Trees ain’t thermometers

I used to work on Mountain Home State Forest in the southern Sierra. MHSF has about 3000 specimen-sized sequoia within its boundaries. Dendrochronolgists often visited to see the stumps from logging in the mid to late 1800s. These were often over 2000 years old when they had been cut.

The Dendrochronolgists were interested in the tree-ring patterns. Trees grow fast or slow in response to many factors and these seasonal factors (light, water, nutrients) created ring signatures or patterns. Certain years might have been favorable for growth with plentiful water, light and nutrients (each favorable year would be marked a large, wide ring) and certain years might have had poor conditions for growth–drought, late spring conditions, early winter–marked by thin (in some cases–microscopic) rings. In general, the wider the ring the more favorable the growing season, the narrower the ring the poor the growing conditions. These ring patterns can be distinctive and can be used to date archeological sites (where wood is present).

Oxford’s Tree-ring Laboratory put it this way:

The way dendrochronology works is relatively simple. As a tree grows, it puts on a new growth or tree-ring every year, just under the bark. Trees grow, and put on tree-rings, at different rates according to the weather in any given year: a wider ring in a favourable year and a narrower ring in an unfavourable year. Thus, over a long period of time (say 60 years or more) there will be a corresponding sequence of tree-rings giving a pattern of wider and narrower rings which reflect droughts, cold summers, etc. In effect, the span of years during which a tree has lived will be represented by a unique fingerprint, which can be detected in other geographically-similar tree-ring chronologies.

Using tree rings as a proxy for temperature however is fraught with caveats and pitfalls.

Mike D.‘s of the Western Institute for Study of the Environment comment (on William M. Briggs’ blog) about using tree ring data as proxies for temperature is an excellent explanation of the problems of using tree ring growth for temperature. He starts with how tree rings are laid down:

Diameter growth on any tree is theoretically a sigmoid growth function. No tree puts on constant radial growth year after year. Trees grow by adding a layer of new wood at the cambium, under the bark. Each year a larger surface area is added. If growth is constant, the rings get narrower. But growth is never constant. There is significant deviation from ideal (model) sigmoid diameter growth in individual trees regardless of the weather. Even when sigmoid growth models are used, the natural variation adds statistical error.

Two sigmoid curves. The taller is the period annual increment for cubic feet; the lower smoother S curve is for mean annual increment of cubic feet.

So as the diameter expands, the amount of material put on would need to be more if the ring’s width was to stay the same as the previous season. Think of a clay disk that you add the same amount of clay to in successive rings. The volume of clay would be the same but the thickness of each new ring would decrease. The ring growth is S-shaped (sigmoid) because initially the tree has little foliage for photosynthesis and often puts its initial years into root development for survival. Then once roots are deep enough the tree puts its growth into height and width.

He then points out that tree-to-tree competition for light, water, and nutrients also affects the ring growth:

Dense stands exhibit narrow rings on individual trees, sparser stands may have wider ring growth, yet both stands may have equivalent gross growth. That’s why only open-grown trees are supposed to be selected for ring studies. But nobody knows what the tree density surrounding an individual tree was 100, 200, 500 years ago. Competitors could have arisen and died without leaving evidence of their presence so long ago. More error.

Besides competition, disease and injury can affect growth.

Trees can sustain injuries that affect growth, such as top and branch damage, that are difficult to detect 200 years later, especially a few feet off the ground where the rings are sampled. There are very few pristine, undamaged trees. I know, having searched for such across broad acreages. Open grown trees at high elevations are always damaged. A heavy winter snow can snap off branches and the tree will exhibit reduced diameter growth for a few years, even if growing season conditions are ideal.

This makes using tree ring data as stand-ins for temperature problematic.

Ring width has all but been abandoned as a temperature proxy. Instead, the latest technique is sampling rings for O18 ratios, under the assumption that O18 varies with temperature. Regardless of the ring width, the O18 ratio is supposed to have recorded growing season temperature. But that theory is fuzzy and mushy, and O18 ratios in living trees correlate very poorly with known growing season temperatures. In other words, it calibrates with much error at best.

Trees are not thermometers, but even thermometers have some serious measurement error problems.

Tree ring studies are a fad akin to phrenology and other discredited pseudosciences that has not dissipated as it should have decades ago.

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A warmer and wetter world

I found a link the other day to a government website with global mean precipitation data from 1900 to 2000. Of course, I can’t find the link now (please comment if you have the link, but first see the note at the end of the post).

Anyway, I put the numbers into an Excel spreadsheet and graphed the data and added a trendline. (If you would like a copy of the xls file, please ask for it in the comment section below.) As the world warms it is getting wetter. As Matt Ridley writes in his book The Rational Optimist:

If you take the IPCC’s [International Panel on Climate Change] assumptions and count the people living in zones that will have more water versus zones that will have less water, it is clear that the net population at risk of water shortage falls by 2100 under all their scenarios. (emphasis added)

Global mean precipitation (1900-2000)

10 yr average-global mean precipitation (1900-2000)

Even the EPA cites the IPCC (2007) to say much the same thing:

As global mean temperatures have risen, global mean precipitation also has increased. This is expected because evaporation increases with increasing temperature, and there must be an increase in precipitation to balance the enhanced evaporation (IPCC, 2007). Globally, precipitation over land increased at a rate of 1.9 percent per century since 1901, but the trends vary spatially and temporally. Over the contiguous U.S., total annual precipitation increased at an average rate of 6.1 percent per century since 1901, although there was considerable regional variability. The greatest increases came in the South (10.5 percent per century), the Northeast (9.8 percent), and the East North Central climate region (9.6 percent). A few areas such as Hawaii and parts of the Southwest have seen a decrease.

Crops may flourish with warmer climes and more CO2. There is some indication that in California some trees are increasing their ranges in response to this change. While increasing temperatures do have their downside, they also have positive benefits as well.

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Making money out of thin air

What do the South Sea Company and carbon exchanges have in common? Everything.

In 1711, Britain’s treasurer, Robert Harley, had an extraordinary idea. He could finance Britain’s war debt by selling shares in a non-existent trading company: the South Sea Company. South America was just opening up and was imagined to be a place where silver and gold flowed as easily as water. But for the scheme to be pulled off, according to a recent Economist article, investors needed to “be persuaded to drive the stock above its par value” in order “to create wealth out of thin air.” It worked for a while. Speculation drove up the price but when negotiations with Spain faltered, the South Sea Company needed government backing to keep the party going. They went old school and bribed people close to the king. Eventually, despite the royal imprimatur, the investors discovered that the scheme contained no substance and was just hot air, and their shares’ par value equaled pond scum.

004 Carnival wind-peddler and wholesaler (stoc...

Today, a number of scientists, companies, and policy-makers are concerned with anthropogenic (man-made) global warming. And, carbon dioxide (CO2), a by-product of burning, has been fingered as the prime suspect. CO2 also happens to be the gas that you and I exhale with each breath. Simply put, CO2 reflects infrared radiation back to earth that would otherwise be lost to the cold cold depths of space–the so-called greenhouse effect.

Climate scientists have built complex computer programs to model the earth’s future climate. Using sophisticated equations with feedback loops and forcings they have “proven” the warming, which vary from 1 to 10 degrees Fahrenheit change, of the worldwide average by the end of this century. For our purposes we can simply say that more CO2 equals a hotter earth. People living at the start of the 20th century who could remember the “little ice age” thought this greenhouse effect beneficial. Today, the warming involved with the higher levels of climate change stands accused of everything from colder winters to cancer, and even illegal immigration (I am not making this up).

Some have suggested that a cap-and-trade system could reduce CO2 emissions; this would be similar to how regulators curbed other smokestack pollutants (such as sulfur dioxide) in the late 20th century. Essentially, regulators “cap” the total output of a pollutant with a limited allowance of CO2, and then polluters can trade their credits. Those who produce less of the pollutant can sell their remaining allowance to those who produce more. The state of New York has collected $282 million under a regional agreement from the auctioning of carbon dioxide credits.

In addition to selling allowances in a cap-and-trade system, indulgences can also be sold in the form of “carbon offsets.” Offsets provide a counter-balance to the CO2-emissions’ damage (presumably) done by flying in an airplane, driving a car, having a child, or all three and more. The offsets vary: one might buy a bit of rainforest (to grow and soak up CO2 through photosynthesis) or fund family planning in Ethiopia (to prevent another carbon emitter from entering the world) as atonement. By buying such carbon-coated indulgences, one can expiate the sins of extravagant western living and transform oneself into a holy carbon-neutral being.

It’s not about saving the world (except for the true believers), it’s about money. Follow the incentives. Baptists and bootleggers, true believers and the buck-seekers, have banded together to make markets out of thin air with offsets or allowances. At the United Nations’ climate change delegate meeting in Cancun that just ended, investment funds, insurance companies and banks have lobbied for a treaty, and not because they are altruistic. Ronald Bailey at Reason writes that the delegates there have decided “to kick the Cancun down the road” because the “rich countries continued their vague promises to hand over $100 billion in climate aid annually to poor countries beginning in 2020.”

Cutting 100 percent of our CO2 emissions lowers CO2 emissions by a whopping 1.5 percent of the carbon cycle, because the rest (210 billion metric tons per year) comes from natural processes. But, “if you’re looking to make money from the trading of carbon allowances (carbon credits) than (sic) it makes a great deal of sense….If you are in the renewable energy business it makes perfect sense to support the reduction of carbon dioxide ‘pollution’,” writes one energy analyst.

I could be wrong, but I see no “there” there. The investment has no portfolio. I think, just as what happened to the British South Sea Company, investors will eventually learn that these hyperventilated bubbles are simply full of hot air. What do the South Sea Company and carbon exchanges have in common? Nothing.

Sources

Buttonwood. “An early attempt to buy government bonds by creating money.” The Economist, November 11, 2010.

Christy, John R. “The Global Warming Fiasco.” In Global Warming and Other Eco-Myths, by Competitive Enterprise Institute, edited by Ronald Bailey, 423. Forum, 2002.

Derbyshire, David. “‘Climate change could give you cancer’: UN report warns of deadly pollutants from glaciers .” Mail Online. December 9, 2010. http://www.dailymail.co.uk/sciencetech/article-1336810/Climate-change-cancer-UN-report-warns-deadly-pollutants-glaciers.html#ixzz17qXOVfeT (accessed December 11, 2010).

Horn, Art. “The Utter Futility of Reducing Carbon Emissions.” Energy Tribune. December 1, 2010. http://www.energytribune.com/articles.cfm/5961/The-Utter-Futility-of-Reducing-Carbon-Emissions (accessed December 1, 2010).

Lindzen, Richard S. “Global Warming: How to approach the science.” Testimony: House Subcommittee on Science and Technology hearing on A Rational Discussion of Climate Change: the Science, the Evidence, the Response. Richard S. Lindzen, 2010.

Lomborg, Bjorn. “Human Welfare: Food and Hunger.” In The Skeptical Environmentalist: Measuring the Real State of the World, by Bjorn Lomborg, 515. Cambridge: Cambridge University Press, 2004.

NAVARRO, MIREYA. “Carbon Auction Yields $16.9 Million for New York.” Dot Green. New York Times. December 3, 2010. http://green.blogs.nytimes.com/2010/12/03/carbon-auction-yields-16-9-million-for-new-york/ (accessed December 12, 2010).

Optimum Population Trust. “Your questions answered.” PopOffets. Optimum Population Trust 12 Meadowgate, Urmston Manchester M41 9LB. http://www.popoffsets.com/faq.php (accessed December 11, 2010).
Revkin, Andrew C. “Cold Weather in a Warming Climate.” Dot Earth – New York Times blog. March 1, 2008. http://dotearth.blogs.nytimes.com/2008/03/01/reconciling-cold-weather-and-a-warming-climate/ (accessed December 11, 2010).

Ridley, Matt. The Rational Optimist: How Prosperity Evolves. New York, New York: HarperCollins, 2010.

Shuaizhang Feng, Alan B. Krueger, Michael Oppenheimer. “Proceedings of the National Academy of Sciences.” Linkages among climate change, crop yields and Mexico–US cross-border migration. Proceedings of the National Academy of Sciences. http://www.pnas.org/content/107/32/14257.long.

Vaughan, Adam. guardian.co.uk,. 10 31, 2010. http://www.guardian.co.uk/environment/2010/oct/31/climate-change-computer-game (accessed 11 20, 2010).

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