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The Critical Decade - Part 1: The Science

Posted on 28 May 2011 by dana1981

The Australian government established a Climate Commission which recently released a three chapter report entitled The Critical Decade.  The first chapter of the report, which we will examine in this post, summarizes the current state of climate science observational data.  But first, a statement in the introduction is worth quoting: 

"Over the past two or three years, the science of climate change has become a more widely contested issue in the public and political spheres. Climate science is now being debated outside of the normal discussion and debate that occurs within the peer-reviewed scientific literature in the normal course of research. It is being attacked in the media by many with no credentials in the field. The questioning of the Intergovernmental Panel on Climate Change (IPCC), the “climategate” incident based on hacked emails in the UK, and attempts to intimidate climate scientists have added to the confusion in the public about the veracity of climate science."

We at Skeptical Science have documented many such attacks on climate science by individuals with no climate credentials, who misrepresent scientific research, and attempt to sow doubt in the minds of the general public through non-scientific issues like Climategate.  But while these introductory comments are worth highlighting, let's move on to the scientific content.

The report is based on the IPCC Fourth Assessment Report (2007) as well as several other more recent studies.  Skeptical Science readers will already be familiar with much of the information in the first chapter, but it nevertheless provides a useful summary of recent climate research.  The main conclusions of Chapter 1 are as follows:

  • The average air temperature at the Earth’s surface continues on an upward trajectory at a rate of 0.17°C per decade over the past three decades.
  • The temperature of the upper 700 meters of the ocean continues to increase, with most of the excess heat generated by the growing energy imbalance at the Earth’s surface stored in this compartment of the system.
  • The alkalinity of the ocean is decreasing steadily as a result of acidification by anthropogenic CO2 emissions.
  • Recent observations confirm net loss of ice from the Greenland and West Antarctic ice sheets; the extent of Arctic sea ice cover continues on a long-term downward trend.  Most land-based glaciers and ice caps are in retreat.
  • Sea-level has risen at a higher rate over the past two decades, consistent with ocean warming and an increasing contribution from the large polar ice sheets.
  • The biosphere is responding in a consistent way to a warming Earth, with observed changes in gene pools, species ranges, timing of biological patterns and ecosystem dynamics.

The report notes that the past decade (2001-2010) was the hottest on record, 0.46°C above the 1961-1990 average.  It also contains many illuminating figures, including this one showing that Arctic sea ice is declining far faster than IPCC models projected, currently approximately 40 years ahead of schedule.

sea ice obs vs. IPCC models

The report also discusses that sea level rise is progressing at the very high end of the IPCC estimates, despite the efforts of certain "skeptics" to downplay the  sea level rise acceleration based on one exceptionally flawed paper

Chapter 1 proceeds to discuss the various signals of a changing Australian climate in the biosphere, including mammalian migrations to higher elevations, earlier arrival and later departure times of migratory birds, and the increase in bleaching events on the Great Barrier Reef (GBR).  There have been eight mass bleaching events on the GBR since 1979 with no known such events prior to that date.  The report goes on to discuss the potential causes of the observed climate change:

  • There is no credible evidence that changes in incoming solar radiation can be the cause of the current warming trend.
  • Neither multi-decadal or century-scale patterns of natural variability, such as the Medieval Warm Period, nor shorter term patterns of variability, such as ENSO (El Niño-Southern Oscillation) or the North Atlantic Oscillation, can explain the globally coherent warming trend observed since the middle of the 20th century.
  • There is a very large body of internally consistent observations, experiments, analyses, and physical theory that points to the increasing atmospheric concentration of greenhouse gases, with carbon dioxide (CO2) the most important, as the ultimate cause for the observed warming.
  • Improved understanding of the sensitivity of the climate system to the increasing atmospheric CO2 concentration has provided further evidence of its role in the current warming trend, and provided more confidence in projections of the level of future warming.

Again, this is not news to Skeptical Science readers, nor are the anthropogenic warming fingerprints the report discusses.  The ensuing discussion of climate sensitivity is fairly interesting, and harkens back to our examination of the cloud feedback:

"An analysis of the transition of the Earth from the last ice age to the Holocene, which infers climate sensitivity from the observed change in temperature and the corresponding changes in the factors that influence radiative forcing, also estimates a value of about 3°C (Hansen et al. 2008). Much of the uncertainty on the magnitude of climate sensitivity is associated with the direction and strength of cloud feedbacks. Recent observational evidence from short-term variations in clouds suggests that short-term cloud feedbacks are positive, reinforcing the warming, consistent with the current model-based estimates of cloud feedbacks (Clement et al. 2009; Dessler 2010).

A recent model study comparing the relative importance of various greenhouse gases for the climate estimates a sensitivity of approximately 4°C for a doubling of CO2 (Lacis et al. 2010). In addition, the study points to the importance of CO2 as the principal “control knob” governing Earth’s surface temperature."

It's worth noting that while Hansen et al. find paleoclimate evidence for a short-term climate sensitivity of 3°C for doubled atmospheric CO2, they also find that when including slow-acting feedbacks, the long-term sensitivity is closer to 6°C.  Next up is a discussion of how the carbon cycle is changing:

  • Despite the dip in human emissions of greenhouse gases in 2009 due to the Global Financial Crisis, emissions continue on a strong upward trend, on average tracking near the top of the family of IPCC emission scenarios.
  • Ocean and land carbon sinks, which together take up more than half of the human emissions of CO2, appear to be holding their proportional strengths compared to emissions, although some recent evidence questions this conclusion and suggests a loss of efficiency in these natural sinks over the past 60 years.
  • If global average temperature rises significantly above 2°C (relative to pre-industrial), there is an increasing risk of large emissions from the terrestrial biosphere, the most likely source being methane stored in permafrost in the northern high latitudes.

There is evidence that the efficiency of natural carbon sinks is declining, particularly in the Southern Ocean, but this possibility remains highly uncertain and controversial.  Thus far natural carbon sinks have kept pace with us, absorbing approximately 57% of human emissions since 1958, but there is of course a limit to their storage capacity.

carbon budget

As the planet continues to warm, approaching the 2°C danger limit, not only is there an increasing risk that these natural carbon sinks will become saturated, but potentially significant releases from other carbon sources (methane beneath permafrost, methane hydrates stored under the sea floor, organic material stored in tropical peat bogs, etc.) becomes increasingly likely.

The final section in Chapter 1 discusses the certainty of our knowledge of climate change:

  • The IPCC’s Fourth Assessment Report has been intensively and exhaustively scrutinised and is virtually error-free.
  • The Earth is warming on a multi-decadal to century timescale, and at a very fast rate by geological standards. There is no doubt about this statement.
  • Human emissions of greenhouse gases – and CO2 is the most important of these gases – is the primary factor triggering observed climate change since at least the mid 20th century. The IPCC AR4 (2007a) report attached 90% certainty to that statement; research over the past few years has strengthened our confidence in this statement even more.
  • Many uncertainties surround projections of the particular risks that climate change poses for human societies and natural and managed ecosystems, especially at smaller spatial scales.  However, our current level of understanding provides some useful insights: (i) some social, economic and environmental impacts are already observable from the current level of climate change; (ii) the number and magnitude of climate risks will rise as the climate warms further.

The report notes that some significant uncertainties remain, such as the exact responses of the Greenland and Antarctic ice sheets, and the hydrological cycle, to the continuing warming of the planet.  But the report also hammers home a key point that we wish "skeptics" would take to heart:

"These uncertainties, however, in no way diminish our confidence in the observation that the Earth is warming and in our assessment that human emissions of greenhouse gases are the primary reason for this warming."

"Despite these seemingly daunting uncertainties, a number of social, economic and environmental impacts can be observed that are consistent with what is anticipated from the current level of climate change. The number and magnitude of climate-related risks will rise considerably as the climate warms towards 2°C above the preindustrial level; and above the 2°C guardrail, the risks may rise dramatically"

In short, despite the uncertainties, the scientific evidence is clear on the main points that humans are causing dangerous global warming.  It's also important to note that uncertainties can go either way, and the consequences of climate change are just as likely to be more damaging than we expect as less.   Uncertainty is not our friend.

In Parts 2 and 3 we will examine the report's chapters on risks associated with climate change and implications of the science for emissions reductions.

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Comments 51 to 100 out of 116:

  1. #51 ... and just what proportion of the whole record is 2002 - 2011? When did we start calculating climatic trends on ~9 years of data? 1992 - 1997 looks slower too, yet the overall trend is clearly much larger than your cherry pick. This reminds me of the way in which you can break down the entire 100+ year GISS tmperature record into short (<10 years or so) negative-trending segments, yet the overall trend is still resoundingly upwards. #51 KL and #48 okatiniko: On acceleration. If there is no acceleration, or indeed if there is a 'flattening' of the trend, then why is it that when you plot the GISTEMP temperature data trend from 1981-2000, then plot the temperatue trend from 1981 to 2010, the trend line steepens up? Do this on woodfortrees if you like. Doesn't look awfully much like a 'flattening' or 'decelerating' trend to me. In fact, it looks rather more like an accelerating trend with entirely expected noise. With HADCRUT3, despite it being very much a non-global series, there's also an acceleration, though smaller, and in UAH there is a large acceleration when 'noughties' data is added. I'll second Tom Curtis' comment in #35 - the diversion by KL onto East Antarctica is truly disingenuous - does he really think we should not worry about Greenland and West Antarctica's melt (which will lead to metre-scale sea level rise) just because East Antarctica is currently relatively stable? To Gish Gallop and plant the seeds of misinformation in the unsuspecting readers takes seconds; to debunk even obvious disinformation like #13 takes rather longer.
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  2. Regarding the absolute nonsense being peddled @51 regarding the trend in global sea level. From the CSIRO sea-level page: [Source] Trend in global SL is 3.2 mm/yr.
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  3. Fascinating. this graph is doing the "denyosphere" rounds, not least of all goddard showing sea level as being the lowest since 2004; but an overall rise of 0.76mm/year... It comes from aviso for Envisat without Glacial Isostatic Adjustments applied. With those corrections it would be 1.6mm/year (2004-2011). The site also allows you to view each altimeter individually, all on the same graph; with and without their various adjustments. In addition to 'just' showing Envisat - the oddest looking results and therefor the favorite of the "denyosphere" - you can see Jason-1 and Joson-2 individually - showing 2.75mm/year (2003-2011) and (a very wobbly) 2.44 mm/year (2009-2011). Their overall processing result is, as in 54, 3.25mm/year (1993-2011) as shown here. My point being that it's just childish to quote one or two numbers out of context and then claim 'fowl'. The data and tools out there are so good... why do people just quote a couple of numbers and 'eyeball' trend-lines. weird!
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    [DB] Les, it's all about adjusting the data to meet one's preconceived curve expectations...

  4. With regard to the NorthWest Passage, you can compare the map given in the link provided by Tom Curtis : (4. ST. ROCH: Northern Deep-Water Route (East-West) 1944 [Yellow line]) With a more recent one giving the likely commercial opportunities opening up :
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    [DB] Fixed images

  5. In reference to the map: 1. The southerly route is used on an annual basis by the Canadian Coast Guard to replish supplies to the cities/outposts on the northern side of Canada. 2. The northerly deep sea route is much more desireable as a commercial route as the water is consistently deep. The area between Banks and Victoria Islands is somewhat treacherous. If the area to the north of Banks open to the Beaufort Sea, that would/could become the route of choice. The black carbon emissions from China/India etc are hastening the ice melt. When and IF the people wake up and demand cleaner skies and healthier lives, that source should become more of a marginal effect. The rate of growth in China of coal fired power plants with wide open smokestacks continues to boggle my mind, so within the next 10 years I don't see any decrease that will slow the melt of the Arctic. The black soot provides approx 4w/sq meter of loss of albedo. This is a huge amount. I don't know how to pressure China/India etc to clean up their acts. Only the people living there can do that. As far as other countries with a lot of charcol burning etc......that is extremely difficult as that is their main source of cooking and heating. This is an area that has only recently been studied, yet has been known about for a long time. The effects are devasting to say the least and the teck is here, proven, and veryyyyyyy benficial to overcome this. Not demanding and doing so is totally foolhardy.
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  6. Being the museum, owners of the log of the St Roch, won't allow it to be digitalized and more readily available, I can only suggest that people purchase the book. It is available on the Vancouver museum site. Capt Larson did not say there was no ice, but I can say that he was very surprised at areas that there was litteraly no ice, where he thought passage would be extremly difficult.
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  7. Camburn #56: You like cherries? especially extra(polated) juicy ones? Have you read Polyak et al 2010 and the attendant sources therein? You would see how picking a carefully-selected single site does not tell you about all the Arctic, and also a wealth of evidence pointing to Arctic sea ice being less extensive now than in several millennia. The graph from Kinnard et al 2008 would show you how ice extent would have to be ~1.5 million sq km (~18%) lower than in any other estimated extent from 1870-1960 in order to be comparable to the past few years. Much like individual logs of submarines surfacing in polynyas at the North Pole say nothing of overall extent, neither does a single log of a single journey in a single part of the Arctic.
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    [DB] To say nothing of logs detailing 12-15 meter thick ice...

  8. skywatcher, I'm not sure of what you're really doing - just comparing two trends with some arbitrary end points ? with a noisy signal, I guess you can easily adjust the end point to get an increase of the trend. But that's not what is usually considered as a significant acceleration - you have to compare the difference with the statistical uncertainty, at least. DB : thanks for the plots, but my question wasn't about the projections, but their validation. I mean, it's easy to plot the result of models, but when do you expect that the acceleration will be clearly measurable ? concerning SLR, what does this GIA stuff really mean ? is the "real", observed, SLR described by the curve with, or without, the correction ? but anyway, since the correction seems to be taken as a constant, it shouldn't influence the acceleration. So what's the current acceleration rate, say for the smoothed 30 last years ?
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    [DB] SLR plots from UCAR/NCAR need to have the corrections applied to them to account for regional isostatic rebound effects and seasonal effects to be properly filtered out.  If using the unadjusted/improperly adjusted data, one risks writing posts on CO2 snow...


    And from Church and White, 2011:

    C&W SLR 1860-2010

    The Tamino posts I linked to were essentially validating the existent temperature records, not models or projections.  Since the future hasn't happened yet (some existentialists are sure to quibble on this point), I supplied you with 2 links discussing 2 recent temperature scenarios, one by MIT and the other by the Royal Society (IIRC).

    If you're asking for clues to recognize when shifts are occuring, then I would suggest monitoring the Mauna Loa CO2 monthly updates (you can also get CH4 updates there as well), the GISS temperature trends (updated monthly), droughts in the Amazon and the volume of Arctic Sea Ice lost each year relative to the mean and the trend.  Also watch for papers on evapotranspiration changes, desertification, arable land crop productivity, etc.

    CO2 and CH4 will give you some idea of temperature trends to come (30-40 year lags built-in to the system...we are currently experiencing the effects of the CO2 emissions of the 1970s now).  The others will give you an idea of how much the rate of change is itself changing.

    If the natural oceanic and land sinks decline in their ability to temporarily sequester anthropogenic GHG emissions (and there is some evidence that they already are), then that will be revealed in the Mauna Loa data.  But keep this in mind:  the past, while a guide, is no good indicator of future results WRT to climate and climate change.  Temperature change and climate change are multifactorial; the change to come, as evidenced in the MIT and RS papers, is expected to be non-linear.

    What to expect when?  This is about as good a guess as any:

    21st Century warming to come

  9. [ Snip ]
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    [dana1981] Please take the time to familiarize yourself with the site Comments Policy.  In particular "No off topic comments".  This topic has nothing to do with cap and trade or Flannery's correct comment that while we can slow global warming, we're not going to cause cooling.  If you would like to discuss Flannery's comments, take it to CO2 limits won't cool the planet

  10. #58 - it's an exercisse in observation, and I think others can do better with statistical assessment etc. The point is that if warming was decelerating, we would expect to see that appending the last decade's data onto the warming trend since the 1970s would result in a decrease of the trend slope. What we actually see is that the first decade of this century was even warmer than we would expect it to be, based on 1970 or 1980 to 2000 data. Hence the trend from 1980-2010 is steeper than the 1980-2000 trend. Use whichever endpoint you prefer, but appending the last decade of data onto the data up to 2000 does not decrease that trend. Year-to-year variations are not important, and record years don't happen every year, hence why you need to use a climatically-significant period of time when discussing whether the trend has decreased or increased.
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  11. Ken Lambert @ 48 would have us believe that SLR does not respond to decadal doubling in the rate of ice loss from the Greenland ice sheet, does not respond to growing loss of ice from WAIS and does not respond to water expansion as a result of ocean warming. Next he will be telling us that Polar ice loss is not occurring and that oceans are cooling. Hansen has a somewhat different view and one which is more credible than the those expressed by Ken Lambert. He appears to have only one mission in life, that of seeking to cast doubt on the views of those who are better informed than he is and who substantiate their views without cherrypicking – or am I being unduly harsh?
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  12. I think Hansen is still searching, which is what a good scientist does. He recognizes that the imbalance is not as he once thought and has started looking seriously at other factors. Like any other person, his search was somewhat in tunnel vision, but have now expanded. KL is showing what current observations show. I posted a paper on Greenland that seems to have disappeared. It showed that two glaciers were shrinking, and one was growing. The rate of ice loss in Greenland has yet to be resolved in a satisfactory manner. It is obvious from earlier periods of the Halocene when temperatures were warmer for 1,000's of years that it will continue to survive for 1,000's more years. This link will take you to course material that I would hope some can learn from.
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    [DB] You are welcome to pick one of the many Greenland threads (use the Search function to find the one most appropriate) & repost it there.  Quite frankly, your comment here about Greenland reveals an opportunity for you to learn much from those many Greenland threads.

  13. Thanks DB. I am always willing to learn if the source documentation is credible. One thing concerning the current loss of ice from Greenland proper I would like all to look at is the current rate of loss verses the rate of loss in the 1938-1950 time frame.
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    [DB] Why the focus on the 1938-1950 time frame?  Those who have looked at that period have not done a good job of examining it.

  14. DB: That time frame had a temp structure simliar to todays temp structure. Actually, the examination of that time frame is quit good. The link you showed quibled that the construction in reference didn't continue to 2010. That is not what was important in the construction as one years values do not detract from the construction.
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    Moderator Response: (DB) The mid-20th century warming experienced regionally in Greenland is a far cry from the global warming of the past 3-plus decades; the disinformation sites obfuscate that fact. Multiple lines of evidence point to a converging and consistent story: the world is as warm now as the HCO (the warm period of about 8000 years ago) and it is largely due to mankind.
  15. Folks, Watch the sleight of hand being perpetuated by the deniers of AGW and "skeptics" on this thread. Note their tendency to cherry pick regional transient events in the past and then confuse them with what has been happening globally and what will continue to happen globally as we continue to emit GHGs. This is nothing but tricks to obfuscate and an attempt to confuse people not familiar with the literature and the science. It is also the height of arrogance for someone to assume that they know more than the Australian climate commission and the US National Academy of sciences. Think of it as someone on the web telling you that the oncologists have gotten it all wrong on the links between tobacco and cancer. Who would you trust them or the oncologists? Well, the oncologists of course. Beware of the omniscient contrarians and confusionists.
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  16. skywatcher , I don't think that a statistically decelerating trend would result in a decrease of all trends computed for any interval. This would be cherry picking. If you find a couple a value for which the trend is decreasing, and then another one for which it's increasing, what's your conclusion then ? DB, sorry, I'm not sure that I understood your explanation : does GIA produce a real decrease of SLR , and does the correction remove this decrease, giving (after correction) a higher result than what is really observed on the coasts ? I understand that the measurements should be corrected from instrumental effects, but GIA is not an instrumental effect : as I understand it is a real effect producing a real negative component, so why correct it ? for instance to my knowledge there is no "correction" from astronomical influences on the average temperatures ? it is just a part of the signal. and actually I didn't catch either your answer on how the model were validated if no statistical acceleration could be measured yet - how do you know that the models are correct ?
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  17. okatiniko: GIA is a local effect. It has to be corrected for when trying to assess changes in global sea level.
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  18. Well said Albatross (#65). It's worth comparing Camburn's comments about Greenland glaciers with John Cook's points made in his article at the Drum. Camburn hopes that by identifying a single, growing glacier in Greenland, we'll ignore the prepondernace of evidence showing accelerating greenland mass loss and global glacier retreat. #66: clearly you don't get what I was alluding to - that the past decade is warmer than expected based on the rate of warming over the previous two or three decades (or more). When you consider temperature change over climatically significant time periods (decades), you find absolutely no evidence that warming slowed at all.
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  19. Thanks for the image fix at #54, DB. They looked alright when I did a Preview but I suppose I should always include that img width="450" bit, just in case.
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  20. skywatcher@68: Wrong. I was pointing out an observation about Greenlands glaciers.
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  21. okatiniko: "I understand it is a real effect producing a real negative component, so why correct it ?" Because they're trying to measure sea level rise, not the rate at which the land is rising in such regions.
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  22. Riccardo #50 DB and others Whether you want to quibble about the Jason 1 & 2 SLR records being 1.6, 1.8, 2.0 or 2.3mm/year for the last 8-9 years, it is surely significantly less than the 3.1mm year average for the UCAR 1993-2011 chart, and the oft quoted figure from the likes of the Australian Climate Commission. This cannot mean anything else than SLR slowing or decelerating - not accelerating. While ice melt is hard to measure, Dr Trenberth suggests in his Aug09 paper that approx 1mm/year is from glaciers and another 1mm/year from major ice sheets. A total of approx 2mm/year from ice melt. This 2mm/year for ice melt estimate leaves nothing much when subtracted from the 1.6-2.3mm/year for the component of steric rise - ie. the thermal expansion of all that heat sequestered in the oceans from global warming imbalance. Hence steric rise estimates like 0.5+/-0.5mm/year and 0.8+/-0.8mm/year pop up in the literature. If I expresed my height as 1.8m +/-1.8m you would not know if I were a giant or a grease spot. This is the state of play in SLR measurement. If the steric rise has almost stopped, then warming imbalance gap is rapidly closing. This is further confirmed by the energy balance budget. If the SLR components are mostly ice melt, the energy needed to melt ice is very small compared with thermally expanding seawater, and the warming imbalance is small for the budget to close. okatiniko is trying to understand DB's 'correction' point for SLR at #58. Please explain to us all DB??
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  23. DB@64: When we are talking Greenland, I am thinking that the temp metrics affecting Greenland would be the source. We all know that temps in and around Greenland in the 1940's are very similiar to temps today. It may be hot or cold in Australia, that will not affect the Greenland area. The temps in and around the Greenland area will affect Greenland.
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    [DB] My point was that you are cherry-picking when comparing the current global warming period (largely caused by man) to the earlier warming period in which Greenland warmed disproportionatley more than elsewhere.

    Glaciologists are well aware that current ice and ice discharge conditions experienced in Greenland have no contemporary equivalent in the past several thousand years.  Consider Mittivakkat Glacier in Southern Greenland:

    Mittivakkat Glacier

    Note the clear progression of ice termination lines, showing the recessionary behaviour of the glacier over the past hundred years.

    The consensus of indicators and information available show that, for Greenland, the current warming period is longer and of greater intensity than that of the mid-20th Century, and that warming still in Greenland's pipeline (relative to that already experienced globally) will bring it to, or exceed, the levels of the HCO.

    And that is without any compounding warming effects from the ongoing albedo flip underway in the high Arctic.

  24. KL: The rate of rise of sea levels has slowed. This is not in question. The current rate is under the 1915-1950 rate, and under the 1970-2000 rate. That is not questioned as it is very well documented. The question is, will the rate continue at its present level or accelerate. I have no clue.
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    [DB] "The rate of rise of sea levels has slowed.  This is not in question."

    Incorrect.  This is well-documented and not in scientific question, as you say.  See my response to okatiniko at 58 above (specifically the Church & White 2011 reference).

    I suggest learning more about the science before making such unreferenced and authoritative statements.

  25. Dear Contrarians, Look at the graph from Chruch and White (2011), I mean actually look at it, now absorb. Or will your preconceived ideas not permit that image to be processed and absorbed by your brains? Also, remember how those in denial about AGW cherry picked 1998 in the global temperatures (some still do) to delude themselves that AGW had stopped....well they are now doing the same using sort of cherry picking the global Sea-level data. And you know what folks, we can continue playing this game come 2100, "Ooh GSL rise slowed the last 5-10 yrs", meanwhile global sea levels will have in all likelihood risen by more than 1 m from current levels. In fact estimates, keep getting revised upwards, not downwards. You are in denial contrarians. Further, your tricks of deception are growing very old. They might work to continue deluding yourself, but don't expect others to be fooled. Moderators, the contrarians , despite being shown the correct data and warned do look at the big picture on Arctic sea ice, Greenland ice mass and now GSL. My suggestion is that future posts which continue to cherry-pick, ignore the science and the facts be snipped.
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  26. Now given that contrarians like to focus on regional trends. Some new science that is not exactly reassuring. From ScienceDaily on a new paper by Howat et al. (2011) [in press], "In the last decade, two of the largest three glaciers draining that frozen landscape have lost enough ice that, if melted, could have filled Lake Erie. The three glaciers -- Helheim, Kangerdlugssuaq and Jakobshavn Isbrae -- are responsible for as much as one-fifth of the ice flowing out from Greenland into the ocean. "Jakobshavn alone drains somewhere between 15 and 20 percent of all the ice flowing outward from inland to the sea," explained Ian Howat, an assistant professor of earth sciences at Ohio State University. His study appears in the current issue of the journal Geophysical Research Letters." And talking of Howat, more "cheering" news, "A dramatic thinning, retreat, and speedup began in 1998 and continues today. The timing of the change is coincident with a 1.1°C warming of deep ocean waters entering the fjord after 1997. Assuming a linear relationship between thermal forcing and submarine melt rate, average melt rates should have increased by ∼25% (∼57 m yr−1), sufficient to destabilize the ice tongue and initiate the ice thinning and the retreat that followed." And yet more "cheering" news from the Arctic and Antarctica in another paper by Thomas et al. (2011), "Ice discharge from the fastest glaciers draining the Greenland and Antarctic ice sheets – Jakobshavn Isbrae (JI) and Pine Island Glacier (PIG)– continues to increase, and is now more than double that needed to balance snowfall in their catchment basins. Velocity increase probably resulted from decreased buttressing from thinning (and, for JI, breakup) of their floating ice tongues, and from reduced basal drag as grounding lines on both glaciers retreat. JI flows directly into the ocean as it becomes afloat, and here creep rates are proportional to the cube of bed depth. Rapid thinning of the PIG ice shelf increases the likelihood of its breakup, and subsequent rapid increase in discharge velocity. Results from a simple model indicate that JI velocities should almost double to >20 km a−1 by 2015, with velocities on PIG increasing to >10 km a−1 after breakup of its ice shelf. These high velocities would probably be sustained over many decades as the glaciers retreat within their long, very deep troughs. Resulting sea-level rise would average about 1.5 mm a−1." The contrarians and 'skeptics' posting here are in deep, deep denial. Fascinating and scary at the same time.
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  27. Albatross: I can only suggest that you read this paper. Some of us contrarians like to try and view SLR in its entirety.
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    Moderator Response: [Dikran Marsupial] hot linked paper
  28. And Albatross: How do you know your papers are correct verses other papers written by distinguished scholars?
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  29. camburn@78 Looking at the number of times the paper has been cited and in what context is usually a good start. Looking at the publication record and expertise of the authors is another. It is always a good idea to apply some skepticism to any new paper, because until there has been time for the research community to digest and either refute, take up or ignore the ideas it puts forward, we are not in a good position to judge its value. This is especially true of papers adopting a controversial stance, they generally turn out to be wrong - for every Galileo, there are thousands of scientists who are simply mistaken. This happens in all fields, not just climatology, I can tell you for certain there are loads of dud papers that get published every year on statistics. Generally their fate is that they are ignored and receive no citations. Most of the papers that form the underpinnings of AGW theory have been in print for a long time, have been widely discussed/criticized, and have withstood the criticism. That means they are very likely (but not certain of course) to be correct.
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  30. Ken Lambert wrote : "This cannot mean anything else than SLR slowing or decelerating - not accelerating." That is so obvious, if you're a so-called skeptic, is it not ? In fact, to take the 'obvious' further, into temperature increases, it is 'obvious' that while temperatures increase as Spring moves into Summer, eight or nine or ten days of cooler than average temperatures mean that temperatures are slowing or decelerating - not accelerating. It cannot mean anything else...if you're a so-called skeptic.
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  31. You are making a strawman argument @78 Camburn, and you know it. Are you going to deny the findings in the scientific literature that I posted @76? Houston and Dean is not good science-- I expect some poor overworked scientist who is an expert in the field now has to waste time refuting yet another dodgy scientific paper published by 'skeptics' in the scientific literature (peer-review is just the first step in establishing whether or not a paper is any good). It was probably also written to feed fodder to those in denial about the seriousness of AGW; people like you Camburn who will uncritically accept their convenient findings. In contrast, the findings of Church and White (2011) [I suggest that you read that, it is comprehensive and rigorous, much more so then Houston and Dean] are not convenient for me, nor do they make me feel better about the reality we are facing. But I am not going to think of every reason under the sun to delude myself that there is not a very real and serious issue that needs to be dealt with. Here is a yet reminder for you: [Source] Until an official refutation of Houston and Dean appears in the reputable literature, we will have make do with this critique of Dean and Houston by a professional statistician. To quote Tamino: "Why do they use tide gauge records from just U.S. stations? Why not a global sample? Why use individual tide gauge records when we have perfectly good combinations, from much larger samples, which give a global picture of sea level change and show vastly less noise? Why do they restrict their analysis to either the time span of the individual tide gauge records, or to the period from 1930 to 2009? Why do they repeatedly drone on about “deceleration” when the average of the acceleration rates they measure, even for their extremely limited and restricted sample, isn’t statistically significant?" And "As for the “bombshell” research from Houston & Dean, I have one more question: with bombshells like this, who needs creampuffs?" Next....
    0 0
  32. Nice analogy @80 JMurphy.
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  33. Albatross There is a certain irony in Camburn claiming that "Some of us contrarians like to try and view SLR in its entirety" immediately after directing you to a paper analysing SLR focussing on a small sample, of tide gauges from the US. ;o)
    0 0
  34. Indeed Dikran @83, if anything the 'skeptics' and those in denial about AGW are very consistent....normally that would be a good thing, but not so in this context.
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  35. I can only urge you folks to read both "Houston and Dean" and Church and White. Using statistical analysis, including error ranges, there is not a lot of difference in their findings. In fact....from Church and White "As in earlier sutdies (using 10 and 20 year windows; Church and White 2006; Church et al 2008), the most recent rate of rise over these short 16 year windows is at the upper end of histogram of trends, but is not statistically higher than the peaks during the 1940's and 1970's."
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  36. Dikran: If you cared to read the whole Houston and Dean paper, you will realize the analysis is much more than US tide gauges.
    0 0
  37. Camburn, I repeat, "Are you going to deny the findings in the scientific literature that I posted @76?"? Also, I am not sure how your quote @85 is meant to support your argument...nice cherry picking too. From Church and White's (2011) abstract: "There is considerable variability in the rate of rise during the twentieth century but there has been a statistically significant acceleration since 1880 and 1900 of 0.009 ± 0.003 mm year-2 and 0.009 ± 0.004 mm year-2, respectively. Since the start of the altimeter record in 1993, global average sea level rose at a rate near the upper end of the sea level projections of the Intergovernmental Panel on Climate Change’s Third and Fourth Assessment Reports" Sea level change for 1870-2001, based on tide gauge measurements, from Church J.A. and White N.J. "A 20th century acceleration in global sea-level rise" Geophys. Res. Lett. 2006; 33: L01602. University of Colorado data are shifted to have the same mean for 1993-2001 as Church and White. The trends were computed for 1870-1920, 1920-1975, 1975-2001 for Church and White data, and 1993 - late January 2011 for University of Colorado data. [Source] As for the recent increases, from Tamino's analysis: "Well well … there seems to be change after all, with both acceleration and deceleration but most recently, acceleration. And by the way, this fit is significant." Tamino also makes this sage observation and calls the 'skeptics' on their game: "And now to the really important part, which is not the math but the physics. Whether sea level showed 20th-century acceleration or not, it’s the century coming up which is of concern. And during this century, we expect acceleration of sea level rise because of physics. Not only will there likely be nonlinear response to thermal expansion of the oceans, when the ice sheets become major contributors to sea level rise, they will dominate the equation. Their impact could be tremendous, it could be sudden, and it could be horrible." Next...
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  38. Albatross: I have no quible with your post at 76, nor am I alarmed by it at present. Sea Level. 1. first off, what are the error bars of the satillite data. The authors of the papers take them into account and present them. 2. GMSL.....both papers that are being talked about express the difficulty in even DETERMINING current GMSL. 3. GPS as an added source to verify information. Not enough time yet, but hopefully within the next 10 years this valuable tool will provide insight into sea level rise, rate, and actual GMSL.
    0 0
  39. Bern & Dhogaza : I don't understand what you mean by local effects and land rising - I thought that satellites measure only the sea level, so why would they be influenced by land rising and anything that happens to coastlines ? I understood that GIA was a global -not local - effect increasing the overall volume of the ocean basin, but it is a real effect. In any case it doesn't change anything to the acceleration term Albatross : the plot of Church & White 2006 is without GIA correction, so actually the rate would have been 3.4 mm/yr in 2006 with GIA correction, and now it is only 3.1 mm/yr, right ?
    0 0

    [DB] Actually, glacial isostatic adjustment (GIA), or isostatic rebound, is a regional effect, confined primarily to areas formerly and currently covered (but losing mass) by continental ice sheets and the areas immediately adjacent to them.  As the basement rocks are relieved of the immense overburden of ice, they rebound upward.  Since the areas next to them had been pushed up slightly while the glaciated areas were depressed, those adjacent areas tend to sink back downwards. This is all well-studied and understood and is incorporated into tide gauge and satellite data.

    For further reference, I suggest this Wiki page as a start, plus this page at SkS:  Greenland-rising-faster-as-ice-loss-accelerates

    You may want to look into the Geoid and Datums if you want even more detail.

  40. Camburn, do you still assert that sea level rise is decelerating, having seen the graphs and sources presented by Albatross in #81 and #87?
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  41. okatiniko. Land rising and coastlines? Remember that GIA includes downward as well as upward movements. Britain is the classic example. The 'advancing' sea in southern England coastal regions is really more like a leverage effect from the rising Scotland land mass. The sea is not advancing so much as the land, in some areas of England, is lowering. Unfortunately, there's no guarantee that the rising/ lowering effects will be matched either in time or in extent. So the GIA numbers are calculated separately to be introduced into the SLR calculations.
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  42. Skywatcher: From the link so graciously given by Albatross: "Greenland and Antarctica have begun to melt faster in the past few years, as shown on Ice Sheet Disintegration page, yet sea level rise slowed slightly in the past few years." So, someone else seems to think that the rate of sea level rise has slowed as well?
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  43. The reason for the slowing or the rate of rise seems to be this: "The reason seems to be that ocean heat storage decreased in the past five years reducing thermal expansion." So, that also tells us that the OHC of the ocean is going down. I have tried to show that to no avail, but at least the Univisity seems to understand this.
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  44. Camburn @93, the rate of expansion of water with increasing temperature changes with increasing temperature. And increase from 0 to 5 degree C will cause the sea water to contract. Another 5 degree increase will result in a four times greater expansion. A further increase of 5 degrees will result in a further expansion at nearly four times the rate for the preceding 5 degrees. Consequently, increases in temperature in the cold depths cause a smaller increase in MSL for the same amount of heat when compared to the surface. So, a reduction in the rate of steric sea level rise may only be telling us that heat is moving from the surface to the depths faster than it is accumulating at the surface.
    0 0
  45. Tom: Please note the table in the link provided. Average salinity for sea water is 35g/kg You will note that sea water expands from 0-5C.
    0 0
  46. DB at #58 DB is confusing me at #58. He seems to suggest that the UCAR satellite plot (top figure) needs further 'correction' and then includes Fig 7 from Church & White 2011 which is based on 'Coastal and Island Sea Level Data'. The latter shows an uptick in the 2000-2011 period. DB - please explaim which is the 'global' sea level measurement? I would have thought that the satellite series from UCAR meauring the surface of the oceans from orbit would be the best theoretical method. Practical degradation problems are encountered in all methods. Unless the instrument is degrading year-year in an uncorrectable way, satellites are supposed to have high precision in year-year measurement for the SAME instrument, with calibration difficulties between different instruments. Are you suggesting that the UCAR chart is not the best measure of global SLR?
    0 0
  47. Camburn, I am done engaging you. You are being disingenuous, and your recalcitrance is astounding. First cherry picking, then quote mining to misrepresent Church and White, and now more quote mining to misrepresent Hansen's group-- they are of the opinion that GMSL increase has slowed somewhat the last few years. Tamino has shown otherwise, but regardless Hansen and Sato are wisely most definitely are not using noise in the data record as a reason to claim that we are not facing a whole lot of trouble down the road if we continue along those path. So you have misrepresented Hansen's position. How about giving the full context of the text from Sato and Hansen's page (unlike your cherry-picked sentence): The reason seems to be that ocean heat storage decreased in the past five years reducing thermal expansion. Reduced heat storage may be related in part to solar minimum radiation. Ocean heat uptake will surely resume, so acceleration of sea level rise in the next few years may occur." That is the peril of you intentionally misleading people, your credibility tanks really fast. The following statement made by the Australian Climate Commission is accurate: "Sea-level has risen at a higher rate over the past two decades, consistent with ocean warming and an increasing contribution from the large polar ice sheets." Feel free to delude yourself, but it is highly irresponsible (and shameful) of you to try and mislead others on this forum. The quoted text by Tamio at #87 perfectly fits what you are trying to. Sadly you do not realize that your posts are only proving him right, again.
    0 0
  48. Albatross: My statement that sea level rise has slowed, which it has, was considered unreliable. I provided, from your link, what others have observed. There is nothing disingenuous about that. What has changed is that according to AGRO data, sea surface temps are presently static. This goes hand in hand with the reduction in the part of sea level rise caused by OHC. I use charts all the time in my business. One of the successful ways to use a chart it to recognize a change in a trend. We are now, for whatever reason, seeing a change in trend. Will it continue for 10 years? 20 years? I don't know, but the preponderance of current temperature evidence indicates that it may. The last sentence is an opinion....."Ocean heat uptake will surely resume, so acceleration of sea level rise in the next few years may occur." I was stateing known facts, not opinions. That is why I did not include it in my quote. The opinion may bear fruit, it may not bear fruit. I am not deluding myself in the least. The evidence is quit clear.
    0 0

    [DB] "What has changed is that according to AGRO data, sea surface temps are presently static.  This goes hand in hand with the reduction in the part of sea level rise caused by OHC."

    ARGO says otherwise:



    As for SST's, they change all the time with the sun rising and setting, with the seasons, and with those oscillations squeptics are so enamored with, like EN/SO:


    [Source; above graphic updates daily]

    The evidence is indeed quite clear.

  49. DB at #98 DB is confusing us at #98. viz: "ARGO says otherwise' - then reproducing Fig 1 of Levitus 2009. Only the 2003 and later portions of the chart are from ARGO. Reason: Full deployment did not start until the 2001-03 period. The step jump in this chart in that 2001-03 period has been discussed elsewhere - and is more likely an artifact of the splicing of Argo to pre-2001 XBT and other methods. Camburn has made several valid and reasonable points to be called 'recalcitrant, deluded, disingenuous' by Albatros. Why is Albatros immune from moderation?
    0 0

    [DB] "DB is confusing us at #98."


    "viz: "ARGO says otherwise' - then reproducing Fig 1 of Levitus 2009."

    If you had clicked on the image itself or had followed the source link you could have easily noted that the graphic in question is hosted by the ARGO website and is used by them to display the very same information as related here.

    "Camburn has made several valid and reasonable points"

    Which fail to stand up to scientific rigor and scrutiny.

  50. Daniel, To add to your Figure above @98. Long-term SST, statistically significant trends are very much UP. [Source]
    0 0

    [DB] Thank you.

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