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angusmac at 16:24 PM on 11 March 2011Climate Emergency: Time to Slam on the Brakes
Albatross @67
I am not aware of any misinformation in my post. All of the data presented by me is in the public domain and is available from the links in my post. Please point out where I am "perpetuating misinformation" and I will make appropriate corrections, otherwise a retraction from you would appear to be appropriate.
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Albatross at 16:18 PM on 11 March 2011Christy's Unconvincing Congressional Testimony
Camburn can you please specifically address Christy's testimony, and if you think what Dana (and others) have noted, then please address those specific points. Quite frankly your posts thus far have been off topic and I'm surprised that they have not been deleted. FWIW, those interested in seeing for themselves the trends in extremes are doing for the USA, go here. -
johnd at 15:55 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
Tom Curtis at 14:53 PM, again go back and read the exchange between Marcus and myself. Clearly the trend maps are totally relevant for the point being made. -
dana1981 at 15:54 PM on 11 March 2011Wrong Answers dot com
By the way, I think the Yahoo Answers system is much better (though full disclosure, I'm the top answerer in the global warming section on that site). On Yahoo Answers, anyone can answer any question, but all answers are posted, whereas on Answers.com, you simply edit or replace an existing answer (if there is one). With Yahoo Answers, you get a lot of really bad answers, but you also get a lot of really good ones. With Answers.com it's really a crap shoot whether the answer provided to any given question is accurate. You only have one to choose from. The layout of Yahoo Answers is much better too. Questions are listed chronologically, so virtually every question gets multiple answers. -
Albatross at 15:54 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
Camburn, In contrast to my previous statement to Tom Curtis, you (like your fellow "skeptics") do not impress. Why? Tom presents facts, links and data...you on the other hand present unsubstantiated opinions. Even though plant physiology is not my field of expertise, my latest research has required that I read quite a bit about it, and the two papers that I cited @51 were from 2010, and were based on real-world data (surface-based and satellite based). Now, if you are willing to make the effort to provide some credible peer-reviewed literature to back up your assertions we can go from there. And Marcus @56 makes some very valid points which you apparently choose to ignore. -
johnd at 15:53 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
Tom Curtis at 14:59 PM, as you apparently have not been following this discussion, go back and read my post-johnd at 21:21 PM and subsequent ones. Most recently, the deliberate usage of the phrase "variable climate" by the outgoing President, and the general thrust of the new President in wanting to see more evidence is a definite shift from their earlier stated position of climate change being the greatest challenge facing farmers over the next century. Perhaps they might revert if sufficient evidence is forthcoming, but apparently what there is so far is not considered clear cut enough. My impression from listening to Jock Laurie is that they should stop and look carefully at all the evidence before rushing in and implementing any new measures as the government is want to do in various ways. It is not unknown for people or organisations to reconsider earlier positions as knowledge and events evolve. -
dana1981 at 15:48 PM on 11 March 2011Wrong Answers dot com
Chemware #1 - as rocco (#3) says, Wikipedia has a good editorial system. Answers.com does not. Anyone can go in and edit any answer in any manner they want on Answers.com, unless a Supervisor has locked the answer. It's just a bad system. rocco #3 - I don't think there's much that we can do, other than expose the flaws of the site and encourage others not to use it unless they're fixed. Several of us have appealed to the higher levels at Answers.com to no avail. It's a matter of choosing our battles, and we felt that the most effective way to respond to the misinformation at Answers.com was simply to expose it in a blog post. MattJ #4 - thanks. I had help from other Skeptical Science authors in compiling the examples of horrible Answers.com answers, although they're sadly not hard to come by. I agree, if you're going to call your site Answers.com, you'd better be able to provide accurate answers. -
The Inconvenient Skeptic at 15:42 PM on 11 March 2011What would a CO2-free atmosphere look like?
I disagree with the aspects of trying to include feebacks to determine the answer to what would the temperature be if the Earth was the same and stable EXCEPT for CO2. Same insolation, same cloud, albedo, the works. What would the greenhouse effect be in that situation? A net energy transfer to the atmosphere is one method that could be used. If one analyzes total energy transfers to the atmosphere by the different components the following table is arrived at: Latent Heat: 80 W/m2 LW Absorption: 23 W/m2 Convection: 17 W/m2 If I use Gavin's paper and the CO2 contribution of 20% to the LW absorption which contributes to 19% of the total energy transfer to the atmosphere from the surface, then CO2 contributes 1.3C of the total GHE. Total energy transfer causes the total GHE. Trying to assume that only the energy transferred by LW absorption causes the GHE is a poor simplification. One could also consider the SW absorption to the total, but much of that takes place in the ozone layer which is independent of the troposphere. So I leave that out of this comment, but I have more here. -
Albatross at 15:27 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
Tom @62, You continue to impress :) The maps that johnd showed are really quite meaningless for the point he is trying to make, although his point is not that clear either. -
MattJ at 15:26 PM on 11 March 2011Wrong Answers dot com
I noticed before on other topics, now poor the quality control is on Answers. com. But I never noticed that it was THAT bad! But I am glad that dana1981 has put so much effort into exposing them for their incompetence and really, dishonesty. For yes, claiming that the way to handle 'controversial' topics by giving equal time to "multiple viewpoints and opinions" really is dishonest. Especially for a site whose very name makes the presumptuous claim to have "The answer". -
rocco at 15:18 PM on 11 March 2011Wrong Answers dot com
Chemware: The main difference is that Wikipedia actually has at least some level of editorial control, which is something that most "citizen scientists" avoid like plague. dana1981: The obvious question: what do? The problems you describe are symptomatic for the entire "debate". We can't possibly be there every time somebody propagates misinformation. -
calyptorhynchus at 15:16 PM on 11 March 2011Wrong Answers dot com
Answers.com is just not a very good site and never has been. Don't bother to try to reform it, just put about the information that it should be avoided. -
Camburn at 15:12 PM on 11 March 2011Christy's Unconvincing Congressional Testimony
It would seem that North America is exempt from weather extremes caused by AGW: http://www.climatewatch.noaa.gov/2010/articles/forensic-meteorology-solves-the-mystery-of-record-snows/1 http://c3headlines.typepad.com/.a/6a010536b58035970c0147e2e84bbd970b-pi Note, the above link is from NOAA And of course, we have the tropical storms. http://www.coaps.fsu.edu/~maue/tropical/ It would seem that the testimony given by the AGW proponent is slightly scewed. -
Chemware at 15:05 PM on 11 March 2011Wrong Answers dot com
Curiously, Wikipedia does not suffer from the same problems to anywhere near the same extent. Perhaps the private sector has a vested interest ? -
Tom Curtis at 14:59 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
Climate change threat must be tackled ‘head on’ 5 February 2007 “THE threat of global climate change is potentially the biggest issue Australian agriculture has ever faced with reports of increasing seasonal variability and more extreme weather events,” National Farmers’ Federation (NFF) President David Crombie declared today in the wake of the Intergovernmental Panel on Climate Change (IPCC) Report, released over the weekend. “The Australian farming sector is utterly dependent on weather conditions and any prolonged change in climatic patterns has the potential to plunge farmers, and the majority of Australia, into the realm of the unknown. Rather than throw our hands up in despair, the NFF is advocating direct and deliberate national engagement on the issue to dispel the myths, measure the realities and identify solutions. “What is already apparent is the need to better position agriculture to manage resources in the context of a changing climate. On this, we cannot, and must not, wait. A vastly increased research effort is needed – sooner, rather than later – to enable all primary industries to plan, adapt and respond to greenhouse and climate change challenges… those of today and those predicted.
From the National Farmer's Federations -
Camburn at 14:54 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
johnd: Go back further in time for your continent. The climate extremes are extreme, and ever changing. North America also has extremes in paloe climate. A little longer timescale than Australia tho it seems. -
Tom Curtis at 14:53 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
johnd @ 58, I cannot help but notice that half the difference in trends between those two maps is just a consequence of the different time periods. If the trend over 80 years is -10.00 per decade, and over 40 years it is -20.00 per decade, then the starting rainfalls are effectively identical, and the greatest similarity is between 1930 and 1970, rather than between either and 2010. Looking at the time series shows that the 1970's was an extrordinarilly wet decade, and that the period since the 1970s is unusual compared to that before the 1970s. Of course, that hides large regional differences.
Comparing trends originating with the 1950s and 1910s shows a much smaller difference than does your choice of comparators, with a large portion of the difference arising solely from the longer period since 1910. Your claim that current conditions are more like those of our grand parents than those of our parents appears to be on very shaky ground.
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Camburn at 14:51 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
Marcus: I will continue to cling to that meme. Also, as far as acclimateing to higher co2, ahhhh.......forget it. ( -snip- )Moderator Response: [DB] Please refrain from being insulting to others if you want your comments to not be deleted. Posting on this site is a privilege, not a right. -
johnd at 14:21 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
Marcus at 13:54 PM, these rainfall trend maps illustrate how conditions, for the present generation of farmers, in this example rainfall, are closer to that experienced by their grandparents, and quite different to that experienced by their parents. As for the present day policy of the NFF, please provide some evidence.
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Marcus at 14:05 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
"I will stand with real world research from fields showing that additional co2 results in higher bio mass and crop yields." ....and which field trials are you referring to? All the FACE trials I've read about suggest that the benefits of extra CO2 have been massively overstated, & usually come at significant cost (as I've highlighted above)-& are ultimately short lived anyway. Still, you go on clinging to that meme if it makes you feel better. -
Tom Curtis at 14:03 PM on 11 March 2011What would a CO2-free atmosphere look like?
From Peru @19, clouds form when water vapour condense from the atmosphere as the surrounding gas cools. With a drier atmosphere, you will also get a greater change in temperature with altitude, and hence a greater relative rate of condensation. So there is at least one solid reason to think cloud cover will not just track water vapour levels unambiguously. -
Marcus at 14:02 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
What you keep forgetting Camburn, is several key things: (1) warmer weather increases the rate of senescence (aging) in plants, meaning that seed ripening tends to occur *before* they have a chance to reach maximum size. (2) most plants tend to be biased towards increasing vegetative biomass over seed biomass. (3) plants exposed to higher CO2, prior to acclimation, require much more nitrogen as they need to produce more of the enzymes needed to utilize the extra CO2 in their bio-synthetic pathways. (4) these plants also require greater energy to build & maintain the enzymes necessary to utilize the extra CO2. (5) over time, these plants become acclimatized, & actually switch off the production of the extra enzyme, meaning biomass increases from extra CO2 usually only last about 2-3 years at most-shorter if the plants lack access to sufficient quantities of nitrogen, water & trace elements-the *real* rate-limiting factors in determining long-term plant growth. (6) several plant types (rice in particular) actually reduce their take up of certain trace elements (such as Zinc) when exposed to above normal levels of CO2. -
Marcus at 13:54 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
"It is interesting that some of those present day farmers whose family holdings extends beyond two generations, are finding that some of the conditions they have experienced were similar instead to what confronted their grandparents." You want to back that up with some *evidence* John? Man, your ability to keep repeating the same falsehoods as though they're indisputable facts is getting somewhat tiresome. Your claims of some magic 30-year cycle is simply not backed up by the wealth of scientific data, nor is your claim that the NFF genuinely reflects the opinions of ordinary farmers backed up by the evidence I've seen & heard with my own senses. So unless you want to start backing up your claims with something approaching *real* evidence, then I simply don't see any point in arguing the case with you. According to PIRSA, btw, the science behind AGW is supported by both the SA Farmers Federation & the National Farmers Federation-so seems like your earlier claim isn't backed by the facts either. -
Tom Curtis at 13:54 PM on 11 March 2011Christy's Unconvincing Congressional Testimony
Rovinpiper @18 & 19, I tend to agree with your political analysis, but disagree with your suggestion on tactics. Expert witnesses called in support of action on climate change should not step outside of their expertise while giving testimony. It is not their role to do so, and it is unethical for them to do so. Further, it would be tactically disadvantageous because when they make mistakes (as they inevitably will speaking outside of their area of expertise), the mistakes will be seized upon and trumpeted through out the blog-0-sphere as a means of discrediting their expertise even in those areas where they are in fact expert. Rather, the tactic that should be adopted is some actual skill in questioning by the Democrats and rational Republicans on the committee. If Christy makes comments about economics, he should be pointedly asked what his claim to expertise in economics is. Given his publication record, his expertise on climate science should be actively challenged by trolling through the example after example of egregious error. I'm sure suitable comments on using the wrong sign for how many years was it? could be judiciously used to make him look a buffoon. The deniers have been playing hard ball on this issue for years, and more rational politicians have been soft on the issue for fear of losing votes. Its about time they toughened up and started pointing out that the emperor of the deniers has no clothes. -
Camburn at 13:53 PM on 11 March 2011Interactive animation of the climate change impact on agriculture
Albatross: I would caution you to use a grain of salt on relying on articles by Dr. Reich. I will stand with real world research from fields showing that additional co2 results in higher bio mass and crop yields. Also, Dr. Reich is wrong on higher co2 effects on corn. The root structure of co2 enhanced corn in unbelievable compared to normal levels of co2. I can only suggest that if you are going to comment on articles such as this that you do a lot more reading and stay abreast of the current research being done. The resutls that you are alluding to are not the results of real world experiments. -
Chris Colose at 13:41 PM on 11 March 2011What would a CO2-free atmosphere look like?
Peru, Keep in mind that clouds make up an extremely small amount of water in the actual atmosphere. From Trenberth and Smith (2005), there's generally about 250 times more water vapor (in mass per unit area) than liquid or ice in the air. I don't know how realistic the cloud feedbacks are in the Lacis paper (that would be a good question to ask the people in the study), but there's a lot of wiggle room to change the water vapor without changing clouds much. It's not the total water in the atmosphere that matters, but how you reach saturation, and lowering the temperature makes condensation easier. As for the albedo effect, the reason clouds are such a problem in the modern atmosphere is because they have two big terms (a longwave and a shortwave term) and constraining climate sensitivity amounts to figuring out the the very small difference between the two competing effects. In the snowball case though, the albedo effect of clouds isn't very important over bright surfaces, so they have an unambiguous warming effect on the snowball climate (as noted in Pierrehumbert 2002, as well as the coming review article). So your argument wouldn't really hold in this case. -
Rovinpiper at 13:29 PM on 11 March 2011Christy's Unconvincing Congressional Testimony
Notice also that other scientists were unwilling to go outside of their expertise but Christy didn't mind jumping right into economics. Trying to take the high road and stay within your expertise will win you no points in this sort of exercise. -
Rovinpiper at 13:28 PM on 11 March 2011Christy's Unconvincing Congressional Testimony
This was a win for the Republicans. All they need to show is controversy about the science and negative economic consequences of regulation. No one challenged Christy on his statements about day vs. night-time temperatures. No one pushed him to explain changes in outgoing and downward IR or stratospheric cooling. No one contested statements by Republican representatives or the skeptics about the negative impacts of regulation. They presented predictions of negative impacts from an increase in the price of energy. This is introductory level economics. People need to be reminded that economics is a model. We all now that model predictions should be validated against empirical data. We have some data now because of carbon emissions controls in the European Union and in part of the Northeast United States of America in the Regional Greenhouse Gas Initiative. These programs have not made those states into third world areas as Rep. Griffith assumes GHG regulation would do to the United States. -
Phila at 13:12 PM on 11 March 2011Examining Hansen's prediction about the West Side Highway
As a PS, Tom Curtis @54 has done a much better job than I of clarifying the difference between legitimate scrutiny and ideologically motivated ankle-biting. -
From Peru at 13:09 PM on 11 March 2011What would a CO2-free atmosphere look like?
In the Lacis et al (2010) paper "Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature" it is shown (figure 1 in this post) that cloud cover remains roughly the same while the Earth cools (it even grows a bit at first before stabilizing at a constant value). How could this be possible, while the water vapor content of the atmosphere drops by 90%? Since clouds are formed by condensed water vapor, should not cloud cover decrease proportionally to the moisture decrease in the air, because there is less water vapor to make clouds? This is a very important point, because if the cloud cover drops while the sea ice cover grow, it is not clear if the total albedo of the planet would grow (due to more ice) or drop (due to less clouds). A cloud-induced drop in albedo would be a negative feedback that may prevent the Earth into entering a snowball state, if it is strong enough to compensate the loss of the greenhouse effect. -
Phila at 13:03 PM on 11 March 2011Examining Hansen's prediction about the West Side Highway
HR: There is nothing I can do if you feel the climate science establishment shouldn't be held to scutiny. This is yet another strawman. I didn't say or imply this, and I don't believe it. Frankly, I don't think you're helping your credibility with this comment. Two other points come to mind. First, AGW has been under incredible scrutiny, as you know perfectly well. I've been following this issue pretty carefully since 1990 or so, so I know that there are few major claims from the consensus side that haven't been challenged, questioned, parsed, anatomized, checked and rechecked repeatedly. That process continues today -- despite efforts to defund or slander the relevant agencies -- and I'm pretty confident that when important adjustments are made to AGW, or its predicted outcomes, they'll come from competent scientists, rather than a flock of willfully ignorant ideologues. Second, "scrutiny" of a scientific theory is valuable laregly to the extent that it comes from informed, intelligent, honest people who are not simply parroting frivolous criticisms they heard on a site like WUWT. We probably don't agree on much, but I hope we can agree on that. -
Tom Curtis at 12:44 PM on 11 March 2011Christy's Unconvincing Congressional Testimony
johnd @16, I find the suggestion that piers would dam the river more than mangroves (the natural river bank vegetation in Brisbane) interesting, but hardly credible. However, the suggestion that changes in geography between 1893 and 2011 rather than, say the 300 mm's (370 at Savages Crossing) rain in three hours dumped onto an already flooded river system are the major oontributor to Brisbane's flood is simply laughable. Below are the rainfall intensity graphs for Helidon (in the Lockyer Valley) and Lowood (just below the Wivenhoe dam wall) to give you some idea of the intensity of the rain involved. The primary flooding in Helidon is associated with the flash flooding in the Lockyer Valley on Monday 10th (google Grantham if you are unfamiliar with it); the peak at Lowood is associated with the second peak that fell mostly on the dam and surrounds. At the same time, Savage's Crossing (just east) received 370 mm in three hours. Note that the white dashed line on the graphs represents the expected intensity of a 1 in 2000 year event.
The Helidon peak is associated with the first peak of inflows into Wivenhoe dam (dark blue line), the one at Lowood with the second peak. The dark red line indicates the peak flow at that location in 1974.
Note, some areas of the catchment did not experience so intense rainfall, so that overall the intensity of the event over the period is about 1 in 200, but it is the peak falls over the Lockyer on the 10th that destroyed the Lockyer valley, and caused most of the flooding; and directly onto the dam and surrounds on the 11th, that necessitated the massive releases from the dam. And those events had probabilities of significantly less than 1 in 2000 per annum.
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Chris Colose at 12:43 PM on 11 March 2011What would a CO2-free atmosphere look like?
HumanityRules, I largely agree with you, but non-linearity in sensitivity is rather small over the ranges of climate of interest to us right now (e.g. http://www.nonlin-processes-geophys.net/18/125/2011/npg-18-125-2011.pdf ). Certainly you don't want to compare snowball Earths to say, the PETM directly, but I haven't seen anything suggesting it's a big deal for evaluating modern global warming. The effect isn't absolutely zero. Colman and McAvaney (2009) did this type of experiment from 1/16th to 32x modern CO2 and found a weaker sensitivity in the warm climate than in the cold cases, but it's not a large effect over a few degrees about the modern climate, so you don't really lose much by using the past as a guide to the future. The albedo feedback does get weaker in the warm simulations, but the water vapor grows in strength in warmer climates as well. The Colman and McAvaney paper have the lapse rate feedback increasing in strength too, essentially offsetting the water vapor feedback over most of the range (So the WV+LR feedback is positive the whole time, but not acceleratingly so), but I'm pretty skeptical of that. Eventually the water vapor feedback makes the sensitivity much higher, eventually getting you to a point where a runaway greenhouse is possible if your solar insolation is high enough. There's some other papers on this (e.g., Crucifix 2006, looking at the LGM vs. present) but the non-linearity is pretty small. -
michael sweet at 12:17 PM on 11 March 2011Examining Hansen's prediction about the West Side Highway
Tomurray: Do you hold Lindzen and Spencer to the same standard you hold Hansen? Remember that in 1988 Lindzen was predicting it would get colder in the next decade. Why are you still listening to him? -
Albatross at 12:12 PM on 11 March 2011What would a CO2-free atmosphere look like?
Well done Chris, you have got Lindzen there. That is just one of several misleading and/or false statements he made that day. -
bibasir at 12:03 PM on 11 March 2011What would a CO2-free atmosphere look like?
Really good article and discussion. It is a shame that someone did not answer Lindzens "guess" with some facts. Now the republicans and deniers go away thinking that CO2 is no big deal up or down. -
johnd at 11:39 AM on 11 March 2011Christy's Unconvincing Congressional Testimony
Tom Curtis at 11:27 AM, there is one dam that is being left out, and that is the city itself, and all the other infrastructure and changes that have occurred in the various water courses that artificially confines the natural flow paths. It is a common change that has happened on every water course where human occupation occurs. Geography has as much influence as the weather on all outcomes except for the timing of the events. -
Chris Colose at 11:39 AM on 11 March 2011What would a CO2-free atmosphere look like?
Bern, It's a good question. Impacts as well as internal heating source can certainly leave you very hot early in history, and in some cases can even push you over a threshold for the runaway greenhouse (tidal interaction with the Moon might have been a major heating source for Earth’s climate too in the first few millions of years). The bombardment period is relatively short though, and certainly the sun was a lot less luminous for a large deal of time when impacts were no longer critical. There's a lot to explore about this super-early stuff though in the context of habitability studies. The other thing is that not all stars evolve like our sun. M-type stars which constitute some 75% of all the stars out there are much more stable over geologic time (the lifetime on the main sequence for a star is inversely related to its mass, usually to a third or fourth power). M-stars are smaller and have a low effective temperature (only a few thousand degrees, in contrast to our own sun which is 6,000 K when it becomes optically thin enough for photons to escape) and so potential habitable planets need to be a lot closer to M-types. But with weak (and stable) luminosity, getting them out of a snowball state once they're in can be very tough. The volcanic outgassing of CO2 that helped Earth recover from snowballs in the past might be less meaningful, since a lot of these planets are so close to the sun that they are tide-locked (always having the same face to the sun) or at least close to it, so on the cold night side CO2 could condense out of the atmosphere faster than it is replenished by outgassing. -
scaddenp at 11:36 AM on 11 March 2011What would a CO2-free atmosphere look like?
"I was hoping you could help with understand something. I've started to think that climate sensitivity (CS) is not a constant figure through the history of the earth." A good question and one I would like to know answer to as well. It certainly seems to me that a planet of mostly ice would have a much higher sensitivity than one that is warm and ice-free. (change in albedo feedback - and change in water vapour feedback). PETM features are difficult to explain with sensitivity of around 3 (Zeebe, Zachos and Dicken 2009) - either its higher then or atmosphere has more methane. -
Tom Curtis at 11:27 AM on 11 March 2011Christy's Unconvincing Congressional Testimony
johnd @10, no! I make it seem, as it is, inappropriate, indeed dishonest, to compare flood levels from different periods without noting the effects of dams built on the river. If you want to defend that practice, please say so. I also rebut the casual repetition of false claims about the flood. Again, if you want to defend those false claims, speak up. Finally, I point out that the events of 2011 are extraordinary by any measure. But, if you had read my linked blog, you would have seen that those of 1893 were even more extraordinary by many measures. Wild weather and floods are a part of Brisbane's history. The only thing that is changing in that regard is that now mere thunderstorms are bringing floods comparable with those brought by cyclones in the past. All I can say is God help us when a cyclone next hits Brisbane in a La Nina year. -
What would a CO2-free atmosphere look like?
Chris Colose - Thank you! This is an excellent and thought-provoking thread. As a further investigation into this, for all concerned - looking at the historic (ice core) temperature record, it appears that temperatures rise (in the Earth system) much faster than they fall. Is this due to differences between the sequestration rates and release rates (clathrates, vegetation rot, vs. weathering, ocean release/uptake) upon phase change initiation? -
Chris Colose at 11:17 AM on 11 March 2011What would a CO2-free atmosphere look like?
On the interpretation of the bifurcation graph, a thing to note is that for very low or very high CO2 levels, the equilibrium states correspond to snowball or ice-free states, respectively. In between however, there are three solutions (indicated by the circles on the diagram). The intermediate solution (white circle) is an unstable one which separates the attractor basin of the upper warm solution with the colder ice-covered solution. It is here that nudging the climate into a warmer or colder direction will make it head to that new state rather than tending to bounce back to where it was. For further clarification, I'm putting a supplementary hysteresis loop (also in the Pierrehumbert paper) below:
Here's an example situation to help read this. Suppose we start off in the warm climate state on the upper branch labeled W1. Now suppose you gradually lower the CO2 a bit. In this case you will get just a bit colder, say evolving toward W2, or decreasing the CO2 a bit more, to W3. This is a steady cooling you expect from lowering CO2, but it isn't an irreversible jump, and if CO2 returns to initial conditions you can return back to W1.
However, suppose we decrease CO2 a lot, such that we reach W4 along the upper branch. This is a rather unstable case (like a ball on the top of a sharply peaked hill just getting ready to be nudged), and further tendency to cool will cause an abrupt jump to the S1 state.
Physically, this is where an ice line starts to advance and the albedo feedback becomes very powerful. Also note that the water vapor feedback becomes negligible once you get tropical temperatures near freezing.
Now if you return CO2 levels back to W2 likes conditions, you don't actually get to the W2 temperature. Now, you only warm a tiny bit to S2. In other words, because of the ice-albedo effect, you have multiple temperature solutions for a fixed solar irradiance and CO2 levels, and what state you're in also depends on the history to get there.
Just how "left" and "right" the boundaries are of the hysteresis loop in the diagram in my post is ultimately critical in understanding how to get in and out of the snowball state. The Pierrehumbert diagram doesn't come from a full-blown GCM, and uses some simple parametrization (for example, what threshold global temperature is appropriate for ice-free conditions? He uses 290 K, but that's an assumption too. Also, how "dirty" is the ice, etc) so I wouldn't try to look an individual numbers too close with a magnifying glass, the point is the concept.
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Bern at 11:17 AM on 11 March 2011What would a CO2-free atmosphere look like?
Great article Chris, I quite enjoyed reading it. Regarding this bit: "This is a big problem in planetary habitability studies, especially if a planet succumbs to a snowball fate early in its history when the sun is faint. Once you begin to melt ice however, the temperature jumps rapidly to a very hot solution." Do these studies include the effects of asteroid impacts? As I understand it, the impact rate was substantially higher early in the Earth's history. Small impacts would result it localised heating, but larger ones can provide quite substantial 'kicks', both in terms of heating from the kinetic energy, and in terms of very rapid increases in CO2 levels. There's also the debris that would be spread globally, which would significantly affect albedo, and these combined effects could lead to substantial warming after the initial aerosol cooling subsided. -
Alexandre at 11:14 AM on 11 March 2011What would a CO2-free atmosphere look like?
HumanityRules #9 Good question. I often wondered if the persistent uncertainty range of CS, particularly the long tail at that longer geological study, could be due to such differences you mentioned. -
johnd at 11:08 AM on 11 March 2011Interactive animation of the climate change impact on agriculture
Marcus at 09:11 AM, who the NFF represents comes both directly, and indirectly through the various state bodies, and in turn the various industry bodies that do closely represent individual farmers. It would be interesting to find out if ordinary farmers consider that the Federal Government or the IPCC more closely represents their views. With regards to your mention of multi-generational family farms, because of the post WW2 soldier settlement scheme, in many areas of Australia, multi-generational means that a large number of family farms are only second generation. When they compare the conditions the present generation are facing, with that their parents faced, then obviously they are confined to a 50 -60 year period, but more importantly a period that their parents enjoyed that was not the normal when compared to what is known about Australia's longer term variable climate. It is interesting that some of those present day farmers whose family holdings extends beyond two generations, are finding that some of the conditions they have experienced were similar instead to what confronted their grandparents. With regards to the 30 year period you mentioned, which is generally taken to be the length of time that will represent a climate cycle rather than weather cycles. I think it is about time that this is re-evaluated as to whether it is still appropriate or not. When it was adopted about 100 years ago, the knowledge of weather and climate, both of then and past, was somewhat limited compared to today, as was the ability to measure and quantify all the relevant parameters. Like the concept of a flat earth, it came about reflecting the level of scientific understanding of the day. Obviously our understanding of both has progressed somewhat since those early days, and perhaps we should look to adopting a more appropriate time frame to define climate. -
muoncounter at 11:07 AM on 11 March 2011Examining Hansen's prediction about the West Side Highway
Tom, When you don't have substance, go with the rhetorical shortcuts. Here's a more recent discussion of the same work, including a more detailed map of lower Manhattan:
A Columbia University study concluded that as sea levels rise, large parts of Lower Manhattan including Battery Park City, part of the World Trade Center site, and the Seaport will experience 10-foot floods after large storms.
1988? Yup, that's what it says up top. For Watt$ to be combing over this is a joke.
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dana1981 at 11:06 AM on 11 March 2011Christy's Unconvincing Congressional Testimony
Ian #13 - thanks for the link. Very good point from Santer about the (mis)use of the debunked Douglass et al. paper. I got hung up on the (worse, IMO) mistake of calling the 'hot spot' anthropogenic, and glossed over that error. Just goes to show what a horrendous Gish Gallop Christy's testimony was. We couldn't even catch all the errors therein in this long rebuttal! -
HumanityRules at 11:04 AM on 11 March 2011What would a CO2-free atmosphere look like?
Chris, I was hoping you could help with understand something. I've started to think that climate sensitivity (CS) is not a constant figure through the history of the earth. The impact of forcings in the form of feedbacks can be markedly different given the prevailling situation especially in the more extreme situations you describe in the final paragraph (snowballs, the PETM, glacial-interglacial cycles). For example the cryospheres in these periods will be very different with very different ice albedo feedback, another issue might be land cover and the biosphere, maybe you can think of more situations. I'm concerned that when scientist attempt to make CS estimates are they making estimates for the version of earth that was prevailing at the time and that this is different to the version we are living through now. Can you help with were I'm going right or wrong and describe how scientists deal with that problem (if it exists)? -
Riduna at 11:02 AM on 11 March 2011The Earth's Sixth Mass Extinction May Be Underway
As far as we know, there have been 5 events causing mass extinction of biota. Those events all have at least 5 things in common. 1. Their effect was global 2. All caused atmospheric changes 3. In geological terms they occurred rapidly 4. All resulted in loss of >50% of plant and animal species 5. All were characterised by destruction of habitat. The most serious of these events was the Permian Extinction which resulted in the loss of >90% of plant and animal species. So severe was this event that rebound of life-forms took 15 million years. In this and other extinction events, deep ocean warming, possibly caused by warming of the earths mantle, resulted in the melting of clathrates. This resulted in triggering of the so called “Methane Gun”, the release of massive amounts of methane from the ocean bed over a prolonged period, though possibly only a few centuries. As this methane percolated from the ocean bed to the surface, it oxidized to form CO2 and in the process deoxygenated ocean waters, causing the death of marine flora and fauna on a massive scale. Both gases may have become atmospheric pollutants, though possibly not as serious as the release of aerosols from volcanism or asteroid collision. Atmospheric pollution would have prevented or at the very least limited photosynthesis and produced rapid cooling, at some stage countered by diminution of aerosols and increase of CO2 and other greenhouse gases. The most vulnerable to extinction events are plants and animals unable to rapidly adapt to increasing atmospheric pollution, those with small populations or large body size and those dependent on limited diet. It is not clear that we are now at the start of an Extinction Event but we may well be, though on this occasion one triggered by the human species rather than “natural” volcanism. What is clear is that if unchecked in the very short term, greenhouse gas pollution will cause relatively rapid global warming having the same effects as those characterising earlier extinction events. Shakhova (2010) has already reported that warming of the ocean and seabed off the Siberian coast is already beginning to melt methane clathates. The result is that atmospheric concentration of methane in the Arctic has already reached the highest levels known in 400,000 years. No less concerning is her estimate that destabilisation of offshore permafrost could result in accelerated melting of clathates with an estimated capacity to release 70 billion tones of methane into the ocean. In addition, melting of Siberian marshland permafrost has potential to increase this total. Significant quantities of methane from shallow offshore waters are likely to reach the atmosphere without oxidizing. The bulk, from deeper water, would oxidize before reaching the surface, reducing oxygen in the Arctic Ocean. Both would add to the level of CO2 in the atmosphere further accelerating global warming, placing the environment of biota under increasing stress. It is possible that we may not be approaching the next Extinction event but the signs are ominous and the past provides a stark warning of what lies ahead unless we act promptly to curb greenhouse gas emissions. -
Albatross at 11:02 AM on 11 March 2011Examining Hansen's prediction about the West Side Highway
Not to be pedantic Muoncounter, but this is about what was said in 1988, not 1998. But I agree with your point, it is absurd, and pathetic that people are having to debunk this nonsense being spread by WUWT and others. Hopefully concrete in cheap post 2050 to increase the height of the the sea walls-- hmm, but making concrete is CO2 intensive.....oh dear, another positive feedback loop.
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