billvon 3,050 #1 September 19, 2014 Climate, stabilty and feedback Thousands of man-years of work has gone into climate modeling in the past few decades. With all that work we are getting better and better at modeling climate change, and indeed IPCC estimates (which use large interdisciplinary models) are becoming more and more accurate, and are matching observed temperature rises quite accurately. One of the reasons for this is that the basic inputs to the models (insolation, reduction of re-radiation, changes in albedo, changes in gas concentration) are easy to measure. A second reason is that we now have decades of models to compare with predictions, and so we now know what works and what doesn't. There are, however, two uncertainties that limit how accurate any model can be as the prediction time is extended. One is human behavior. Like the stock market, the future climate is dependent on human behavior. For example, a future where we return to emitting a lot of high altitude aerosols while dramatically cut down on CO2 production will look very different than a future where we avoid high altitude aerosols and decide to abandon renewable energy and efficiency standards in faavor of cheap coal. The second factors are nonlinear feedbacks. These are feedbacks that change with the temperature. Thus even though we may have an understanding of what they are doing now, we don't have a full understanding of what they will do when the temperatures increase. Some of these are pretty straightforward, especially on the negative side, For example, re-radiation will increase as temperatures climb. Since blackbody radiation goes up as the fourth power of temperature, there is a strong negative feedback that will, for example, prevent temperatures rising infinitely high. As temperatures climb, the Earth will radiate more heat until we reach a new equilibrium at a higher temperature, Others include chemical weathering (rocks, concrete and other minerals react with CO2 and take it out of the atmosphere) and biological uptake (higher CO2 levels = more plants = less CO2.) The positive feedbacks are a lot more worrisome. One common one is methane release from frozen sequestration (tundra, clathrates.) As these materials melt methane and CO2 are released, and methane is a strong greenhouse gas. (CO2 is relatively weak in comparison.) Thus more methane = more temperature increase = more melting = more methane. Another is albedo change; as snow and ice melt, darker surfaces are exposed to the Sun and absorb more heat. A third category of feedbacks are as yet unknown, since they can drive the climate in either direction. Daytime clouds greatly decrease albedo and lead to cooling. Nighttime clouds trap heat and lead to warming. Thus, an increase in cloudiness (likely as the Earth heats up and more water evaporates) can drive climate in either direction, depending on the time of cloud formation - and we don't have a good predictor of that, That uncertainty, on the surface, is a bad thing because it leads one to believe that we can't predict what will happen in the future. Fortunately, we have some other tools - behavioral observation. In engineering, we often design structures that must be kept stable with feedback loops (flight controls, electronic amplifiers, hydraulic systems.) The rigorous way to analyze whether a system will be stable is to do a control system analysis - figure out the expression that describes the system, plot the poles and zeros and look for basic indications (poles on the wrong side of the plot) that indicate the system is unstable. In many cases, though, engineers cannot do that, since they do not always know everything about the system. In a hydraulic system, for example, you may not be able to account for the exact amount of air in the system - and that affects compressibility of the fluid and hence overall system response. Fortunately they have another option - testing the system. Through either accurate simulation or actual testing, they can build the system and see if it's stable. The most useful method of testing is to apply a stimulus - a step or an impulse - and see how it responds. If it stabilizes at a new level it is stable. If it starts increasing and does so without limit, it is completely unstable. If it "rings" (oscillates) it is dynamically unstable. Thus by testing the response of the system, you can learn a a lot about it. We cannot (or more accurately should not) do that to the Earth. However, we are fortunate in that we have historical proxy records in the form of ice cores, sedimentation, tree growth rings etc that allow us to see what has happened in the past. Thus we can look back in time at other "step changes" in the climate and see how the planet has reacted. One of the big worries for some is that the climate is inherently unstable. Give it a step change and first all the methane is released from melting permafrost, and that warms us 20 degrees. Then the oceans evaporate, and all that water in the atmosphere traps all our heat and raises it another 50 degrees. Then some of the water turns to steam and that raises the temperature even more. (Same fear for the other direction - it snows, the snow reflects more light, it gets colder, it snows more, the oceans freeze, it gets colder still etc.) In an inherently unstable climate, a large enough step change will cause an irreversible slide in one of these directions as the positive feedbacks outweigh the negative ones. Fortunately, in our entire 4.5 billion year history, that has never happened - and that is a strong argument for negative feedback dominating over positive feedback in the long run. However, there are good indications that positive feedback is a significant event in the short term. We have seen several rapid warming periods where a step increase (caused by, for example, an increase in insolation) activates some of the above-mentioned positive feedbacks, and for a time the Earth sees a rapid increase in temperature. The biggest one of these, the Paleocene Eocene Thermal Maximum, resulted in a 6 degree C rise in temperature - higher than almost every conceivable scenario that we could drive by 2100. Fortunately, that data shows that those positive feedbacks are eventually swamped by the negative feedbacks. One of the strongest drivers of this is likely blackbody radiation. It is a small negative feedback at first, but since it increases by the fourth power of temperature, it very rapidly becomes significant and slows down further temperature rise - and thus the Earth stabilizes at a new, higher temperature. So overall the news is pretty good. If anything, we have learned that although we certainly have the power to change the climate by driving modest climate changes (2-3C worldwide), we don't have the power (yet) to send it to either deadly extreme. Whether or not we want to make those 2-3C changes, of course, is still an excellent question. Quote Share this post Link to post Share on other sites
winsor 236 #2 September 19, 2014 Stability in the sense of Liapunov buys us little regarding climate. In any event, your post suggests that you basically get it. My concern is that, even if Al Gore had a valid point, by far the biggest issue we face is overpopulation. Carbon footprint and all that is a secondary issue in the long run. As a Thermodynamicist I am greatly in favor of sustainability; addressing the 'climate change' part of the equation without treating the overall condition of our species from a systemic standpoint is a fool's errand. Then again, we're all doomed so what the hell. BSBD, Winsor Quote Share this post Link to post Share on other sites
billvon 3,050 #3 September 19, 2014 >As a Thermodynamicist I am greatly in favor of sustainability; addressing the >'climate change' part of the equation without treating the overall condition of our >species from a systemic standpoint is a fool's errand. I agree. But the good news here is that the second derivative of population is now negative, and if that trend continues, population will peak around 2050 at about 9 billion and decline from there. So while it is still a serious issue, the problem has gone from "how do we stop this population growth?" to "how do we keep the trend going?" And in general supporting an existing trend is miles easier than creating a new trend. Quote Share this post Link to post Share on other sites
DiverMike 5 #4 September 19, 2014 Could you site your source that the second derivative is negative? I googled it and could only come up with a Woods Hole Oceanographic Institution paper using the population growth of a tropical herb as a case study. I haven't been able to find a source that the 2nd derivative of global population growth is negative. For the same reason I jump off a perfectly good diving board. Quote Share this post Link to post Share on other sites
billvon 3,050 #5 September 19, 2014 I've seen it in a few places. Here's one (describing a TED talk) http://forums.anandtech.com/archive/index.php/t-2158382.html From Wikipedia: For the world as a whole, the number of children born per woman decreased from 5.02 to 2.65 between 1950 and 2005. . . . Excluding the observed reversal in fertility decrease for high development, the projected world number of children born per woman for 2050 would be around 2.05. Only the Middle East & North Africa (2.09) and Sub-Saharan Africa (2.61) would then have numbers greater than 2.05. 2.1 is generally accepted as the replacement threshold. Quote Share this post Link to post Share on other sites
DiverMike 5 #6 September 19, 2014 wow - a Ted talk by Hans Rosling from 4 years ago. I looked at the transcript of the speech and there was nothing about rate of change of population growth http://www.ted.com/talks/hans_rosling_and_the_magic_washing_machine/transcript?language=en I can't give a lot of credence to a Wikipedia article either. Those aren't the best sources you have ever quoted. I would really like to believe the 2nd derivative is negative because that is good news. I can't based on those sources. Is it negative .0001 or negative 100? Wikipedia also shows based on UN estimates the 2nd derivative could be positive, negative, or zero based on different estimates. http://en.wikipedia.org/wiki/World_population#mediaviewer/File:World-Population-1800-2100.svg edited to add pretty wikipedia graph For the same reason I jump off a perfectly good diving board. Quote Share this post Link to post Share on other sites
billvon 3,050 #7 September 19, 2014 I haven't looked into this for a while and when I did some additional research, I found that the estimates are changing. Previously populations were predicted to level off by 2050, but now scientists are predicting growth (slower growth, but growth) beyond that point as well. From New Scientist: ================================= Global population may boom well beyond the year 2050 18 September 2014 by Andy Coghlan There may not be a let-up after all. The human population is unlikely to stop growing this century as expected, according to new projections. That could add to the pressure on the environment and accelerate climate change. The research concludes that the population of Africa will grow much faster than expected, overwhelming the slower growth and even declines in other regions. But it is an overly pessimistic conclusion that flies in the face of other analyses, critics argue. The general consensus is that the rapid growth in the human population will slow over the next few decades and level off well before the end of the century. "Projections up to about 10 years ago projected world population to keep growing to about 9 billion in 2050, and then to level off or decline," says Adrian Raftery of the University of Washington in Seattle. "But our results suggest this levelling off is unlikely." Instead, Raftery and his colleagues have estimated that the world population will soar from the current figure of 7.2 billion to between 9.6 and 12.3 billion by 2100. Africa boom "The biggest difference between our results and the older projections is that ours expect a large increase in the population of Africa, from the current 1 billion to more than 4 billion in 2100, with a lower bound of 3.5 billion," says Raftery. Fertility rates in Africa have fallen from their peak of 6.5 children per woman, thanks to greater prosperity and better conditions for women. But Raftery says they have levelled off at around 4.6 instead of continuing to drop as expected. The main reasons are better survival from HIV – which often kills mothers and their babies – and lack of available contraception, the researchers say. . . . His team has also calculated the probabilities that particular population scenarios will materialise, which has not previously been done. They estimate that the likelihood of the global population stabilising by 2100 is only 30 per cent. ========================= Quote Share this post Link to post Share on other sites
DiverMike 5 #8 September 19, 2014 Yep - what I get out of this is nobody has any idea what is going to happen to population growth in the next 50 years. Depending on the source (and their agenda) it will either stay the same, soar, or drop precipitously. 78% of all statistics are made up 34% of the time. For the same reason I jump off a perfectly good diving board. Quote Share this post Link to post Share on other sites
GeorgiaDon 378 #9 September 19, 2014 Of course, a big unknown in all of this is the probability that increasing population density and mobility will culminate in a major pandemic. While that would not be the ideal way to cull the world's population, it might be effective. I wonder if these population projections take into account the influence of certain religions that forbid access to birth control. The Catholic Church is not particularly effective at enforcing it's edicts (for example, Quebec is >90% Catholic but has the lowest birthrate in Canada), but other religions are much more "motivational". There is a reason Islam is the fastest growing faith in the world, and it isn't all due to converts. Here in the Western World (AKA "liberal democracies") we tend to take it for granted that people will more or less make up their own minds about birth control and family size. But then, we don't stone or behead people for following their own conscience. Don_____________________________________ Tolerance is the cost we must pay for our adventure in liberty. (Dworkin, 1996) “Education is not filling a bucket, but lighting a fire.” (Yeats) Quote Share this post Link to post Share on other sites
billvon 3,050 #10 September 19, 2014 >Here in the Western World (AKA "liberal democracies") we tend to take it for >granted that people will more or less make up their own minds about birth control >and family size. But then, we don't stone or behead people for following their own >conscience. Agreed, and in fact the end of that article makes the point that ensuring women's rights, providing education for both men and women and making contraception available are the three most important things we can do to reduce birthrate. Quote Share this post Link to post Share on other sites
kallend 2,098 #11 September 20, 2014 DiverMikeYep - what I get out of this is nobody has any idea what is going to happen to population growth in the next 50 years. "Prediction is very difficult, especially about the future"; Neils Bohr, 1934... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
lawrocket 3 #12 September 20, 2014 There is actually one uncertainty - assumption. You hit on a fundamental issue with climate models - all climate models are based on assumptions. What will the albedo be? What will affect it? What do we value the solar constant? All kinds of assumptions get put in to a climate model and it runs the calculations. This is why climate models do not give predictions. They give "projections." They aren't "testable" or even falsifiable because they are supposed to be. They are meant to provide insight into effects of scenarios. You hit upon engineering. That's another crucial difference. Engineers have an end goal - an answer that they look for a system to reach it. Science has a different objective - find the answer using a system. The scientific method and the engineering system have different ebjectives. Climate models are like a mix between science and engineering. A climate modeler may assume average albedo at 2050 is .2 and see what it does. Or may assume no climatically significant volcanic eruptions in the interim. Of course, either of these would be engineering a result because we know damned well what that will do do a climate projection. If I want to show a meter of sea level rise in five years, I know how to do it. Which is exactly what Mann did in his article in Scientific American a few months ago. It's as if he asked, "I need to show climate catastrophe before 2037. How do I do it?" And then he did so by making assumptions, some of which were not viable even in the data he provided or within logic, such as exponential decrease in troposheric aerosols (his own cited data showed we are already near pre-industrial levels). I'm seeing a lot of mixing between engineering and science. They are closely related but have different objectives. I don't think we should be looking to engineering to answer scientific questions. I think that if we DO use engineering it should be clearly explained that engineering methodologies were used in reaching the conclusion. Again, engineering has as a startung point a desired end result. The engineer uses creative process to develop methodology to achieve that end, develop a prototype, test it, and then see whether it worked. Engineers come up with ways of changing the climate. Climate models are. I think, best described as engineering tools. "Let's say we seed 100 tons of SO2 into the stratosphere next year. What will happen?" Run the model and check the result. The engineer says, "Scientist - we don't know what happens to stratospheric SO2 over time. Can you run some experiments and give us an equation we can use? While you're at it, can you tell us the effect of SO2 on water droplet formation at tropopause?" You've really got me thinking about engineering looking like science... My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
Boomerdog 0 #13 September 22, 2014 Desperate concern is at the core of every Progressive idea. There is an emergency, only Progressives understand the emergency, only Progressives can solve the emergency, it's only the "ignorance" of those who disagree that refuses Progressives emergency powers. Global Warming is a very large Reichstag Fire, combined with Earth Mother mystic nonsense that has been in vogue since the Manson Family. Quote Share this post Link to post Share on other sites
rushmc 23 #14 September 22, 2014 The AWG crowd is a group of those trying to create an emergency to help support a political agenda For the most part (not all) this is what the green movement is all about Oh And of course I want dirty air and water for all to shareJust thought I should get that out of the way "America will never be destroyed from the outside, if we falter and lose our freedoms, it will be because we destroyed ourselves." Abraham Lincoln Quote Share this post Link to post Share on other sites
DanG 1 #15 September 22, 2014 Corrected: Quote The Benghazi crowd is a group of those trying to create an emergency to help support a political agenda For the most part (not all) this is what the conservative movement is all about Oh And of course I want Americans to be killed by terroristsJust thought I should get that out of the way And you think "your side" is so much better. Of course, climate change is backed up by mountains of scientific research, and the only political end you can identify is "control", which is just nebulous and scary enough to work on like minded people. - Dan G Quote Share this post Link to post Share on other sites
rushmc 23 #16 September 22, 2014 DanG Corrected: Quote The Benghazi crowd is a group of those trying to create an emergency to help support a political agenda For the most part (not all) this is what the conservative movement is all about Oh And of course I want Americans to be killed by terroristsJust thought I should get that out of the way And you think "your side" is so much better. Of course, climate change is backed up by mountains of scientific research, and the only political end you can identify is "control", which is just nebulous and scary enough to work on like minded people. No It is NOT backed up by science It has assumptions and predictions NONE of which are coming true today"America will never be destroyed from the outside, if we falter and lose our freedoms, it will be because we destroyed ourselves." Abraham Lincoln Quote Share this post Link to post Share on other sites
DanG 1 #17 September 22, 2014 QuoteNo It is NOT backed up by science It has assumptions and predictions NONE of which are coming true today Sure. If it helps you sleep better at night, keep believing that. - Dan G Quote Share this post Link to post Share on other sites
rushmc 23 #18 September 22, 2014 DanGQuoteNo It is NOT backed up by science It has assumptions and predictions NONE of which are coming true today Sure. If it helps you sleep better at night, keep believing that. I sleep just fine And what has been coming out lately fully supports what I am saying Look at what billvon has to do Post something from years back In any event, we have seen no warnimg in over 18 years Unless of course the data is fucked with"America will never be destroyed from the outside, if we falter and lose our freedoms, it will be because we destroyed ourselves." Abraham Lincoln Quote Share this post Link to post Share on other sites
rushmc 23 #19 September 22, 2014 Case in point from yesterday QuoteA former high-ranking Obama administration official says climate science and the implications of global warming are not "settled," insisting such claims are "misguided" and stifle debate on the matter. Writing a Page One story in the Wall Street Journal Weekend Review section, Dr. Steven Koonin argues that group think among experts has been inhibiting "the scientific and policy discussions that we need to have about our climate future." Koonin, who served at the Energy Department as President Obama’s undersecretary for science in the Energy Department, is director of the Center for Urban Science and Progress at New York University. I coped this from a newmax report Thought you would like that"America will never be destroyed from the outside, if we falter and lose our freedoms, it will be because we destroyed ourselves." Abraham Lincoln Quote Share this post Link to post Share on other sites
rushmc 23 #20 September 22, 2014 To add to it QuoteKoonin’s position strikes a blow against climate change activists as People’s Climate March organized demonstrations at more than 2,000 locations worldwide. In New York, tens of thousands participated in the demonstration demanding urgent steps against carbon emissions as the United Nation’s General Assembly opened. "We often hear that there is a 'scientific consensus' about climate change," writes Koonan. "But as far as the computer models go, there isn't a useful consensus at the level of detail relevant to assessing human influences." Koonin says his extensive training as a computational physicist with a 40-year career of scientific research and management, has given him an up-close knowledge of climate science. "Detailed technical discussions during the past year with leading climate scientists have given me an even better sense of what we know, and don't know, about climate," writes Koonin. The point, Koonin says, isn't whether the climate is changing, as "the climate has always changed and always will." Further, he says, there is little doubt that humans are influencing climate change, as greenhouse gases, mainly from carbon-dioxide emissions, have had an effect. But the main question remains about how the climate will change under both natural and man-made influences, which will affect energy and infrastructure choices. "Those questions are the hardest ones to answer," writes Koonin. However, Koonin adds, while humans can cause serious issues for the climate, "they are physically small in relation to the climate system as a whole," with additions to carbon dioxide to "directly shift the atmosphere's natural greenhouse effect by only 1% to 2%." http://www.newsmax.com/Newsfront/climate-change-science/2014/09/21/id/595969/ Edited to add the url There is even more in the article"America will never be destroyed from the outside, if we falter and lose our freedoms, it will be because we destroyed ourselves." Abraham Lincoln Quote Share this post Link to post Share on other sites
kallend 2,098 #21 September 22, 2014 Ah, Newsmax, the peer reviewed climate science journal.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
wmw999 2,509 #22 September 22, 2014 Well, I will agree that it's unseemly for members of the scientific community to engage in groupthink, even if the reason for that groupthink is to prevent naysayers from getting undeserved traction. We all will pay the price of short-term climate thinking and action . But I think that we'll pay more in the long run if we allow both ends of the political spectrum to drive science. Of course it's conducted by humans, and funded by money, but somehow scientists need to be able to bite the hand that feeds them when it comes to results. Of course, that's what tenure is about, too, isn't it. Wendy P. There is nothing more dangerous than breaking a basic safety rule and getting away with it. It removes fear of the consequences and builds false confidence. (tbrown) Quote Share this post Link to post Share on other sites
rushmc 23 #23 September 22, 2014 kallend Ah, Newsmax, the peer reviewed climate science journal. Keep hanging you hat on that one too John"America will never be destroyed from the outside, if we falter and lose our freedoms, it will be because we destroyed ourselves." Abraham Lincoln Quote Share this post Link to post Share on other sites
lawrocket 3 #24 September 22, 2014 kallend Ah, Newsmax, the peer reviewed climate science journal. He's not putting out any peer-reviewed science. He's saying that the administration is stifling dissent. Let's put that up for peer review. "Hey, I'm seeing a lot of group think." - let's put that up for peer review. How about applying the peer review standard to everything? Opinion is not subject to peer review. But people of the same opinions tend to stick together. And when they are in power, they tend to push others out. And when the President calls anyone who takes issue with climate projections as "flat earthers" (which was not peer-reviewed) then it's not like the guy is saying anything other than the President meant what he said. Just as Dubya wouldn't want anybody openly questioning his motivation to invade Iraq... My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
billvon 3,050 #25 September 22, 2014 >It is NOT backed up by science >It has assumptions and predictions >NONE of which are coming true today Let's compare the IPCC's predictions to the predictions of some of the contrarians you are always posting about: Quote Share this post Link to post Share on other sites