One of the interesting things about being a scientist is seeing how unexpected observations can galvanize the community into looking at a problem in a different way than before. A good example of this is the unexpectedly low Arctic sea ice minimum in 2007 and the near-repeat in 2008. What was unexpected was not the long term decline of summer ice (this has long been a robust prediction), but the size of 2007 and 2008 decreases which were much larger than any model had hinted at. This model-data mismatch raises a number of obvious questions – were the data reliable? are the models missing some key physics? is the comparison being done appropriately? – and some less obvious ones – to what extent is the summer sea ice minimum even predictable? what is the role of pre-conditioning from the previous year vs. the stochastic nature of the weather patterns in any particular summer?
The concentration of polar expertise on the last couple of questions has increased enormously in the last couple of years, and the summer minimum of 2009 will be a good test of some of the ideas that are being discussed. The point is that whether 2009 is or is not a record-setting or near-record setting minimum, the science behind what happens is going to be a lot more interesting than the September headline.
In the wake of the 2007 minimum, a lot of energy went in to discussing what this meant for 2008. Had the Arctic moved into a different regime where such minima would become normal or was this an outlier caused by exceptional weather patterns? Actually this is a bit of false dichotomy since they aren’t exclusive. Exceptional patterns of winds are always going to be the proximate cause of any extreme ice extent, but the regime provides a background upon which those patterns act. For instance, in the paper by Nghiem et al, they showed the influence of wind patterns in moving a lot of thick ice out of the Arctic in early 2007, but also showed that similar patterns had not had the same impact in other years with higher background amounts of ice.
This ‘background’ influence implies that there might indeed be the possibility of forecasting the sea ice minimum a few months ahead of time. And anytime there is the potential to make and test predictions in seasonal forecasting, scientists usually jump at the chance. So it proved for 2008.
Some forecasting efforts were organised through the SEARCH group of polar researchers, and I am aware of at least two informal betting pools that were set up. Another group of forecasts can be found from the Arctic ice forecasting center at the University of Colorado. I personally don’t think that the intrinsic worth of a successful prediction of overall sea ice extent or area is that societally relevant – interest in open shipping lanes that might be commercially important need much more fine-grained information for instance – but I think the predictions are interesting for improving understanding of Arctic processes themselves (and hopefully that improved understanding will eventually feed into the models and provide better tests and targets for their simulations).
What was particularly interesting about last years forecasts was the vast range of forecasting strategies. Some were just expert guestimates, some people used linear regression on past data, some were simply based on persistence, or persistence of the trend. In more mature forecasting endeavours, the methods tend to be more clustered around one or two proven strategies, but in this case the background work is still underway.
Estimates made in June 2008 for the September minimum extent showed a wide range – from around 2.9 to 5.6 M km2. One of the lowest estimates assumed that the key criteria was the survivability of first year ice. If one took that to be a fixed percentage based on past behaviour, then because there was so much first year ice around in early 2008, the minimum would be very low (see also Drobot et al, 2008). This turned out not to be a great approach – much more first year ice survived than was predicted by this method. The key difference was the much greater amount of first year ice there was near the pole. Some of the higher values assumed a simple reversion to trend (i.e. extrapolation forward from the long-term trend to 2008).
Only a couple of the forecasts used physics-based models to make the prediction (for instance, Zhang et al, 2008). This is somewhat surprising until one realises how much work is needed to do this properly. You need real time data to initialise the models, you need to do multiple realisations to average over any sensitivity to the weather, and even then you might not get a range of values that was tight enough to provide useful information.
So how did people do? The actual 2008 September minimum was 4.7 M km2, which was close to the median of the June forecasts (4.4 M km2) – and remember that the 2007 minimum was 4.3 M km2. However, the spread was quite wide. The best estimates used both numerical models and statistical predictors (for instance the amount of ice thicker than 1m). But have these approaches matured this time around?
In this year’s June outlook, there is significantly more clustering around the median, and a smaller spread (3.2 to 5.0 M km2) than last year. As with last year, the lowest forecast is based on a low survivability criteria for first year ice and I expect that this (as with last year) will not pan out – things have changed too much for previous decades’ statistical fits on this metric to be applicable. However, the group with the low forecast have put in a ‘less aggressive’ forecast (4.7 M km2) which is right at the median. That would be equal to last year’s minimum, but not a new record. It would still be well below the sea ice trend expected by the IPCC AR4 models (Stroeve et al, 2008).
There is an obvious excitement related to how this will pan out, but it’s important that the thrill of getting a prediction right doesn’t translate into actually wanting the situation to get worse. Arctic ice cover is not just a number, but rather a metric of a profound and disruptive change in an important ecosystem and element of the climate. While it doesn’t look at all likely, the best outcome would be for all the estimates to be too low.
BobFJ writes:
Re:increased precipitation and evaporation
1)Globally speaking: the average humidity of the atmosphere is not necessarily related to average water vapor residence time in the atmosphere. The latter controls the flux per unit time of water into the air thru evaporation and return thru precipitation, or, if you like, the velocity of the water cycle.
2)Locally speaking: I seem to recall some work that indicates extreme precipitation and drought events are likely to increase? For hurricanes, in intensity, and for droughts, in frequency ?
Can anyone display the CICE animation?
http://gcmd.nasa.gov/records/LANL-CICE.html
It seems projection nearly 0 sea ice by 2040 minima:
http://www.lanl.gov/news/index.php/fuseaction/1663.article/d/20078/id/11863
Which seems more correct to Hadley by a wide margin…
“Might there be increased precipitation, with higher albedo fresh snow somewhere? ”
Might there be less, with less high albedo fresh snow in more places?
” It seems this year will be similar to 2008 give or take 100,000 sq km.
Comment by dave p”
Yup, they’ll be the same if you ignore the differences.
Like the old joke says: what’s the difference between a duck’s legs?
Wayne Davidson Reur 691, in part:
Thank you for all the links, certainly interesting.
However, just because I quote the following from a NASA article, does not mean that I’m obsessed by winds:
“The winds causing this trend in ice reduction were set up by an unusual pattern of atmospheric pressure that began at the beginning of this century,” Nghiem said.”
I also went on to say (678):
To elaborate; sea-ice melt is affected by at least winds, air temperature, thermohaline circulation, water temperature, precipitation, cloud cover, solar variations, black carbon, dust….. will that do?
Well if you want more, there are also some oscillations such as NAO right?
Finally my grasp on these complexities is not as impressive as you claim, and I think that anyone who claims to understand the frailties of sea ice is simplistically speculating. There are simply too many unknowns to draw any conclusions.
Even the more robust Jakobshavn glacier apparently has no correlation to air temperatures, paradoxical though that may seem.
Barton Paul Levenson (679)
No one disputes that water vapor feedback with warming should be expected to be positive.
But the constant RH assumption results in a gross exaggeration of this feedback and its 2xCO2 impact.
Max
BobFJ writes:
It isn’t. Radiation is.
Hank Roberts (660)
In response to my 653 to Barton Paul Levenson you stated (relating to solar studies I had cited which show significant 20th century warming attributed to high level of solar activity):
“Yes, post the cites, and the page of the second- or third-hand website where you’re reading this spin, since you’re not quoting from the primary source.”
Hank. You are wrong again. No “spin”, no “second-or third-hand websites”. Here are five of the studies:
Lean et al.
http://www.geo.umass.edu/faculty/bradley/lean1995.pdf
Scafetta and West
http://www.scribd.com/doc/334163/Phenomenological-solar-contribution-to-the-19002000-global-surface-warming
Shaviv and Veizer
http://www.gsajournals.org/perlserv/?request=get-static&name=i1052-5173-14-3-e4&ct=1
Solanki et al.
http://cc.oulu.fi/~usoskin/personal/nature02995.pdf
http://www.ncdc.noaa.gov/paleo/pubs/solanki2004/solanki2004.html
Soon et al.
http://adsabs.harvard.edu/abs/1996ApJ…472..891S
Max
[Response: None of these are proper multi-factor detection and attribution papers. Correlation is not enough. – gavin]
Kevin McKinney
Thanks for links to albedo observations (652). These are a bit lower for snow/ice than those I have seen before (0.75 vs. 0.8 for the upper value).
I believe we all agree that sea ice has an empirically observed higher albedo than sea water, so that a significant net melting of sea ice should lower the average albedo of Earth.
I posted another link to a study on the albedo of sea surface water on this site (296). This study shows that this varies strongly with latitude and degree of waviness.
http://www.terrapub.co.jp/journals/JO/JOSJ/pdf/2104/21040148.pdf
Using these data plus the high estimate of sea ice albedo (0.8) and the changes in Arctic plus Antarctic sea ice, I calculated very roughly that to date the average albedo of the Earth was lowered by 0.06% (from the estimated 30% to 29.94%).
Taking the pessimistic assumption that there would eventually be an “ice free summer” in the Arctic plus no further growth of Antarctic sea ice, I came up with a future reduction of the average albedo of the Earth by 0.6% (from 30% to 29.4%).
Posters opined in response that my calculation was oversimplified, but no one came up with a better figure for the overall impact of global sea ice changes on the average albedo of the Earth.to date or a better estimate for the future.
Do you have any ideas on this?
Max
FurryCatHerder
Your comment on Arctic sea ice recovery 1995/1996 being comparable to the recent recovery since the 2007 all-time low is interesting.
I would also agree with your estimate that 2010 will probably also be well above the 2007 low.
The overall trend (since 1979) is still downward, of course. Whether or not the current reversal is part of a longer-term cyclical trend (as postulated by a Russian study citing the previous shrinking/warming of the 1930s/40s) or whether ASI will continue shrinking in response to a continuation of the currently interrupted warming trend is anyone’s guess.
I think it is safe to say that the moderators of this site (RC) believe the latter will be the case.
Max
Gavin
To the five solar studies I cited which showed significantw20th century warming attributable to the unusually high level of solar activity you commented:
“None of these are proper multi-factor detection and attribution papers. Correlation is not enough. – gavin”
Can you be a bit more specific here, gavin?
Thanks.
Max
[Response: If two or more things (A, B, C…) happen at the same time that a particular effect (X) is observed, a statement that X must be caused by C (and not mentioning A or B) is not going to be very robust. – gavin]
Gavin
Can you point me to “proper multi-factor detection and attribution papers” that confirm that AGW is a potentially serious threat? “Correlation is not enough.”
Also I would like this to be based on empirical data rather than simply model studies. Okay?
Thanks.
Max
[Response: All D&A studies require a ‘model’ – either statistical or physical. Lean and Rind (2006?) was a statistical one, while chapter 8 in AR4 gives a larger discussion of other recent approaches. None give large numbers for solar. – gavin]
Barton Paul Levenson (650)
Here is a model study on cloud feedbacks using super-parameterization and showing a strongly negative net cloud feedback, resulting in a global climate sensitivity of only 0.41 K/(W / m^2).
http://www.usclivar.org/Newsletter/VariationsV4N1/BrethertonCPT.pdf
I usually prefer empirical data to model studies, but since you cited a model study on clouds in your 650, I thought I’d return the favor.
Max
Gavin
The “correlation” between solar activity and global climate since the early 17th century has been empirically demonstrated, even though the physical mechanism for this correlation, which would prove causation has not been defined.
There have been proposed mechanisms (ex. Svensmark cosmic/cloud connection), but these have been discarded by IPCC.
IPCC limits its definition of solar impact to the direct solar irradiation, stating that this is much too small to have caused any significant warming.
Yet the warming since the early 17th century is unequivocal and there are no other natural or anthropogenic forcing factors other than solar that have been shown to be the cause for this warming up to the early 20th century when human GHGs started to appear on the scene.
The CO2/temperature “correlation” fits into the same category with one notable exception: a mechanism has been postulated based on the greenhouse theory. In addition, there is the suggestion that a variety of model-derived positive feedbacks will lead to a 3 to 4-fold increase in the GH impact as specified by the GH theory.
So in both cases we have “correlation”, but no direct empirical support for “causation”.
Please explain to the essential difference here, Gavin.
Why can the unusually high measured level of activity of the sun not have been the cause of a significant portion of the warming we have measured since the modern record started around 1850?
Max
[Response: First off, there is still substantial disagreement about the level of solar activity prior to the satellite record. You get different answers if you use 14C, or 10Be from Greenland or 10Be from Antarctica and even the sunspot record is not as solid as one might think. Second, changes in volcanism are a significant player in the pre-industrial and could well have been as important or even dominant. Single factor correlation studies – like Soon or Scafetta’s papers are inherently unstable to the presence of confounding factors when you basically only have a small number of degrees of freedom. D&A for the twentieth century is not based on a naive correlation of temperature and CO2 – and you know that full well. Read the IDAG report for instance. – gavin]
Mark
AIS extent:
“It seems this year will be similar to 2007 give or take 500,000 sq km.”
Yup.
Max
Sidd
You asked (701):
“ I seem to recall some work that indicates extreme precipitation and drought events are likely to increase? For hurricanes, in intensity, and for droughts, in frequency ?”
IPCC SPM 2007 (p.8) tells us:
“Heavy precipitation events” are “likely” (>66%) to have increased “in the late 20th century”, that the “likelihood of a human contribution” to this trend is “more likely than not” (>50%) with the footnote:
“Magnitude of anthropogenic contributions not assessed. Attribution for these phenomena based on expert judgment rather than formal attribution studies.”
Yet the likelihood of future trends based on projections for 21st century are listed as “very likely” (>90%).
So a 66+% likelihood with a 50-50 “expert” guess on cause (rather than a study) becomes a 90+% sure thing for the future!
The same is true for increased “intense tropical cyclone activity” (e.g.. hurricanes) and “area affected by droughts”.
Believe you can forget these forecasts as highly speculative.
Check the expert papers, such as that of Dr. Chris Landsea on hurricanes for some real information.
Max
“…whether ASI will continue shrinking in response to a continuation of the currently interrupted warming trend is anyone’s guess. I think it is safe to say that the moderators of this site (RC) believe the latter will be the case.
Yeah, I’m sure they believe that the decline in arctic sea ice is due to the lack of warming over the last several years. I mean what could be clearer right? And I think it is safe to say that whatever they believe, your imterpretation of their explanation thereof will be about 180 degrees off.
Gavin
Thanks for your explanation and link to 2004 IDAG report.
This report does indicate that the warming contribution from individual natural forcings and internal variability remains controversial. They do cite a solar report (which I did not include in my list) by Stott et al.
http://climate.envsci.rutgers.edu/pdf/StottEtAl.pdf
This report concludes:
“It is found that current climate models underestimate the observed climate response to solar forcing over the twentieth century as a whole, indicating that the climate system has a greater sensitivity to solar forcing than do models. The results from this research show that increases in solar irradiance are likely to have had a greater
influence on global-mean temperatures in the first half of the twentieth century than the combined effects of changes in anthropogenic forcings. Nevertheless the results confirm previous analyses showing that greenhouse gas increases explain most of the global warming observed in the second half of the twentieth century.”
This is exactly the point I was trying to make, based on the other solar studies I cited, namely the early 20th century warming may have been driven largely by solar forcing with some small GHG effect while the late 20th century warming may have been driven largely by the GH effect, with a small solar component.
On average, this would have led to a roughly 50/50 attribution.
Max
[Response: Perhaps you’d care to mention how old that paper is, which out of date solar reconstruction they used, and why no more modern study has come up with the same answer? But regardless, this is a big step up from what you were claiming as evidence earlier. – gavin]
My link to Trenberth’s recent paper on the Earth’s Energy Budget didn’t quite work. Let’s try again.
http://www.cgd.ucar.edu/cas/Trenberth/trenberth.papers/BAMSmarTrenberth.pdf
Mark (703)
“Might there be increased precipitation, with higher albedo fresh snow somewhere? ”
“Might there be less, with less high albedo fresh snow in more places?”
Yup, to both.
Max
Max / manacker does the usual — posts one thing from the old literature and claims to have contributed some useful information, while spinning the conclusion toward the PR line.
Nonsense, again. Look up the author; look up the author’s subsequent work.
Max / manacker doesn’t like to give cites to published sources — that makes it easier for people to click the links on the publication pages for subsequent and cited material.
No, Max / manacker likes to drop misleading posts and hope nobody follows up.
I’m about done following this elephant; anyone else want to pick up the dustpan and broom and take on the chore of improving on what he leaves behind?
Just for the record, Max / Manacker did it again — posted a poor reference to an older earlier study that hasn’t held up, according this time to the same authors’ more detailed work.
How do you find this? Look up the authors in Google Scholar.
This is just ONE of the many newer papers
that Max / Manacker must have ignored while digging
out the old preliminary work to spin his posting.
Or, of course, he could just be mining this crap out of
denial/PR sites, since he never seens to have references.
Shame, manacker — pretending to discuss science, doing PR.
Just one of the many updates that belies Max’s spin above:
http://scholar.google.com/scholar?hl=en&scoring=r&q=Bretherton+cloud+feedback+sensitivity&as_ylo=2009
ftp://eos.atmos.washington.edu/pub/mwyant/papers/blossey_bretherton_wyant2009.pdf
Journal of Advances in Modeling Earth Systems
Subtropical Low Cloud Response to a Warmer Climate in a
Superparameterized Climate Model. Part II. Column Modeling with a
Cloud Resolving Model
Peter N. Blossey, Christopher S. Bretherton and Matthew C. Wyant
… With SP-CAM grid resolution, the CRM shows +2 K low cloud increases similar to SP-CAM. With fine grid resolution, the CRM-simulated low cloud fraction and its increase in a warmer climate are much smaller. Hence, the negative low cloud feedbacks in SP-CAM may be exaggerated by under-resolution of cloud-topped boundary layers …
…
… A practical modeling implication of our study is
that a superparameterized GCM or global CRM likely
needs very high resolution — on the order of ∆x=250m
and ∆z=100m — to realistically simulate subtropical85
boundary layer cloud feedbacks on climate. While the
required resolution is computationally infeasible for a
global CRM for the foreseeable future, it might be within
reach of a suitably designed superparameterized GCM ….
——-
Max / manacker / bogus / spin / why bother
“It seems this year will be similar to 2007 give or take 500,000 sq km.”
So ignoring the differences, they’ll be the same.
Colour me unsurprised.
““Might there be less, with less high albedo fresh snow in more places?”
Yup, to both.
Max”
So discuss the second one.
“But the constant RH assumption results in a gross exaggeration of this feedback and its 2xCO2 impact.
Max”
So since there is no assumption of constant RH, there is no gross exaggeration of CO2 doubling effect.
Correct?
Bob , saying that we dont understand everything is true, but it does imply that we know a lot more than we use to. Ignorance is not an excuse for causing doubts and confusion. What is at doubt is what we specifically dont discuss.
Lets go back to 1979…
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/ARCHIVE/19790810.png
And you can go back to 1597, Barents sea was and almost is usually open during the summer.
With winds or no winds. But near land, sea ice was much more prominent in 1979. Solid enough for Caribou to cross. Look at 2009,
http://arctic.atmos.uiuc.edu/cryosphere/NEWIMAGES/arctic.seaice.color.000.png
Every where near land, either on the Canadian or Russian side of the Pole. There is less ice. Either
you can explain that the winds are all conspiring to make it so, extremely unlikely? Would you say?
Or as land warms, so does adjoining sea.
The bigger issue, is salinity, and the existence of fresher water, either in ice or in the Arctic ocean surface, and as to, whether constant wind battering of the open ocean surface will increase sea surface salinity and affect the entire Arctic circulatory cooling engine, transforming it to circulate differently. Winds from any direction causing upwelling will be a factor in this case, upwelling deeper more saline water will change the entire system gradually. As you can see this system still holds, for now, as is, despite warmer temperatures, giving similar melt areas over the wider Arctic ocean since 1979. But the release of fresh water found in the multi-year ice over the last few years means that there is a new salinity balance in the works.
Any glacier around Greenland is vulnerable to one thing simultaneously, warmer temperatures on its flanks during the warming season, and to say that one glacier is not moving as expected during warmer conditions is silly. Should all others more erratically as well?
re #708
That’s a dreadful lot of cherrypicking manacker. It’s easy to hunt around for old papers that might provide temporary support of an agenda, but one should at least run papers through Google Scholar to determine whether the old papers, and even what their authors think in the light of recent evidence, have stood up to the test of time! Your examples fail:
ONE: The old Lean paper that you cited – way out of date. Here’s what Lean (and in fact pretty much all the proper solar scientists) have established from analysis of solar contributions in the almost 15 years since the old paper you cited:
J. L. Lean and D. H. Rind (2008) “How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006”, Geophys. Res. Lett.35, L18701., who conclude their analysis with:
Lean’s analysis certainly doesn’t support your agenda!
TWO: The Shaviv/Veizer paper you cited. This has nothing to do with 20th century temperature variation. It’s about a flawed hypothesis on the role of CRF variations in the deep past (the ~500 million years of the Phanerozoic era). Veizer himself has re-assessed this putative relationship, reinterpreted his previous paleotemperature analysis and concluded that the paleotemperature data correlates with the atmospheric CO2 levels (rather than a putative CRF flux variation):
Came RE, Eiler JM, Veizer J, Azmy K, Brand U, Weidman CR (2007) Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era Nature 449, 198-201
Abstract: Atmospheric carbon dioxide concentrations seem to have been several times modern levels during much of the Palaeozoic era (543-248 million years ago), but decreased during the Carboniferous period to concentrations similar to that of today(1-3). Given that carbon dioxide is a greenhouse gas, it has been proposed that surface temperatures were significantly higher during the earlier portions of the Palaeozoic era(1). A reconstruction of tropical sea surface temperatures based on the delta O-18 of carbonate fossils indicates, however, that the magnitude of temperature variability throughout this period was small(4), suggesting that global climate may be independent of variations in atmospheric carbon dioxide concentration. Here we present estimates of sea surface temperatures that were obtained from fossil brachiopod and mollusc shells using the ‘carbonate clumped isotope’ method(5)-an approach that, unlike the delta O-18 method, does not require independent estimates of the isotopic composition of the Palaeozoic ocean. Our results indicate that tropical sea surface temperatures were significantly higher than today during the Early Silurian period (443-423 Myr ago), when carbon dioxide concentrations are thought to have been relatively high, and were broadly similar to today during the Late Carboniferous period (314-300 Myr ago), when carbon dioxide concentrations are thought to have been similar to the present-day value. Our results are consistent with the proposal that increased atmospheric carbon dioxide concentrations drive or amplify increased global temperatures(1,6).
The Shaviv/Veizer article certainly doesn’t support your agenda either!
THREE: The Solanki paper. Like the other solar scientists, Solanki has made rather more detailed analyses using new understanding of solar contributions to surface temperature and determined that the entire solar irradiance contribution to earth’s temperature since the Maunder minimum is 1.3 W. This gives a contribution to warming of around 0.2 oC [1.3 * 0.25 (geometry)* 0.7 (albedo)* 0.8 (sensitivity)] over this entire period of which 0.1 oC or less is 20th century. A very similar conclusion to that of Lean.
L. Balmaceda, N.A. Krivova and S.K. Solanki (2007) “Reconstruction of solar irradiance using the Group sunspot number” Advances in Space Research 40, 986-989
Abstract: We present a reconstruction of total solar irradiance since 1610 to the present based on variations of the surface distribution of the solar magnetic field. The latter is calculated from the historical record of the Group sunspot number using a simple but consistent physical model. Our model successfully reproduces three independent data sets: total solar irradiance measurements available since 1978, total photospheric magnetic flux from 1974 and the open magnetic flux since 1868 (as empirically reconstructed from the geomagnetic aa-index). The model predicts an increase in the total solar irradiance since the Maunder Minimum of about 1.3 Wm−2.
So Solanki certainly doesn’t support your agenda opinion either!
And so on….
Mark
You asked:
“So since there is no assumption of constant RH, there is no gross exaggeration of CO2 doubling effect.
Correct?”
Umm…
Check IPCC AR4 WG1 Ch. 3, p.374 and Ch.8, pp. 632, 633, 635 for confirmation of constant RH assumption. .
Max
[Response: Please look up the difference in definition between “assumption” and “result”. It might help. – gavin]
Chris (726)
Let me digest your long post, check out the references you cited and get back to you.
Max
> manacker says:
> 10 August 2009 at 3:09 PM
> Chris (726)
> Let me digest your long post, check out the references
> you cited
Max / manacker — you’re ignoring the basic skill needed to get out of the slough of denial.
Look papers up for yourself with Google Scholar.
Look at the primary source, at least the abstract.
Click the links for supporting material if available
Read the footnotes.
Click the “cited by” links (sometimes several different services provide these and they may differ)
As long as you focus on individual papers, wherever you’re getting them (co2science is typically the source for this kind of spin) — you’ll never have good information.
You’ll just continue posting bad outdated information with spin wrapping around it.
Science is like that. Follow it forward.
Anyone can do it, as a blog reader at least, trying to find the best information — and ask smart questions after reading it.
Jeff, Reur 696:
If you wish to visualize that the 396 w/m^2 EMR leaving the surface (cooling) to be HEAT, don’t overlook the fact that 333 w/m^2 EMR is being back radiated, and if also visualised as HEAT, then this is a heating effect, replacing the heat loss.
The net HEAT loss via EMR is (396 – 333). See also this for example from NASA Earth Observatory:
http://earthobservatory.nasa.gov/Features/EnergyBalance/images/surface_energy_balance.jpg
BobFJ (730):
Your comment applies equally as well to latent heat. The energy provided to the atmosphere by latent heat is back radiated in much the same manner that the radiant heat is back radiated. Why discriminate? You are applying different standards to each forcing. The truth is that the radiative process produces 5 times the forcing that latent heat does. That, my friend, is inescapable.
BobFJ says:
10 August 2009 at 9:16 PM
If you wish to visualize that the 396 w/m^2 EMR leaving the surface (cooling) to be HEAT, don’t overlook the fact that 333 w/m^2 EMR is being back radiated, and if also visualised as HEAT, then this is a heating effect, replacing the heat loss.
The net HEAT loss via EMR is (396 – 333).
The heat returning via EMR didn’t get there exclusively via upwelling EMR, it makes no sense to consider it as a net effect.
Why are you so fixated on talking about ammunition: High Explosive Ant-Tank, Bob?
Heat is merely kinetic energy of a bulk mass randomised through elastic collision.
It transports either by the bulk movement of the medium (convection), the equipartitioning of energy when the average energy of the medium changes (conduction) and release of electromagnetic waves (radiation).
Yet you keep writing HEAT as if it is some magical thing that only YOU know the meaning of.
You are more apparently LESS knowledgeable of what heat is than the layman.
“Check IPCC AR4 WG1 Ch. 3, p.374 and Ch.8, pp. 632, 633, 635 for confirmation of constant RH assumption. .
Max”
And the RH constant is a result, not an assumption.
Since your only meme against CO2 being the cause is that constant RH is assumed and that this is not an assumption being made, I take it you will now accept that CO2 effect isn’t being overestimated, yes?
Sidd reur 701, you wrote in part:
But I think everyone agrees that in a warming world there will be increased forcing from water vapour. (positive feedback). For that to be the case there MUST be an increased average level of water vapour in the atmosphere. I don’t understand why you think the residence time or cycle time is important. Surely what matters is the average level of water vapour that is being constantly lost and replaced?
For instance, if it rains more, (just to take your point 2), that implies a responsive reduction in some water clouds and/or water vapour, but the precipitation on land will result in increased evaporation and biological transpiration activity.
To me, it seems fundamental that because there is water vapour positive feedback, then it is strongly intuitive that there must be increased evapo-transpiration to enable that to be so.
[Response: Sidd is correct – gavin]
manacker writes:
Empirical evidence says you’re wrong:
Brown, S., Desai, S., Keihm, S., and C. Ruf, 2007. “Ocean water vapor and cloud burden trends derived from the topex microwave radiometer.” Geoscience and Remote Sensing Symposium. Barcelona, Spain: IGARSS 2007, pp. 886-889.
Dessler AE, Zhang Z, Yang P 2008. “Water-Vapor Climate Feedback Inferred from Climate Variations.” Geophys. Res. Lett. 35, L20704.
Philipona, R., B. Dürr, A. Ohmura, and C. Ruckstuhl 2005. “Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe.” Geophys. Res. Lett., 32, L19809.
Santer, B. D, C. Mears, F. J. Wentz, K. E. Taylor, P. J. Gleckler, T. M. L. Wigley, T. P. Barnett, J. S. Boyle, W. Bruggemann, N. P. Gillett, S. A. Klein, G. A. Meehl, T. Nozawa, D. W. Pierce, P. A. Stott, W. M. Washington, M. F. Wehner, 2007. “Identification of human-induced changes in atmospheric moisture content.” Proc. Natl. Acad. Sci., 104, 15248-15253.
BobFJ writes:
You’re seriously confused, dude.
Sunlight and atmospheric back-radiation HEAT the surface.
IR radiation from the ground, conduction/convection, and evapotranspiration COOL the surface.
Both numbers are equal over the long run. By your definition, that would mean no heat is being transferred.
Sorry, but you can’t say evapotranspiration cools the surface and infrared radiation doesn’t. That’s just illiterate from a physics point of view.
Mark
You posed a rather convoluted question (734):
“Since your only meme against CO2 being the cause is that constant RH is assumed and that this is not an assumption being made, I take it you will now accept that CO2 effect isn’t being overestimated, yes?”
No.
I can accept the GH theory that CO2 might theoretically cause somewhere around 1C warming if doubled (ex. from “pre-industrial” 280 to “year 2100 maybe” 560 ppmv), all other things being equal. But, Mark, as we are seeing “all other things” are not “equal”, and these have been overlooked by IPCC in its myopic fixation on anthropogenic forcing factors (primarily CO2).
I have a very hard time accepting that the 2xCO2 impact of net cloud feedbacks is an increase of 1.3C (as estimated by IPCC), especially when there are data out there telling me that the net impact of clouds on our climate is one of strong cooling (over four times the theoretical 2xCO2 impact) and physical studies showing a strong net negative feedback from clouds with warming over the tropics.
This is a much smaller bone of contention, but I also doubt seriously that atmospheric water vapor content will increase in goose-step with temperature according to Clausius-Clapeyron to maintain constant RH. A serious study has shown that RH decreases with temperature over the tropics. So I believe that the impact of the water vapor feedback on the 2xCO2 climate sensitivity is overstated by IPCC.
So I’d say that (as a result of these discrepancies) the 2xCO2 temperature “effect is being overestimated”.
Hope this answers your question and clears up my position
Max.
Gavin
Thanks for tip on ‘difference in definition between “assumption” and “result”‘.
This has been helpful.
Without getting too much into the nitty gritty mechanics, let me summarize:
Computer models provide “results”.
These are strongly influenced by the “assumptions” fed into these models.
It is all very clear to me now, Gavin.
Max
“These are strongly influenced by the “assumptions” fed into these models”
However, one of those “assumptions” wasn’t that RH was a constant.
Most of the other assumptions were things like adding 1 to 1 makes 2, and that PV=nRT.
““Since your only meme against CO2 being the cause is that constant RH is assumed and that this is not an assumption being made, I take it you will now accept that CO2 effect isn’t being overestimated, yes?”
No.”
Why not?
You didn’t believe the models when it said about 3C because you thought that this was a result of a constant RH being assumed in the models.
Now that you’ve been told that there is no such assumption made in models by someone who writes such models, you should now be admitting that your assumption was faulty and the result of that faulty assumption needs to be revisited.
Yet you still cling to the idea that CO2 doubling will cause much less temperature increase than evidence shows is the case.
Why?
“especially when there are data out there telling me that the net impact of clouds on our climate is one of strong cooling ”
But there’s data out there telling you that cloud cooling cannot cause the temperature sensitivity to be less than about 2.5C per doubling of CO2.
And the datum of the IPCC report, based on scores of papers.
You cling to data that says the sensitivity is low and ignore that your assertion that this was due to RH constancy being assumed is provably wrong.
Why?
“A serious study has shown that RH decreases with temperature over the tropics.”
And serious studies (note the plural) have shown that RH globally is pretty well constant.
But you go with the minority view.
Why?
“So I’d say that (as a result of these discrepancies) the 2xCO2 temperature “effect is being overestimated”.”
But how do you say that when your only point to “prove” overestimation was the incorrect assumption that a constant RH was an input parameter for models?
You DID say that.
And it is wrong.
But despite that assumption being wrong, which should (if you are being logically consistent) result in the warming per doubling being HIGHER than you thought before being corrected, it is still much lower than almost all serious papers on the subject say it can be.
Why?
Re Max #739:
> Computer models provide “results”.
So do empirical studies — without the quotation marks. Why are you so fixated on computer models? Did a computer treat you badly when you were little?
Chris (726)
Looks like the latest study by Lean and Rind (2008) which you cited disagrees with the Scafetta and West (2008) study, which concludes that 69% of the warming of the past 100 years can be attributed to the sun (L+R state that this is only 10%).
The studies, which I cited, concluded on average that this was around 50% over the entire 20th century, with a higher percentage of the early 20th century warming period (1910-1944) attributable to solar factors than of the late 20th century warming (1976-2005), where the solar contribution was estimated to be relatively minor.
Looks like we have a “take your pick situation”, and there is still “controversy” on the relative impact of solar and anthropogenic factors on observed 20th century climate changes, which is the point I made earlier.
As far as Shaviv and Veizer, the report I cited states: “Once this solar amplification is included, the paleoclimate data is consistent with a solar (direct and indirect) contribution of 0.32 ± 0.11 °C toward global warming over the past century”.
As for the L. Balmaceda, N.A. Krivova and S.K. Solanki (2007) study, which you cite, the study does state “The model predicts an increase in the total solar irradiance since the Maunder Minimum of about 1.3 Wm−2.”
This does not appear to contradict the earlier Solanki et al. study, which pointed out that the 20th century level of solar activity was the highest in several thousand years, and “although the rarity of the current episode of high average sunspot number may be taken as an indication that the Sun has contributed to the unusual degree of climate change during the twentieth century, we stress that solar variability is unlikely to be the prime cause of the strong warming during the last three decades.”
Again, reference is made to “the last three decades” as the period where solar factors had less influence than during earlier periods of the 20th century.
I’d say that all of the studies show that there is still a lot that is not yet known about the mechanisms involved in solar warming of our planet or about the relative role played by the sun in our planet’s past and most recent climate.
But thanks for links anyway. The reports were interesting.
Max
For someone who’s repeatedly rebuked for hsi posts and who’s advised people to ‘disregard anything that is posted by RealClimate. This is not a serious blogsite on climate science’, I hope Manacker appreciates the tolerance he’s been offered at Realclimate.
I suspect it won’t be for much longer though.
Barton Paul Levenson (736)
Here is some “empirical evidence” from the cited Minschwaner + Dessler report (Fig. 7), showing observed water vapor increase with warming and comparing this with the “constant RH assumption” line as well as with the line from the simplified M+D model.
http://farm4.static.flickr.com/3347/3610454667_9ac0b7773f_b.jpg
Looks pretty clear to me. This evidence shows that you are wrong, but let’s not belabor that point.
Max
Mark Vermeer
You wrote (742):
‘Computer models provide “results”.
So do empirical studies — without the quotation marks. Why are you so fixated on computer models? Did a computer treat you badly when you were little?’
No problem with computers, Mark.
You just have to see them for what they really are and are not: They are not oracles providing prophesies for the future or fountains of wisdom, but simply monstrously expensive, highly sophisticated reincarnations of the old slide-rule of the past.
Observed empirical data provide tangible support for hypotheses or theories.
Computer model outputs (or “results”) per se do not.
Max
[Response: They do when they provide a match between observed effects and model results – implying that physical causes and effects can be attributed. – gavin]
Just curious . . . did anyone see Scafetta’s talk at the Fall 2008 AGU meeting? In his abstract he states “A cooling of the global climate, not predicted by the Intergovernmental Panel on Climate Change (IPCC) projections, has been observed since 2002.” Was he roundly ridiculed for not knowing the difference between weather and climate?
Re: #725
Right now I have a real problem with the quality of data coming out of University of Illinois and NOAA. They both appear to lack proper quality controls and corrective action plans.
For the last couple of weeks, the Cryosphere Today website has been displaying the formation of Sea Ice on coastlines around the world. Some of that sea ice supposedly forming in waters which have nighttime SST’s in the 20C range. (Germany, Denmark, etc…. Totally Impossible outcomes…)
I’ve emailed and called them up in person about these gross errors.
So far, ZERO corrective action @ UIUC !!
In the same vein. NOAA has been using ICE map masks upwards of a month out of date!! That error masks the true SST’s in open water areas near the poles. I’ve called, and talked to them about it, looks like NOAA is using historic ice cover masks instead of realtime data to mask off SST’s.
http://www.osdpd.noaa.gov/ml/ocean/index.html
They have access to the data needed to fix this error..
http://www.osdpd.noaa.gov/data/mirs/mirs_images/n19_sice_des.png
http://www.osdpd.noaa.gov/data/mirs/mirs_images/n18_sice_des.png
http://www.osdpd.noaa.gov/data/mirs/mirs_images/m2_sice_des.png
I’m really surprised that errors of this magnitude could have been overlooked !!!
Until NOAA and Cyrosphere today resolve these issues, I will treat their web based data products with suspicion, and will NOT cite any of their mapping/summary as an authoritative reference. I.E. Mapping and summary data fails the obvious error test.
“You just have to see them for what they really are and are not: ”
Would have to ask you do do that yourself?
It doesn’t seem as though you do.
Computer models do the physical maths. The empirical evidence PROVES (in the old-fashioned sense of “test”) the physical maths as implemented in the model.
Since we have no time travel, we cannot get future trends now. Since we have the option of complete disaster in the future if we do nothing, we can’t wait for the future to hit us like a freight train with the lights out in a tunnel.
So we use the empirical evidence as proving the model works like real life (or close enough) and then use that model to predict the future course.
Just like the bombing computer works out when the bomb should be dropped to hit target. A computer model that is EXTREMELY limited in resources and time. Yet it has turned the average bombing error from over 200 feet in WW2 to less than 30 feet today.
“For someone who’s repeatedly rebuked for hsi posts and who’s advised people to ‘disregard anything that is posted by RealClimate.”
What you don’t realise Nelson is that Max is talking about his own posts. He’s advising that his posts should be ignored. Just leaving out that it is HIS posts he’s talking about, leaving the impression of all posts being wrong without actually *specifically* lying about it.
Weasel wording at its finest!