by Roger Cohen, Lyncean Group, July 10, 2010
I’m going to look at the global warming issue through a prism that focuses on the dynamics of the debate itself. There will be plenty of science, but it will all lead to a perspective on the debate.
A remarkable feature of the dynamic is what happens when you ask the simple question:
“What is the case for serious anthropogenic global warming?”
Responses tend to fall into three categories:
- Appeal to authority: “All scientific societies (or whole armies of scientists) agree that carbon dioxide emissions are causing (fill in the blanks)” Or, “Don’t you know that the evidence is overwhelming?”
- The “It doesn’t matter” response: “Even if the science is wrong, it is still important to do something about it” (that “something” is always big and expensive). I’m going to call this the “Precautionary Principle” response – the idea that if there is any risk at all, we need to do something heroic to reduce it.
- Out-and-out anger: “You denier, oil company shill (or some other ad hominem). How dare you try to tell me there won’t be a catastrophe.” This is a favorite of even otherwise dignified groups such as the National Academy of Sciences.
A Debate Dynamic
Question: “What is the case for significant anthropogenic global warming?”
- Answer #1: Appeal to Authority, E.g., “Well, all scientific societies agree that carbon dioxide emissions are causing (fill in the blank).” Or… “Don’t you know; the evidence is overwhelming.”
- Answer #2: The “Precautionary Principle,” E.g., “It doesn’t matter. Even if the science is wrong, it is still important to do (something big and expensive) about it.”
- Answer #3: Anger, E.g., “You (denier, tool of special interests, dogmatic #@$%…)! How dare you tell me there will not be a climate catastrophe!”
Notably, what you don’t get is an answer to the question.
So let’s look at the case for AGW. It has nothing to do with the literally hundreds of alleged effects of global warming that have been claimed and reported in the media –from shrinking ice caps to shrinking sheep. Those effects may or may not be happening – and many are not; and those that are happening may or may not be due to global warming – and many are not; and those that are due to past global warming may or may not have been caused by human activity.
I want to tell you about the case for what is called “attribution” – the assignment of past and future global warming primarily to human activities.
The case boils down to two assertions.
- The recorded 20th century warming was exceptional when compared with previous climate change. Therefore, we must have caused it, and it was mostly our CO2 emissions that did it.
- Things will get much much worse in the future.
The Case for Attribution to Human Activity
1. Evidence That Twentieth Century Warming Was Exceptional
2. Models Say Future Warming Will Be Much Worse
If 20th century warming was in fact exceptional, then previous warming episodes and all natural variations must have been smaller.
Interestingly, in the first IPCC report of 1990, we saw this graphic of global average temperature since about the year 1000. The range of temperatures is about 2 degrees C across the millennium. There is a strong Medieval Warming Period, a deep Little Ice Age, and a sporadic warming trend since around 1700.
Early IPCC Report Found Current Temperatures Unexceptional
But when we get to the 2001 Report, we are presented with something much different–the Hockey Stick. It was based on various proxy “thermometers” such as tree rings. It suggests temperature purrs along merrily and constantly for a thousand years until the 20th century, when rapid warming takes off.
IPCC 2001: Hockey Stick as “Smoking Gun” 20th Century Warming Was Exceptional
The hockey stick became the poster child of global warming, the most celebrated graph since Descartes invented the idea of graphs. We saw it in Gore’s movie. It appeared over and over again in the IPCC report. Let me read from that report,
“The rate and duration of warming of the 20th century has been much greater than in any of the previous nine centuries. Similarly, it is likely that the 1990s have been the warmest decade and 1998 the warmest year of the millennium.”
End of argument? Well no. We now know that this statement is baseless; it rests on work laden with technical errors and outright finagling.
Climategate told us about the behind-the-scenes manipulations to promote and defend the stick, and to prevent opposing views from being published. But even before Climategate, the work of Steve McIntyre, Ross McKitrick, Hans Von Storch, and others had disposed of it from a science perspective. There are many documented serious problems with the stick.
The early statistical methods were found to be flawed:
- They would produce an upward “blade” even from bogie proxies with no trend whatsoever.
- The proxy method itself inherently underestimates past temperature changes by a factor of two or more.
- There is cherry-picking: the consistent and repeated inclusion of a small number of favorable proxies, while excluding many others from nearby locations that don’t show stick behavior.
- There is the arbitrary upward adjustment of at least one 20th century tree ring density decline.
- There is even an example of contrary data entered upside down so as to contribute to rather than subtract from stick behavior.
The most notorious issue involves a widely publicized e-mail string that has scientists discussing a so-called “trick” to “hide the decline.”
They were talking about how to deal with a problem in showing how tree ring proxies stack up to the actual temperature record.
The problem is that tree rings show a decline in their inferred temperature after 1960, while the actual temperature is believed to have increased. This is called the “divergence problem.”
At issue is whether tree rings can be trusted as proxy “thermometers” going back 1,000 years or more if they can’t reproduce the last 40. The divergence problem was well known before the revelations. What is new is that we now know the details of an organized effort to cover up the discrepancies.
[Slide 5] So in this graph from IPCC 2001, you see four proxy reconstructions wiggling along pretty flat for centuries, then starting up, but if you look closely, they mysteriously end around 1960. The actual instrumental record is spliced on to create an upward sweeping blade. The proxy data are actually deleted.
“Hide the Decline” Proxies Do Not Agree With Instruments Post 1960 – But Data Deleted in IPCC 2001
Delete proxy data and splice on temperature data