Comments on this topic are closed. There is a new article on sea level where comments are welcome.
Sou24 October 2014
Anthony Watts has seen fit to post a rather silly comment from Eric Worrall about a new PNAS paper on sea level and ice. Anthony also adds his tuppence-worth. (Archived here.)
The paper is from a team led by Professor Kurt Lambeck of The Australian National University (ANU).
A fascinating journey up and down the seas
What the Kurt Lambeck and his co-authors have done is paint a wonderfully vivid 35,000 year history of changes in sea level and major ice sheets.
It's taken me a while to read the paper. In part because the subject matter is provided in rich detail, and in part because I found it so fascinating. It's extraordinarily well written. The authors have managed to cram a huge amount of information into the few words allowed by PNAS, while writing in a manner that a lay person like myself could understand.
I was struck by the intense CO2 phobia that commenters at WUWT suffer from. They obviously don't understand the carbon cycle or the role of carbon dioxide in climate. Nor do they understand the CO2/ocean interaction. A lot of them have never heard of Milanković cycles (and extensions to his theory). Not that I claim expertise or specialist knowledge, but the basics of all these are straightforward and not all that difficult to comprehend. (I did a search at WUWT for Milanković cycles and it's pretty clear why the people who don't venture beyond WUWT don't know anything about the subject.)
(If you're on the home page, click "read more" to find out more about the paper and see the reaction at WUWT.)
Wondering Willis Eschenbach writes another post about volcanoes, which he's done before on Anthony Watts' fake sceptics' blog, wattsupwiththat. When he's not speculating that occasional landings at remote airports are causing global warming, Willis is a proponent of a type of Gaia hypothesis. I believe he calls it his "thunderstorm hypothesis" or "thermostatic hypothesis". He thinks that the earth is self-regulating when it comes to climate and that it's regulated by tropical thunderstorms or some such thing. I won't go into the detail of his mathturbations in his article (archived here - updated WUWT archive here), but I will make a few observations.
Wondering Willis builds a strawman
First up Wondering Willis builds a strawman. He talks about an urban legend. He doesn't state which urban area has this legend but anyone who has read climate science would know that it's not a city in which climate research is carried out. He writes:
The amazing thing to me is that this urban legend about volcanoes having some big effect on the global average temperature is so hard to kill. I’ve analyzed it from a host of directions, and I can’t find any substance there at all … but it is widely believed.
The only volcanoes that have "some big effect on the global average temperature" or indeed any effect that's discernible enough to be measured are quite big volcanic eruptions, especially those that occur closer to the equator (but see update below). But from what I've read - in the main it takes a lot of detailed analysis to separate the signal of a single volcano from the noise in the temperature record. Dr Hansen and his colleagues on Pinatubo:
With a single volcano it may be hard to identify a climate "signal" among the large amount of weather and climate "noise", that is, the unforced chaotic fluctuations of the atmosphere and ocean. So the Pinatubo team first looked at the average climate response after the five largest volcanos this century. They found (Figure 1) that there was a small cooling, about 1/4°C (1/2°F), which peaked 1-2 years after the eruption. This tends to confirm that volcanos do cause a small global cooling.
Even so, the effect of a single volcano is temporary because aerosols eventually dissipate.
Another weird thing Wondering Willis writes is this - that climate sensitivity is 0.2 degrees Celsius. He says:
...At the end of the day, what we have is a calculated climate sensitivity (change in temperature with forcing) which is only about two-tenths of a degree per doubling of CO2.
Now that is truly weird. It's even odder because Willis himself in the very same article put up a chart of global temperature anomalies. He showed monthly anomalies of HadCRUT4. I'll show annual anomalies:
Over that period, global temperatures rose by around 0.8 degrees Celsius while carbon dioxide rose by around 40%. It has a way to go before it doubles. Willis inexplicably leaves a rise of around 0.7 degrees Celsius unexplained!
My question to Willis is - what has caused global surface temperature to rise by 0.8 degrees Celsius well before CO2 has doubled, if the climate sensitivity is only 0.2 degrees? (Willis has stated he is using climate sensitivity to mean the rise in global surface temperature from a doubling of CO2.)
The weirdest thing of the lot (not really, given it's WUWT) is that no-one at WUWT asks him this question. Not a soul.
How does Willis Eschenbach explain ice ages?
Short answer? He doesn't!
In the comments someone asks a good question. How does Willis Eschenbach reconcile glaciations and deglaciations with his "thermostatic" hypothesis:
Thomas says:
September 22, 2013 at 10:30 am
Jim S, the emissions from individual eruptions is pretty much negligible. Overall volcanoes emit around 1% of the amount from fossil fuels.
Maybe Eschenbach has written about it before, but I’m a bit confused on how he can reconcile “I hold that changes in forcing only marginally and briefly affect the temperature. Instead, I say that a host of emergent thermostatic phenomena act quickly to cool the planet when it is too warm, and to warm it when it is too cool” with the existence of ice age cycles. Whatever thermostat the Earth has doesn’t seem all that good.
In WUWT-land ice ages are caused by a "snap" and "flip" called "hits the rails"?
Greg Goodman comes to Willis' aid with a sciency explanation (WUWT-style): "we don't know" - but says it could be caused by a magic "snap" and "flip" called "hits the rails":
September 22, 2013 at 10:43 am
Thomas: ” Whatever thermostat the Earth has doesn’t seem all that good.”
what happens at glaciation and deglaciation is clearly different from what happens in between.
There is apparently two stable states ( attractors ) for the climate system. A positive feedback seems to make it snap form one state to the other. We don’t really know what triggers the change-over.
Assuming Willis is basically correct there are limits to the tropical storms range as a feedback mechanism. It cannot go beyond totally clear skies or fully cloud covered tropics. May be when it hits the rails the climate state flips?
I don’t see glaciation as being a major argument against what Willis is proposing.
Greg says that the pseudo-scientists at WUWT "don't really know" what causes ice ages!
In other words, Greg is saying that Wondering Willis' "thermostatic" or Gaia hypothesis is bunkum. Either that or he thinks that there is some huge sudden impact that has happened at the start of a glaciation and deglaciation. He doesn't know what this is.
Later in the thread, Willis directly responds to Thomas' question by avoiding it - and in the process shows he can't read his own chart. Willis says, after quoting Thomas' comment above:
The planet’s temperature varied by ± 0.3°C over the last century. This is a regulation to within about ± 0.1% … on a free-running system which is regulated by nothing more substantial than wind and water. If you know anything about heat engines, you’ll agree that that is a fantastic governor …September 22, 2013 at 1:10 pm
Willis has shrunk the observed temperature range in his own chart, which is a rise of 0.8 degrees Celsius to a mere ± 0.3°C. Wondering Willis has a very severe case of confirmation bias!
Climate scientists do know what precipitates an ice age
Although WUWT-ers don't know what precipitates ice ages, climate scientists do. Climate scientists have found that variations in eccentricity, axial tilt and precession of the Earth's orbit, when combined in a certain way, affect earth's energy balance with resulting feedbacks. A drop in surface temperature will cause atmospheric CO2 to fall which causes a further drop in surface temperature leading to an ice age; while a rise in surface temperature will cause CO2 to rise, which in turn affects global surface temperature causing the ice to melt. (Milankovitch cycles).
Here is an insight into Willis' thunderstorm hypothesis - if you can call in an insight. This is what Willis reckons happens "when the globe cools"!
When the globe cools, the tropical clouds form a few minutes later, the thunderstorms form a few minutes later … and that brings the global temperature back up. September 22, 2013 at 2:19 pm
WUWT-ers might think that Willis invented the notion that the hydrological cycle plays an important part in moderating the weather on earth, but of course he didn't. It's basic thermodynamics. When water evaporates it cools the surface. When it condenses into clouds the heat is moved to the atmosphere. But that's no more than an exchange of energy within the system. It doesn't explain the extra energy being stored on earth as evidenced by the recent very rapid warming. The only thing that explains that is the huge increase in atmospheric greenhouse gases.
Still, I expect the WUWT-ers will be relieved by Willis telling them that the earth won't have any more ice ages and that David "funny sunny" Archibald has it all wrong!
Update - Willis is "not even wrong" about Super-Volcanoes
Willis Eschenbach shows he doesn't keep up with the latest science when he says "temperature has always recovered" from supervolcanos and that his "hypothesis" explains this but "models" don't.
September 22, 2013 at 6:15 pm
Jim G says: September 22, 2013 at 5:10 pm A true super eruption of a super volcano might be at odds with your “self regulating” surface temperature hypothesis.
We’ve had supervolcanoes in the past, and the temperature has always recovered. Under the models’ view, that wouldn’t happen … with my hypothesis, it would.
w.
The “Super Volcano Project” is a crosscutting science projects of MPI-M in cooperation with the Univ. of Cambridge. At present the project involves ca 25 scientists from the MPI-M and 7 external scientists.
The major goal of this MPI-M Earth System Modelling (ESM) project is the investigation of the effects that volcanic super eruptions have on the climate system, employing the coupled MPI-M Earth System model. ...
Climate effect of larger volcanic eruptions are weaker and smaller than previously thought.
The global temperature signal is determined by the strength of the SO2 emission and not by the latitude of the eruption.
Post-eruption oceanic and atmospheric anomalies describe a decadal fluctuation in the coupled ocean–atmosphere system.
Improved description of processes acting on multidecadal timescales is pivotal to constrain the climate response to the 1809 and Tambora tropical eruptions.
Radiative heating from volcanic ash cause rotation of volcanic cloud, which influences the transport in the first days on local scale.
Eruption season has a significant influence on aerosol optical depth and clear-sky shortwave (SW) radiative flux anomalies and for large volcanic eruption also on the all sky SW flux anomalies.
Annular mode response after volcanic eruption increases logarithmically with increasing eruption magnitude.
Deposition of sulphate to the Antarctic polar ice sheet is strongly dependent on eruption magnitude
Mt. Pinatubo eruption causes the observed delay of the QBO cycle in 1991/1992.
Post-eruption sea ice anomalies show strong hemispheric differences dependent on the magnitude of the eruption.
Bare soil coverage is strongly increasing after a very large volcanic eruption with fewer trees and more grass.
Post-eruption atmospheric CO2 anomalies are explained mainly by changes in land carbon storage in the initial phase. In the longer term, the ocean compensates for the atmospheric carbon loss.
In the past couple of days, HotWhopper has had some visits by someone who seems to think the only thing that has a marked effect on climate is the sun. There was much talk of ice ages and insolation. So when I came across a couple of stories about ice and sunshine today, it seemed fortuitous.
Garwood Valley, Antarctica:- Tenfold increase of ancient melt rates
The first one is about Antarctica, specifically Garwood Valley near McMurdo Bay.
The valley is below freezing for most of the year. It's in a zone of continuous permafrost and has remnants of the Ross Sea Ice Sheet. It's the sun that is melting the ice more quickly. From the LA Times (my bold):
The tenfold increase from ancient melt rates evident in a dry valley near McMurdo Bay over little more than a decade comes despite a local two-decade cooling trend.
Cliff-face measurements of the buried ice in the four-mile-long Garwood Valley revealed melt rates that shifted from a creeping annual rate of about 40,000 cubic feet per year over six milleniums, to more than 402,000 cubic feet last year alone, according to the report published Wednesday in the journal Nature Scientific Reports. (That’s a leap from the capacity of about eight standard railroad boxcars to 77.)
“We think what we’re seeing here is sort of a crystal ball of what coastal Antarctica is going to experience,” said geologist Joseph Levy, of the University of Texas, lead author of the study. “When you start warming buried ice and other permafrost in the dry valley, it’s going to start to melt and it’s going to start melting in a style that’s consistent with permafrost thaw in the Arctic.”
Levy et al (2013) Accelerated thermokarst formation in the McMurdo Dry Valleys, Antarctica, Scientific Reports 3, Article number: 2269 doi:10.1038/srep02269
The mechanics of ice formation and retreat in an ice age
This second paper explains more about the ice ages - glaciation and retreat every 100,000 years or so.
Insolation + glaciated continents + climate
The ice ages that occur every 100,000 years or so are the product not just of variations in insolation, but also the mutual influence of glaciated continents and climate....
...Using computer simulations, a Japanese, Swiss and American team including Heinz Blatter, an emeritus professor of physical climatology at ETH Zurich, has now managed to demonstrate that the ice-age/warm-period interchange depends heavily on the alternating influence of continental ice sheets and climate.
The topography is completely different under ice
“If an entire continent is covered in a layer of ice that is 2,000 to 3,000 metres thick, the topography is completely different,” says Blatter, explaining this feedback effect. “This and the different albedo of glacial ice compared to ice-free earth lead to considerable changes in the surface temperature and the air circulation in the atmosphere.” Moreover, large-scale glaciation also alters the sea level and therefore the ocean currents, which also affects the climate.
Weak effect of insolation + feedback effects = strong impact
As the scientists from Tokyo University, ETH Zurich and Columbia University demonstrated in their paper published in the journal Nature, these feedback effects between the Earth and the climate occur on top of other known mechanisms. It has long been clear that the climate is greatly influenced by insolation on long-term time scales. Because the Earth’s rotation and its orbit around the sun periodically change slightly, the insolation also varies. If you examine this variation in detail, different overlapping cycles of around 20,000, 40,000 and 100,000 years are recognisable.
Given the fact that the 100,000-year insolation cycle is comparatively weak, scientists could not easily explain the prominent 100,000-year-cycle of the ice ages with this information alone. With the aid of the feedback effects, however, this is now possible.
Astronomical parameters, ground topography, climate and feedback effects
The researchers obtained their results from a comprehensive computer model, where they combined an ice-sheet simulation with an existing climate model, which enabled them to calculate the glaciation of the northern hemisphere for the last 400,000 years. The model not only takes the astronomical parameter values, ground topography and the physical flow properties of glacial ice into account but also especially the climate and feedback effects. “It’s the first time that the glaciation of the entire northern hemisphere has been simulated with a climate model that includes all the major aspects,” says Blatter.
Why ice ages start slowly and end quickly
Using the model, the researchers were also able to explain why ice ages always begin slowly and end relatively quickly. The ice-age ice masses accumulate over tens of thousands of years and recede within the space of a few thousand years. Now we know why: it is not only the surface temperature and precipitation that determine whether an ice sheet grows or shrinks. Due to the aforementioned feedback effects, its fate also depends on its size. “The larger the ice sheet, the colder the climate has to be to preserve it,” says Blatter. In the case of smaller continental ice sheets that are still forming, periods with a warmer climate are less likely to melt them. It is a different story with a large ice sheet that stretches into lower geographic latitudes: a comparatively brief warm spell of a few thousand years can be enough to cause an ice sheet to melt and herald the end of an ice age.
The Milankovitch cycles
The explanation for the cyclical alternation of ice and warm periods stems from Serbian mathematician Milutin Milankovitch (1879-1958), who calculated the changes in the Earth’s orbit and the resulting insolation on Earth, thus becoming the first to describe that the cyclical changes in insolation are the result of an overlapping of a whole series of cycles: the tilt of the Earth’s axis fluctuates by around two degrees in a 41,000-year cycle. Moreover, the Earth’s axis gyrates in a cycle of 26,000 years, much like a spinning top. Finally, the Earth’s elliptical orbit around the sun changes in a cycle of around 100,000 years in two respects: on the one hand, it changes from a weaker elliptical (circular) form into a stronger one. On the other hand, the axis of this ellipsis turns in the plane of the Earth’s orbit. The spinning of the Earth’s axis and the elliptical rotation of the axes cause the day on which the Earth is closest to the sun (perihelion) to migrate through the calendar year in a cycle of around 20,000 years: currently, it is at the beginning of January; in around 10,000 years, however, it will be at the beginning of July.
Based on his calculations, in 1941 Milankovitch postulated that insolation in the summer characterises the ice and warm periods at sixty-five degrees north, a theory that was rejected by the science community during his lifetime. From the 1970s, however, it gradually became clearer that it essentially coincides with the climate archives in marine sediments and ice cores. Nowadays, Milankovitch’s theory is widely accepted.
“Milankovitch’s idea that insolation determines the ice ages was right in principle,” says Blatter. “However, science soon recognised that additional feedback effects in the climate system were necessary to explain ice ages. We are now able to name and identify these effects accurately.”
Speak no more of the glacial epoch as 80,000 years agone. The glacial epoch is ahead. Sir Robert Ball says that the next ice age is due in 200,000 years. In the course of long periods the earth's orbit round the sun changes from being nearly a circle, as it is now, to a long ellipse or oval, and in the last case the summer may be only 166 days long, while the winter lasts 199 days. There is a short hot summer, followed by a long, excessively cold winter, so that more ice is formed in the cold than can be melted in the warm season.
On purely astronomical grounds, even if geologists had not discovered the ice ages from the records of the globe's surface, astronomers would have demonstrated that ice ages must have happened. When the next chilly epoch arrives posterity may see all Northern Europe under an ice-cap that will o'ertop the highest mountains and last for many thousands of years.
Interesting to look back over old news articles. This one pre-dates Milutin Milanković by a few years.
Sir Robert Stawell Ball FRS (1 July 1840, Dublin – 25 November 1913, Cambridge) was an Irishastronomer. He worked for Lord Rosse from 1865 to 1867. In 1867 he became Professor of Applied Mathematics at the Royal College of Science in Dublin.
