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There are questions that require answers,
1. The source of internal variability;
2. how that evolves over time; and
3. how that modulates the planetary energy budget?
" We are living in a world driven out of equilibrium. Energy is constantly delivered from the sun to the earth. Some of the energy is converted chemically, while most of it is radiated back into space, or drives complex dissipative structures, with our weather being the best known example. We also find regular structures on much smaller scales, like the ripples in the windblown sand, the intricate structure of animal coats, the beautiful pattern of mollusks or even in the propagation of electrical signals in the heart muscle. It is the goal of pattern formation to understand nonequilibrium systems in which the nonlinearities conspire to generate spatio-temporal structures or pattern. Many of these systems can be described by coupled nonlinear partial differential equations, and one could argue that it is the field of pattern formation is trying to find unifying concepts underlying these equations." http://www.ds.mpg.de/LFPB/chaos
Patterns in the Earth system are perturbation - greenhouse gases, solar, orbital variability - induced regime shifts in quasi standing waves - ENSO, PDO, AMO, AMOC, PNA, IOD, etc. - in the infinitely coupled spatio-temporal chaotic flow field of our spinning nonequilibrium planet.
It evolves as perpetual change in regimes at decadal to millennial scales. At a decadal scale in the modern era?
The PDO is part of the Interdecadal Pacific Oscillation (IPO) that has implications for the global energy budget via Rayleigh-Bénard convection - as in the Max Planck Institute link above.
But evident in TOA energy flux. It results in changes in the outgoing energy flux of the planet and modulates long term heat accumulation in oceans dependent on long term changes to the mean Pacific state especially.
Kevin Tremberth asked if the hiatus is over.
The gyre hypothesis is that solar mediated polar surface pressure anomalies drive ocean circulation in all the oceans - and upwelling in the eastern Pacific. The hiatus is about to start - within a decade perhaps as the sun dims and climate shifts again. If it is not happening now.
Welcome to the world of climate science. There is a lot of magical thinking involved and it gets deeper the more you dig into it. I’ve read papers where there are hundreds of estimates and assumptions but the authors seem to have supreme confidence in their findings. It is a world unto itself.
But a tangential benefit is that when problems are pointed out or questions raised the ad hominem attacks begin. A joy to watch and one reason I took an interest in the issue, since 20 years ago I accepted the whole package of AGW.
<blockquote>I don’t understand why you said this Javier.</blockquote>
I'll write an article about it in the future so I can show the evidence, but the effect of solar activity on climate is asymmetric. Low solar activity has a disproportionate effect on climate, much larger than high solar activity. That is the reason why there are no warming Abrupt Climate Events (ACEs) during the Holocene. Not a single one has been identified and named. By contrast there are about 10 cooling ACEs identified. Climate change is also asymmetric. Obviously such asymmetric effect cannot be due to linear changes in TSI. The mechanism is partially identified and acts at the atmosphere level, not at the sea surface level. It may be mediated by ozone from changes in UV.
It is surprising that the cooling bias of Holocene ACEs has not been given any attention.
I’m interested in your thoughts about what caused the warming during the Roman Warm Period and the MWP. For the sake of discussion I would like to set aside the usual debate about the amplitude, synchronicity and global coverage of the previous warm periods and, if you agree, stipulate that some warming took place in some parts of the globe for some extended periods of time. If there was warming regardless of where, timing and amount for those periods, what do you see as the mechanisms or causes at play?
"Cryospheric effects from sea‐ice extent and snow cover, oceanic effects from North Atlantic sea‐surface temperatures and tropical influences such as the El‐Niño Southern Oscillation, and stratospheric effects due to stratospheric circulation variability, solar variability, volcanic eruptions and the Quasi‐Biennial Oscillation are all identified in the literature as factors that impact on the Atlantic Polar Front jet stream. These drivers of jet stream variability can oppose or reinforce one another, and there are some indications of possible nonlinear interactions between them."
Solar variability may bias the system to one state or other - but a focus on one driver of polar annular modes is misguided. AGW is one of these drivers and collectively they result in AMOC and ice sheet feedbacks.
Reblogged this on <a href="https://hifast.wordpress.com/2019/01/05/sea-levels-atmospheric-pressure-and-land-temperature-during-glacial-maxima/" rel="nofollow">Climate Collections</a>.
For a standard atmospheric lapse rate of 6.49 deg C/km, the 195 m change would be equivalent to 1.27 deg C.
Interesting, but some of it doesn't seem quite right - I'll need to think about it a bit more. But, for example ...
- "Taking 100 m as a working estimate for average deformation, this volume had to be filled with air molecules causing a further drop in global atmospheric pressure." - I don't see why the land dropping should cause a drop in atmospheric pressure; the same surface area is under the same air volume. Maybe the whole atmosphere just drops a bit, rather than expanding to keep the TOA at the same place?
- "Forests rot much faster than they grow and a tropical/subtropical area the size of Brazil would have been submerged in just a few thousand years." - Is this really so? A few thousand years to be submerged and rot is surely far more time than would be needed for a forest to grow??
I am also skeptical that forests rot much faster than they grow. In anaerobic marsh conditions, logs can last a very long time.
> I am an economist/econometrician by training (1963-68) so, though stale in practice, I can spot foolishness in calculation, estimation and regression.
I am a ninja, and can spot Freedom Fighters:
Board of Trustees
Mr. Gregory M. van Kipnis, Chairman
Debiasing is minimal in that time peroid.
Judith: Some comments that may be ofvalue:
1) All too often "confidence" is the Bayesian output of evidence and a prior based on personal expectations/objectives. That may explain why the description of levels of confidence all sound more confident than you find appropriate. You might want to try to get such descriptions vetted by a group without an agenda and that doesn't know how they will be used.
2) Who cares whether the last thirty years is the warmest period in the past millennium or two millennia or ten millennia? If it wasn't true in 2000 (AR3), it may have hasn't happened since, and it will happen sooner (if climate sensitivity is high, AOGCMs) or later (EBMs). AFAIK, the nearly 1 K of warming we have experienced in the last half century is one of the biggest fluctuations in the Holocene proxy record - and it comes after the warming that ended the LIA. Mid-century wasn't an unusually cold starting spot! Recognition of an appropriately larger role for unforced and naturally-forced variability is a reasonable objective, but recognition for the possibility of a lower climate sensitivity is THE most important goal. That drives estimates of the social cost of carbon and all policymaking. And unforced variability undermines confidence in low CS from EBMs. (For me personally, the debate about the MWP is most useful in demonstrating how politics has corrupted climate science.)
3) Why is our National Climate Assessment duplicating the work of the IPCC and not focusing on issues of special importance to the US? In paleoclimate, the extreme droughts in the Southwest during? the MWP are far more important than the temperature of the MWP.
" if you agree, stipulate that some warming took place in some parts of the globe for some extended periods of time."
Can we also agree that no global warming occurred to any significant degree as indicated by the negligible changes in sea level from geology and eclipse records and the slightly increasing land ice mass balance during the Holocene.
Javier: An volcanic forcing is the perfect reason for abrupt cooling events in the alleged absence of abrupt warming events. Wasn't the 97/98 an abrupt warming event?
Given the stratification of the ocean - a warmer, less dense mixed layer floating on a much colder deeper ocean - the ocean become more unstable in the presence of surface cooling and more stable in the presence of warming.
Frank: I liked this post. However, I wish the index for ENSO was decoupled from overall warming. The oldest index was based on the atmospheric pressure difference between Tahiti and ?. That pressure difference drives the shift in winds from east to west to west to east and the amount of warm water moving east. Atmospheric pressure is conserved; it doesn't drift with global warming.
Greg wrote: "I would have expected, and therefore wrongly assumed, that the insulating effect of H2O, CO2, CH4, or other gases, would have been calculated in the laboratory under controlled conditions. That is normal practice in science when trying to determine the insulating properties of many substances."
Those laboratory experiments and [radiative transfer] calculations have been done and form the foundation for our expectations about radiative forcing. However, the reduction in the rate of radiative cooling to space caused by say a doubling of CO2 depends on the composition (including clouds) and temperature of the atmosphere through which thermal IR is traveling. The idea that an instantaneous doubling of CO2 causes a 3.7 W/m2 instantaneous reduction in radiative cooling to space comes from the most thorough calculations based on the atmosphere as it currently is. However, different AOGCMs with 2XCO2 produce atmospheres somewhat different from today and each other and the reduction associated with 2XCO2 ranges from about 2.5 to 4.5 W/m2 in these models. "Effective radiative forcing" for all agents have been derived from experiments with AOGCM. See: https://en.wikipedia.org/wiki/Schwarzschild%27s_equation_for_radiative_transfer
Greg wrote: "You have made ∆T a relationship with a single regressor, i.e., an instrumental variable ∆F, as if it is exogenous. However, there is good reason to believe ∆F is itself a function of other independent and dependent variables. Econometricians struggle with this all the time and wish they con run controlled experiments."
∆F is the sum of the change in radiative imbalance at the top of the atmosphere determined for all "forcings", mostly anthropogenic ones. In economics, all? inputs may be expressed in dollars, while in climate science W/m2 are the "currency". In the real world, forcing is not uniformly distributed over the globe, so a global average forcing measured in W/m2 is a first approximation.
When instantaneous radiative forcing is used, there is a second kind of input called a feedback which is expressed in terms of W/m2/K. Water vapor is a potent GHG and rising water vapor associated with warmer temps reduces radiative cooling to space proportionately to rising temperature. You probably have also heard of lapse rate feedback, surface albedo ("ice-albedo") feedback, and a variety of cloud feedbacks in both the SWR and LWR channels involving changing cloud amount, altitude, etc. Cloud feedback is the big unknown. If you sum up all of the feedbacks including "Planck feedback" (the increased emission of thermal IR with temperature), one obtains an overall climate feedback parameter measured in W/m2 that tells us how much more radiation the planet emits or reflects per degK of warming. If you knew the climate feedback parameter (in W/m2/K), you could calculate the amount of steady state warming needed to eliminate the radiative imbalance created by a forcing. However, climate scientists prefer to discuss the reciprocal of the climate feedback parameter and replace W/m2 with doublings of CO2 (1 doubling = about 3.5 W/m2). The result is equilibrium climate sensitivity (ECS) expressed in terms of K/doubling, and then doubling is omitted. (ERF is supposed to include the effect of all these feedbacks in the measurement of forcing.)
Frank: Thanks for standing by and lining out some basics for some disputants. I appreceate your positive feedback. The index SOI ( delta p Tahiti/Darwin) is very volatile and influenced also by the Madden Julien Oscillation. Therefore the MEI also takes advantage from the SST (i.e. Nino3,4) which are also forced. "Tamino" used this index ( as many others IMO) without mentioning the forcing. It's a small amount however I mentioned it for completness.
And Christie (!) used a "cumulative MEI index" to prove that global warming wasn't driven by radiative forcing! IMO, things would be cleaner with a proxy based on the SOI. Could you smooth out the 2-month? MJO and retain the ENSO signal (6+ month? rise and fall)? You know what you are looking for: something with a high correlation to the MEI without the baseline drift and possibly leading the MEI slightly since it take some time for the winds (theoretically driven by the pressure difference) to move warm water to the east. I presume that warmer water in the Eastern Equatorial Pacific transfers heat to the atmosphere and that air warms the rest of planet. Again, a slight lag is likely.
Thank you for this interesting post.
<blockquote>Slow cooling leads to a glacial minimum at about -120m below the present level, rapid warming to a new equilibrium at around current values. The question is not so much why these cycles occur, but why do they stop at these depths?</blockquote>
I suggest the answer to this question might be that the glacial cycles are roughly the same time span (82 ka to 123 ka, or roughly 100 ka); GMST declines for about 80 ka, rises over about 10 ka, and interglacial is about 10 ka. GMST has declined by about the same amount over the cooling period and risen about the same amount over the warming period in each glacial cycle over the last 500 ka. So, roughly the same amount of water is held in ice at each glacial maximum, and similarly at each glacial minimum. Therefore, the sea level range is roughly similar in each of the glacial cycles. Much more water was tied up in ice during Snowball Earth periods, than now, and much less when there was no polar ice sheets (which was the case for ~75% of the past 500 Ma).
Leaving this aside, I am interested in your comments about the amount of carbon tied up in the biosphere during glacial versus interglacial times. IPCC AR4 WG1 Chapter 6 says there is about 50% more carbon tied up in the biosphere now than at the LGM. Is this consistent with what you are saying?
I understand that during the Eocene Thermal Optimum, 50 Ma ago, GMST was about 11 C warmer than present, and average temperature of tropical seas was about 6 C warmer than at present. Tropical rain forests extended from pole to pole. Crocodiles and frost intolerant vegetation, such as palm trees, existed in the polar regions. That indicates no frosts even during 6 months of night. The mass of carbon tied up in the biosphere was some 5 times higher than now. CO2 concentrations in the atmosphere was about 1000 ppm.
These conditions suggest that, during the Eocene Thermal Maximum,
• sea levels were high (no ice caps),
• CO2 concentration was high (~1000 ppm), and
• the mass of carbon tied up in the biosphere was ~5 times higher than now.
Can the high CO2 concentration and high mass of carbon in the biosphere be explained?
Is the answer that the mass of C in the oceans and in carbonate deposits in the oceans reduced?
>Can the high CO2 concentration and high mass of carbon in the biosphere be explained?
>Is the answer that the mass of C in the oceans and in carbonate deposits in the oceans reduced?
Part of the answer is that evergreen forests are in carbon balance with the atmosphere and don't sequester carbon in soils, so a pole to pole tropical forest would have removed almost all the carbon in the soils.