cockpit of a commercial airplane, it is going to crash and a lot of people are going to die; but we don't armor the cockpits of our aircraft against such meteors (we could, but we don't), and given the odds of a fist-sized meteor hitting a flying airplane we are right (IMO) to do so. It is my opinion that the immaturity of the current generation of GCMs and the corresponding low probability that their severe projections will come to pass do not merit significant efforts at mitigation at this time. I'm not saying AGW is falsified, or that it is fundamentally flawed (although the projection onto public policies such as cap and trade CO2 systems certainly is), I'm saying we've got finite resources and AGW doesn't merit allocation of anything beyond research funding and a trickle of concurrent engineering when measured against the high-probability problems of the future or the known problems of the present. To invoke one final analogy: my opinion is that AGW is to the current status of the human race as telling you that you may have cancer right after you've been hit by a truck. Should the doctors ignore your hemorrhaging to take you in for chemotherapy? No. Should they spend some time keeping an eye out for tumors while they operate? Probably, if circumstances permit. If you survive the trauma from being hit by a truck you may still die of cancer - if you actually have it. That doesn't mean your doctors are negligent if they focus on more urgent problems in the short term. I think you make good points. The key flaws in what you say are these: 1. Even though the model projections are flawed (yes I admit that), we have the basic physics that says CO2 causes warming all else being equal. We also have observational evidence that feedbacks to warming are positive - the evidence is by far from being wholly model-based. 2. The costs of mitigation are, I think, deliberately overstated. Our economy changes radically year on year, so arguments stating that "business as usual" is the only way to go are flawed (particularly in the current environment); there will be business advantages that arise from whatever method of carbon pricing evolves. If it improves capital flows towards energy efficiency, renewable energy and so forth we can start the long job of putting human civilisation on a footing for a post-oil future. 3. The reason we got hit by a truck was because we borrowed too much money from China to buy consumer crap from China. Yes it was nice to have, but Western civilisation would have survived just fine even if it had had to wait an extra couple of years for the latest Ipod. I see no reason why we can't fix the economy *and* tackle energy efficiency at the same time - it's called thrift. Look what trying to avoid the inevitable has done to the US car industry!
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Post by gridley on Apr 10, 2009 14:29:32 GMT
Steve,
OK, let's talk about the basic flaws. :-)
1. Yes, all else being equal, CO2 causes warming. But all else isn't necessarily equal. In fact, right now the sun is very unequal. Yes, the models show warming and we've had warming. But there are an infinite number of paths between two points. That the observed behavior of the earth happens to be within the error bars of many of the GCMs is circumstantial evidence only.
2. I'm not really in a position to comment on the true costs of mitigation, though I'll note a shift to nuclear power would constitute mitigation of CO2 emissions, get us off foreign oil, and provide long-term sustainable power. So why aren't Gore/Hansen/etc. running around screaming for nuke plants? We could have switched over half the country to nuclear power for the cost of just one of the bailout spending bills.
3. Please note I said "we" the human race, not "we" the US. Yes, the US bought a lot of stuff from China. So did Europe. Together, however, they comprise only a fraction of the human race. I wasn't talking about the current economic woes, I was referring to the global energy situation, which has been unbalanced for quite a bit longer and is far more serious in the long run.
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Post by steve on Apr 10, 2009 17:00:41 GMT
1. You might believe that, but evidence that the sun caused the last 30 years' warming is sketchy to say the least.
3. Well, CO2 mitigation will help solve the global energy imbalance too.
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Post by gettingchilly on Apr 10, 2009 20:53:29 GMT
1. You might believe that, but evidence that the sun caused the last 30 years' warming is sketchy to say the least.
Now amended by the truth checker app.
1. You might believe that, but evidence that CO2 caused the last 30 years' warming is sketchy to say the least.
Now that's much more realistic don't you think. Yeah, me too.
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wylie
Level 3 Rank
Posts: 129
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Post by wylie on Apr 10, 2009 21:30:28 GMT
Steve, the Greenland ice cover area is a bit over 1 800 000 squarekm and the average ice thickness is somewhat more than 1,5 km (Swedish National Encyclopedia). Thus the volume of Greenland ice is about 2 800 000 cubic kilometres. Look at an ice pillar, 1500 m high and having a cross-sector area of 1 squaremeter. It contains about 0,9 x 1500 tons of ice, i e 13,5 x 10 exp9 grams of ice. To melt it down, there is a need of 333 x 13,5 x 10exp9 Ws = 450 x 10 exp9 Ws. To get this energy in 1000 years or 1000 x 365 x 24 x 3600 = 31,54 x 10 exp9 seconds, a power of 14,3 W/sqmetre is needed, i e ten times more than you stated. ;D The 14.3 W/m**2 of additional heat (an impossibly large number) to melt the Greenland icecap in a 1000 years assumes that this heating could take place 24 hours a day for 365 days of the year. Since most of Greenland is above the Arctic circle and in darkness for 6 months of the year, this is nearly impossible. Does anyone believe that 14.3 W/m**2 of extra heat could be supplied to Greenland during the Winter in the dark??? So that leaves the summer months and increases the number to 29 W/m**2. A ridiculous number. There is another problem. We already have a historical record to assess the likelihood of the Greenland ice cap melting in the face of a MUCH warmer climate for thousands of years. That is during the Eemian interglacial (the last one before this one) about 110,000 years ago. During that time the estimated termperature was 5 degrees celsius warmer than it is today!! There was a flourishing coniferous forest on the southern coast of Greenland BUT the northern half (or more) of the icecap DID NOT MELT. We have ice cores going back ~2 million years proving a continuous presence of ice on at least the northern section of the Icecap for at least 5 interglacials. Something tells me that this "global warming" is not going to melt the icecap!! Hope this helps, Ian
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Post by poitsplace on Apr 11, 2009 1:43:11 GMT
1. You might believe that, but evidence that the sun caused the last 30 years' warming is sketchy to say the least. Agreed, evidence that the sun cause a substantial amount of the warming is sketchy at best. HOWEVER...evidence that the sun has caused a significant amount, but certainly not all,of warming since 1900's and such. It would even be understandable to write off the solar activity increase as most of it occurred earlier in the century. Its absence would have made most change their tune on "global warming". Remember, .2C lower temperatures would mean the 50's, 60's and 70's would have had winters just like those of the early 1900's. It's amusing (yet sad) to listen to all the AGW people talking about MILD TEMPERATURES as if they were horribly dangerous for mankind. Bitter cold is our real enemy. Heat is only annoying. Winter storms drop even industrialized nations to their knees. The cold kills within hours sometimes even with proper clothing. Had we not gained that additional energy from the sun during that period (and which WE ARE NOW MISSING) they would have PRAYED for global warming during the last cooling period (and actually, many did) Of course the evidence is pretty clear on one thing, MOST of the warming of the last warming period was in fact from the natural warming period. Assuming it's normal .4C fluctuations. Now don't get all freaked out by that, there was overall warming. HOWEVER, if you'll look at the temperature record you'll notice that the cooling period was a little less pronounced, the warming period a little more pronounced. The warming was spread between the two...hence my repeatedly trying to point out the smoothed peak to smoothed peak temperatures as the TRUE, observed rate of warming. Another important factor in global warming is volcanic activity...well, more specifically the lack of it. We haven't had any significant volcanic activity in quite a while. That's another chunk of our warming. Since there was only about .5C/century of warming over the last complete cycle, there's not a whole lot of room for catastrophic warming. After factoring in the lack of volcanic activity and solar forcing, our base temperature would probably be about .4C lower with warming of .3C/century or so. Ooooh, I'm scared. [/quote]3. Well, CO2 mitigation will help solve the global energy imbalance too.[/quote] Not allowing coal creates an even WORSE energy imbalance. If you'll break out a map you'll find that most of europe is as far north as canada. It's not a great place for solar. Being that far north DRASTICALLY reduces the cost effectiveness. Russia and scandanavian countries are screwed as well. Wind power has similar issues. The UK is one of the best places for it and even they can't manage to get it workable. The netherlands are famous for wind power...but they've got issues. Wave power only works at the coast and won't ever make it past the eco-nuts anyway. We just don't have many good options to solve this not even remotely pressing "problem".
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Post by jimg on Apr 11, 2009 5:49:47 GMT
Perhaps didn't cause warming per-se, but perhaps it has been causing a reduction in the rate of heat loss.
This should show up as an increase in Tmin temps, but not necessarily Tmax temps. Since Tmin increases, this would also show up as a higher average temperature.
As the sun becomes less active, it reduces the thickness of the atmosphere allowing greater heat loss.
During long active periods, or periods with a shore minimum, then the upper atmosphere expands, or does not contract as much as has been seen recently.
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Post by ron on Apr 11, 2009 10:00:20 GMT
First it was "20 more years of cooling" then it was "never because all the scientists can't be wrong" now it is "My estimate is better than most of the scientists and the IPCC" and "if 20 more years happened, then all the scientists would have changed their minds, so I would too" and "a deep solar minimum might be masking AGW"
Wow. What a great series of answers.
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Post by steve on Apr 11, 2009 12:46:58 GMT
Steve, the Greenland ice cover area is a bit over 1 800 000 squarekm and the average ice thickness is somewhat more than 1,5 km (Swedish National Encyclopedia). Thus the volume of Greenland ice is about 2 800 000 cubic kilometres. Look at an ice pillar, 1500 m high and having a cross-sector area of 1 squaremeter. It contains about 0,9 x 1500 tons of ice, i e 13,5 x 10 exp9 grams of ice. To melt it down, there is a need of 333 x 13,5 x 10exp9 Ws = 450 x 10 exp9 Ws. To get this energy in 1000 years or 1000 x 365 x 24 x 3600 = 31,54 x 10 exp9 seconds, a power of 14,3 W/sqmetre is needed, i e ten times more than you stated. ;D The 14.3 W/m**2 of additional heat (an impossibly large number) to melt the Greenland icecap in a 1000 years assumes that this heating could take place 24 hours a day for 365 days of the year. Since most of Greenland is above the Arctic circle and in darkness for 6 months of the year, this is nearly impossible. Does anyone believe that 14.3 W/m**2 of extra heat could be supplied to Greenland during the Winter in the dark??? So that leaves the summer months and increases the number to 29 W/m**2. A ridiculous number. There is another problem. We already have a historical record to assess the likelihood of the Greenland ice cap melting in the face of a MUCH warmer climate for thousands of years. That is during the Eemian interglacial (the last one before this one) about 110,000 years ago. During that time the estimated termperature was 5 degrees celsius warmer than it is today!! There was a flourishing coniferous forest on the southern coast of Greenland BUT the northern half (or more) of the icecap DID NOT MELT. We have ice cores going back ~2 million years proving a continuous presence of ice on at least the northern section of the Icecap for at least 5 interglacials. Something tells me that this "global warming" is not going to melt the icecap!! Hope this helps, Ian Sorry, this post is completely irrelevant! Why is it that even when I indicate that something is unlikely, people assume I am saying that it is inevitable! The question was posed as to whether the melting of ice and increase in stored chemical energy in plants would be sufficient to prevent the atmosphere and ocean from warming in response to the currently 1.5W/m^2 of forcing from increased greenhouse effects. When you do the maths, you find that even if Greenland were to be melting at 1% every 10 years (which it clearly isn't) it would only be taking up 10 percent of the CO2 forcing, leaving the other 90% to warm the planet. Since Greenland is *not* melting anywhere near that quickly (and may even increase in mass due to more precipitation), the proposition that was put to me is falsified!
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Post by icefisher on Apr 11, 2009 13:22:02 GMT
3. Well, CO2 mitigation will help solve the global energy imbalance too. What imbalance are you talking about?
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Post by duwayne on Apr 11, 2009 19:31:52 GMT
I think you make good points. The key flaws in what you say are these: 1. Even though the model projections are flawed (yes I admit that), we have the basic physics that says CO2 causes warming all else being equal. We also have observational evidence that feedbacks to warming are positive - the evidence is by far from being wholly model-based. 2. The costs of mitigation are, I think, deliberately overstated. Our economy changes radically year on year, so arguments stating that "business as usual" is the only way to go are flawed (particularly in the current environment); there will be business advantages that arise from whatever method of carbon pricing evolves. If it improves capital flows towards energy efficiency, renewable energy and so forth we can start the long job of putting human civilisation on a footing for a post-oil future. 3. The reason we got hit by a truck was because we borrowed too much money from China to buy consumer crap from China. Yes it was nice to have, but Western civilisation would have survived just fine even if it had had to wait an extra couple of years for the latest Ipod. I see no reason why we can't fix the economy *and* tackle energy efficiency at the same time - it's called thrift. Look what trying to avoid the inevitable has done to the US car industry! I accept that all other things being equal, additional CO2 causes some small amount of warming, but I question whether "we have observational evidence that feedbacks to [CO2] warming are positive." 1) You have said that GHG's warm the earth some 30 degrees above what it would be without them. My understanding of GHG theory is that the current concentration of GHG's would warm the earth by a further 30 degrees or so if it weren't for the negative feedback of weather, Ocean Currents, albedo, etc. There isn't a cumulative positive feedback to GHG forcing. This doesn't prove that forcing from additional CO2 does not have a positive feedback, but it does bring it into question. 2) If one adjusts the Global temperatures for warming/cooling caused by Ocean Currents (ENSO, PDO, AMO, etc.) during the rapid CO2 growth over the past century , the temperature rise is slower than would be expected from CO2 forcing alone indicating no positive feedback. And this is particularly true when one factors in that there was an underlying warming trend before CO2 began to increase significantly. 3) And, if one looks only at the recent years, there is little sign of warming despite the growing CO2 concentration. Again no sign of positive feedback. This is particularly cogent for those who downplay the affect of Ocean Currents on Global Temperatures. There is some logic for the positive feedback as proposed in the models but earth is a complicated place and negative feedback seems to be the reality. What is the “observational evidence” of positive feedback that you refer to ?
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