“No matter whose carbon dioxide emissions estimate is used, the climate impact of the oil transported by the pipeline is too small to measure or carry any physical significance. In deciding the fate of the Keystone XL pipeline, it is important not to let symbolism cloud these facts.” 
Climate change results from a variety of factors, both human and natural. The primary concern raised over the pipeline involves the carbon dioxide emissions that will result from the production and use of the oil that the pipeline will carry. It is the potential climate change from these emissions that will be the focus of my testimony.
In its Draft Environmental Impact Statement, the State Department finds, and I think that there is broad agreement on this point, that a barrel of oil produced from the Canadian tar sands carries about a 17 percent carbon dioxide emissions premium compared to the average barrel of oil finding its way into the U.S. market.
Disagreement: EPA vs. State Department
The disagreement between the State Department, the Environmental Protection Agency, and several environmental groups, involves how many new carbon dioxide emissions this 17 percent premium results in when considering the 830,000 barrels of oil that the pipeline will carry each day when operating at full capacity.
The State Department concludes that the economy of the tar sands oil is such that it will come to market one way or another whether or not the Keystone XL pipeline is ever built. It thus finds virtually no additional carbon dioxide emissions resulting from the project.
The EPA contends that the State Department is too quick to reach such a conclusion. The EPA argues that without the pipeline, much of that oil will remain in the ground, and thus, while the existence of the pipeline won’t result in more oil being used in the U.S., it will result in a 17 percent emissions premium on the pipeline’s portion that oil.
The EPA gives this extra amount as 18.7 million metric tons of carbon dioxide per year.
Several environmental organizations take the view point that while the pipeline may not increase the amount of oil used in the U.S., the oil that it displaces from the U.S. market will be consumed by other countries as the global demand for oil continues to grow. They calculate that the pipeline will result in about 181 million metric tons of additional carbon dioxide per year.
In these terms, the differences among the groups appear large and contentious, and much of the protestation involving the Keystone XL pipeline focuses on these emissions numbers. But, these protests are largely misplaced.
“CO2 Emissions are Not Climate Change”
It is imperative to keep in mind that the end game is climate change. Carbon dioxide emissions are not climate change. They influence climate change, but they are not a measure of it.
Therefore, before any type of assessment as to the potential climate impact of the pipeline can be made, it is essential to translate carbon dioxide emissions into climate units—such as the global average temperature. In other words, how much global warming will the pipeline produce? Isn’t that, after all, what everyone wants to know?
Why is it then that such numbers are absent in discussions of the impacts of the pipeline?
It is not as if there is no good way of calculating them—that is precisely what climate models are designed to do. Climate models emulate the earth’s climate system and allow researchers to change various influences upon it—such as adding additional carbon dioxide emissions—and then see what happens in the computer simulations.
So why haven’t they been applied to predict the climate impact of the pipeline? Because, if they were, the answer would be exceedingly tiny.
One One-Hundred Thousandths of a Degree (rounded up)
For example, using a climate model emulator that was developed by the EPA, I find that in the case of the State Department’s analysis, as there are very few additional carbon dioxide emissions resulting from the pipeline, there is essentially no associated climate change. Under the EPA’s assumptions, the average temperature rise works out to less than 0.00001°C per year—that is one one-hundred thousandths of a degree. 
And even under the assumption that all Keystone XL oil is additional oil in the global supply, the extra warming is still less than one ten-thousandths of a degree per year.
In other words, if the pipeline were to operate at full capacity for the next one thousand years, it would raise the global average surface temperature by less than 1/10th of a degree!
It is this information, not the information on carbon dioxide emissions, that is required to properly assess the climate change aspect of this or any other proposed project or regulation.
In these terms, the difference between the State Department’s Environmental Impact Statement and those of its critics all but vanish.
No matter whose carbon dioxide emissions estimate is used, the climate impact of the oil transported by the pipeline is too small to measure or carry any physical significance. In deciding the fate of the Keystone XL pipeline, it is important not to let symbolism cloud these facts.
 Oral Statement: Joint Hearing, “Keystone XL Pipeline: Examination of Scientific and Environmental Issues,” U.S. House of Representatives, Committee on Science, Space, and Technology, Subcommittee on Energy and Subcommittee on the Environment (May 7, 2013). For the past 25 years, Knappenger has conducted research on climate and climate change, including the impact of potential human influences on climate.
 The exact number is closer to 0.0000055degC/yr.
The full testimony of Mr. Knappenberger can be found here.