Now for some possible really bad news for the Climate

I didnt say global. The hydrological cycle is hemispheric.

 

Still, wouldn't you need at least two samples to get a clear picture of global temperature changes?

 

So you are now discounting all the northern hemispheric temperature reconstructions such as MBH98/99 Briffa etc?

PS. While antarctic ice cores tend to have lower resolution its safe to assume that southern hemispheric temperature has been just a chaotic as northern.

 

This is a fun thread for me, since my current area of PhD research is doing oxygen isotope modeling and looking at the influence of volcanic eruptions on climate. So, perhaps a bit of guidance here:

1) In order to understand or model the evolution of climate during the Last Millennium (in particular), it is necessary to account for the influence of known forcings-- including the evolution of Earth's orbital parameters, greenhouse gases, volcanic forcing, solar irradiance, and land use changes. Of these, the first two are well understood and the last three are fairly well constrained but are still an active area of research. Because of this, a few different plausible reconstructions of volcanic forcing, solar, and land-use histories exist, and the uncertainty due to forcing has generally not been thoroughly well sampled (the approach by NASA GISS is to run many different simulations with many combinations of forcings for the Last Millennium, other groups have different strategies). The rationale for including volcanic forcing is therefore not to match any paleoclimate reconstruction (or theoretical expectation), just that you simply cannot get a right answer without it.

2) Volcanic forcing on climate depends largely on the injection of sulfur containing species into the stratosphere. A number of indices have been developed over the last several decades as a measure of volcanic activity: for a few examples, these include the Dust Veil Index (Lamb, 1970) , although this uses climatic information in its derivation, and so results in some circular reasoning when trying to use DVI to compare temperature changes; another index is the Volcanic Explosivity Index (Newhall and Self, 1982) which compares eruptions by explosivity, but this has limited climate utility(e.g., Mt. St. Helens produced a smaller climate impact than Mt. Agung even though the former was more explosive). Another drawback of these are reliance on whether observers were located near the volcano of interest. The Sato index (Sato et al., 1993, and updates, see http://data.giss.nasa.gov/modelforce/strataer/) uses estimates of volume ejecta between 1850 and 1882, optical extinction data between 1883-1978, and satellite data for the period after 1979, which includes the best observations of the latitudinal and temporal extent of aerosol clouds- thus, it uses multiple inputs of source data and only goes back to 1850.

Thus, the current way to create a continuous record of volcanic activity on millennial timescales that is useful to climatologists is through ice cores, which record sulfur and acidity, and networks of such cores can be used to extract common signals and understand the magnitude of various eruptions. The index developed by such work is the Aerosol Optical Depth perturbation exerted by past eruptions, which is the metric used to force modern global climate models and related to the radiative forcing of a given eruption. Anomalies in sulfur isotopes (via photochemical chemical processes in the stratosphere that causes mass-independent fractionation of the isotopes) can also be used to distinguish between eruptions confined to the troposphere vs. those that inject large quantities of material into the stratosphere. One note is that currently, some differences exist in the reconstructions of Icelandic eruptions, including ongoing debate on the magnitude of potential stratospheric inputs for the 1783 Laki eruption.

3) There is a very large literature on what oxygen isotope signals "mean," and my own approach is to use fully-coupled climate models that explicitly forward model oxygen isotopes in a manner that is self-consistent with the model's thermodynamics and dynamics, including all processes occurring from source to sink. This is different than the inverse approach in which a site's oxygen isotope signal (from an ice core or cave record, etc) is inverted to reconstruct a climate variable that we think it most likely resembles- local condensation temperature seems to work good for that interpretation in high-latitude regions such as Antarctica (it's certainly not a hemispheric-mean temperature), and the influence of source temperature variations can be inferred in some other ways (e.g., deuterium excess) but this is a whole field of research on its own. However, isotopes don't generally reflect temperature variability in the tropics. There is no unique interpretation of the oxygen isotope signal across all regions, timescales, and climate events.

 

When MBH98 included several proxies from the southern hemisphere (see below), while MHB99 and Briffa are clearly identified as Northern Hemisphere temperature reconstructions, why would I discount them?

Regional climate can be chaotic and highly variable, which is why the more proxies you combine the better.

http://www.sciencemag.org/content/339/6124/1198

 

One of the reasons you can discount them is the 'hide the decline' in Mann's reconstruction. The Briffa samples showed cooling when the known temperature was warmer. The 'hide the decline was grafting on data pre-decline to hide it. That does not mean that tree samples are not useful, mostly for regional construction, but not necessarily for global construction. A good example is the current decline in temperature in the Midwest while Greenland shows warming.

 

Gee, I wonder what possible reason someone would have for excluding tree ring data from their temperature reconstruction when dendroclimatologists say it doesn't agree with actual temperature measurements?

 

So you think you don't need to discount them because they don't actually agree with the temperature records? Go figure.

 

I'm not a dendroclimatologist, but there's a lot of literature on the 'divergence' issue...I can't be too informative on this topic, but it would be advisable to consult the literature before accepting or discounting records with a known issue, yet are still used.

However, if you are insistent in not trusting tree ring records that exhibit the divergence problem, that's fine, you can always consult temperature reconstructions not based on tree ring records that aren't affected by this, or those screening out trees altogether.

 

There are numerous other proxy records but the problem with proxy records is that the further back you go, the wider the error is. For instance, if you go back 10,000 years your range in that period may be a few hundred years give or take. Even then, all proxy records are regional and may show trends counter to other proxy records. Hard to guess a global mean from that.

 

Averaging 73 temperature records spread across the globe would probably be a good start, don't you think?

 

The "error" in the proxy to target conversion is distinct from dating uncertainty...which may be be large or very small even going back 10 kyr (depending on the proxy). Some cave and ice core records have annual to decadal resolution for the last deglaciation. We have 120,000 year cave records at ~100 yr precision now. Some ice cores in Greenland have annual resolution well beyond 10,000 years.

As in the Marcott study and multiproxy reconstructions, no one tries to infer global temps from one location. The sensible approach is to use networks of available data. Moreover, in regions where proxy interpretation is not of temperature (e.g., oxygen isotopes in the tropics reflecting precipitation amount), asymmetries in oxygen isotope imprints in different regions can reflect ITCZ migration, etc.

 

From Wikipedia;

Since 1000 AD

Pinatubo, island of Luzon, Philippines; 1991, June 15; VEI 6; 6 to 16 km3 (1.4 to 3.8 cu mi) of tephra; an estimated 20,000,000 tonnes (22,000,000 short tons) of SO
2 were emitted.
Novarupta, Alaska Peninsula; 1912, June 6; VEI 6; 13 to 15 km3 (3.1 to 3.6 cu mi) of lava
Santa Maria, Guatemala; 1902, October 24; VEI 6; 20 km3 (4.8 cu mi) of tephra
Krakatoa, Indonesia; 1883, August 26–27; VEI 6; 21 km3 (5.0 cu mi) of tephra
Mount Tambora, Lesser Sunda Islands, Indonesia; 1815, Apr 10; VEI 7; 150 km3 (36 cu mi) of tephra; an estimated 200,000,000 t (220,000,000 short tons) of SO
2 were emitted, produced the "Year Without a Summer"
Grímsvötn, Northeastern Iceland; 1783–1785; Laki; 1783–1784; VEI 6; 14 km3 (3.4 cu mi) of lava, an estimated 120,000,000 t (130,000,000 short tons) of SO
2 were emitted, produced a Volcanic winter, 1783, on the North Hemisphere.
Long Island (Papua New Guinea), Northeast of New Guinea; 1660 ±20; VEI 6; 30 km3 (7.2 cu mi) of tephra
Kolumbo, Santorini, Greece; 1650, September 27; VEI 6; 60 km3 (14.4 cu mi) of tephra
Huaynaputina, Peru; 1600, February 19; VEI 6; 30 km3 (7.2 cu mi) of tephra
Billy Mitchell, Bougainville Island, Papua New Guinea; 1580 ±20; VEI 6; 14 km3 (3.4 cu mi) of tephra
Bárðarbunga, Northeastern Iceland; 1477; VEI 6; 10 cubic kilometres (2.4 cu mi) of tephra
1452-53 New Hebrides arc, Vanuatu; the location of this eruption in the South Pacific is uncertain, as it has been identified from distant ice core records; the only pyroclastic flows are found at Kuwae; 36 to 96 km3 (8.6 to 23.0 cu mi) of tephra; 175,000,000–700,000,000 t (193,000,000–772,000,000 short tons) of sulfuric acid
Quilotoa, Ecuador; 1280(?); VEI 6; 21 km3 (5.0 cu mi) of tephra
Samalas volcano, Rinjani Volcanic Complex, Lombok Island, Indonesia; 1257; 40 km3 (dense-rock equivalent) of tephra, Arctic and Antarctic Ice cores provide compelling evidence to link the ice core sulfate spike of 1258/1259 A.D. to this volcano.

Today with increased population around the globe, air travel, other technology, droughts, food growth, economies, and already increasing CO2 levels, a volcanic eruption in the right location, for the right duration, for the right amount of emissions, etc. can certainly cause chaos. It's a given there is nothing proactive that we can do...short of not living within the kill zone. Same with hurricanes, tornadoes and earthquakes. I'm one of them living about ten miles from the San Andreas fault. Most of us in parts of CA expect something bad to happen one day but we don't dwell on it and just hope for the best when it does happen...a couple of weeks ago a 6.1 in the Napa area for example. Bottom line...we're just along for the ride while mother nature will determine our fate...

 

You can include as much (*)(*)(*)(*) as you want. The method still mines for hockey sticks. MBH is entirely dependent on a single series of trees from Northern Colorado.

You dont make better soup by simply adding more ingredients. Especially when those ingredients are (*)(*)(*)(*).

 

Marcott is not a straight average nor is any hockey stick. All hockey stick reconstructions weight series. His series' shape is 100% dependent on a miss dated alkenone series.

 

In the modern world where there is so much pressure to publish why do you think that just becuase there has been stuff published that the issue has been answered???

There is still no answer for the divergence problem. The prevailing and published reasoning on the part of the dendroclimatologists was stated in and published by Dr. Briffa in Briffa et. al 2002.

"In the absence of a substantiated explanation for the decline, we make the assumption that it is likely to be a response to some kind of recent anthropogenic forcing. On the basis of this assumption, the pre-twentieth century part of the reconstructions can be considered to be free from similar events and thus accurately represent past temperature variability."

That is the "scientific reasoning" the dendros have been running with since even before Brifa published it.

Do you believe that to be a scientifically correct conclusion. Do you believe it to be scientifically valid to say that since we don't know the cause we can assume it to be X?

You are aware that is a logical fallacy called appeal to ignorance.

 

Global warming implies the average temperature of the Earth is increasing.

This DOES NOT imply that in local and regional 'weather' events that it won't be wetter and colder.

From day one, it has been stated that warm and dry regions will become hotter and dryer while cool and wet regions will become wetter and cooler. But the overall result will be an increase in the average global temperature.

You seem to find humor in politicizing global climate change no matter the horrific potential that exists...

 

That is part of the politicization right there. That is also an unanswered question, whether warming is bad or not. It might be inconvenient for some but horrific? That is really just more alarmism with no proof.

 

Whether or not the causes of 'divergence' have been satisfactorily answered is not the point. It's a recognized issue that only applies to certain records in northern forests, and the community that has expertise on the topic has thus far come to a conclusion that a relationship to temperature can still be obtained in past records...this is demonstrably the case for the last 150-200 years or so in some locations; uncertainty still exists as to whether divergence has manifested itself in these records in the more distant past, although comparison to records not exhibiting this issue suggests it is confined to the post-1960 period or so. However, if you do not like this assessment then you do not need to give those records any weight in your analysis.

I'd be much more interested in this whole issue of tree rings if it seemed to matter for anything of substance regarding the large-scale temperature trends during the Common Era and future climate.

 

What actual expertise does Dr. Briffa, Dr. Mann or any of the big names in dendroclimatology have on tree biology?

Why should I listen to Brifa who knows bupkis on tree biology?

 

Sorry, I'm not interested in entertaining distracting arguments predicated on attacking an entire discipline (owing to what you think you know about individual scientists, though other people can make their own judgment on their credentials). The fact is some people spend their lives on studying dendroclimatology, entire courses and textbooks are devoted to the topic, and thousands of papers have been written (including on the "divergence problem"). I'm sure you've read the handful of blogs that purport to show it's all nonsense, and if that's what you choose to believe then just don't give the tree ring studies it any weight in your opinion of how climate works and how it has evolved.

I've seen enough of the blogosphere to understand how this all goes- we can agree to discuss other aspects of modern climate change or paleoclimate to avoid the always unresolvable back-and-forths about what McIntyre or Watts or those guys think about Mann, what an e-mail said, why you don't trust some other guy, etc, etc. All of this is a poor representation of how scientific knowledge progresses.

 

I've stated that in my area, which is about 99% wine business, if we have a 1-1/2 to 2 degree F. average rise in temperature, we may lose 25-50% of our grape yields. This puts farmers out of business. This threatens the multi-billion$ wine industry. This ruins the economy of Napa and Sonoma counties. Now in my book this would be horrific!

I am positive the same scenarios exist across the USA...it's not alarmism...it is ignorance to blow off the data and potential...

 

You should listen to everyone, to all information, to all opinion, then digest and think and act on this information in a prudent and rational way. If someone is providing data, or quoting data of others, do some research on that data to understand it's context. This is how we learn and move forward instead of being stuck in the political quagmire...

 

How have you tested that theory of yours?

 

Dr. Richard Lindzen supplied me several years ago a huge amount of studies by climate experts such as he is.

He blows this off for the most part. He has a lot of papers you can read and are on the internet. A man of his qualifications at least ought to be studied. I suggest you locate his papers given you know his name and examine them.

http://www-eaps.mit.edu/faculty/lindzen/PublicationsRSL.html