by Michael Mann and Gavin Schmidt
Roughly a year ago, we summarized the state of play in the ongoing scientific debate over the role of anthropogenic climate change in the observed trends in hurricane activity. This debate (as carefully outlined by Curry et al recently) revolves around a number of elements – whether the hurricane (or tropical cyclone) data show any significant variations, what those variations are linked to, and whether our understanding of the physics of tropical storms is sufficient to explain those links.
Several recent studies such as Emanuel (2005 — previously discussed here) and Hoyos et al (2006 — previously discussed here) have emphasized the role of increasing tropical sea surface temperatures (SSTs) on recent increases in hurricane intensities, both globally and for the Atlantic. The publication this week of a comprehensive paper by Santer et al provides an opportunity to assess the key middle question – to what can we attribute the relevant changes in tropical SSTs? And in particular, what can we say about Atlantic SSTs where we have the best data?
This role of SST remains pivotal in understanding long-term trends in hurricane activity, regardless of whether the SST increases are natural or anthropogenic in origin. Mann and Emanuel (2006) noted that once SST is accounted for as a factor, there is no apparent multidecadal signal in long-term hurricane numbers, regardless of what that signal might be (i.e., SST, wind sheer, or any other factors that potentially influence activity). Other studies (e.g. Bell and Chelliah, 2006) generally agree that the ‘memory’ of any multi-decadal osillation (whether forced or natural) lies in the ocean, and atmospheric simulations using observed SST data in the Atlantic reproduce many of the observed correlations (Zhang and Delworth, 2006). So understanding the origin of the warming SSTs is central to understanding changes in hurricane behavior.
The essential question, then, is what has caused the long-term SST changes? This question is sometimes reduced to the ‘straw man’ of whether tropical SSTs trends (which are very clear in the data) are internal (i.e., due to a natural oscillation of the climate system) or anthropogenic (i.e. forced by some combination of human-related causes)? Of course, this is a over-simplification since there always at least some role for internal variability. So a more useful question is to what extent SST changes can be attributed to various possible causes.
In the Atlantic, the proposition advanced by some is that a natural oscillation known as the Atlantic Multidecadal Oscillation (AMO) is responsible for the observed trends in SST (and by extension, North Atlantic hurricane activity). To examine that question requires a clear analysis of the data, and examination of what models suggest regarding the likely amplitude, spatial extent and physical mechanisms underlying this oscillation.
First of all, how is the AMO defined? It is intrinsically quite difficult to detect any multidecadal oscillation in roughly only one century of instrumental data. Simply put, separating an oscillation from trend becomes exceedingly tricky (and increasingly dependent on statistical assumptions) as the timescale of the oscillation approaches the length of the record. Unfortunately, this situation holds for the AMO, which has been attributed periodicities anywhere from 40-100 years, the latter approaching the length of available instrumental climate observations. In some earlier studies, the AMO was defined using multivariate signal detection procedures to tease oscillatory patterns apart from long-term (potentially non-linear) trends (e.g. Mann and Park, 1994) or using climate model-based estimates of forced trends to estimate a possible residual oscillatory component (e.g. Schlesinger and Ramankutty, 1994).
In some more recent studies, however, the AMO has been defined simply as the residual low-frequency pattern after linear detrending of SST observations (e.g. Goldenberg et al, 2001). The linear detrending is intended to remove any potential forced signal, under the assumption that it is linear in time. However, if the forced signal is not linear, then this procedure can produce a false apparent ‘oscillation’ purely as an artifact of the aliasing of the non-linear secular trend (Trenberth and Shea , 2006). In fact, we have very strong indications for the 20th Century that the forcings over that period have not varied in a smooth, linear fashion.
Because of the procedural difficulties in isolating the AMO signal in the instrumental record, the estimated attributes of the signal are quite sensitive to how it is defined. The earlier studies mentioned above (i.e., Mann and Park, 1994; Schlesinger and Ramankutty, 1994) found an AMO signal with a large projection onto high-latitude North Atlantic SST variations, but little projection onto tropical North Atlantic SST. This contrasts with studies using the linear detrending procedure described above, which indicate a sizeable impact of the AMO on tropical North Atlantic SST.
In a regression analysis using instrumental observations, Emanuel and Mann (2006) find that the estimated temporal history of the anthropogenic climate change signal in tropical North Atlantic SST superficially resembles the temporal pattern often ascribed to the AMO (i.e., early 20th century and 1960s-1980s cool phases, and 1930s-1950s and recent warm phase). However, they identify this irregular warming pattern with a combination of greenhouse gas warming influences and late 20th century sulphate aerosol cooling influences (which are especially large during the late boreal summer in the tropical Atlantic). It is therefore likely that the non-linear temporal history of anthropogenic tropical Atlantic warming has masquaraded as the ‘AMO’ in some studies.
Does the AMO even exist as a climate phenomenon absent the complications in detecting the signal in actual observations? Here the answer is probably yes. Within coupled models, enhanced multi-decadal variability with an apparent origin in Atlantic ocean-atmosphere dynamics, does occur. This was shown in work published in the early 1990s by Delworth and collaborators using the GFDL coupled ocean-atmosphere model (see the update and review in Delworth and Mann, 2000), and in more recent work by Knight et al (2005 and 2006) with the Hadley Centre coupled model. This AMO signal, in the model simulations, is associated with oscillatory variations in the meridional overturning circulation such that when the overturning is stronger than normal, there is a warming pattern in the North Atlantic (and vice versa). However, the warming in the model simulations is largely confined to the extratropical North Atlantic, with only a small (roughly 0.1 C maximum) projection onto the Main Development Region (MDR) for Atlantic hurricanes. The model simulation results therefore appear consistent with those analyses of observations which find that the AMO signal does not have a substantial projection onto tropical Atlantic SST. This does not mean that the AMO could not in principle influence tropical Atlantic Hurricane activity. In fact, detailed analyses of both the GFDL and Hadley Centre simulations indicate that the AMO is associated with moderate changes in wind sheer in the tropical Atlantic, which could potentially influence Atlantic hurricane activity. However, as discussed earlier, a number of studies find that it is the SSTs that have played the primary role in the observed increases in hurricane intensities in recent decades.
An alternative approach to the problem is a formal ‘detection and attribution’ analysis which seeks to establish the role of a potentially forced signal in the midst of climate ‘noise’. This is where the new Santer et al paper comes in. Here, the authors examine the model simulations for the 20th Century that were coordinated for the IPCC AR4 and which now form a very valuable database that can be used in addressing issues such as those which concern us here. For each of the models, the trends in key Atlantic and Pacific regions can be compared in the runs with and without forcing. Assuming for the moment that the models produce a reasonable approximation for the naturally occurring decadal variability, it can easily be seen whether a) the trends in the models are similar to those in the real world, and b) to what extent they can be explained by the forcings. In the Santer et al study, they find that the model trends when driven with the 20th Century forcings do match the observations, and moreover, are clearly larger than can be explained by internal variations (see the figure extracted from Figure 2 of their paper). Interestingly, the study also supports the observation-based finding of Emanuel and Mann (2006) that sulphate aerosols are likely to have masked a significant component of the late 20th century tropical Atlantic greenhouse warming.
But do the models produce a reasonable amplitude of internal variability? This is a difficult question to answer because it can’t be easily deduced from the climate record (since there are many forcings, some natural, some anthropogenic) that are potentially obscuring the internal signal. However, over the period when we have good data, we can certainly check whether the models amplitude of variability is in the ball park of the observations. Santer et al did this as well, and find that indeed, there is no reason to think that models as a whole are systematically underestimate the internal component. One of the advantages of the IPCC AR4 data is that with so many models participating (22 models here), there will be a range of results – some models have more variability than observed, others less. A robust conclusion can therefore be drawn if the signals are clear regardless of the magnitude of any one models’ representation of the internal variability. (Santer et al have posted an illuminating Q&A on their study that discusses this point further.)
This result (and an associated paper by Knutson et al who look in more detail at the GFDL simulations) is particularly notable because among the models they look at at precisely the GFDL and HadCM3 models known to generate the ‘AMO’ in control simulations. Thus even in those models which exhibit oscillatory ‘AMO’ behavior, the observed tropical SST trends can only be explained when anthropogenic forcing is included.
In total, at least four studies, two based entirely on analyses of observations, and the other two based on climate model simulations, independently come to the conclusion that warming tropical Atlantic and Pacific SSTs cannot be purely attributed to any natural oscillation. These studies do not conclusively show a hurricane/global warming link, let alone determine what it’s magnitude might be, but they do strengthen one pillar of that linkage.
57 Responses to "Tropical SSTs: Natural variations or Global warming?"
Ferdinand Engelbeen says
May we disagree on the following quote from the Q&A of Santer:
Some of the main climate models (which includes the HadCM3 model!) don’t even predict the global variability (“climate noise”) of ocean heat content (as surrogate for SST…), let it be for regional changes, where the accuracy of any model is even worse. See figure S1 of Barnett ea.
The models significantly miss any cycle between 10 and 100 years, that includes the 11-22 year solar cycles or any form of AMO…
Further, there is a significant decrease of SO2 emissions in North America since the mid-seventies. This should have been noticed as an increase of the North Atlantic Ocean heat content, if there was a substantial effect of aerosols. But the North Atlantic shows a substantial cooling trend in the period 1980-1990. See Fig. S1 of Levitus ea.
This means that models still are far from able to match observed (natural) changes in global/regional ocean heat content/SST… But may capture the average century trend for the wrong reasons (different weights of attributions…).
Btw, how does the recent (still discussed) observed change in ocean heat content/SST fit in this picture?
Why are you contributing the SST warming over a single century as THE result of gloval warming? How can any “century set” of data conclusively determine the cause-effect when global climate changes are marked in thousands of years?
C. W. Magee says
How do anthropogenic sulphates end up shading the tropical Atlantic? I was under the impression that the dominant winds in the tropical Atlantic were the easterly trade winds, which blow in from Africa, a continent noted for its lack of industrialization. As such, wouldn’t Saharan dust transport (of the type that has been strangling tropical waves this summer) be more important to tropical SST than anthropogenic sulphate?
[Response: Its not that simple. The mean surface winds in the tropical Atlantic are of course easterlies, but this is just the average over many individual synotopic states. Mid-latitude frontal systems moving west over North America occasionally penetrate far into the tropical North Atlantic. Such events mix in any tracers (e.g. aerosols) those systems may be carrying with them. Climate models such as those used in the Santer et al study capture this sort of mixing, though in an admittedly somewhat crude manner. – mike]
Dianne Fristrom says
So the AMO is one of those “natural variations” that compete with GHGs for repsonsibility for global warming! (a new one for a non-climatologist). I am trying to write an article for a small publication. After summarizing the evidence implicating GHGs (I’m on firm territory there) I’ve written (so far):-
” The other oft cited suspects in global warming are “Natural Causes.” Science has identified several of these. The most important is a series of very long term cyclical changes in the Earth’s circumnavigation of the Sun known as Milankovitch cycles. There is also a correlation between sunspot activity, and earth’s temperature although the mechanism is not understood. Natural catastrophic events, such as the collision with an asteroid or massive volcanic eruptions can have profound effects on climate as demonstrated in our geological past. However, none of these natural causes are operating now to explain this climate change. To think that the present global warming is due to natural causes is a bit like believing that a blood-covered corpse lying next to a man holding a smoking gun died of natural causes.”
Could you comment please – is this statement valid? Is the metaphor is “way over the top”
[Response: Milankovitch cycles are too slow. http://www.grida.no/climate/ipcc_tar/wg1/442.htm is good. http://en.wikipedia.org/wiki/Attribution_of_recent_climate_change may be useful – William]
Brad Arnold says
Frankly, I’m surprised about the debate. Tropical SSTs are proven to be strenghtened by warmer ocean surface temperatures. In fact, Tropical SSTs can’t form on ocean water cooler than approximately 82F, and the body of eastern African Atlantic water that temperature has enlarged in the past years.
It is undeniable that the trend is hotter surface ocean temperatures, particularly around the Gulf Coast and eastern seaboard of the US. Furthermore, the trend is toward a larger band of surface water in the eastern African Atlantic reaching the necessary temperature to form SSTs.
My main concern is the bias climate models have against prediction of abrupt climate change. They instead are bias toward linear predictions. Dr Lovelock is predicting that in the next decade or so the earth will reset it’s thermostat 10C higher. This predicted “climate surprise” is downplayed by most scientists, partially because of climate model bias.
[Response: But its not at all clear *why* Lovelock thinks this will happen. Missing “surprises” from the model is a distinct possibility; but its a long step from that to predict unknown things happening soon – William]
It is virtually certain that increased levels of greenhouse gases in the atmosphere from both humans and (increasingly) natural sources will lead to increased ocean surface temperatures, leading to more intense tropical SSTs. The solution is to wait for the signature of global warming to be more clear, so even the most contrary skeptic sees the relationship. Hopeful, the increase in signature won’t be expotential.
Eric (skeptic) says
Question from another forum: why was the increased wind sheer (and fewer hurricanes) not predicted by the climate models? Second question, are you also considering the spatial variability of SSTs and how those might break down into direct anthroprogenic forcing (e.g. sulfates), weather, and long term patterns? Even with the chaotic variation in weather at a small scale, aren’t there larger scale patterns (e.g. NAO) that can be predicted?
Bob Maurus says
Sorry for the off-topic, but I’ve not yet seen any peer comment on Yde and Knudsen’s Disko Island Glacier melt paper. All that’s out there is the rightwing blog stuff based on the press release, far as I can tell. Has anyone with creds weighed in on it yet? I’d appreciate any information.
L. David Cooke says
I just wanted to pop in an share a few quick observations. Everyone keeps alluding to GHG and THC as primary reasons for SST increases. I’m sorry, I lived for over 15 years in Florida and my perceptions of the character of the ocean/air temperature to storm count/intensity ratios in the North Atlantic do not seem to correlate with the study materials presented as of late.
I can share with you that there appears to be characteristics you can see in Winter that will indicate the likely development of hurricanes next Fall. The primary characteristic is a lack of or reduction of the Eastern Trades as far north as 28 Deg. The secondary characteristic is a stagnant anti-cyclonic pressure zone in late Nov. that persists until early Janurary. (I do not know if there was sufficient daily sampling to establish the net change in high altitude temperatures prior to and after the NA spring thunderstorm and the fall hurricane seasons. I do know when the Gulf SST’s are higher there are more Central US tornados, though it appears most are at lower F-# values then when the count is lower.)
As to hurricanes, when you have a warm Winter start you appear to have a reduction in the loss of SST in the Gulf and the Caribbean. This loss of convective dumping during the “Trades” season ends up leaving a signature elevated SST with an early and sultry Spring.
Now if you can link the GHGs to the formation of the Anti-Cyclonic zones or to the stagnant characteristic and the characteristic retrograde of the Bermuda High in early spring I will be glad to consider joining the “True Believers”.
However, I do not see the GHG driving the pressure fluxes or the speed by which they circle the globe. Matter of fact, up until this past spring I almost could see the GHG being a participant with the lower upper level temperatures as a participant in hurricane strength. It was quite possible that GHG could be causing a reduction in the upper air temperatures and hence the stronger winds. However, the correction of the data this past spring indicates that this supposition was not true and the upper atmospheric temperatures did indicate a warming.
That SSTs are a participant in the development window and the size of the storm I believe a correlation can be verified. As to the strength being driven by the increased SSTs (Yes, I mean the top winds and minimum pressure, not just the total wind shield.) are likely driven by the reduced tropopause air temperatures and not SSTs. Now I begin to wonder if it is possible that the lower air pressures and higher winds speeds could be related to the a higher altitude that the rising water vapor must travel before condensing.
And finally let me share that as to the SSTs being the sole indicator of storm character potential is not valid based on my experience. Increased SSTs are clearly part and parcel with additional weather events and do not occur without association of other characteristics. The trades, the SST’s, the stangnant pressure zones, whether or not the pressure zones are floor to ceiling or just an “upper level” pressure zone, the high altitude air temperatures, the saturated adiabatic altitude (Humidity-vs-Temp curve), the SiO2, NaCL and organic aerosols size and distribution at altitude all appear to play a part. This is not something you can simply through over the wall and attribute the character to only one issue such as SSTs or what I fear are possibly non-existant AMOs.
I do not know that these observations are useful; however, it becomes a little frustrating watching what appears to me to be, a lot of digging holes in the ground trying to find a buried treasue that simply does not exist. (I apologize if these are preceptions only and not verifiable. I have attempted my best to correlate my observations; but, I am not a professional in this field. Nor do I have the expertise or credentials to support a professional study.)
Chip Knappenberger says
Let me try this one out on everybody:
1) anthropogenic influences on the atmospheric composition have resulted in rising SSTs in the North Atlantic over at least the past several decades and probably for decades previous
2) pseudo-cyclic natural oscillations occur in the North Atlantic environment at multidecadal timescales (these include co-varying SST, wind shear, static stability, etc.), let’s call this the AMO
3) the natural variations influence tropical cyclone formation and development
4) as the natural variations occur on top of anthropogenically-warmed SSTs, their effects can be enhanced
Thus, as the AMO has swung into its positive phase (good for hurricanes) this time around (since 1995) it is operating on SST that are much higher than last time the AMO was in a favorable state. Thus, as the AMO brings it’s lower wind shear (as evidenced by Hoyos et al. and the recent papers by Knight et al. and Zhang and Delworth) and decreased vertical stability (Hoyos et al.) and maybe even a bit warmer SSTs to an environment with already high (and getting higher) SSTs, the stage is set for some pretty impressive hurricanes.
In fact, perhaps we are currently in as ideal an environment for frequent strong storms as we are ever going to get. For as the greenhouse effect continues to enhance, climate models project that vertical stability will increase and aren’t quite sure how vertical wind shear will evolve (see Knutson and Tuylea, 2004). Presumably, in a couple of more years to decades, the AMO will switch back to a negative (unfavorable) state, and while Atlantic hurricanes may not go back to being as quiet as they were in the 1970s and 1980s, they will probably quiet down a bit from their currently very active level. With the next AMO positive (favorable) state, even though SSTs will likely be higher still, it is possible that the vertical stability and wind shear influences of an enhanced greenhouse effect will be large enough that they may act to offset, to some degree, the influence of the AMO variability, thus producing a situation that is less favorable as it could be.
So, perhaps what we are witnessing now, and for as long as the AMO is in it’s current positive phase, is the ideal breeding grounds for Atlantic hurricanes – a result of natural variability acting on top of human-induced climate changes.
To me at least, this would help to explain why the trend in hurricane activity during the past several decades has been much greater than SST-theory alone would suggest.
[Response: Seems reasonable to me Chip. – mike]
supported, to some degree, by the fossil fuel industry since 1992
Hurricanes are mainly driven by the heat of deposition (8 mm Hg partial pressure of H20 and above) and heat of condensation (4 mm Hg partial pressure and below) of water vapor. Tropopause temperatures have almost no effect on this as the water vapor density at -100C or so is minuscule (the website I’m using doesn’t handle temperatures below 0C as it’s geared towards steam turbines – so you’ll have to trust me that the partial pressure is indeed tiny), though the height of the tropopause might have some effect by increasing the vertical relief.
On the other hand, the partial pressure of H2O grows extremely fast in the range of 0C (ice) to about 120C or so. It’s 4 mm Hg at 0C/ice but 760 mm Hg at 100C/water.
The density of saturated steam for tropical SST-type temperatures is as follows: (This is the same as the density of the water fraction of saturated air at that temperature)
28C: 27.3 g/l
29C: 28.8 g/l
30C: 30.4 g/l
31C: 32.1 g/l
32C: 33.8 g/l
33C: 35.7 g/l
34C: 37.6 g/l
What this shows is that each degree of increased SST increases the water vapor density (and thus energy density) available to the hurricane by about 6%. That is an extreme response considering that 27C is 300K, so each degree is only about a 0.33% change in Kelvin temperature. (Note: The change in the heat of vaporization per mol of H20 due to the higher temperature is pretty much meaningless, though it does serve to slightly reduce the free energy available – the effect is very small unless temperatures in the core of the hurricane approach or pass 374C and the pressure approaches or exceeds 220 atmospheres – very unlikely indeed).
Now there are other factors that play into hurricane development and life-cycles, but the energy available is almost entirely dictated by SSTs and water vapor.
Hank Roberts says
Eh? typo, it’s Knutson and Tuleya, 2004.
Do you have the full text source somewhere? All I find is the abstract:
“… Convective available potential energy (CAPE) is 21% higher on average in the high-CO2 environments. One implication of the results is that if the frequency of tropical cyclones remains the same over the coming century, a greenhouse gasâ��induced warming may lead to a gradually increasing risk in the occurrence of highly destructive category-5 storms.”
Hank Roberts says
Oh, I see there’s been much more discussion:
will find their reply to the Michaels & Knappenberger paper in the first dozen results.
Pete Altman says
Some folks might be interested in seeing an animation showing the correlation between Atlantic seasonal SSTs and seasonal hurricane PDIs, over the last thirty years. The animated chart is based on a recent update to the dataset Kerry Emanuel assembled for his 2005 paper, and was developed by my colleagues and I at Clear the Air.
Stephen Berg says
Great link, Pete!
Chip Knappenberger says
Hmmm. Here is an interesting article that I just came across that hasn’t seemed to be getting much attention: Bengtsson et al., 2006, Storm Tracks and Climate Change, J. Clim., 19, 3518-3543. Using the European Centre/Hamburg Model Version 5 (ECHAM5) and the SRES A1B scenario, they find, when analyzing tropical cyclones in a globally-warmed future, “a general reduction in activity in the Atlantic storm track as well as a general reduction in the amplitude of the storms, in particular in the main development region (MDR) for tropical cyclones.” And further, “The Atlantic storms are reduced in number, in particular the stronger ones, while the storms in the eastern Pacific are virtually unchanged though there is some indication of fewer storms. It is interesting to note that the changes in SST by between 2ºC and 3ºC has not had any influence on the numbers and intensities of the more powerful tropical storms.” (emphasis in original). The authors go on to suggest that a reason for this may be that the patterns of climate change in their model are similar to those of a warm ENSO event, which is not good for strong tropical cyclones.
Anyway, just thought I’d take the time to point out that there is reseach out there that isn’t in total agreement that global warming will make hurricanes worse.
to some degree, funded by the fossil fuel industry since 1992
Chip Knappenberger says
Re #13. I’d be interested in seeing your animation on the annual values of SST and PDI rather than the smoothed values. After all, this year’s storms are responding to this year’s conditions, so the smoother is unnecessary.
funded by the fossil fuel industry, to some degree, since 1992
L. David Cooke says
I would suggest the data you are referencing may be appropriate for steam turbines operating at ambient surface pressures; but, may not apply to atmospheric adiabatic processes. It is clearly visable in the CloudSat/Calipso Lidar images that in the heart of a great storm such as a Hurricane the temperature appears to remain above freezing above 12-14 Km in opposition to the normal 0 Degree C altitude for these latitudes.
There appears to be a clear indication that the altitude for the conversion from saturated and non-saturated adiabatic transition is far above the altitude and apparently well below the pressure of where this transition point would normally be. Given this I do not know that your data tables would necessarily apply. When I look at your last paragraph of your posting a thought occurs to me that the SSTs and water vapor may only relate to the top altitude and the width of the updraft window of the storm.
(A greater width of an eye should result in higher pressures and lesser cyclic winds. The falling condensed water vapor at higher altitude before transition should drive the Cyclonic wind speeds and the pressure differential between the top and the bottom of the storm.)
If you have a source that can demonstrate how SSTs or a similar effect can drive water vapor to higher altitudes and not be subject to the saturation altitude, I would be intrested in reviewing it. In the meantime, what you have provided does not appear to match my research and/or observations. Any assistance or reference in helping me to understand the storm processes are welcome.
ike solem says
The news reports of this study are worth looking at, as they contain the official skeptical response as delivered by Philip Klotzbach, William Gray and Chris Landsea. In fact, a majority of the press reports prominently featured these three voices.
“No credible observational evidence is currently available that directly associates global surface
temperature change with changes in hurricane frequency or intensity,” Klotzbach said.
Recall that the first link is between human influences on atmospheric carbon dioxide and the resulting warming effects on the atmosphere, oceans and land masses. The next link in the chain is between sea surface temperature and hurricane intensity trends. Total heat storage in the surface ocean might be a better parameter than SST’s, but that data is more difficult to obtain.
“They make a very good case that the trends in sea surface temperatures are at least in part, if not substantially, due to man-made global warming,” said Chris Landsea, a noted hurricane researcher from South Florida. “But this is not a hurricane study.”
Landsea is attacking the study by claiming it doesn’t directly involve hurricanes – so is he saying that sea surface temperatures have nothing to do with hurricanes? Or is he saying, as he did previously, that trends in hurricane intensity are not detectable? Take a look at the animation posted in #13, which seems to refute both Landsea and Klotzbach.
Gray said the models do not deal with all necessary ocean processes and called the report “a desperate attempt to keep the bandwagon going. They’ve kept it going with global warming and now they want to keep it going with hurricanes.” “I am very sure over the test of time it will not hold up,” said Gray, who was not part of the research team.
Right after Katrina, William Gray had this to say (ABCNews): “This is just the way nature behaves and I find it astounding how tremendously lucky this country’s been in the past 20 years in the lack of a major landfall,” said Bill Gray, a professor of atmospheric science at Colorado State University. “People need to view this as a tragedy, an event of nature that occasionally occurs, and we shouldn’t blame anybody for it.”
Where is the scientific argument? This is just how nature behaves? There is nothing to address in Gray’s comments; all he does is rail against “the bandwagon”.
The problem is that these news reports are not examining any of the statements that Gray, Klotzbach and Landsea are making. Gray’s comments are not scientifically based; they are just an unsupported rant against the paper. That’s not science, that’s opinion. Klotzbach denies that the evidence is there, and Landsea claims the study isn’t relevant to hurricanes! What is fairly odd is that most of the news reports contain statements of one or all of these three official skeptics. Considering that there are hundreds of climate scientists in the US to choose from, it’d be interesting to know why news editors and reporters are relying only on these three, particularly when their scientific stance is so non-sensical. What is even more disturbing is the lack of basic scientific discussion in the news reports – the story is presented as a conflict between two groups of experts, and even a basic discussion of SST effects on hurricane intensity is excluded.
Even if the current crop of official climate skeptics is discredited, the industry will just find a few more fresh faces to take their place: http://www.motherjones.com/news/feature/2005/05/some_like_it_hot.html .
C. W. Magee says
Re. response to 3:
Is there any actual data to support the models that suggest that westerlies can penetrate into the tropics while carrying aerosols?
[Response: Trailing mid-latitude cold fronts coming off North America plunge well into the tropical Atlantic quite often. You can find a beautiful example in Figure 1 of this NOAA page. This is most frequent during mid-winter, but certainly also takes place during the crucial (in the context of Tropical Cyclone discussions) boreal Autumn season. – mike]
I would think that Pb isotopes on planktonic forams would be able to distinguish between pollution coming west from the US, as opposed to south from Europe. Coupled with temperature proxies, it might even tell you if the source changes as a result of seasonality. Might be worth talking to an oceanographer about…
Hank Roberts says
>15, Chip K’s suggested article is here in PDF form:
Google Scholar finds these cites (many familiar names among listed authors)
But Chip, Knutson and Tuleya – Journal of Climate, 2005 – adsabs.harvard.edu
replied to the critical paper you coauthored with Michaels arguing that warming would reduce storms:
saying: “A response is made to the comments of Michaels et al. concerning a recent study by the authors. Even after considering Michaels et al.’s comments, the authors stand behind the conclusions of the original study. In contrast to Michaels et al., who exclusively emphasize uncertainties that lead to smaller future changes, uncertainties are noted that could lead to either smaller or larger changes in future intensities of hurricanes than those summarized in the original study, with accompanying smaller or larger societal impacts.”
Just asking if you and Michaels wrote that as advocacy for New Hope or in a spirit of evenhandedness about uncertainties, but didn’t find any on the upside when you tried to?
Hank Roberts says
While waiting for Chip K …
William, inline response in #5 you said Lovelock’s not explaining why he expects a rapid heating. In today’s NYT here
he’s quoted thus:
“…A. I think we’re headed straight back to the Earthâ��s second stable state, which is a hot state that it’s been in many times before in the past. It’s about 14 degrees warmer than it is in these parts of the world now.”
Seems to me he’s looking at the carbon currently immobilized by the unusual cold of recent years (hydrates and permafrost) and saying we’re in a tippy unstable time. Given his success supposing where feedbacks might be found and finding them (over many decades) I think he’s saying, he has a strong hunch. And, I imagine, a prepared mind. Hard to falsify such an expectation, easy to imagine ways he could be right and warming could indeed be very fast. Hydrates. Permafrost. Plankton dieoffs with acidity.
Lots of past, much of it quite warm, compared to now:
Urs neu says
There is an important question remaining:
– considering that there are no adequate measurements of the evolution of the THC until now (besides Bryden et al. whose results are based on very few data) and we don’t know the current state with respect to the assumed natural cycle, and
– considering that the Atlantic SSTs follow the evolution of global temperature very closely over the last few decades and thus the global temperature evolution (due to GHG) could fully explain the recent increase, and
– considering that we don’t know the period length of the AMO very well (modelled period lengths vary by several decades, reconstructions as well; the observed period length in the 20th century depends strongly on the recent increase!):
How can you tell that the AMO is in its positive phase already? How can you tell that the switch to the positive phase isn’t still to come?
Do I miss something?
Tony Noerpel says
Re 21 Hank
As I understand it, there is 800 Gtons of carbon stored in ocean life which through respiration and photosynthesis exchanges with the atmosphere very fast, i.e., 100 Gtons per year each way. If Phytoplankton die off, as has been suggested due to more acidic and warm oceans, this will effect all marine life, possibly releasing 100’s of Gtons of Carbon into the atmosphere in a very short time. There may be as much carbon in the permafrost and hydrates, as you suggest, which can be released very suddenly. Though I doubt this would turn Earth into Venus, it would make human life difficult. Do we know if this is what happened during PETM? Also are my numbers correct? Thanks
I am curious about something. You state here about the difficulties of separating an oscilation from a trend when the timescale of the observed record is not sufficiently long enough to capture the entire oscilation. How is it then, that with global temperatures (where the ‘observed’ temperature record is only 150 years) you can state in MBH 98 et cetera that there is an observed trend?
It is my understanding that global climate oscilations are on the order several hundred years. For example the MWP lasted approximately 400 years and the LIA was about 300 years. Our observational data only goes back 150 years and the reconstucted data is only valid back about 400 years (per NAS review of MBH in June 06). So it would appear that we have a similar problem with climate reconstructions as you have identified with the AMO. Our reliable dataset for climate is approximately as long as the oscilation timescale.
How then are these cases so different that you can determine a trend in one (climate) when you can not in the other (AMO) when both suffer from the same problem of an observational record that is not sufficiently longer than the timescale of the oscilation?
[Response: First off, we are discussing attribution of observed trends, not the estimation of the trends themselves, so MBH98 or the other reconstructions are not really relevant. You are also confused about the validity of the proxy reconstructions: estimates prior to 400 years ago are just more uncertain than more recent data, not completely invalid. But on your main point, there are a number of differences between the global signal and any regional signal – the amplitude of the trend compared to the variability and the physical consistency of any natural component to that variability. At the global scale, the signal is much larger than the noise, but as you get to smaller regional signals, this is less and less true (so therefore it’s harder to attribute to any particular forcing). Secondly, at the regional scale natural osicllations produce warming in one part of the domain and cooling eleswhere – i.e. the energy is sloshing around the system. At the global scale this is much more limited. You could make an argument that atmospheric changes over the last 100 years are driven by energy coming out of the ocean, but the evidence is that the oceans are warming too. Instead, we have consistent theory and modelling that explain a large part of the changes as a response to known forcings with known physics and so the attribution is easier. In summary, the consensus on the driving of the global mean temperature is not a function of the mere existence of a trend, it is because we think we can explain the trend. – gavin]
Thomas Lee Elifritz says
The difference between then (PETM) and now (PANIC, PAIN) is that we have a tremendous climatic and environmental buffering capacity, of which only the surface has recently been saturated. That is, of course, the oceans and ice sheets. Once we start gnawing away at those, which we now certainly are, then we really need to start acting on, rather than thinking about, the problem. Certainly the top level carbon sinks are already saturated.
L. David Cooke says
If what I have read is true, humans emit around 26 Giga Tons/year. If this is true and they are contributing around 3% per year, the annual generation by all of earths biologic sources should be around 867 Giga Tons. If this is true and the average annual amount of CO2 not being removed from the atmosphere, (since around 1972) is around 26 Mega Tons (.03% * 867) then this must be the average annual amount not processed and sequestered by the natural boiologic systems. (Though how much of this amount is feedback and how much is forcing is, to my knowledge, not defined yet.)
To me the data would indicate > 867 Giga tons per year both ways. However, to increase the CO in the atmosphere would seem to indicate you only need a loss of biologic reduction greater then .03% annually or an annual increase of 26 Mega Tons of fossil based CO2. The point being a loss of only a small fraction of biologic function can cause massive increases of CO2 in the atmosphere over time.
This “CO2 sensitivity”, is the concern many have been indicating that could easily be remedied by reducing Human generation of CO2 by 10% annually could provide a 0 net impact. By the same token, if the biologic processes are in trouble, just a very small improvement of their “diet” could have a similar impact. The only difference is do you “pay” after or before you make a mess. Meaning the difference may be do you or do you not breath the mess you made? (With the apparent limitation in economic fossil fuel resources it appears clear that we will have to adopt different technologies. This then takes our technology back to the early 1900’s as we define the power source for the next 100 years. (This will answer the prior question and will make that decison for us.))
Let me quickly wrap up as this post is off the mark for this forum. The question actually is what is the best means moving forward. Do you limit human appetities for resources, arrange for more expensive alternatives and subsidize them, or do you enrichen the means to process them. All have a price, which is the most favorable economic decision? (BTW, the extra carbon does have a small effect on temperature deviations (Average high/low) and future climate; however, it is not likely to be sufficient in the long term to cause a catastrophic meltdown, we would run out of economically extractable fossil fuels before then. As to the geologic deposits though they could quickly add to the current load in the long term they could easily be processed with as little as .01% increase in biologic processing, all it takes is a little lime, iron and time….)
Iron seeding of the oceans has been tried, and shown to be quite ineffective (as well as having pretty large ecological consequences).
As far as available fossil fuel reserves go: There’s enough to cause an easy 10C or warming, perhaps more, if it’s all burned. Oil and natural gas aren’t all that abundant (probably about half of all conventional oil has already been burnt as of today), but coal, bitumen (tar sands), peat, kerogen (oil shale), and other lower grade fossil fuels certainly are. All of those low grade fossil fuels are copious emitters of CO2 as they are tend to be water and carbon rich (the water lowers the free energy of combustion and requires processing to use it as anything more than boiler fuel).
As far as technology goes, the Rankine cycle (compress, boil, expand, condense – generally with H20) that the Newcomen engine first harnessed in the early 18th century still powers most of our electric grid. If you include a similar cycle used in internal combustion engines and jet engines, you account for virtually all non-heating use of energy. It would be a sucker’s bet to think that the Rankine cycle (steam turbines and steam engines) are going away anytime soon considering that it works quite economically even with very low grade fuel and can run on just about anything (some people have even proposed using a Rankine cycle turbine to generate energy from thermal gradients in the oceans).
L. David Cooke says
As to iron testing that was done, the test was a massive single point test and not a distributed ocean surface low level test. Of course if you dump a massive concentrate in any one location you will fail to do any good. You will get a local burst of activity and then a excessive generation of O2 depleted water and massive CH4/CO2 out gassing when you simply dump and not “seed your garden”. This is not unlike dumping a concentration of fertilizer in your yard and having it burn a brown spot for a few seasons.
As to how much atmospheric heating the remaining fossil fuels will deliver is unsupportable at this time to my knowledge. How did you derive this value and at what point did you determine the economical cut off level to be. Is it possible you are calculating for the total reserves and not the extractable reserves?
As to Rankine cycle engines to allude to the idea that the process is similar to atmospheric processes does not seem logical in your earlier post. What is you allusion here, are you saying that the long term future appears to be locked into a fossil fuel system? You are aware that a Nuclear Rankine cycle engine is also viable for stationary power generation. Are you considering that the conversion to nuclear is simply a matter of policy with construction cost deviations on the order of less then 25% in the current regulatory environment, (According to recent popular news articles, with offsetting costs of fueling and operation making them around only @ 10% higher.)?
(Drs. Schmidt/Mann, my apologies, this should be taken offline or placed under a different topic. I leave it up to your discretion to post.)
Chip Knappenberger says
Hank (re #20),
Pat Michaels, Chris Landsea, and I commented on Knutson and Tuleya (2004) because we felt that they were too confident in their statement that we would be able to detect an anthropogenic impact on hurricanes by the latter half of this century. In our comment, we laid out the reasons why: 1) K&T used a rate of increase of CO2 that we felt was too rapid, 2) we attempted to show that the observed relationship between SST and storm intensity was not as strong as K&T’s model suggested, and 3) that in an operational mode, their model did not show predictive skill. We suggested that for the reasons above, coupled with the high interannual and interdecadal variability in Atlantic hurricane characteristics, that the detection and attribution of the influence of anthropogenic alterations to the earth’s atmosphere on future Atlantic hurricane intensities was still a long way off.
Our contention was not so much that a warming of Atlantic SSTs wouldn’t influence hurricanes, just that the effect was small – as K&T modeled – and thus its detection, in the light on natural variation, was further away than K&T suggested.
K&T defended their work in their reply, stating, among other things, that they had confidence in their model’s ability. For more in depth details of our Comment and K&T’s reply, I refer you to the actual publications.
In our later GRL piece (Michaels and Knappenberger, 2005), we found that observations of the relationship between SST and Atlantic tropical cyclone intensity suggested that a future warming along the lines of 2ºC would produce an effect similar to the one described by K&T for a similar amount of warming. (We did not comment on the in period involved.)
Observations of the trends in tropical cyclone intensity in the Atlantic appear to show that the increase in intensity has been far greater than that which could be caused by the observed rise in SST alone – either based upon the modeling efforts of K&T, or upon our analysis of the historical relationship during the past several decades (Michaels and Knappenberger). I think other observational and theoretical studies suggest this as well.
The bottom line is that, at least in my mind, the recent increase in hurricane intensity is too large to be produced by SST changes alone – whether they be from human activities, natural variations, or more likely, from some combination of the two. And that the evolution of these other influences, such as wind shear and vertical stability, is not as clearly anticipated from anthropogenic global warming as SSTs.
I hope that this answers your questions.
to some degree, funded by the fossil fuels industry since 1992
as far as fossil fuel reserves go:
Proved coal reserves (profitable at today’s prices and technology) are about 1 teraton with a resource base of perhaps 7 teratons. I don’t have solid info on the other stuff like kerogen and bitumen, but the amounts are substantial – Alberta alone has several times more bitumen than Saudi Arabia has oil. Because prices for coal and other low-grade fossil fuels are so low, it can be expected that reserves would rise a lot should coal prices rise substantially.
As to the warming it would generate, estimates are that a doubling of CO2 should warm the planet from 2.5C to 4C. I’m just extrapolating from those numbers, taking into account that a teraton of carbon converts to somewhere on the order of 400 ppm CO2 in the atmosphere, or over a tripling of atmospheric CO2.
Chip Knappenberger says
Although this is only marginally related to this topic, a new paper in GRL by Meinen et al. doesn’t lend any support for Bryden et al.’s contention that the MOC has slowed by 30% (covered in RC here). The Meinen paper doesn’t disprove Bryden et al. either, but it clearly doesn’t find evidence to support Bryden et al. when it could have. Instead, Meinen et al.’s findings seem to be more in line with the comment (#25 in the above mentioned RC article) made by Martin Visbeck. That is, the evidence for a decline in the MOC is not as clear has Bryden et al. suggests.
L. David Cooke says
Thanks! So do I understand that you are saying that the 100ppm rise we are seeing today means hmans have used only 250 Giga Tons of fossilized carbon in the last 150 years? (Extrapolating backwards from your statement of 400ppm atmospheric CO2 per tera ton.) BTW so that we aren’t monopolizing the opportunity here would you be willing to take this offline, you can reach me at email@example.com.
(FYI: As to the reserves according to Hinrichs and Kleinbach’s (“Energy it’s Use and the Environment” 4th Ed.) On Pg. 209 the 2003 proven reserves were in the order of less then 2 Tera tons (Of course my conversions of bbl and cf to tonage may be off significantly). On Pg. 217 they suggest about 45% of the total reserves were were recoverable using Enhanced Recovery methods. As to total Oil Sands they claim a world total of 272 x 10^9 bbl as compared to total 262 10^9 bbl Saudi Oil, Pg. 212.)
Hank Roberts says
Tony — I can’t correct your numbers, I’m just another person reading, not a climatologist. Search — Google is good; Google Scholar often is better; and “to get good information on the Internet, post what you believe and await correction” is advice that often works for me (grin). The ‘Search’ box at top of main page here also will help; there’s discussion of Venus.
On hurricanes — Chip K., re 15, 20 — when you and Michaels were writing about lowered storm intensity, was that advocacy writing, maybe for New Hope? Or did you find no chance of increases while writing what you consider an evenhanded study?
Advocacy writing is okay — just needs to be identified clearly as meant to present only one side of a question, and I can’t tell with Michaels and your work which is climatology and which is ‘advocacy science’ work.
ike solem says
It is worth noting the difference between the El Nino/Southern Oscillation and the AMO-hurricane issue. The series of events that are involved in the onset of a strong El Nino year have been studied in great detail, and the effects of warming on El Nino has also been modelled at the Hadley Center:
ENSO studies at Hadley Center
The general focus of the studies on ENSO address how ENSO frequency will change under warming conditions, and the results point towards more frequent ENSO events. Noone is trying to claim that ENSO is contributing to the increasing trend in hurricane intensity (because the time period of ENSO cycles is all wrong for that argument). On the other hand, ENSO effects on the jet stream position do affect hurricane development.
From above, “Other studies (e.g. Bell and Chelliah, 2006) generally agree that the ‘memory’ of any multi-decadal oscillation (whether forced or natural) lies in the ocean…”. This makes sense because the atmosphere mixes so quickly that any long-term memory would be erased, but ocean mixing times are far longer. In all this, it is worth noting that the observational data for ENSO stretches back over a century to the anecdotal reports of South American fisherman.
This is not the case for the AMO – To take a quote from above again, “This AMO signal, in the model simulations, is associated with oscillatory variations in the meridional overturning circulation such that when the overturning is stronger than normal, there is a warming pattern in the North Atlantic (and vice versa).”
The meridional overturning circulation refers to the sinking and spreading of cold water, but the observational data for understanding fluctuations in the MOC-THC still seems poor.
See for example: http://www.ifm.uni-kiel.de/allgemein/research/projects/clivar/send/clivar.html , and also http://www.ees8.lanl.gov/gcm.html
Claiming that the increase in hurricane intensity is due to a poorly understood mechanism like AMO makes little sense when warming of the ocean via increased atmospheric heat retention is such a clear mechanism for increases in hurricane intensity. This still demonstrates that in climate science the most important issue is getting better data (well, good models are important too). What makes more sense – putting another man (or woman) on the moon, or putting more data collectors in the oceans and more Earth-directed satellites in orbit?
Technical responses to climate change are a physics & engineering issue, but deciding to make those technical responses – that is a political, social and economic issue.
This is such an intelligent question, I think it deserves a thorough response.
First of all, as Gavin said, the NAS report did not state that paleoclimate reconstructions more than 400 years long are invalid. It simply expressed “less confidence” in reconstructions for the last 900 years than in those over the last 400 years. It also expressed “low confidence” in reconstructions 2000 years back, but stated that they are “plausible.” If we go back 900 years, we get the classic “hockey-stick” graph, which makes it clear that the current era is not part of a natural oscillation.
Even if we do restrict ourselves to just the last 400 years, it’s still evident that we’re not in a natural cycle. This is because the size of the change observed in the last century, and the extremes that have been recorded, are so much beyond what happened in the preceding three centuries that we’ve clearly entered a new regime. It’s not unlike monitoring your weight over a 4-month period and noting that it fluctuated (naturally) by as much as 25 pounds throughout the first three months, but in the fourth month you gained 300 pounds. Clearly, you’ve entered a new regime (and should consult your physician). Note: I’m exagerating to make the point, but that’s really what’s going on.
Even if we refuse to accept any paleoclimate reconstructions-by-proxy, we can still go back far enough in time for half a dozen or so locations to note exactly the same behavior using strictly instrumental records. The longest record (from thermometers!) is Central England Temperature (covering three and a half centuries; you can download the data from the Hadley Center website), and it shows that recent times represent such a large departure from what happened before that we’re not just in the upswing of a natural oscillation. The other long-term (300 years or so) thermometer records show essentially the same thing.
Also, there are some events that have been observed which argue strongly for unnatural changes in the globe’s temperature regime. For example, the collapse of the Larsen B ice shelf represents a change in ice that has certainly been accumulating for many thousands of years.
Finally, global temperature is not an entirely “independent” variable. It depends on energy balance, so unless the system is changed in a fundamental way there are severe limits to how much variation can occur naturally. The extreme rate of change observed over the last century therefore argues for a fundamental change in the earth’s energy balance. Also, the idea that GHGs trap heat isn’t complex; it’s basic physics. If GHGs did not cause global warming, it would require some intricate theorizing to understand why.
Tony Noerpel says
re 33, 26 and 30
Hank, Dave and Yartrebo
Maybe off topic but carbon is carbon. Maybe a good time for real climate to publish an update on the numbers. :+)
In 2003, emitted industrial carbon from fossil fuels was 7.3 Gtons. Probably 7.7 Gtons now? From 1751 to 2003 305 Gtons total emitted by human activities including burning fossil fuels, cement and deforestation. Pre-industrial numbers were 278 ppm and 570 Gtons. 200 Gtons of emissions stayed there and 105 Gtons were absorbed by the oceans?
Deforestation plus farming adds 2.5 Gtons per year.
So total anthropogenic would be around 10 Gtons per year at present.
The oceans are passively absorbing 0.5 Gtons and actively absorbing 2 Gtons. And vegitation adding 2 Gtons over respiration. So we are contributing 6 Gtons or so which is staying in the atmosphere, maybe?
Interestingly, melting permafrost is releasing maybe 40 Mtons but this is methane not CO2. This is not included in IPCC 2001. Also I think the permafrost contains 700 Gtons of carbon.
If global warming due to acidic oceans or warmer oceans or both causes Phytoplankton die off then much of the ocean’s current 800 Gtons could be emitted suddenly as compared to the 770 Gtons current atmospheric carbon.
Numbers from various sources.
Are the least well understood feedback effects melting permafrost, deforstation and phytoplankton die off?
Regards how much coal and tar sands the Earth has, the worse part of such fuels may not be the emissions, which are bad enough, but the effects of mountaintop removal and strip mining on the Earth’s carrying capacity, at least IMHO.
Gavin, has real climate updated these numbers in a recent post? Could such an update be a future topic? You were quoted in an article on planned coal-burning power plants in the US, China and India, that the possible addition of an extra 2.5 Gtons per year would put us on the worse case IPCC scenario. Correct?
Thanks again all
L. David Cooke says
To start with I suggest you might want to review this site:
“Comparison of CO2 emissions from volcanoes vs. human activities.
Scientists have calculated that volcanoes emit between about 130-230 million tonnes (145-255 million tons) of CO2 into the atmosphere every year (Gerlach, 1999, 1992). This estimate includes both subaerial and submarine volcanoes, about in equal amounts. Emissions of CO2 by human activities, including fossil fuel burning, cement production, and gas flaring, amount to about 22 billion tonnes per year (24 billion tons) [ ( Marland, et al., 1998) – The reference gives the amount of released carbon (C), rather than CO2.]. Human activities release more than 150 times the amount of CO2 emitted by volcanoes–the equivalent of nearly 17,000 additional volcanoes like Kilauea (Kilauea emits about 13.2 million tonnes/year)”
It is likely your anthropogenic CO2 contribution data is a little low, note this was based on 1998 data. I could go further; however, the additional reference list is a little long. The reference I added up at posting #32 should be sufficient for most of your needs in regards to your posting, if you want the following URL may be a useful reference:
Keep up the good work.
L. David Cooke says
RE: 36 & 37
My humble apologies, I decided to go back and review my first source and found that the data presented in the USGS link was in error. I then linked to the CDIC at Oak Ridge and found the more recent data. To that end disregard my earlier calculations regarding the est. 26 Giga tons.
I will go ahead and provide a top link to related infomation for the Oak Ridge reference for those readers that may find this information useful.
You can then go through the links and generate your own references.
Again, my apologies Tony…
L. David Cooke says
RE: 36 & 37
Another small correction, the link I meant to include to the CDIAC should have been one of the two below:
The other link was related to some minor research I was pursuing.
Tony Noerpel says
These are all very good links, thanks. But some of the data is already old by a few years and trying to update all of the entries on a carbon cycle figure by looking for say 2005 data for each entry is exhausting.
We are in the right ball park, though. 7 Gtons of carbon is about 26 Gtons of CO2 when one adds the weight of the O2. I don’t know which is a more appropriate way to think about it. The 40 Mtons of carbon being released by the melting permafrost is only significant because it is methane and not CO2 as with volcanic emissions. But what I was wondering was whether or not enough time had passed since IPCC 2001 to determine which of the 12 scenarios we were actually on, or if that was even meaningful. Each of the 12 suggests levels of emissions by 2010 and it would be a good exercise to see if any of them actually seem to apply.
Also most carbon cycle figures show atmospheric carbon at 750 Gtons including Wikipedia, but the text there says 810 Gtons. Most figures also show industrial emissions of 5.5 or 6.5 Gtons but it must be closer to 8 Gtons by now. If that’s true then the 2.5 Gtons of new emissions from the planned coal fired power plants plus the 1 to 2% annual growth in oil consumption surely puts us beyond A1B with no reason to think we were not on a long term trajectory beyond A1F1.
To add to my personal nightmares, permafrost melting is not included at all. Deforestation and other land use emissions seem underestimated. Phytoplankton attenuation is not accounted for. Perhaps the Fourth IPCC will add clarity but I was wondering if an up to date accounting of all carbon in the carbon cycle is available or if this would be a appropriate future posting for Gavin to consider. Maybe this had already recently been done on real climate and I simple missed it. As an aside, what would be interesting would be a side-by-side comparison of the pre-industrial carbon cycle with the current carbon cycle.
L. David Cooke says
Just a heads up, a response requires a vaild source address. local.localdomain.com may not work as a reply to:…
Eli Rabett says
In general, when you are talking about the carbon cycle Gt of carbon is best because what you want to do is follow the flow of the carbon through many molecular forms from fossil fuel to carbonates to CO2.
If you are talking about atmospheric science, then Gt CO2, because you want to figure out the greenhouse forcing and the forcing from Gt CO2 is not that from Gt CH4.
Different strokes for different folks. You just have to be careful to indicate which you mean.
John Buchanan says
In the interest of “post what you observe and wait for correction” I submit the following observations. These observations are a rough statistical analysis of the issue of wind shear vs SST measures of correlations to Atlantic storms and Hurricanes. I am not a climatologist (I am an actuary), so I apologize if in earlier blogs this issue has aready been raised and killed off. This may also be a bit off topic but after a quick perusal I didn’t see a more germane blog to post this into.
Basically the results below show, from an empirical standpoint, the 35 year (1971 to 2005) correlations between Named Storms, Major Hurricanes, MDR Wind Shear, MDR SSTs, and Eastern Pacific SSTs (El Nino/La Nina – ENSO). The shear and (~)MDR SSTs are from the July 2006 BAMS report, while the other values are from various NOAA web locations. Based upon comments from a noted member of this community, for sensitivity due of the re-analysis of pre 1980 shear values, I used the smaller 25 year observation period. The smaller period produced very similar (quite interesting) results.
Correlations (1971-2005) All Named / Major HUs
HU vs. MDR Shear -70% / -74%
HU vs. MDR SST 48% / 44%
HU vs. EPac SST -29% / -32%
EPac SST vs. MDR Shear 39%
MDR SST vs. MDR Shear -51%
MDR SST vs. EPac SST 11%
All Named Storms vs. Major HUs 77%
A number of interesting observations can be made about these results. Shear’s strong negative correlation (e.g. low shear = more hurricanes) was the most significant. Basically, using a somewhat contrived horse racing analogy, based solely on these stats and a three horse race between MDR Wind Shear, MDR SSTs, and EPac SST’s the order of finish would be:
MDR Wind Shear – Win
MDR SSTs – Place
EPac SSTs – Show
There are of course other horses to consider. Various steering currents, low/high pressure systems around Bermuda and elsewhere, dry air intrusion, Saharan dust levels, etc. all with their own cross-correlations and causations would need to be included in some robust modeling. There may be other dark horses as well. Presumably modelers are busy putting together comprehensive dynamic models that will help bring all the relevant ranked factors together.
In addition to the above statistical tests, anecdotally the active 2005 and 2004 years had 2 of the lowest amounts of MDR sheer in the last 35 years. In fact, the five lowest wind sheer years produced 17.2 named storms on average vs. a 35 year average of 11.1 (majors had an equally impressive showing of 5.2 actual vs. 2.3 long-term average). In contrast, for the El Nino signal, EPac SSTs were very close to normal for 2005 while 2004 actually had a weak El Nino signal (which in theory should have been an HU inhibitor). Based solely on these statistics, relying heavily on El Nino/La Nina signals may be somewhat faulty.
Could expand analysis to include Goldenberg’s shear factors (which go back further than 1971) and to include Chris Landsea’s Power Dissipation Index but didn’t want to duplicate work that may have already been done.
What did I miss?
Urs Neu says
John, what July 2006 BAMS report are you talking about? Can you provide the exact citation or a link? Thanks.
Hank Roberts says
Bulletin of the American Meteorological Society
Volume 87, Issue 7 (July 2006)
Article abstracts are available to everyone. Full-text HTML and PDF articles may be access controlled.
John Buchanan says
It’s been pointed out that the BAMS selected region is not the traditional MDR selected region (apparently 1 of many). The BAMS region (selected apparently to more mimic the 2005 storms), contains more Gulf and East of Florida, vs. the traditional MDR which starts south of Cuba and runs to close to Africa. This change actually produces a fairly large difference as noted below.
Correlations (1971-2005) All Named / Major HUs
HU vs. MDR Shear -70% / -74%
HU vs. MDR SST(traditional) 72% / 67%
HU vs. BAMS SST 48% / 44%
HU vs. EPac SST -29% / -32%
EPac SST vs. MDR Shear 39%
MDR SST vs. MDR Shear -51%
MDR SST vs. EPac SST 11%
All Named Storms vs. Major HUs 77%
Also, I must apologize. After I posted the above “guest” entry, my overzealous well-meaning teenage daughter posted a comment along the lines of saying that she was “quite impressed with your work”. When I saw it I was quite upset with her and immediately sent a note to the blog police and asked them to remove it, which they did. My wife said I shouldn’t have been so upset with her as she likened it to somebody being all dressed up at a dinner party and the daughter coming into the room with chocolate all over her, hugging the dad and saying “I love you”, while getting chocolate all over him in front of his guests.
So again I apologize if anybody was misled by the errant entry, but I mostly apologize to Megan.
Urs Neu says
Thanks, however, I cannot find any shear or SST data in this issue.
Hank Roberts says
I’m not sure the link I posted above is the source for what John B. is referring to — it’s just my best guess about what “July 2006 BAMS Report” means.
— Bulletin of the American Meteorological Society Volume 87, Issue 7 (July 2006)
John Buchanan says
Hank R is correct about the reference. However, the BAMS month edition is June 2006. The seasonal Shear values are from supplemental Fig. 4.7, while the BAMs SST region values are from Fig. 4.12.
Urs Neu says
O.k. now I’ve found it.
I just wonder, why in the BAMS article they chose such a different data base to calculate the trends compared to the anomalies in Fig. 4.7. They not only used a different area (only about half of the ususal MDR) but they also restricted the time frame to August-October compared to June-October which would be usual.
They do not provide any comment on this choice. I can’t resist to the suspicion, that the trend might be smaller if the usual area and time frame are used. It does not make sense to adapt the regions to the 2005 conditions when calculating the time series over decades.
Another striking issue is that the hurricane activity in 2005 for the most part took place outside of the region with the high wind shear anomlay presented in Fig. 4.7b, namely in the Gulf of Mexico and north of 25deg. northern latitude. See http://www.nhc.noaa.gov/2005atlan.shtml