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The Global Warming Debate
09-20-2012, 02:07 AM (This post was last modified: 09-20-2012 04:00 AM by nomoon.)
Post: #1
The Global Warming Debate
The debate over man made global warming has become quite politicized, so I think that it’s an appropriate topic for this forum. I’ve been very up front about my position on the global warming debate. I’m skeptical that man made CO2 emissions are causing catastrophic warming. In this posting, I’ve given a overview of my reasoning. This posting is organized into the following categories:

I. Definitions
II. Strawman Delimas
III. A Summary of the Scientific Case for Catastrophic global warming.
IV A Rebuttal of Three Scientific arguments for Catastrophic global warming.


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I. Definitions:

Alarmists: Those who believe that man made CO2 emissions are causing catastrophic warming. This term is not intended to be derogatory, but merely a descriptive term to distinguish people from those who believe that we do not need to be alarmed.

Skeptics: Those who are not convinced that man made CO2 emissions are causing catastrophic warming.

Anthropogenic Global Warming (AGW): The “anthropogenic” term means “human,” or man-made global warming. However, I consider the term to be ambiguous, since I’ve seen it used to imply that man merely has a non-zero impact on global temperatures, as well as implying that man has a dominating influence on the climate change. It also can include man made influences which are not due to CO2, such as land use, deforestation, other gases, etc…


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II. Straw Man Dilemmas: Here are two snippets that I’ve seen used as reasons to cut CO2 emissions. I thought that it would be a good idea to get these out of the way first.

Strawman #1: It’s indisputable that global warming is real and is happening now. Therefore, we need to cut CO2 emissions.

Strawman #1 Rebuttal: Most believe that there has been some warming over the past 150 years. However, this does not say anything about the cause. Many believe that the Earth cooled as it went into the Little Ice Age about 500 hundred years ago, and then started warming about 150 years ago as we came out of it. The existence of warming over the past 100-150 years does not mean that man-made CO2 emissions are causing most of it.

Strawman #2: It’s indisputable that CO2 causes global warming. Therefore, we need to cut CO2 emissions.

Strawman #2 Rebuttal: All scientists acknowledge that CO2 absorbs infrared energy, and that all other things being equal, increasing CO2 levels is likely to increase global temperatures. However, there are several other known factors which are known to affect the climate. In order to show that CO2 emissions should be lower, it would need to be proven that expected CO2 levels are causing a significant part of the climate change beyond what would be expected from natural variation.

Both of these strawman issues above often lead to the flawed and sometimes leading question: Do you believe in global warming? Often, the questioner really means: “Do you believe that man-made CO2 emissions are causing catastrophic warming?” In this case, I’d answer “no.” However, if the question is answered as it was asked, I’d have to say that “yes, there probably has been some warming over the past 150 years.” Problems occur when the questioner makes one assumption and the answerer makes another assumption about the question. For example, I’ve seen discussions where this question is answered by a skeptic who replies “no” and then the questioner ridicules the skeptic by stating something like “every respectable scientist believes in global warming”



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III. A Summary of the Scientific Case for Catastrophic global warming.

Items A, B, & C below are what I consider to be the main categories for the scientific case for catastrophic warming caused by man-made CO2 emissions. I give brief description below, and section IV will give quick rebuttals for each of these three categories.

A. Paleoclimate reconstructions which show almost 1000 years of stable temperatures followed by ~100 years of dramatic temperature increases which roughly coincide with increased levels of CO2 in our atmosphere.

B. Models which show that the recent warming could only be explained by increased levels of CO2. Natural variations have been studied, and their influence is too small to have this much impact.

C. Ice core data which shows a correlation between CO2 levels and temperatures.



=============================================

IV. A Rebuttal of Three Scientific arguments for Catastrophic global warming.


A Quick Rebuttal of Paleoclimate Reconstructions: : The most famous of these is the Mann-Bradley-Hughes (MBH) hockey stick that was used in the report from the 2001 Intergovernmental Panel on Climate Change (IPCC). One of the key problems with this study is that the hockey stick result relies on a set of data made from bristlecone pines from the western part of the United States. Additionally, this study used a non-standard statistical method which gave inappropriately large weighing to this series. Also, many of the trees that he measured were “strip barked,” where at least some of the outer bark has died, which affects growth rates. The original researcher, Don Graybill, a dendrochronologist, who collected the data for this set of bristlecone pines, stated that tree ring measurements from these pines should not be used for temperature reconstructions.

If the bristlecone pines are removed from the data set, the hockey stick shape goes away. There have been a few attempts to show that other studies with different data asset have also replicated the MBH hockey stick, such as this spaghetti graph. However, many of these reconstructions have the same bristlecone series used in MBH, which dominates their results. Other reconstructions have dominating series with other data quality issues, and some have allegedly been cherry picked to give the desired results. Even if you believe that the dominating series are valid data, I think that it’s hard to argue that these results are robust if the hockey stick shape disappears if a single data series is removed.

Michael Mann, of the original MBH articles, more recently published a hockey stick shaped reconstruction in 2008 which did not use any tree ring measurements. However, the hockey stick shape relied on a single set of lake bed sediments (Tiljander). Other non-tree data was used in the study. However, if the Tiljander sediment measurements were removed, the hockey stick goes away. Again, this is hardly a robust result if the hockey stick shape goes away if a single data series is removed. Worse still, the “foot” of the hockey stick is from a period of time in which the original data collectors said cannot be used for temperature reconstructions because sediments were contaminated by upstream dredging. WORSE STILL, the sediment density data shows strong COOLING during this period, and not warming. Mann’s publication simply used an algorithm which places a negative calibration for the sediments in order to obtain the result that he wanted. Mann has vigorously defending the calibration technique and has sharply criticized those who claim that he has used his data “up side down.” In my opinion, the critics are correct, and Mann’s defense relies on the parsing of words. I have also read that Mann has attempted so show that his 2008 results are robust, but showing that the hockey stick shape remains even when the Tiljander sediment density measurements are removed, but that his analysis actually replaces the Tiljander measurements with a data series that contains Bristlecone pine data.

Rebuttal of the other arguments will come in a followup posting.
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Messages In This Thread
The Global Warming Debate - nomoon - 09-20-2012 02:07 AM
RE: The Global Warming Debate - refill - 09-20-2012, 07:53 AM
RE: The Global Warming Debate - nomoon - 09-21-2012, 01:36 PM
RE: The Global Warming Debate - refill - 09-23-2012, 02:02 PM
RE: The Global Warming Debate - refill - 10-07-2012, 03:43 PM
RE: The Global Warming Debate - nomoon - 10-20-2012, 03:09 AM
RE: The Global Warming Debate - nomoon - 10-25-2012, 12:09 PM
RE: The Global Warming Debate - refill - 10-26-2012, 02:06 AM
RE: The Global Warming Debate - nomoon - 10-26-2012, 01:13 PM
RE: The Global Warming Debate - jharry - 11-12-2012, 11:56 AM
RE: The Global Warming Debate - jharry - 04-16-2013, 01:08 PM

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