What do You Choose to Believe?

The Medieval Warm Period was only a regional event. If that is your belief, then warming in the 20th century has to be abnormal and require explanation. The chart above is my mine using the South American Temperature Reconstruction of R. Neukom1, J. Luterbacher2, R. Villalba3, M. Küttel1,4, D. Frank5, P.D. Jones, M. Grosjean1, H. Wanner1, J.-C. Aravena7, D.E. Black8, D.A. Christie9, R. D'Arrigo10, A. Lara9,11, M. Morales3, C. Soliz-Gamboa12, A. Srur3, R. Urrutia9, and L. von Gunten1,13. I don't know any of those people, but they seem to believe that the Medieval Warm Period was not a regional event. Looking at their data, South America has been warming since the 1400s. South American may have had its MWP, just a little out of sequence with some parts of North America.

" Although we conclude, as found elsewhere, that recent warming has been substantial relative to natural fluctuations of the past millennium, we also note that owing to the spatially heterogeneous nature of the MWP, and its different timing within different regions, present palaeoclimatic methodologies will likely "flatten out" estimates for this period relative to twentieth century warming, which expresses a more homogenous global "fingerprint." Therefore we stress that presently available paleoclimatic reconstructions are inadequate for making specific inferences, at hemispheric scales, about MWP warmth relative to the present anthropogenic period and that such comparisons can only still be made at the local/regional scale." That quote is by D'Arrigo, R.; Wilson, R.J.S.; Jacoby, G.C. from their abstract in the D'Arrigo et al. 2006 Northern Hemisphere Tree-Ring-Based STD and RCS Temperature Reconstructions.

If you focus on regions, your belief would be that AGW is not as much of a factor as natural warming, recovery from colder times caused by the Little Ice Age. If you look at the massive land use changes in the Northern Hemisphere, nearly 3% of the total surface area of the globe converted from wilderness to human habitat, you would assume there is some Anthropogenic warming that is beneficial and needed.

If you focus on CO2, you can determine that CO2 is causing global warming and that it is bad, because it is unintentional.

If you look at everything objectively, you may believe that some warming is good, some is natural and some may be bad, but we really don't know how much of any warming is due to any specific cause.

To my mind, having any opinion other than we don't really know, requires belief, not science.

Volcanoes, Ice Ages and Average Temperatures?

Michael Mann has a post on Real Climate on his new paper about the Little Ice Age and volcanoes. The image above is from that post with part of the text to explain the different plots.

This is a plot I made of GISS temperatures I downloaded for the NASA GIStemp site. Since the data for the Antarctic starts around 1902, I averaged all the latitude bands for the period 1902 to 2011 and plotted the global temperature average with and without the poles. With those is a plot of the average of the two poles alone. You can see the familiar shape of the global temperature average in the average of the pole much more clearly than in the global averages as this chart is scaled. For simplicity, the data is plotted "as is" from the GIStemp site in hundreds of degrees. So 200 would actually be two degrees.

While looking into the Siberian agricultural impact on northern hemisphere temperature I noticed that regional volcanoes had a strong impact on temperatures. Kamchatka, the Kurril Islands, Iceland, the Aleutian Islands and Alaska mainly, though Washington State and Japanese volcanoes also have some impact.

Here the Arctic and Antarctic are plotted separately with the global no poles. The Antarctic data is not all that great because of conditions and it is pretty obvious that the fluctuations in measurements start decreasing as we approach the 1960s. What is particularly interesting, is that the 1960 to present period shows a large increase in temperature that is not evident in any of the satellite records.

Here I have plotted the Global average using 1902 to 2011 base period without the Antarctic. The Antarctic is still on the plot so the pre-1960s noise really stands out. Polar amplification of the Greenhouse Effect is projected and a big deal. Other than the surface temperature records, there has been no measurable warming in the Antarctic and the surface stations in the Antarctic are notorious for having issues with being covered with snow drifts which can cause higher than average temperatures of not covered which could give the impression of variability that does not exist. Such is life, but how much impact could errors have on the global temperature average?

First Attribution:
Southern South America Multiproxy 1100 Year Temperature Reconstructions
-----------------------------------------------------------------------
World Data Center for Paleoclimatology, Boulder
and
NOAA Paleoclimatology Program
-----------------------------------------------------------------------
NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!!


NAME OF DATA SET:
Southern South America Multiproxy 1100 Year Temperature Reconstructions

LAST UPDATE: 3/2010 (Original receipt by WDC Paleo)
CONTRIBUTORS:
Neukom, R., J. Luterbacher, R. Villalba, M. Küttel, D. Frank,
P.D. Jones, M. Grosjean, H. Wanner, J.-C. Aravena, D.E. Black,
D.A. Christie, R. D'Arrigo, A. Lara, M. Morales, C. Soliz-Gamboa,
A. Srur, R. Urrutia, and L. von Gunten.

IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2010-031

WDC PALEO CONTRIBUTION SERIES CITATION:
Neukom, R., et al. 2010.
Southern South America Multiproxy 1100 Year Temperature Reconstructions.
IGBP PAGES/World Data Center for Paleoclimatology
Data Contribution Series # 2010-031.
NOAA/NCDC Paleoclimatology Program, Boulder CO, USA.


ORIGINAL REFERENCE:
Neukom, R., J. Luterbacher, R. Villalba, M. Küttel, D. Frank,
P.D. Jones, M. Grosjean, H. Wanner, J.-C. Aravena, D.E. Black,
D.A. Christie, R. D'Arrigo, A. Lara, M. Morales, C. Soliz-Gamboa,
A. Srur, R. Urrutia, and L. von Gunten. 2010.
Multiproxy summer and winter surface air temperature field
reconstructions for southern South America covering the past centuries.
Climate Dynamics, Online First March 28, 2010,
DOI: 10.1007/s00382-010-0793-3

I hope that covers everyone :) The comparison of the GISS Antarctic region versus the temperature reconstruction by all those guys, does look to me to be all that great of a match. Polar amplification due to greenhouse gas forcing can have a large impact on global temperature. Polar amplification due to poor instrumentation can also have a large impact on global temperature. Which is which in this case, seems to go to the poor instrumentation part of the puzzle. There reconstruction uses tree rings which are not thermometers, so one would be more likely to trust the instrumentation, that is not always the best choice though. Trust nothing - verify everything.

This post is just on some of the questions I have on what data should have more weight in determining average global conditions. The long term tree ring proxies do not provide a good range of temperatures, but they should provide a fair indication of what "average" conditions should be.

The Tropopause and the 4C Ocean Boundary Layers

I have a nasty habit of comparing the the Tropopause and the 4C ocean thermal boundary layer in a way that is not very clear. This is mainly due to my looking at the situation more as a puzzle than a serious fluid dynamics problem. As I mentioned in a previous post, I am looking for a simple back of the envelope method of proving the limits of CO2 radiant forcing to a reasonable level of accuracy.

The main similarity is that both are thermal boundaries with sufficiently large sink capacity to buffer changes in radiant forcing. Their mechanisms are different but the impacts are very similar.

The ocean 4C boundary is a combination of thermal and density mechanisms that result in interesting thermal properties. Warming the 4C boundary from above results in upward convection which tends to reduce the impact of the warming. The heat loss from the 4C layer has to be from warmer, 4C to colder but also has to allow for constant density. If not, there would be turbulent mixing and there would be no 4C boundary layer.

So cooling or actually maintenance, of the 4C boundary occurs mainly in the Antarctic region where the air temperature is cold enough to cause the formation of sea ice. This also occurs in the Arctic, but seasonal melting produce less dense fresh water that has to mix, with turbulence, with the denser saltwater. If there were no turbulent mixing there would be lens of fresh water constantly in Arctic summer. In the Antarctic, much more of the sea ice survives the summer months, so there is continuous replenishment of the 4C maximum density salt water slowly sinking in the southern pole that creates the deep ocean currents. Turbulent warming of the 4C layer in or near the tropics causes rising convection from the 4C boundary layer which impacts the rate of replenishment from both poles. It is a very elegant thermostat for the deep oceans, laminar replenishment versus turbulent withdrawal.

The Tropopause is similar but different. Non-condensation greenhouse gas radiant forcing balance conductive, convective and latent cooling response. The Antarctic winter conditions are controlled by the non-condensible radiant effect primarily which result in a maximum low temperature equal to the amount of non-condensible radiant forcing for that temperature range.

The lowest temperature ever recorded in the Antarctic is about -90C and that would be the lowest temperature in the Tropopause if it were not for non-radiant energy flux. The average temperature of the Tropopause is closer to -60C, which indicates that the average impact on non-radiant energy flux is on the order of 30C in the Tropopause. That is a fairly large buffer range. In addition to that range, the Tropopause altitude can vary so for short term perturbations, the temperature can drop to -100C possibly a little more. The Tropopause temperature cannot decrease much lower because stratospheric warming due to ultra violent solar radiation interacting with oxygen in the dry region above the Tropopause.

Non-interactive outgoing long wave radiation, the atmospheric window portion of the spectrum is less in the Antarctic due to the Stefan-Boltzmann relationship, ans should be on the order of 9Wm-2 at -90C implying that the actual CO2 portion of the Tropopause limit is on the order of 55 to 60 Wm-2. As more CO2 forcing is applied, the percentage of non-interactive OLR would increase, offsetting approximately 15% of the impact.

As surface temperature increases, the non-interactive response would continue to offset approximately 15% or the non-condensible GHG forcing and the conductive/convective and latent fluxes would offset more with the changes in temperature, gas mix and pressure. Convection, which is a function of temperature, density and conductive properties, is the non-linear part of the puzzle that causes the uncertainty in a pure energy perspective while albedo, surface and atmospheric, change just adds a new layer of complexity.


In both the 4C and tropopause boundary layers, virtually immeasurable changes can have a significant impact on the heat sink capacity of each and each have extremely different time constants. More complexity, making this an outstanding puzzle!

So this post hopefully will explain why I compare these two thermodynamic layers as I do, though the mechanisms are very different.