WUWT readers may recall yesterday where Dr. Mann was so eager to list this paper on his resume/CV, he broke the embargo set for 15:00 EST June 20th, today, at which time this blog post appears.
As much as this is an editorial target rich environment, I’m going to publish this press release and paper sans any editorial comment. There’s plenty of time for that later. Let’s all just take it in first. Below, figure 2 from the Kemp et al 2011 paper. It should look familiar. Note the reference in Figure 2 to GIA (Glacial Isostatic Adjustment) adjusted sea level data, which has recently been the subject of controversy, it was first noted here on WUWT.
First the press release:
Contact: Evan Lerner
215-573-6604
Penn researchers link fastest sea-level rise in 2 millennia to increasing temperatures
PHILADELPHIA — An international research team including University of Pennsylvania scientists has shown that the rate of sea-level rise along the U.S. Atlantic coast is greater now than at any time in the past 2,000 years and that there is a consistent link between changes in global mean surface temperature and sea level.
The research was conducted by members of the Department of Earth and Environmental Science in Penn’s School of Arts and Science: Benjamin Horton, associate professor and director of the Sea Level Research Laboratory, and postdoctoral fellow Andrew Kemp, now at Yale University’s Climate and Energy Institute.
Their work will be published in the journal Proceedings of the National Academy of Sciences on June 20.
“Sea-level rise is a potentially disastrous outcome of climate change, as rising temperatures melt land-based ice and warm ocean waters,” Horton said.
“Scenarios of future rise are dependent upon understanding the response of sea level to climate changes. Accurate estimates of past sea-level variability provide a context for such projections,” Kemp said.
In the new study, researchers provided the first continuous sea-level reconstruction for the past 2,000 years and compared variations in global temperature to changes in sea level during this time period.
The team found that sea level was relatively stable from 200 B.C. to 1,000 A.D. During a warm climate period beginning in the 11th century known as the Medieval Climate Anomaly, sea level rose by about half a millimeter per year for 400 years. There was then a second period of stable sea level associated with a cooler period, known as the Little Ice Age, which persisted until the late 19th century. Since the late 19th century, however, sea level has risen by more than 2 millimeters per year on average, which is the steepest rate for more than 2,100 years.
To reconstruct sea level, the research team used microfossils called foraminifera preserved in sediment cores from coastal salt marshes in North Carolina. The age of these cores was estimated using radiocarbon dating and several complementary techniques.
To ensure the validity of their approach, the team members confirmed their reconstructions against tide-gauge measurements from North Carolina for the past 80 years and global tide-gauge records for the past 300 years. A second reconstruction from Massachusetts confirmed their findings. The records were also corrected for contributions to sea-level rise made by vertical land movements.
The team’s research shows that the reconstructed changes in sea level during the past millennium are consistent with past global temperatures and can be described using a model relating the rate of sea-level rise to global temperature.
“The data from the past help to calibrate our model and will improve sea-level rise projections under scenarios of future temperature rise,” research team member Stefan Rahmstorf said.
In addition to Horton and Kemp, the research was conducted by Jeffrey Donnelly of the Woods Hole Oceanographic Institution, Michael Mann of Pennsylvania State University, Martin Vermeer of Finland’s Aalto University School of Engineering in Finland and Rahmstorf of Germany’s Potsdam Institute for Climate Impact Research.
Support for this research was provided by the National Science Foundation, the National Oceanic and Atmospheric Administration, United States Geological Survey, the Academy of Finland, the European Science Foundation through European Cooperation in Science and Technology and the University of Pennsylvania.
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Here’s the abstract:
Climate related sea-level variations over the past two millennia
Andrew C. Kempa,b, Benjamin P. Hortona,1, Jeffrey P. Donnellyc, Michael E. Mannd,
Martin Vermeere, and Stefan Rahmstorff
We present new sea-level reconstructions for the past 2100 y based on salt-marsh sedimentary sequences from the US Atlantic coast. The data from North Carolina reveal four phases of persistent sea-level change after correction for glacial isostatic adjustment.
Sea level was stable from at least BC 100 until AD 950. Sea level then increased for 400 y at a rate of 0.6 mm/y, followed by a further period of stable, or slightly falling, sea level that persisted until the late 19th century. Since then, sea level has risen at an average rate of 2.1 mm/y, representing the steepest century-scale increase of the past two millennia. This rate was initiated between AD 1865 and 1892. Using an extended semiempirical modeling approach, we show that these sea-level changes are consistent with global
temperature for at least the past millennium.
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Figure 1: Two points in salt Marshes in North Carolina are used as the basis for the study:
Materials and Methods
Sea level in North Carolina was reconstructed using transfer functions relating the distribution of salt-marsh foraminifera to tidal elevation (7, 12). Application of transfer functions to samples from two cores (at sites 120 km apart) of salt-marsh sediment provided estimates of PME with uncertainties of <0.1 m. For each core a probabilistic age-depth model (10) was developed from composite chronological results and allowed the age of any sample to be estimated with 95% confidence. In Massachusetts, plant macrofossils preserved in salt-marsh sediment overlying a glacial erratic, were dated using AMS 14C and pollen and pollution chronohorizons (Fig. S1). The modern distribution of common salt-marsh plants was used to estimate PME. Sea level was reconstructed by subtracting estimated PME from measured sample altitude. Corrections for GIA were estimated from local (13) and US Atlantic coast (15) databases of late Holocene sea-level index points. Detailed methods are presented in SI Text.
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They compare data at points around the world to the new SL hockey stick (in pink in the background):
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Conclusions
We have presented a unique, high-resolution sea-level reconstruction developed using salt-marsh sediments for the last 2100 y from the US Atlantic coast. Post-AD 1000, these sea-level reconstructions are compatible with reconstructions of global temperature, assuming a linear relation between temperature and the rate of sea-level rise. This consistency mutually reinforces the credibility of the temperature and sea-level reconstructions. According to our analysis, North Carolina sea level was stable
from BC 100 to AD 950. Sea level rose at a rate of 0.6 mm/y from about AD 950 to 1400 as a consequence of Medieval warmth, although there is a difference in timing when compared to other proxy sea-level records. North Carolina and other records show
sea level was stable from AD 1400 until the end of the 19th century due to cooler temperatures associated with the Little Ice Age. A second increase in the rate of sea-level rise occurred around AD 1880–1920; in North Carolina the mean rate of rise was 2.1 mm/y in response to 20th century warming. This historical rate of rise was greater than any other persistent, century-scale trend during the past 2100 y.
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The full paper is available here: PNAS_Kemp-etal_2011_Sea_level_rise
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Maybe we could pick back up on just how the oceans are warming. Sea level rise is attributed to many things but AGW’ers think it is because the ocean is absorbing far infrared heat re-emitted by greenhouse gases to such a degree that it is significantly related to this rise: more greenhouse gas – more atmospheric heat re-entering the oceans at the sea surface – warmer ocean – greater sea level rise. There are lots of “papers” out there that say the oceans are anthropogenically warming. They link correlation with an as yet unmechanized cause. So they usually don’t specify the mechanism or show their maths. They just state that it does. Kind of like Sunners who state that it is the Sun.
Papers and bloggers who link ocean warming with AGW heat transfer from the air to the ocean should be required to prove it. State the mechanism and show the maths.
Mike Jonas says:
June 23, 2011 at 4:19 pm
I note that you have not replied to my comment http://wattsupwiththat.com/2011/06/20/manns-new-sea-level-hockey-stick-paper/#comment-686300, addressed to you, in which I explain how other physical observations also disprove the models, and how the models are built on supposition (cloud feedback)
And
“If the troposphere warms more, then the hypothesis is verified (NB. not proved), but if the surface warms more, then the hypothesis is disproved. Others (Roy Spencer, eg) have done more sophisticated analyses than me, and found the hypothesis disproved,”
I have not had chance to look at look at cloud feedback, but on the tropospheric hotspot…
I went through this at great length before, to no avail. So, to repeat, the tropospheric hotpsot is not a signature of GHGs. Of course, no one here believes me, so how about Dr. Roy Spencer himself (emphasis mine):
“But the hotspot is not a unique signature of manmade greenhouse gases. It simply reflects anomalous heating of the troposphere — no matter what its source. Anomalous heating gets spread throughout the depth of the troposphere by convection, and greater temperature rise in the upper troposphere than in the lower troposphere is because of latent heat release (rainfall formation) there.
For instance, a natural decrease in cloud cover would have had the same effect. It would lead to increased solar warming of the ocean, followed by warming and humidifying of the global atmosphere and an acceleration of the hydrologic cycle.
Thus, while possibly significant from the standpoint of indicating problems with feedbacks in climate models,the lack of a hotspot no more disproves manmade global warming than the existence of the hotspot would have proved manmade global warming. At most, it would be evidence that the warming influence of increasing GHGs in the models has been exaggerated, probably due to exaggerated positive feedback from water vapor.”
http://www.drroyspencer.com/2009/10/hotspots-and-fingerprints/
John said:
“Edim said “Soon, the atmospheric CO2 will follow”. How do you figure that? I can see why you might doubt that CO2 caused the warming, but are you also doubting the the CO2 was from human emissions at all?”
John,
I think more of the atmospheric CO2 increase (~1960 – ~2000) was from the warming than from anthropogenic emissions. I also think that natural CO2 cycle(s)/fluxes are still uncertain, but it can still be concluded that natural inputs/outputs are overwhelming, compared to anthropogenic input. Furthermore, even variations of natural inputs/outputs are overwhelming, compared to ACO2 input.
We have a test in the making, thanks to nature. If the cooling continues, which is very likely, I predict atmospheric CO2 will decrease.
John B – re the last para that you quote from Roy Spencer “Thus, while possibly significant from the standpoint of indicating problems with feedbacks in climate models, the lack of a hotspot no more disproves manmade global warming than the existence of the hotspot would have proved manmade global warming. At most, it would be evidence that the warming influence of increasing GHGs in the models has been exaggerated, probably due to exaggerated positive feedback from water vapor.“. [my bold]
Please note that I drew attention to the lack of a tropical troposphere hotspot precisely in the context of feedbacks and exaggeration of the warming effects of GHGs. Also please note that I didn’t claim that “the lack of a hotspot” disproved AGW, but that the failure of the tropical troposphere to warm as much as the surface did disprove AGW (check my original wording “if the surface warms more, then the hypothesis is disproved“). A subtle distinction maybe, but very important.
Jonas,
I am trying to unsderstand your subtle distinction. I thought that in common usage, the “lack of a hotspot” is synonymous with “the surface warms more”. Are you saying they are different things? can you provide links to others making this subtle distinction?
It seems we agree that the lack or otherwise of a tropospheric hotspot does not disprove AGW. On what is your claim that ““if the surface warms more, then the hypothesis is disproved“ based?
John
John – “lack of a hotspot” includes the situation where there is no discernable difference. Under the AGW hypothesis, the warming begins in the tropical troposphere and the heat flows by various means from there to the surface. Under that hypothesis, it is therefore not possible for the tropical troposphere to heat by less than the surface. It is possible, however, if the heat distribution mechanisms are efficient, for the the surface to warm at virtually the same rate.
If the surface warms more than the troposphere – as it does indeed appear to do – then the extra heat cannot be flowing primarily from the troposphere to the surface. If there is any connection between troposphere and surface (and I think everyone agrees that there is), then the extra heat must be flowing from the surface to the troposphere.
@Mike Jonas
You really need to do some reading on the greenhouse effect:
“Because it is warm, the surface radiates far IR thermal radiation that consists of wavelengths that are predominantly much longer than the wavelengths that were absorbed. Most of this thermal radiation is absorbed by the atmosphere and re-radiated both upwards and downwards; that radiated downwards is absorbed by the Earth’s surface.”
i.e. the greenhouse effect warms the surface (which then warms the lower atmosphere)
http://en.wikipedia.org/wiki/Greenhouse_effect
John B once again tries to re-frame the discussion, this time away from what Mike Jonas wrote. Why? Because the “fingerprint of AGW”, the tropo hotspot, never appeared as widely predicted by the alarmist crowd, as shown by Prof Ross McKittrick: click
As Mike Jonas pointed out, the 2nd Law does not allow a net heat flow from a colder [troposphere] to a warmer region [land], thus debunking the predictions by the warmist contingent. John B can either admit the predictions were wrong… or tapdance.
Smokey, for Pete’s sake. Nobody (sane) argues that the greenhouse effect violates the 2nd law of thermodynamics. And on the hotspot, argue it out with Dr. Roy Spencer!
http://en.wikipedia.org/wiki/Greenhouse_effect
http://www.drroyspencer.com/2009/10/hotspots-and-fingerprints/
John B – sorry, but you haven’t read that correctly.
The explanation in Wikipedia is essentially correct. What happens is this (direct Wiki quotes are in italics):
Solar radiation at the high frequencies of visible light passes through the atmosphere to warm the planetary surface […]. This process happens all the time, and at this stage has no connection with global warming. It is simply saying that the continuous stream of sunlight warms the surface. The significance of the high frequencies is that they pass through the atmospheric GHGs with very little absorption on their way to the surface. The part that you quoted – “because it is warm […]” – is saying simply that the the surface is warm (from the sun), and it is not yet a reference to global warming.
[…] which then emits this energy at the lower frequencies of infrared thermal radiation. Again, this is a continuous process and still has no connection with global warming, not quite yet.
But now the AGW hypothesis kicks in: [the outgoing] Infrared radiation is absorbed by greenhouse gases, which in turn re-radiate much of the energy to the surface and lower atmosphere.. Because there are more GHGs in the atmosphere than there used to be – attributed to man-made emissions – AGW hypothesis says that more of the outgoing IR is absorbed and re-radiated back to (amongst other places) the surface. It is significant that the mechanism here is that when the GHGs absorb the outgoing IR, they heat up, and it is the extra heat that causes them to re-radiate more IR. In other words, the increase in re-radiated IR is driven only by the higher temperature of the GHGs. Because the surface is now receiving more re-radiated IR than it was before, it doesn’t cool quite as fast as it did, ie. it warms up. The significance of the “lower frequencies” is that, unlike the original higher frequencies of the incoming sunlight, these frequencies are absorbed by the GHGs.
So, according to AGW hypothesis, the global warming begins when GHGs in the tropical troposphere heat up. It is shown pictorially in IPCC report AR4 Fig. 9.1(c).
The extra IR returned by the troposphere GHGs to the surface is generated by extra heat in the GHGs. The amount by which it heats the surface cannot be more than the amount by which the troposphere has heated. Actual temperature measurements indicate that the surface has in fact warmed more.
Virtually no-one disputes the basic mechanism involving IR and GHGs. But there is dispute over whether the GHGs have reached the limit of their ability to absorb and re-radiate IR (in which case there will be no further warming from this mechanism), and even if they haven’t reached their limit, there is dispute over the extent of the extra warming. If the mechanism is, as claimed, responsible for most of the observed temperature increase, then the tropical troposphere must warm by more than the surface. It does not. Therefore something else must be causing most of the warming.
Mike,
There is one flaw (that I can see) in your argument. It is where you say: “In other words, the increase in re-radiated IR is driven only by the higher temperature of the GHGs.”
from here:
http://en.wikipedia.org/wiki/Electromagnetic_radiation
“When electromagnetic radiation is incident on matter, it causes the charged particles to oscillate and gain energy. The ultimate fate of this energy depends on the situation. It could be immediately re-radiated and appear as scattered, reflected, or transmitted radiation. It may also get dissipated into other microscopic motions within the matter, coming to thermal equilibrium and manifesting itself as thermal energy in the material.”
In the GH effect, it is the re-radiation that is important. Some of the energy absorbed by the GHGs get “dissipated” and becomes “thermal energy” (i.e. warms up the atmosphere), but the re-radiated portion does not change the temperature of the atmosphere. In a gas, the ratio of re-radiated energy vs. dissipated energy if much higher than in a solid or a liquid due to the relatively long time between collisions of gas molecules. That is why the IR energy is <primarily scattered by the GHGs in the atmosphere, but primarily dissipated (i.e. absorbed as warming) at the surface.
Apologies if I described it poorly but that is, as I understand it, the generally acepted explanation.
And back to the hotspot, it is not caused by the GH effect. It is caused by the “moist adiabatic lapse rate”. Hence, as even Dr. Roy Spencer agrees (not an appeal to authority, just an interesting example), the tropical tropospheric hotspot is not a signature of AGW.
John B – I am going partly by logic and partly by the IPCC report eg. 9.2.2.1 “Greenhouse gas forcing is expected to produce warming in the troposphere, cooling in the stratosphere, and, for transient simulations, somewhat more warming near the surface in the NH due to its larger land fraction, which has a shorter surface response time to the warming than do ocean regions (Figure 9.1c). […] The simulated responses to natural forcing are distinct from those due to the anthropogenic forcings described above. Solar forcing results in a general warming of the atmosphere (Figure 9.1a)“. [my bold]
Figure 9.1 is here: http://members.westnet.com.au/jonas1/IPCCFig9p1_LowRes.jpg, and the caption is: “Figure 9.1. Zonal mean atmospheric temperature change from 1890 to 1999 (°C per century) as simulated by the PCM model from (a) solar forcing, (b) volcanoes, (c) wellmixed greenhouse gases, (d) tropospheric and stratospheric ozone changes, (e) direct sulphate aerosol forcing and (f) the sum of all forcings.“.
I am also going by observation. Observation, that is, (a) that there isn’t an observation that tallies with the IPCC report, and (b) that the AGW scientists (Sherwood, eg.) have tried desperately to show that there is.
There is only one reference to adiabatic lapse rate that I can see in the IPCC report, in 8.6.3.1.1 “At low latitudes, GCMs show negative lapse rate feedback because of their tendency towards a moist adiabatic lapse rate, producing amplified warming aloft. “. It doesn’t look like that is happening either, or maybe it too is weaker than the natural forces that the IPCC has missed.
Smokey – you say “As Mike Jonas pointed out, the 2nd Law does not allow a net heat flow from a colder [troposphere] to a warmer region [land], thus debunking the predictions by the warmist contingent.“.
That isn’t actually what I was saying, though it might have sounded like it. The part of the AGW hypothesis that I was addressing doesn’t require a net heat flow from a colder region to a hotter region, it only requires the rate of net heat flow from the hotter region to decrease. But the fact does still remain that it isn’t possible for an increase in temperature in the colder region to produce a greater increase in temperature in the hotter region. I have done back-of-envelope calcs based on Stefan-Bolzmann, and get a factor of around 2 at equilibrium, but that is of course not the real-world situation. Wikipedia http://en.wikipedia.org/wiki/UAH_satellite_temperature_dataset says “Climate models predict … in the tropics, the troposphere should warm about 1.5 times more than the surface“, and SPPI http://scienceandpublicpolicy.org/monckton/greenhouse_warming_what_greenhouse_warming_.html says “Within the tropical “hot-spot” at about 8 to 12 km altitude, the [predicted] rate of increase in warming is more than twice and up to three times the rate of increase in warming at the Earth’s surface.“. Better references would be nice. I don’t think the IPCC report puts a specific figure on it.
In an earlier comment, I said re the AGW hypothesis “… it is therefore not possible for the tropical troposphere to heat by less than the surface. It is possible, however, if the heat distribution mechanisms are efficient, for the the surface to warm at virtually the same rate.“. On reflection, I don’t think the latter part of that is correct – I think the troposphere does actually have to warm at a greater rate. However, what I did say gave AGW a lower hurdle, and it still failed.