Schwartz in the news again:
Stephen Schwartz of Brookhaven National Laboratory makes our weekly roundup again this week. This time, its for a comment/reply in the latest issue of Nature concerning a previously published Nature piece “Quantifying climate change — too rosy a picture?” by Schwartz et al. In the original piece, Schwartz and co-authors argue that the IPCC Fourth Assessment Report (AR4) presents an overly confident assessment of climate sensitivity and potential future climate change. In the response by Forster et al, a number of IPCC lead authors point out that the Schwartz et al critique ignores or misinterprets several key IPCC findings.
update: if you don’t have a subscription, the original Schwartz et al Nature article is available here and the recent comment/reply is available here
update #2: It has been pointed out to us that the commentary by Stephen Schwartz and co-authors was published on the Nature Reports Climate Change website, rather than in the print journal Nature.
Hmmm, over 240 Google hits on that editorial, almost entirely cut-and-paste copies of claims from it. Nobody has a Washington Post archive to see who said what in the original story?
It sounds from the timing like it would be in reference to the Rassool/Schneider Science article about global dimming and dust and albedo controlling climate, which was certainly a big factor up til about 1970 — but faded after the Clean Air Act started controlling sulfate emissions from the world’s then biggest polluters in the USA.
Coalfield Fires:
http://findarticles.com/p/articles/mi_qn4158/is_20060802/ai_n16655192
I’ve been attempting to discover what proportion of the about 8 Gt of carbon added to the active carbon cycle these fires represent. While nothing definite has yet turned up, it appears that 4% is a fair estimate. To put this in perspective, here are some other estimates, given without attribution and with varying accuracies:
coalfield fires (est. 4%)
cement production (3%)
world’s ocean vessel fleet (2.7%)
U.S. cars and light trucks (ets. 2.5%)
world’s airlines (2.2%)
When will it end?
David Benson et al; Thanks for the pointers to rising sea level predictions.
When I speak to people who have a few clues about climate change they seem reasonably accepting of the fact that we will get a few centimetres rise this century, and they become mildly surprised when I mention that the folks in the know (Hansen et al) are now talking about multi-metre rise by then.
But what makes them look at me like I have just lost all credibility is when I then say that the rise is going to continue for a long time, probably until all the ice is gone and the beach is 70 to 80 metres above where it is today.
And (I say) we wont be able to afford to shift all our infrastructure, all our homes, our businesses, our farms away from the coast every hundred years as the rising waters chase us, so we might as well shift it all to the ultimate high-tide mark once and for all and figure out how to cope while we still have access to the resources, machinery, industrial plants and energy needed to build what must be built. We will need a complete new model of property ownership, essential food production, housing and international agreements on resource-sharing if internal strife and global conflicts are to be avoided.
In most cases the raw response to all this will involve shifting everything about 80m up the hill, but in the sad cases like New Orleans, and the Netherlands they need to look for a place up to 100m higher than where they are. They will be gone soon. Places like Bangladesh, and the great river delta populations are gone too – most of them by 2100. All these folk should cease investment in local infrastructure forthwith, and start getting on very friendly terms with their uphill neighbours.
I say that because we are NOT going to keep CO2 below 450ppm and we ARE going to get the 3 degrees warming that we are advised is a point beyond which return is impossible. There will be nothing mankind can do to reverse the natural processes (in spite of Hansens most earnest and politically-correct wishes we will not start capturing any useful amount of carbon emissions before its too late, let alone all of them tomorrow), and the natural processes will simply apply the maths and do do that voodoo that they do so well.
With Greenland and West Antarctic Ice Sheets alone holding enough water for about 15m rise between them, if they just melt by a measly 10% over the next few decades we will get 1.5m. They will (They ARE!); we will.
Now I notice that places like USGS put out fact sheets discussing coastal vulnerability to future sea level rise. PDF version of this fact sheet .
In these fine reports (and in all other reports Ive seen – even Hansens) the talk is all about the rise estimated until 2100. Nobody that I have found has ever officially pointed out that once we get to 2100 and we have our 30 centimetres (or what ever other insanely optimistically small number they want to hang their hats on) then next century we will get the same again, but probably exponentially more as more of the grounded ice gets warm water around its ankles, and the seas warm and it rains in the Artic and Antarctic. Until its all gone.
So, please, just how loopy am I in my suggestion that now that it has started it is going to keep on until the end? Until it is all done and we have 70 metres to 80 metres rise in global sea level and the world has changed forever.
Link to USGS reports
http://woodshole.er.usgs.gov/project-pages/cvi/
“So, please, just how loopy am I in my suggestion that now that it has started it is going to keep on until the end? Until it is all done and we have 70 meter to 80 meter rise in global sea level and the world has changed forever.”
Comment by Nigel Williams
Not loopy at all, Nigel. When I first got back online 2 1/2 years ago after an almost 15 year hiatus, I immediately told people that they should move above the Fall Line. Sea level will probably never raise above that point, the ONLY question is WHEN it will happen, not WHETHER it will happen. I fear it will be much sooner than anyone with scientific credentials is predicting, because it’s ‘loopy’ to think that people alive today might experience such a rapid sea level rise.
Have you ever watched the ice on a river breakup in the spring? One morning it’s frozen solid and later that day it’s all moving not to solidify again until next winter. Or snow on a pitched roof suddenly slide off on a warmish winter day? Or have you ever defrosted an old non-frost free refrigerator? Ice melt is a very difficult to predict phenomenon. The ice is melting now and with positive feedback it’s not going to stop. The melting will accelerate. Rates of acceleration are usually determined experimentally, and later the math is worked out. Welcome to the experiment.
http://en.wikipedia.org/wiki/Fall_Line
The mean annual temperature of the Antarctic interior is about -55 C . McMurdo statation – which is on the coast – has never yet recorded an average monthly temperature above -3 C, and the annual average is about -15 C.
Think about that -55 C for a bit. Suppose climate sensitivity is 3 C, and CO2 stabilizes at 4x, or 1120 ppm. That’s +6 C. Assume polar amplification is about 2x in Antarctica. That’s +12 C. That still leaves the majority of EAI colder than -40 C . Much warmer, but not melting yet. To put this another way – even if all known fossil fuels are burned, ice-albedo feed backs from GIS and WAIS, and CO2 feedbacks would still need to warm EAIS by a whopping 40 C.
The ~57 meters of ice (in SLR) in EAIS is not going anywhere anytime soon.
Thanks for that Llewelly. I agree that it will take a bit for EAIS air temperatures to get into the positive, but the internal dynamics of these higher altitude ice sheets seems to hinge more around the effects of the lakes and rivers beneath heating and lubricating them from the bottom up.
So I dont accept that these areas will be unaffected until the air temperature is forced above zero, instead I think it more likely that the ice will be moved to increasingly susceptible climate zones of the continent (well, actually its a bunch if islands, isnt it) where it will be subjected to the same indignities the WAS is enduring today.
These residual areas will obviously be among the last to go, but go they will.
and fellow readers, please note that I speak from a laymans perspective here. I make what I believe are reasonable assertions that I want to see our resident experts rebut, clarify or confirm. These issues are of vital importance for our world, and I do not see them being discussed or clarified anywhere else from a reasoned scientific basis. So Gavin, Ray, Rasmus, Stefan et al, your input is needed here, please.
Antartica Rock Surface image
http://en.wikipedia.org/wiki/Image:AntarcticaRockSurface.jpg
llewelly writes:
[[The mean annual temperature of the Antarctic interior is about -55 C . McMurdo statation – which is on the coast – has never yet recorded an average monthly temperature above -3 C, and the annual average is about -15 C.
Think about that -55 C for a bit. Suppose climate sensitivity is 3 C, and CO2 stabilizes at 4x, or 1120 ppm. That’s +6 C. Assume polar amplification is about 2x in Antarctica. That’s +12 C. That still leaves the majority of EAI colder than -40 C . Much warmer, but not melting yet. To put this another way – even if all known fossil fuels are burned, ice-albedo feed backs from GIS and WAIS, and CO2 feedbacks would still need to warm EAIS by a whopping 40 C.
The ~57 meters of ice (in SLR) in EAIS is not going anywhere anytime soon.]]
Is the interior of Antarctica always at exactly -55 C, or does it vary by season?
Re: melt in antarctica
the web page at
http://www.nasa.gov/centers/goddard/news/topstory/2007/antarctic_snowmelt.html
has some scaterrometer data on melt in Antarctica.
I quote: “…found snow melting in unlikely places as far inland as 500 miles away from the Antarctic coast and as high as 1.2 miles above sea level in the Transantarctic Mountains.”
sidd
Thoughts about sudden change:
Remember water doesn’t melt at the regional average temperature; it melts at the local immediate momentary temperature. Water moves down through ice and refreezes, but transfers heat in the process.
Remember that at the base of the ice, there’s melted water now where the drills have penetrated — sometimes a lot of it.
When did the North American continental glaciers collapse?
Ever visited the Channeled Scablands in Idaho and Washington?
> 290
More and better info here:
http://environment.newscientist.com/article/dn12681-us-set-to-violate-its-standards-on-cosub2sub-emissions-.html
“… If governments do nothing to limit greenhouse-gas emissions, CO2 levels in the oceans will rise to a point where, by 2050, ocean acidification will reach a level considered to be industrial waste by the US’s own standards, found the study to be published on 25 September.
…
The US Environmental Protection Agency (EPA) water quality criteria, states that the pH of ocean waters beyond 200 metres deep should not be changed more than 0.2 units outside natural levels. Estimates put natural levels at a range from 8 to 8.25 pH. Anything beyond this is considered industrial waste. However, these standards are not enshrined in US law….”
Re #311 [When did the North American continental glaciers collapse?]
It would be more interesting to know how long the collapse/retreat took. I don’t think I’ve ever seen anything explicit on that, but I’ve gotten the impression that it was comparatively fast.
James (313) — From LGM to the so-called Holcene climatic optimum was from 20,000 years ago, approximately, to 10,000 years ago. During that interval all the continental ice sheets melted away, except of course in Antarctica and Patagonia.
Just noting two bits of good news according to BBC:
1) A deal in Montreal on speeding up the elimination of HCFC use to 2030 instead of 2040 – could be faster of course, but this will help on both the ozone layer and AGW.
2) Apparently there’s a paper in Science reporting that measurements from the 2005 drought suggest the Amazon may be more resilient than expected at least short-term – the trees are thought to have been accessing water deeper down than the models that suggest a shift to savannah allowed for. Doesn’t mean the longer-term response won’t be as the models predict, though.
>how long
Still uncertain, though I recall a recent abstract somewhere suggesting that about 8,000 years ago a sea level rise came from a pulse of meltwater to the North Atlantic matched up with collapse of the last N.Am. continental glacier (rather than a meltwater lake outburst, the older idea).
Can’t find it right now. Here’s a survey article:
http://www.clim-past.net/3/15/2007/cp-3-15-2007.pdf
If you get to p.29, therein, the ice goes away quite fast, compared to its accumulation rate. That matches the icea age info elsewhere.
If you get to p.32, they begin their Conclusion with:
“The comparison of our simulated ice sheets with geological
and sea-level data highlights the importance of some major
ice-climate feedbacks and raises the question of to which
extent this kind of approach enables to test the ability of
GCMs to simulate a climate leading to ice sheets compatible
with available geological and geomorphological reconstructions.
The differences between observations and simulations
may come from i) the method of the climatic index,
which may induce artifacts because the climatic variations
during the last glacial-interglacial cycle are unlikely
to be the same than those recorded at the GRIP site, ii) the
choice of the vertical lapse rates which may overestimate the
ice volumes if they are set to too high values, iii) the climate
models or lacking processes in the ice-sheet models,
iv) the-ICE-4G reconstruction: this work highlights the importance
of having an accurate ice-sheet boundary condition
for paleo-intercomparisons of GCMs. Actually, none of the
simulations presented in this study is able to reproduce ice
sheets in full agreement with observations.
The main points of disagreement…..”
Nigel Williams (and others) — Climate scientists hopeful despite climate signs:
http://news.yahoo.com/s/ap/20070923/ap_on_re_us/optimistic_doomsayers
which quotes, among others, Michael Mann…
Hank Roberts #312 , Glad you mentioned the scab-lands and the Bonneville ice dam collapse. According to the Nova TV program it could have happened many times, each time, quickly without warning. The Greenland Ice Sheet is probably not immune to such a rapid collapse.
http://www.pbs.org/wgbh/nova/megaflood/
National Geographic had an article about global warming in the October 1990 issued (p66) not available online. The science hasn’t changed much since then.
But what is even more interesting are the Letters to the Editor found in the February 1991 issue about this article. There are what could serve as templates for skeptics and deniers arguments. Here’s one:
“February 1991
The idea of global warming has gone from a modeler’s dream to popular environmental wisdom and is about to take the expensive last step: government appropriations to avoid the ” crisis.” Politicians are preparing to save us by introducing legislation to spend plenty of money or pass complicated restrictions on one thing or another. Overreaction to environmental ideas that are not well founded can result in huge economic costs.
George E. Ribble
Bakersfield, CA”
Obviously most of those steps were never taken and little or no cost to was incurred. On the other hand, we have crazy climate change 17 years later.
Ok then:
*Dangerous human-made interference with climate: a GISS modelE study*
Hansen et al 7 May 2007
Our conclusion that global temperature is nearing the level
of dangerous climate effects implies that little time remains
to achieve the international cooperation needed to avoid
widespread undesirable consequences. CO2 emissions are
the critical issue, because a substantial fraction of these emissions
remain in the atmosphere “forever”, for practical purposes
(Fig. 9a). The principal implication is that avoidance
of dangerous climate change requires the bulk of coal and unconventional
fossil fuel resources to be exploited only under
condition that CO2 emissions are captured and sequestered.
A second inference is that remaining gas and oil resources
must be husbanded, so that their role in critical functions
such as mobile fuels can be stretched until acceptable alternatives
are available, thus avoiding a need to squeeze such fuels
from unconventional and environmentally damaging sources.
The task is to achieve a transition to clean carbon-free energy
sources, which are essential on the long run, without
pushing the climate system beyond a level where disastrous
irreversible effects become inevitable.
—
Saying in part:
…little time remains to … avoid widespread undesirable consequences.
And
…requires …the bulk of …CO2 emissions are captured and sequestered.
If I may politely suggest; This is not Pygmalion Likely within the requisite time frames.
*Climate change and trace gases*
Hansen et al 18 May 2007
Our concern that BAU GHG scenarios would cause large sea-level rise this
century (Hansen 2005) differs from estimates of IPCC (2001, 2007), which foresees
little or no contribution to twenty-first century sea-level rise from Greenland and
Antarctica. However, the IPCC analyses and projections do not well account for the
nonlinear physics of wet ice sheet disintegration, ice streams and eroding ice shelves, nor are they consistent with the palaeoclimate evidence we have presented for the absence of discernable lag between ice sheet forcing and sea-level rise.
The best chance for averting ice sheet disintegration seems to be intense
simultaneous efforts to reduce both CO2 emissions and non-CO2 climate forcings.
As mentioned above, there are multiple benefits from such actions. However,
even with such actions, it is probable that the dangerous level of atmospheric
GHGs will be passed, at least temporarily. We have presented evidence (Hansen
et al. 2006b) that the dangerous level of CO2 can be no more than approximately
450 ppm. Our present discussion, including the conclusion that slow feedbacks
(ice, vegetation and GHG) can come into play on century time-scales or sooner,
makes it probable that the dangerous level is even lower.
Present knowledge does not permit accurate specification of the dangerous
level of human-made GHGs. However, it is much lower than has commonly
been assumed. If we have not already passed the dangerous level, the energy
infrastructure in place ensures that we will pass it within several decades.
We conclude that a feasible strategy for planetary rescue almost surely requires a
means of extracting GHGs from the air. Development of CO2 capture at power
plants, with below-ground CO2 sequestration,may be a critical element. Injection of
the CO2 well beneath the ocean floor assures its stability (House et al. 2006) …
—
Saying in part:
If we have not already passed the dangerous level, the energy infrastructure in place ensures that we will pass it within several decades
and
The best chance for averting ice sheet disintegration seems to be intense
simultaneous efforts to reduce both CO2 emissions and non-CO2 climate forcings.
and
…planetary rescue almost surely requires a means of extracting GHGs from the air…
My point (and Ive not heard anything to the contrary) is that these sequestration technologies simply do not exist at commercial scale yet; the energy required to reverse the combining of carbon with oxygen is a large proportion of that required to burn the fossil fuel in the fist place, meaning to achieve sequestration at the scale Hansen says we need to avert ice sheet disintegration we must either massively increase energy use to run the sequestration and disposal plants, or reduce net output to a small fraction of present day levels. Neither is likely using present economic instruments.
Its my view that Hansen et al are great at climate science but rather weak when it comes to the technical solutions they suggest to address the problems they so accurately identify. I still haven’t seen a convincing full analysis of the all-in carbon cycle for bio-fuels, and until its done its rubbish – a feel-good diversion. The idea of ocean disposal of CO2 is unrealistic, as the depths required to keep CO2 solid (>2000m) are not found close to shore making transport of the CO2 very energy expensive, and in-situ trials have found that for some as yet unknown reason the slush of CO2 on the sea floor is apparently very attractive to fish, but also (for fairly obvious reasons) kills them in droves. The impact on the local ocean’s pH will be predictable and enormous. What the deposition of the worlds CO2 would do to global sea life I shudder to think.
Of course I respect the friendly and optimistic murmurings of our esteemed climate scientists, and I know they have to keep on friendly terms with the masses and the politicians. Presenting a grumpy face is not conducive to good communications, but I think it is fair to say that unless the impossible becomes a miracle we are not just at the End of the Beginning, we are, instead, and the Beginning of the End. We need to be told this in unambiguous terms so that we can arrange our affairs accordingly.
David, thanks for that pointer; a brief excerpt here:
——
….That optimism is based on science and faith.
The science, Mann said, is because climate researchers are sure of one thing that the public isn’t: The numbers show that there is still time to avert the worst.
NASA’s James Hansen, who forecasts some of the bleakest outlooks on global warming, said in an e-mail: “I am always surprised when people get depressed rather than energized to do something. It’s not too late to stabilize climate.”
“I am not about to give up,” Hansen wrote. He has hope, he says, because he has grandchildren.
The scientists say the public now understands how bad the problem is. So these researchers have faith that society will rally in time.
Bob Corell, an American Meteorological Society climate scientist, is hopeful because even industry is pushing for change — and will make money in the deal….
—————————-
Nigel Williams (319) — Let’s look at some numbers. Properly done, carbon capture and sequestration (say as carbon dioxide in deep saline aquifers) is expected to cost about $10 per tonne of carbon dioxide, so about $37 per tonne of carbon. This assumes we continue to burn fossil coal but use a efficient capturing process. Currently fossil coal used in the U.S. costs about $58 per tonne of carbon so the price of electricy goes to 160% of current prices, if entirely borne by consumers.
Using just that technology cuts the U.S. contribution in half. The U.S. uses about 600,000 tonnes of carbon per year in the form of fossil coal. (I’m assuming the bituminous coal most widely used is 60% carbon.) Using just this technology costs, then, about $22.2 billion dollars (which if borne by the federal government is a drop in the big bucket.)
I’m not claiming this alone is enough. I am claiming that where there is a will there is a way, because the economics clearly favor doing this rather than letting coastal cities drown…
Thanks for the figures David 321. Try these:-
It took a couple of hundred years of men running around wearing funny hats to find these carbon fuels and build the infrastructure to make it fit for our use and to move it about and to get it to us.
The volume of CO2 will be greater than the volume of fuel used (especially with the fuel used to run the sequestration process and transport added) so even if we just want to put it all back where we found it we will have to duplicate 150% of the capacity of the present global fuel production and transportation infrastructure! That will take a bit of time and money to implement.
It wont be practical to cart or pump CO2 as gas (to volumetrically inefficient) or as a solid (truck-fulls – nah!) so preferably it should be pumped. Thats not nice as at 20C its only liquid at around 30bar pressure, or its triple point of minus 57C and 5.1bar, and it’s a very fine solvent for hydrocarbons, so it will be a dog to handle and seal. Not like good old crude oil that just quietly sits there. So even the transport system of your captured CO2 will require lots of energy for pressure and/or temperature control.
http://scifun.chem.wisc.edu/chemweek/CO2/CO2.html
And it looks like very few sites are suitable for storage of as troublesome a material as liquid/solid CO2 – I believe that properly sealed deep saline aquifers are not that common, and of course deep ocean is just silly.
You make my point well:
*Properly done, carbon capture and sequestration…* Done how, exactly?
and
*Using just that technology…* What technology? Its vapourware!
I don’t recall ever seeing anything about the bedrock sink (rain absorbing CO2 and evenyually turning it into carbonaceous rock) which I’m told is by far the largest CO2 sink in the Earth system. What’s the deal with this? Though I can not visualize at all how this could be exploited for designed CO2 sequestration.
Re #311 Hank: Yes, and a point Hansen is making is about the surface meltwater lubricating not only the ice interface with rock below, but also the internal interfaces within the ice mass. Wetted ice blocks show very low friction, compared with colder blocks. Lower friction translated into a higher speed of flow. There was recently on TV a fleeting glimpse which could be interpreted as such a situation. A wide and smooth ice field collapsing at an edge into a chaotic stream of blocks. It also depends on local geography, of course.
I believe one real key is in the spreading surface melt and its role. A part of this water percolates into the ice as there are some cracks in any glacier. The heat transport is initially very efficient as re-freezing in the ice interior liberates the energy that was tied up to melt the ice and snow on the surface. It heats the cold interior, until the “wet glacier” condition occurs. Warming is much faster than the slow conduction of heat that occurs in a cold glacier case.
Overall the issue is about capture and storage of heat energy. Surface melting is like sea ice melting in summer heat: A large increase in efficiency of energy capture. The difference is that in the case of ocean, most of this extra energy is stored in seawater and held there as a result of mixing and sea currents. In Greenland and in Antarctica, the surplus is stored in the interior of the glaciers through the percolation process. The end result in both cases is that the energy is trapped for tens of years or centuries and not radiated away during wintertime.
A difference might be that the glacier depends strongly on atmospheric warming to initiate the process in the spring. The process is reset every year as there is little re-flow of heat from the interior to the surface during the winter. In the ocean mixing brings back a part of the stored energy and a feed-forward resulting in lesser freezing extent and/or depth is stronger.
In the wintertime, the polar areas have a role as radiators. Energy carried into the region by ocean currents and winds is radiated out and that process remains.
How fast these feed-forward processes work (quantitatively, and what their impacts are) seem to be still a subject of research. Presently my view is that this is a very high risk, comparable to the one of maybe “accidentally” liberating vast amounts of gases from the permafrost.
The Business As Usual crowd’s grip on the global economy is weakening.
“The Carbon Disclosure Project (CDP), a collaboration of over 315 institutional investors with assets under management of more than $41 trillion, releases its 5th annual global report, providing the largest and most comprehensive database of strategies from the world’s largest corporations regarding the impact of climate change on shareholder value.”
‘The report concludes that the world’s corporate giants have made “significant progress in understanding and disclosing their positions relative to the risks and opportunities associated with climate change.” ‘
http://sciencemode.com/2007/09/24/global-climate-change-report-released-315-investors-41-trillion-in-assets/
Nigel Williams (322) — Try
http://www.fossil.energy.gov/programs/sequestration/index.html
to see some of the demonstration projects underway. Australia also has one. The $10 per tonne of carbon dioxide is what U.S. DoE believes is achievable.
There are plenty of papers which discuss transporting carbon dioxide via ocean vessel and pipeline. Also, there are several papers pointing out that majority of the surface area of land is underlain by deep saline formations. So transportation is not needed for those CCS projects right over a suitable formation.
So the only question is how rapidly this sequestration gets underway. As, for example, the James Hansen et al. 2007 paper that you quoted indicates, we have some time, but not a lot.
And yes, it is vaporware in that everybody seems to propose using gaseous carbon dioxide. :-)
Here is a company putting $100 million into a biomethane plus carbon capture. The goal is to build these units at sequestration sites:
http://biopact.com/2007/09/greatpoint-energy-closes-100-million.html
Thanks David et al. There’s a lot going on, but as Hansen and co say, time is of the essence. Watching with interest. N
Well here’s a pleasant prospect to contemplate as our lakes and rivers warm:
6 die from brain-eating amoeba in lakes
“This is a heat-loving amoeba. As water temperatures go up, it does better,” Beach said. “In future decades, as temperatures rise, we’d expect to see more cases.”
http://news.yahoo.com/s/ap/20070928/ap_on_he_me/killer_amoeba;_ylt=Al0maALo5VDbKcLkuUfwU0J34T0D
With Sea water just measured more than -1 C by the North shores of Barrow Strait at low tide, more than -1 C because of waves coming back and forth on the exposed shore when its -6 C outside. Measured in darkness right by the Arctic jelly fish flashing blue light. If there is a good near live sst map out there , would like to cross check this measurement with remote sensing…
Rod, you asked about ‘bedrock sink’ above — look up “biogeochemical cycle” or “cycling” and CO2, that covers everything from acid rain and karst formation to the “White Cliffs of Dover” and similar. When you read people claiming that human activity makes only a tiny change to the total amount of CO2 measured somewhere, they’re talking about the amount known to be cycling. What they miss is it’s a slow process, though immense, and that slow massive cycling process was able to handle only about half of the amount from fossil fuel burned; the other half, that natural cycling couldn’t handle, is what’s measured as an increase in atmospheric CO2.
Re my #146 (Friday roundup) and Tamino’s #154
Part 1
Tamino and I have been having a discussion (as referenced) on whether the last 20 years look like a linear trend, or a sudden jump around 1996. In this Part 1 I shall continue this further, but readers should note that I now believe that neither model is adequate, which I discuss in Part 2 below. Therefore this Part is somewhat moot, but it raises some interesting questions of statistical interpretation. Here is a recap of the bidding, all based on HadCRUT3 data:
a. I said that the period 1970.0-2000.0 saw a mean annual rise of .013C.
b. Tamino said that should have been .016 based on linear regression.
c. T. said that global warming was accelerating, with .020C in the last 7 years.
d. I said “sorry”, b. was correct (if one accepts linear regression, giving .0161).
e. I said that to study possible acceleration, it was a good idea to look at the last 20 years (c. 2 solar cycles), and that splitting the last 20 years into two 10-year periods made one think that each period was flat with a big (0.248C) jump between them. This model gave a lower sum of squared errors (.1094 versus .1360), and in addition the Maximum Likelihood Estimates give a Bayes factor of 8.8 in favour of the “jump” hypothesis over the linear trend.
f. T. reminded me that I had admitted not having the exact calculation available to “prove” that the difference was significant.
g. T. said my conjectured bound on the result did not break a 5% significance level, so should be discounted.
h. T. said that with my Bayes factor of 8.8 I didn’t quote any statistics.
i. T. said I should study the monthly figures, as these would give higher significance levels.
j. T. said that in studying the period 1987.0-2007.0 I had chosen badly.
I now respond as follows.
Re f., it is interesting that Tamino does not know of ways to calculate P[sum a_i X_i^2 there is nothing sancrosanct about 5% (is 4.5% significance worth that much more than 5.5%?).
Re g. also, T. is claiming the moral statistical high ground (if that is not an oxymoron ;-)) for the linear trend to be the null hypothesis. Occam’s razor demands that a model with fewer degrees of freedom be placed as the null hypothesis over one with more d.o.f. But the “linear hypothesis” has the same number of degrees of freedom (n-2) as the “jump hypothesis” (if there is just one jump as in thepresent case). The linear hypothesis can be argued for in terms of an expected behaviour from increasing CO2. But it is not inconceivable that the oceans (say) absorb some warming for a while and then bubble and say “hey, have some of that heat back!”, which could lead to a jump.
It is easier if you are a Bayesian (see h.), apart from that danged thing of having to choose your prior. In h. Tamino says I didn’t produce any statistics. I assume that he knows that the Maximum Likelihood Ratio (value 8.8) is a statistic, but that he is living in a frequentist world and wants a significance level from it. But that isn’t how Bayesian statistics works.
Suppose I can find a Bayesian who from general a priori arguments as above thinks the jump hypothesis is less plausible than the linear hypothesis, but only by a factor of 3 (i.e. 75% to 25%). Then can I say to her, after you apply the Bayes factor of 8.8, your posterior odds should now be 8.8/3 = 2.9 in favour of the jump hypothesis.
Re i., the monthly statistics are only more useful if there is actually more information in them. But it is not clear that this is the case – with them the Durbin-Watson statistic plunges to an awful 0.55 (from a respectable 1.70), and the high serial correlation means that the extra amount of information available is rather small. It is no doubt possible to attempt to retrieve the situation by estimating an AR(1) underlying process and subtracting the effect, but I note from Tamino’s own critique of Schwartz’s paper (see Climate Insensitivity of September 15) that he does not have any faith in that process for temperature data, and I agree with him there. Without any such correction a disturbing feature beyond DW is that while the purported standard error for the trend goes down (.0034 to .0014), the mean standard error for the data goes up (.0869 to .1228). So, I don’t find the monthly data suitable for regression analysis.
Part 2
In order to study further the question of the jump hypothesis versus the linear hypothesis, I followed the standard exhortation in the literature: examine the residuals from the regressions. Both the monthly and the yearly data confirm that there were two intervals of unrepresentative temperatures: around 1992-1994 when temperatures were depressed, generally attributed to the eruption of Mt. Pinatubo, and 1997-1999, associated with a massive El Nino event.
1998 was certainly an inconvenient year. It was inconvenient for the solar brigade when it happened, because the CO2 brigade were able to say “look how warm it’s getting, even faster than we predicted”, but now it’s actually inconvenient for the CO2 brigade, because it
knackers the trend line for the last 10 years (and 10 or 11 years is arguably a good period to use in order to balance out one solar cycle).
In the yearly data, the 3 most extreme residuals in the linear model are 1998: .250, 1992: -.138, and 1993: -.110. Since these have a believed physical explanation, and since they certainly contribute strongly to my jump hypothesis, I decided to regress the annual data with these 3 years censored (deleted). Compared with the uncensored data the linear trend comes down from .0197 to .0177, the standard error in that comes down from .0034 to .0027, and the standard error in the data comes down from .0869 to .0670. So this is definitely a better fit. But it contradicts Tamino’s claim at c. that global warming is significantly accelerating (since .0177 is only 0.6 times the s.d. .0027 higher than the trend .0161 as per d.).
To summarize this Part, I now see that the appearance of a temperature jump in the mid-90’s is heavily influenced by the anomalous temperatures in 1992, 1993, and 1998. When these years are removed from the analysis, I am reasonably happy with the linear hypothesis, giving .0177+/-.0027Cp.a. – but it’s not significantly higher than the 1970.0-2000.0 trend, so we cannot on the basis of this comparison say that global warming has accelerated.
Part 3
In this part I wish to close with a few remarks, as objective as I can be, on the state of play between the CO2 brigade and the solar brigade regarding the past and future of HadCRUT3. The years 2002-2007 are looking very flat (but I am resisting the temptation of a statistical analysis on that period which would be criticized as both short and cherry-picking). Nevertheless, this period must no doubt give encouragement to the solar brigade, as they can believe that Cycle 24 will be weak and that global warming will soon be a mirage of the past. In contrast, the CO2 brigade might actually be hoping that my jump hypothesis has some merit, since a new jump in a few years’ time would verify again the concept of AGW.
And in fact the Hadley Centre are forecasting a further flat year or two and then a rise of 0.3C by 2014. I am surmising that they have noticed that the solar minimum is having an effect, but believe that once Cycle 24 gets underway then global warming will continue apace. Or possibly they know stuff about oceanic heat exchange and PDO and NAO etc; I wish in any case they would tell us the basis of their projections.
May you live in interesting climes…
See – owe to Rich and Tamino — The sharpest statistical test that I know about is to compute the Bayes factor for the evidence given the two competing hypotheses. The logarithm (base 10) of this are in units called bans by A. Turing. Often tenths of these are used, then decibans. Harold Jeffrey suggested appropriate terms for ranges of decibans indicating the degree with which the weight of the evidence suggests one hypothesis rather than the other.
With just this much one can go quite far without having to assign explicit priors. Sometimes (probably not this case), the weight of the evidence very strongly suggests a hypothesis to be preferred (at least 22 decibans, according to Sir Harold).
Re: #332 (see-owe to rich)
I get the impression you’re having fun exploring the surface temperature record, and reporting your findings here as you go along. That’s a good thing.
But bear in mind you’re not the first to do so. In a previous comment you expressed surprise that I had responded so quickly. I suspect you thought that I was overly eager to contradict your model. This is not so, the reason for the quickness of my response is that I had done the analysis already; I’ve been looking at these data for a long time. I had even explored the “jump” model (which I usually call a “step-change” model) myself. And this isn’t even my field of research; there are many others who have been looking at it longer than I have.
I am not an ideological frequentist, in fact my work (which is unrelated to climate science) requires a lot of Bayesian analysis. In my opinion it’s a mistake to marry oneself to either approach.
I do indeed know of ways to calculate the likely significance of the difference between two competing models, and my earlier calculations indicated that it was in fact not significant.
As for my earlier claim of acceleration of global warming recently, that opinion was formed in response to a specific question (a long time ago in a galaxy far, far away) about the time interval 1970 to the present. But I regard 1975 to the present as the “modern global warming era,” and for that time frame I have lately reversed my opinion, as I expressed in this blog post.
Estimating error ranges based on the red-noise character of data doesn’t depend on assuming an AR(1) model, although that is a common approach. I use a different method, which takes into account the full autocorrelation structure of the available data. That’s what was done in the aforelinked post. It seems to me that the response to Schwartz’s analysis actually proves that the data do not follow an AR(1) model adequately to derive an accurate value for the time constant of the global climate, even if there is one (and it’s overwhelmingly likely that there is more than one applicable time constant).
I think your assigning the monikers “co2 brigade” and “solar brigade” is misleading (but not an intentional deception). Those who agree that greenhouse gases are the primary cause of modern warming do not deny the solar influence. Those who argue that the primary cause is solar variations have to overcome the difficult fact that solar variations simply don’t fit the bill, and have yet to offer any explanation that I’ve heard, how greenhouse gases can fail to warm the planet significantly.
I have several objections to the “jump” model. First, it has no basis (that I’m aware of) in physics; given two models which are statistically indistinguishable, it seems logical to prefer the one which has a sound physical interpretation. Second, in order to isolate the long-term signal it helps to remove the known short-term factors as much as possible, i.e., to remove the el Nino and Mt. Pinatubo (and el Chicon, etc.) signal; doing so seriously undercuts the jump model. Third (for me, most persuasive), even without removing the el Nino signal the period 1997-2007 shows a statistically significant (even within stringent red-noise limits) deviation from flatness, rejecting this hypothesis.
I encourage your continued exploration of the data.