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littlerobbergirl at 23:41 PM on 7 February 2011How We Know Recent Global Warming Is Not Natural
would Bayesian analysis help? a very very low chance he is right, a very high chance everyone else is. (i had to look up the spelling, shouldnt use stuff i dont really understand lol) -
dorlomin at 23:38 PM on 7 February 2011Articgate: perpetuating the myth that Arctic sea ice has recovered
Bern at 23:16 PM on 7 February, 2011 Schmitt is a geologist. What is it about some geologists that they get climate so completely wrong, to the point of making statements that are flatly contradicted by recent measurements? = = = = = = = = = = = = = Some of them do get quite foxed by CO2 levels in the early and mid Phanerozoic, they were notably higher. But then again that is more the solution to how we avoided freezing over with much lower solar energy. -
Kevin C at 23:27 PM on 7 February 2011How We Know Recent Global Warming Is Not Natural
Dikran: "Spencer has a hypothesis, but it is not yet a scientific hypothesis as it hasn't reached the point where it can make prohibitions on what we can observe so that it has the potenital of being falsified even if it is false. Until the null hypothesis is well-defined is meaningless to ask for papers where it has been rejected." Oh yes, you're right. I hadn't picked out the full nuance there. I think there is a rhetorical game going on too - labelling a particular hypothesis as 'null' in all but the most trivial cases has become a game of trying to grab the 'neutral' ground. -
Bern at 23:16 PM on 7 February 2011Articgate: perpetuating the myth that Arctic sea ice has recovered
Schmitt is a geologist. What is it about some geologists that they get climate so completely wrong, to the point of making statements that are flatly contradicted by recent measurements? -
Esop at 22:50 PM on 7 February 2011How We Know Recent Global Warming Is Not Natural
Seems like at least some of the "skeptics" are already abandoning the Global Cooling meme that they have been pushing for a number of years. I expected them to do that and replace it with "ok then, it is warming, but it is natural" sooner or later, but I had not expected it until 2012/13, as that will likely be the new record year. -
Eric (skeptic) at 22:47 PM on 7 February 2011The 2010 Amazon Drought
Rob Painting, I think that is an oversimplification. Reading through the Zeng paper (link in 20) I noticed that Zeng cannot separate the Atlantic warming from ENSO. It is certainly no coincidence that El Nino was present in 2005 and 2010. But it is true that ENSO is not the only factor involved. It is also true that El Nino does not always cause Amazon drought, but it is correlated along with La Nina and more rain in the Amazon. -
Dikran Marsupial at 22:30 PM on 7 February 2011How We Know Recent Global Warming Is Not Natural
Kevin C "Spencer has a hypothesis involving clouds, it's just not fleshed out to the same level of detail as the mainstream CO2 hypothesis." That is essentially my point, Spencer has a hypothesis, but it is not yet a scientific hypothesis as it hasn't reached the point where it can make prohibitions on what we can observe so that it has the potenital of being falsified even if it is false. Until the null hypothesis is well-defined is meaningless to ask for papers where it has been rejected. The funny thing is that climate modellers are perfectly happy to tell you what is consistent with climate variability, just look at the spread of the model runs (it is why model ensembles are useful). So we are in the funny situation where a challenge has been laid down where the challenger (apparently) won't say what is consistent with "natural variability" is, and won't accept the answers of climate modellers who will! -
Kevin C at 22:01 PM on 7 February 2011How We Know Recent Global Warming Is Not Natural
Actually, I think it is a little more subtle than a simple falsification question. If the 2nd-hand sources I'm reading are correct, Spencer has a hypothesis involving clouds, it's just not fleshed out to the same level of detail as the mainstream CO2 hypothesis. So the ideal here would be to develop a detail climate model based on Spencer's hypothesis and test its performance against existing climate models. It might perform better or worse, although I'd expect several iterations of peer review before drawing a fair conclusion. But here we run into a difference between 'the scientific method' and 'how science is done'. What I've described above is consistent with the scientific method (falsification, Bayes, etc), but falls down in practice because resources are finite. The system as described could be sabotaged by a flood of underdeveloped hypotheses which need to be tested and falsified. Indeed this may already be happening. 'How science is done' brings in extra factors - peer review, consensus. Things which have evolved as practical measures to make science work reasonably efficiently. Peer review as a junk filter, consensus as a mechanism to say 'stop - we've tested this hypothesis enough different ways, we haven't proven it (and never will), but it is good enough to be going on with'. Without these, science becomes bogged down (and thus Delingpole's peer-to-peer science can never work - under his model biology would do nothing but retest the theory of evolution over and over again to try and satisfy the IDers). So, I think on the basis of 'how science is done', the onus is on Spencer to demonstrate that his model can provide predictions which are both testable and as specific, and at least comparable to those provided by existing models. If he can do that, the 'the scientific method' will come into play to test them further. I may of course be giving him too much benefit of the doubt - after all I haven't read his papers and would not be qualified to judge them if I did. -
BillyJoe at 21:35 PM on 7 February 2011How We Know Recent Global Warming Is Not Natural
Post #1 is an "ad hominem" attack. I trust it will be removed by the censor. (Otherwise I want my comment about Monckton restored ;)) -
JMurphy at 21:16 PM on 7 February 2011CO2 lags temperature
Funny (but unsurprising, going by past form) to read Poptech 'correcting' others (this time Scopus) and telling them the 'truth' as he sees it - just like he did with Pielke Jr when he decided (against Pielke's wishes) to include his papers in his little list of what he believes confirms his own version of AGW 'alarm' - whatever that is. No matter. He will believe what he wants to believe and no-one else can tell him otherwise. And he does have to do his utmost to defend E&E, because so much of his little list rests on papers from that source, but we can look at some quotes to do with E&E, with links from the same WIKIPEDIA page that Poptech failed to acknowledge : "On our Energy and Environment paper from 1999, had we known then how that outlet would evolve beyond 1999 we certainly wouldn't have published there. The journal is not carried in the ISI and thus its papers rarely cited. (Then we thought it soon would be.) We were invited to submit a piece in 1997 or 1998 and we had this in prep and sent it in." Roger Pielke Jr again (Wait for Poptech to 'correct' Pielke Jr...) "Sonja Boehmer-Christiansen[Editor of E&E], a reader in geography at the University of Hull, in England, says she sometimes publishes scientific papers challenging the view that global warming is a problem, because that position is often stifled in other outlets. "I'm following my political agenda -- a bit, anyway," she says. "But isn't that the right of the editor?"" Chronicle of Higher Education, 4 September 2003 "Plimer repeatedly veers off to the climate sceptic's journal of choice, the bottom-tier Energy and Environment, to advance all manner of absurd theories: for example, that CO2 concentrations actually have fallen since 1942." Michael Ashley, Professor of Astrophysics at the University of NSW -
Paul D at 20:49 PM on 7 February 2011Monckton Myths - a one-stop-shop for Monckton misinformation
I think Monckton brings a new meaning to the term 'political science' :-) -
Rob Painting at 20:29 PM on 7 February 2011The 2010 Amazon Drought
Chris G @ 16 - There is evidence that they have become more intense over the last century (at least one coral study that I remember but can't cite at the moment There's a few, but this study illustrates what your're talking about: Teleconnection between tree growth in the Amazonian floodplains and the El Niño–Southern Oscillation effect - Schongart 2004 From the abstract: "El Niño causes anomalously low precipitation in the catchment that results in a significantly lower water discharge of the Amazon River and consequently in an extension of the vegetation period. In those years tree rings are significantly wider. Thus the tree-ring record can be considered as a robust indicator reflecting the mean climate conditions of the whole Western Amazon basin. We present a more than 200-year long chronology, which is the first ENSO-sensitive dendroclimatic proxy of the Amazon basin and permits the dating of preinstrumental El Niño events. Time series analyses of our data indicate that during the last two centuries the severity of El Niño increased significantly. -
Rob Painting at 20:21 PM on 7 February 2011The 2010 Amazon Drought
Eric (skeptic) - as far as 2005 & 2010 Amazonian drought are concerned, they are unrelated to ENSO (El Nino). They arise from the warm sea surface temperatures in the tropical Atlantic. From your comments thus far, it's not clear you have understood this. -
HumanityRules at 19:25 PM on 7 February 2011A Case Study of a Climate Scientist Skeptic
Glenn the difference between your analogy (#69) and mine (#68) seems to be that you are changing the flow rate between the two vessels while I alter the flow rate into the whole system. I would have thought the effect of CO2 is to alter the rate of in flow into the whole system rather than between the two vessels. Stabalizing CO2 would return the net infow to the whole system to zero and equilibria is restored by the natural flow of water into the ocean vessel. I accept that the ocean vessel should be much larger than the air vessel but shouldn't the value in your system be controlling flow into the system rather than between the two vessels? I also didn't mention in my example when the radiative forcing stops increasing and after equilibria is restored then both vessels will be fuller than before the increase of radiative imbalance. -
Dikran Marsupial at 19:14 PM on 7 February 2011How We Know Recent Global Warming Is Not Natural
The fundamental problem with Spencer's hypothesis is that it is unfalsifiable. As there is no specified mechanism or model that can be used to predict what observations are and are not consistent with the hypothesis, it is impossible to disprove. Karl Popper (very influential figure in the philosophy of science) wrote that the thing that distinguishes science from pseudo-science (e.g. astrology) is that there is always at least the possibility that a scientific hypothesis can be falsified. This means the hypothesis needs to make prohibitions on what can happen, the more prohibitions it makes, the better the theory. Clearly Spencer's hypothesis of "natural cycles" is not a scientific hypothesis, at least until he specifies the mechanism sufficiently that something is ruled out by it. Essentially, you can't prove any hypothesis by experiment or observation, all you can do is disprove, and to disprove a hypothesis it needs to be falsifiable (i.e. if the hypothesis is false, it must in principle be possible to show that it is wrong, and to do that there has to be some observation that would be impossible if the theory were true.). Note that mainstream climatologists do that all the time, that is exactly what climate models are for, making predictions that can be proven wrong by observation. Now where are the skeptics falsifiable predictions? I pointed out this objection on Dr Spencer's blog, last time I looked (Saturday), he hadn't answered it and my subsequent posts are in some sort of moderation limbo, make of that what you will. -
Dikran Marsupial at 18:55 PM on 7 February 2011CO2 lags temperature
Poptech@253 I agree, E&E *is* a peer reviewed journal; the problem is that the peer viewiew at E&E regularly fails and publishes papers with obvious gross errors (e.g. Beck). As a result, the journal is not very highly regarded, the papers it publishes are not widely cited and it has a low Impact Factor. That doesn't mean papers are wrong just becuase they are published in E&E, they stand and fall on their won merits. -
Glenn Tamblyn at 18:50 PM on 7 February 2011A Case Study of a Climate Scientist Skeptic
HR #67 I think you might be misunderstanding this a bit because you question you ask suggests you are only considering the flows between atmosphere & ocean without putting this into the context of the other flows in the system. Perhaps I can explain this best with a simple analogy. I have a small water tank. A pipe at the top delivers a constant flow into the tank. And an outlet at the bottom allows the water to drain away again. What is the water level in the tank? 1. It will be at a level where the water depth in the tank creates a pressure at the bottom of the tank sufficient to cause a flow in the outlet pipe equal to the inlet flow. Then everything stabilises. This is the simplistic case of an Earth with no Ocean effects and no GH Effect. The tank is the atmosphere and the water level is the temperature. 2. Then we add a valve on the outlet that constricts the outlet flow somewhat. Now, the level in the tank rises until the pressure at the bottom is high enough to generate the required balancing outlet flow even with the constriction. This is the GH effect. 3. Next we close the valve a little bit more. So the level rises again to a new equilibrium to overcome the greater constriction. This is AGW - the Enhanced Greenhouse Effect. But so far we are only considering the atmosphere alone. Now lets add the oceans. We add a humungously big tank; and this is connected to our little tank by a pipe. Repeat our process. 1 & 2. Eventually the common level of our 2 tanks stabilises at the level that still lets the small tank come into equilibrium with its inflows and outflows. And the NET flow between the huge tank and the tiny one is zero - they are in balance 3. Then we tighten the valve a bit. The small tank starts to fill because the outflow is constricted. So the flow in the outlet starts to slowly rise. But now the small tank's level has grown compared to the large tank, so there is now a net flow from little to large. So the level in the small tank at any one time is determined by the inbalance between the inflow and the TWO combined outflows. And since the other tank is so huge, adding more water to it only changes its level VERY SLOWLY. So the level in the small tank can rise substantially before it generates a sufficient flow to the large tank to bring everything into temporary balance. Then, if the constriction on the valve isn't changed, the level in the small tank is lower than in our first example since most of the imbalance is going to filling the large tank. Eventually the large tank approaches the level of the small tank and the small tank can rise further. Eventually it all comes back into balance again but in the intermediate period the small tank is being artificially drained by the imbalance with the large tank compared with the first, atmosphere only, situation. So the small tank isn't higher than what it will be in the long term, it is lower. And if we keep restricting the valve, the small tanks level can be continually diminished by the sheer volume of the large tank and never reach equilibrium. -
HumanityRules at 18:11 PM on 7 February 2011A Case Study of a Climate Scientist Skeptic
66 dana1981 "He noted that by subtracting off the heat going into the oceans from the total forcing, I was basically treating the thermal inertia as a negative feedback to the surface air temperatures" The thing I'm struggling with is that given Glenn's explanation in #63 I had it that the ocean is acting in exactly the opposite way to this ATM. I'll have a go at explaining what I see, somebody can can point out where I'm going wrong. So the imbalance is not in the amount of energy in the system as a whole (ocean, air and others) but in how the energy is distributed about the different parts of the system. If we are going to imagine the system returning to equilibria then we have to imagine the radiative forcing no longer changing. If the dis-equilibrium is represented by the temperature differential between the ocean and air (as Glenn suggests) and the disequilibrium is only restored once the forcing stops changing then the only way to restore the equilibrium is by a net flow of energy into the ocean (from the air). While I take that thermal inertia can be seen as a sort of forcing I'm going to suggest that once the system is returned to equilibrium that the thermal inertia is 'forcing neutral'. You could divide the disequilibrium phase into two sections, the period when the radiative forcing is increasing and energy continues to build up in the system and the period when radiative forcing stops increasing and the system slowly restores the thermal differential and equilibria. It strikes me that in the first period thermal inertia appears as a positive forcing warming the surface more relative to the ocean. In the second phase there is a net flow of energy into the ocean (from the air) and this phase appears as a negative feedback. The overall impact is neutral in terms of it's forcing-like appearance. This is obviously ignoring the complexities of the climate system, slower feedbacks etc. So I've thought of an analogy for my description because I've never really understood the significance of a boiling pot of water. Imagine two large vessels half filled with water connected by a very, very thin tube. One of the vessels has a large tap above it. The vessel with the tap represents the air, the other vessel the ocean. The thin tube is 'thermal inertia', the tap is radiative forcing and the water is energy. Turn the tap on and the 'air' vessel begins to fill up, because the flow through the tube is slower than from the tap then the water in the 'ocean' vessel increases much more slowly. Turn off the tap then there is no further forcing of the system but the water level in the 'air' vessel begins to drop and the level in the ocean rises as wtare continues to slowly pass through the tube restoring the system to equilibria. As I said this is for a simple system ignoring long term feedbacks and chnaging feedbacks during the restoritive phase. Anyway where am I going wrong? -
villabolo at 16:59 PM on 7 February 2011The 2010 Amazon Drought
MattJ @21: But what this latest news shows is that even cockroaches are going to have trouble surviving. Even without extreme temperature change, the disappearance of humans from the environment, for whatever reason, will have drastic effects on cockroaches. Cockroaches, like rats, are commensal with humans. They eat our waste food. We're the ones who have made their populations explode and niches expand unnaturally. -
John Chapman at 16:34 PM on 7 February 2011How We Know Recent Global Warming Is Not Natural
Surely there are numerous peer-reviewed papers (e.g. Hansen) that model the temperature based on the various contributing factors and conclude that observations only match theory if one includes CO2 increases. Combined with other papers that report the increases in CO2 cannot be from volcanoes or termites and that it is man, then we have a reply to Spencer's challenge ruling out natural cycles. -
Andy Skuce at 15:44 PM on 7 February 2011If you don't have 93 spare minutes to watch this film, make the time
Thanks for the recommending that movie. I liked the repeated comment towards the end: "It's too late to be a pessimist". -
HumanityRules at 15:21 PM on 7 February 2011A Case Study of a Climate Scientist Skeptic
63 Glenn Tamblyn There's one problem I have with your explanation. You say that air heats up quicker than ocean. This causes a temperature differential. This disequilibrium is restored by a net flow of energy into the oceans to restore the equilibrium. This suggests to me that the atmosphere is now actually warmer than it should be during the disequilibrium phase (i.e. now). If we imagined that we stopped adding CO2 to the atmosphere today it seems that the return to equilibrium would occur via a net flow of energy into the ocean. More explanation is required for my tiny mind. -
Meadon at 15:13 PM on 7 February 2011How We Know Recent Global Warming Is Not Natural
You're right overall, certainly, but two criticisms. (1) The leprechauns comparison is unfair. We know climate change can be natural, but we don't have any evidence leprechauns exist. The plausibility of the first is thus several orders of magnitude greater than the plausibility of the second. (2) Your discussion of onus is a bit confused. Spencer doesn't suggest his cloud theory should be the null hypothesis, he's suggesting one or another natural process should be the null hypothesis. (Which is rather different). And in the absence of studies showing global warming is anthropogenic, the onus is clearly on showing it is. What's happened is that the null hypothesis has shifted due to the weight of evidence in favour of AGW. -
Eric (skeptic) at 13:53 PM on 7 February 2011The 2010 Amazon Drought
I should have said: the 2009 maximum is not on the graph in the paper, but it can be put in context using the graph in figure 3. -
Eric (skeptic) at 13:50 PM on 7 February 2011The 2010 Amazon Drought
muoncounter, I'm glad you liked the paper. I liked the first paper also which more properly (IMO) attributes the droughts to both AGW and ENSO (my theory is above). Here's the most severe Amazon drought of the 20th century http://www.scielo.br/pdf/aa/v35n2/v35n2a13.pdf caused by the 1925-1926 El Nino http://www.meteohistory.org/2004proceedings1.1/pdfs/07cushman.pdf The record low last October of 13.63 meters is in line with previous droughts. The 2009 maximum (see graph in the paper) was 29.71 meters, an extreme in the other direction. I don't have data for the 2010 maximum but it is likely well above the 1926 maximum. -
jyyh at 13:20 PM on 7 February 2011How We Know Recent Global Warming Is Not Natural
Good effort. I think you refer 'natural' as 'that which has not been modified by tools or been a subject to the usage of tools or has used tools' and 'internal' as 'referring to a happenstance inside of a specified system, exluding any supernatural influence' or something like that, I reserve the right formulate these definitions better, as leprechauns are thought to exist by some. -
scaddenp at 13:05 PM on 7 February 2011Global Warming and Cold Winters
"None of this takes into acount changes in economic behaviour, fuel shortages, or the effect of carbon saturation on heat retention. It's a model projection....true or false....not a reality. " What are we to make of you asserting the above when I gave you a link the SRES scenarios above which shows that this is not true? Your percentage calculation is ignoring that preindustrial baseline is around 280. This is screwing up your logic. Use the trend and extrapolate if you want simplistic results. However, SRES scenarios are not simplistic. As to other points - these seem to also uninformed but there are too many and you should take them to the appropriate places on the website. (especially Its not bad). And please back your assertions. -
MattJ at 13:04 PM on 7 February 2011The 2010 Amazon Drought
This is a good example of why, when the youthful optimists among the Caltech alumni dream of geo-engineering solutions to global warming, I always remind them: "it is too late, we have missed our chance to avoid a huge surge in war, pestilence and famine due to AGW". But what this latest news shows is that even cockroaches are going to have trouble surviving. -
MarkR at 12:41 PM on 7 February 2011How We Know Recent Global Warming Is Not Natural
7 chemware: there is a suggested cause of a change in cloudcover. If cloud cover's radiative forcing is nonlinear in temperature (say), then simply by redistributing heat around the world you get a non-zero change in cloud cover. e.g. cloud forcing might be related to temperature by C = T2. In which case if you had 2 places at T=10, you start with C=200. But if you move 1 up by 1 and the other down by 1, such that new temperatures are 9 and 11 then you still have the same mean temperature but C=202. This highlights the principle and I think it makes sense. But the evidence for climate sensitivity of order 3 C to CO2 doubling is very strong. IMO it's possible that Spencer is right, and it's about the only non-AGW theory that actually makes sense as an explanation for recent warming... and there should be more work done on it. Spencer has demonstrated that a strong negative cloud feedback might exist, but multiple lines of evidence suggest that it doesn't which makes me feel pretty confident that we don't have one. And without a strong negative cloud feedback or a massive screw up in the water vapour one then most global warming since the 70s is human caused. -
mozart at 12:37 PM on 7 February 2011Global Warming and Cold Winters
And Michael if you look at records so far in 2011 you find lows far outnumber highs. But of course this is too short a time frame...as is 2010 as a whole. Nobody is denying there is an increase in temperatures.....it's the extrapolations that are at issue. CO2 increased 17% (approx) from 1950 to 2000....but it's going to increase 100% from 2000 to 2050. Temperature increased less than one degree in 150 years and now it's going to soar 6 degrees or more, depending on the model. And the figure was much higher than that, until the models were improved. None of this takes into acount changes in economic behaviour, fuel shortages, or the effect of carbon saturation on heat retention. It's a model projection....true or false....not a reality. And anybody who has worked with mathematical models knows how easily they are tweeked...the dropping forecasts being a good example. Of course, none of this even begins to address the question of how we change things. We are facing unrest around the world as we chat....the product of food shortages. Misguided attempts to divert arable land to ethanol production are playing an increasing role in this. Attempt a rapid switch from fossil fuels and the Global Financial Crisis will be a minor inconvenience by comparison. We have a vast infrastructure based on fossil fuels and rapidly growing populations that will ensure this network is used. Take a look at the rush hour in any big city and ask yourself how we change that picture in a hurry. Fortunately the effect on climate continues to be modest at best. -
Chemware at 12:01 PM on 7 February 2011How We Know Recent Global Warming Is Not Natural
There are three guiding principles in any scientific investigation:- The existing body of scientific knowledge;
- Disproving hypotheses (ideas), until all are eliminated except one;
- If more than one hypothesis is left after (2), then Occam's Razor: the simplest complete explanation is most likely the correct one.
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dana1981 at 11:39 AM on 7 February 2011How We Know Recent Global Warming Is Not Natural
I got all the bases covered, sout :-) -
Miriam O'Brien (Sou) at 11:28 AM on 7 February 2011How We Know Recent Global Warming Is Not Natural
I now see the ALO theory has already been discussed in the original article. I really must stop rapid reading and peruse more carefully. -
Miriam O'Brien (Sou) at 11:21 AM on 7 February 2011How We Know Recent Global Warming Is Not Natural
The ALO* explanation, which shows that it's actually cooling, is more credible than that proposed by Dr Spencer. I found this terrific explanation on Tamino's blog at Open Mind, scroll down to see the upcoming WUWT post by Ned: http://tamino.wordpress.com/2011/02/03/a-challenge-to-dr-roy-spencer/ *ALO = Atlantic Leprauchaun Oscillation -
scaddenp at 11:19 AM on 7 February 2011Global Warming and Cold Winters
Mozart - They are sensitive to minor changes in dependent variable settings. ??? I dont think I am understanding you are all. What a model should be doing, is predicting the long term trends for a given scenario of forcings. Are you suggesting that those trends are sensitive to minor changes in model parameters? Can you provide some link or other evidence to support this? As to "we wont double this century", well as CO2 is increasing at 3ppm/year, I make that 57 years to 560. For more detail on what the scenarios actually assume and how the calculations are done, see SRES. Read instead of guessing. -
Riduna at 11:09 AM on 7 February 2011How We Know Recent Global Warming Is Not Natural
A cogent argument that Dr Spencer is wrong. It is all very well to put forward a null hypothesis and claim that it offers an alternative explanation but such claims have to be sustained by empirical evidence or, at the very least, be consistent with and explain such evidence. Dr Spence does neither. Anthropogenic global warming does both. -
muoncounter at 10:47 AM on 7 February 2011The 2010 Amazon Drought
#18: "a trend in "100 year events": how are they defined" Hundred year events are specifically defined as those events with a 1 in 100 probability of occurrence in any given year. Methods for calculating that statistic have been around since the days of Gumbel graphs. The Zeng paper I referenced here specifically states Amazon droughts are better correlated with Atlantic SSTs. Really, you've can't blame it all on el Nino. The paper you referenced here has a fascinating map depicting how the Palmer Drought Severity Index (PDSI) changed during the periods 1900-1949 and 1950-2002.
-- Figure 7 from Dai et al 2004
Maps of linear trends of PDSI [change (50 yr), calculated with both precipitation and temperature changes] during (top) 1900–49 and (middle) 1950–2002. (bottom) The trends of PDSI calculated without temperature changes. Red (blue) areas indicate drying (wetting).
The more recent 50 years sure look more severe than the prior 50. The graph ends in 2002, the beginning of the most recent 100 year events in the Amazon.
The authors conclude:
Our PDSI results, which are based on atmospheric moisture supply and demand near the surface, are consistent with increased evaporation under greenhouse gas–induced warming, as predicted by comprehensive coupled climate models. Global temperature increases have become pronounced after the 1970s and have been attributed to human-induced climate changes arising primarily from increased greenhouse gases.
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JMurphy at 10:33 AM on 7 February 2011How We Know Recent Global Warming Is Not Natural
Spencer would also presumably make the following challenge : "Show me one peer-reviewed paper that has ruled out god as the cause of life, the universe and everything" One query about the 'challenge' he did make, though - why did he mention only the "thermometer record" and not also the satellite record ? -
r.pauli at 10:33 AM on 7 February 2011How We Know Recent Global Warming Is Not Natural
Saying this is a scientist "who remains unconvinced" is far too kind and forgiving. Instead I would say he may be functional but is deluded. (so Leprechauns is a good argument ) He goes beyond just making trouble -- sounding more like a pathetic cheerleader for a lost cause. -
adelady at 10:23 AM on 7 February 2011The 2010 Amazon Drought
#4 Dan. I know that sinking feeling, only this is worse. It looks as though the Amazon is declining (or reacting or whatever) at the same kind of much faster than expected rate as Arctic ice. I've acquired a bit of fascination and interest with the ice statistics and a couple of lively blogs. The excitement and the learning tends to keep the omg feeling at bay. But this is just plain, everyday, unadorned awful.Moderator Response: [Daniel Bailey] I had the same reaction when I read this. -
Eric (skeptic) at 10:03 AM on 7 February 2011The 2010 Amazon Drought
#12 muoncounter, is there a trend in "100 year events": how are they defined and what is the trend of those events? Or is drought length increasing? There seems to be just one longer drought in 2005 so far. Also while there are currently longer N. American droughts http://www.agu.org/pubs/crossref/2007/2007GL031764.shtml that paper indicates that longer droughts have occurred in the past. #14 Rob Painting, and #16 Chris G, I think you are both making the same basic point that ENSO is highly correlated to the droughts (although perhaps as muoncounter pointed out shorter droughts rather than longer). My conclusion is that while ENSO is natural, the magnitude of the effects of ENSO are increased by AGW. I'm not so sure about the AGW directly influencing the magnitude of ENSO
but we'll probably find out in the next 5 years or so if we start getting large El Ninos contrary to the diminished El Ninos that we would expect from a natural cycle.
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Matthew at 10:01 AM on 7 February 2011The 2010 Amazon Drought
So in 2010 the amazon released more co2 emissions then China and India put together. So if this becomes once every 5 years instead of 100 or 200 year event then it may speed up the green house effect and make it far harder for us humans to do anything about it. A run away feed back. -
michael sweet at 09:34 AM on 7 February 2011Global Warming and Cold Winters
Mozart: According to this link in August, 17 countries had recorded record highs while only one had recorded a record low during 2010. I have not seen the final yearly data (does anyone have a link?). Are you suggesting that there have to be zero record lows before you agree that it is getting warmer? It seems to me that 17:1 is a significant shift in the probability distribution from the expected 1:1 ratio. How high does it need to go before you think it is significant? 25:1? 100:1? 1,000:1? -
Chris G at 08:36 AM on 7 February 2011The 2010 Amazon Drought
Couple of thoughts: Eric, An El Nino is not a magical event, the energy released during an El Nino had to come from somewhere. There is evidence that they have become more intense over the last century (at least one coral study that I remember but can't cite at the moment; I'm sure Google-Scholar would be helpful there.) Also, I wonder how much organic material is washed out to sea from the Amazon. Of course, any number of things could happen to it at that point, but I think it would be fair to say that a rain forest absorbs more CO2 than, let's say, a savanna. -
muoncounter at 07:29 AM on 7 February 2011Global Warming and Cold Winters
#95: "we wont see that this century, given we have a 24% increase for the whole of the 20th century." That's not a valid trendology. The rate of fossil fuel CO2 emissions boomed after WW2; we've released half of the total of all CO2 emissions just since 1974. CDIAC has these numbers. Reasonable scenarios put doubling -- 560ppm -- shortly after mid century. Your 'dwindling crude supplies' won't play: there's lots of coal. But that's a topic for Its not us or Human CO2 is a tiny %. -
Trueofvoice at 07:27 AM on 7 February 2011Global Warming and Cold Winters
Mozart, Even if CO2 emissions remained at the current 2.2 parts per million per year, we would see more than a doubling of pre-industrial CO2 levels by the end of the twenty-first century. Unfortunately our CO2 emissions have increased exponentially since the start of the industrial revolution. The key point when looking at an exponential increase is that one cannot expect future growth to look similar to that observed in the past. An exponential increase looks linear until it hits a certain point, at which time that slowly rising line on the graph suddenly looks a lot more vertical. -
mozart at 06:46 AM on 7 February 2011Global Warming and Cold Winters
I apologize for being vague. They are sensitive to minor changes in dependent variable settings...they are not sensitive in terms of prediction. As for a doubling of CO2....we wont see that this century, given we have a 24% increase for the whole of the 20th century. More realistic is a doubling by 2200 with a 1.5% C increase in temperatures. If...and it's a big if...we don't adapt to lower carbon usage by sheer economic pressures. What is missing here is a sense of what will happen as our crude supplies dwindle. The natural economic forces unleashed by attendant price increases will stimulate real(not subsidised) search for alternative fuels. Leave it to the market. So I'd be offering odds for less than a one degree C rise....if only I'd be around to cash in. -
scaddenp at 06:31 AM on 7 February 2011Global Warming and Cold Winters
"The fact is these models are inherently extremely complex and sensitive. In the absence of clear cut warming consistent with a 24% rise in CO2, one must remain unconvinced." mozart - there are problem with this statement. Can I suggest you get a better background by reading the relevant sections in IPCC WG1. Firstly, the models aren't "sensitive" in the normal sense of the word. They do not have the skill to make decade (or less) level predictions. However, the models unequivocal at the 30 year level. Secondly, the model/data concordance is excellent for a sensitivity of 3 degree per doubling. See here for a discussion. -
Rob Painting at 06:13 AM on 7 February 2011The 2010 Amazon Drought
Pikaia @ 1 - I have never understood how the forest can be a carbon sink. In a stable world the amount of carbon in the forest would be constant The prevailing view is that the increased growth is down to the CO2 fertilization effect, although it has not been proven. Another hypothesis is that the increase in sunlight (cloud cover has reduced in the last few decades) may have also helped to increase growth. See Arias 2010 - Changes in Cloudiness over the Amazon rainforests during the last two decades. Because of the persistent cloud cover over the Amazon, green-up (a spurt in plant growth) can occur during the early stages of a dry period. Assuming of course, there is sufficient ground water available to the plants. Obviously in 2005 & 2010 there wasn't enough water. -
Rob Painting at 05:57 AM on 7 February 2011The 2010 Amazon Drought
Eric @ 11 - The 2005 & 2010 droughts were driven by warmer than normal sea surface temperatures in the tropical Atlantic. Hence the large coral bleaching events in the Caribbean in both those years too. The too warm SST's in the tropical Atlantic drives the ITCZ further northwest over the Northern Hemisphere summer. The result is the "rain-making engine" moves out of the Amazon, exaggerating the effect of the dry season.
El-Nino causes drought in the Amazon by shifting the convective area over to the eastern tropical Pacific Ocean, where the SST's along the South American coast are ramping up. Once again the rain-making shifts toward the area of greater sea surface temperatures.
The connection between drought/wet episodes in the Amazon are very consistent throughout the 20th century. 16 out 17 El- Nino caused drought, and 14 out of 16 La Nina caused wet episodes in the Amazon. See Ropelewski & Halpert 1987. The figure jumps higher when the 1990's Amazonian droughts are included.
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