Transcript of My Talk “Considering the Human Influence on Climate” At The George C. Marshall Institute

The Transcript of my presentation “Considering the Human Influence on Climate” by Dr. Roger A. Pielke, Sr. May 14, 2009 is now available, courtesy of the George C. Marshall Institute.  The transcript also includes questions from the audience along with my answers. The overview of the talk is also available.

Dr. Mike Macracken and I both have discussed the talk in weblogs (see and see).

Excepts from the transcript include the discussion on vulnerability where, I said

So what is my suggestion? There is no doubt in my mind that there are multiple types of human climate forcings. CO2 is important and we need to look at it, but there is a range of other forcings. Policymakers should look for win-win policies in order to improve the environment that we live in. The costs and benefits of the regulation of the emissions of CO2 into the atmosphere need to be evaluated together with all other possible environmental regulations. The goal should be to seek politically and techno-logically practical ways to reduce the vulnerability of the environment and society to the entire spectrum of human-caused and natural risks.

I want to give an example here. Figure 28 is from some work that I published about a year ago8 with respect to a Colorado report on climate change. In that report they took the IPCC model assessments and were trying to tell the water managers in Colorado and other parts of the west what the weather conditions are going to be for the next twenty, thirty, forty and fifty years into the future. I was asked to write a short essay, because they knew I disagreed with taking the IPCC models and using them on a regional scale. I said, “Let’s look at the natural variation in the past.” This is work by Connie Woodhouse at the University of Arizona. The graph in Figure 28 is tree ring data and is basically a measure of dryness in the western part of the United States go-ing back to about 800 A.D. What you see is that it goes up and down and the message of this data is that there were more serious droughts in the natural record prior to European settlement than there have been in the 20th century. That means that we are already at risk and we don’t know whether human disturbance of the climate system pushes us toward or away from having more frequent droughts. The bottom line is that because they have happened in the past, we need to be prepared for droughts anyway. That is a bottom-up, resource-based perspective; it is not one you can drive by changing CO2. I think this is a message that needs to be communicated.

I asked one of the IPCC authors whether his model results fall inside or outside of this envelope. He said it falls inside of the envelope. The bottom line is that in spite of what the IPCC models state, we need to do something. In fact, if you are a strong advocate of the IPCC models, factor that into your vulnerability assessment, but don’t consider that is the universe of what could happen in the future, because that is not what has happened in the past. You can also see this is a very chaotic signal and it never repeats itself. We have a different environment now with different CO2, land use, and aerosols. We do not know our trajectory, and here is how I propose that we move forward: we need a bottom-up, resource-based focus rather than relying on downscaling from global climate models. I have done a lot of work on downscaling and showed that you are not really adding anything with downscaling. I can talk about that at another time, if you like. The IPCC focus is top down, meaning you take a global model and downscale it and give it to the resource people and say, “this is what is going to happen in 2030 or 2040.” I think that is a mistake. What we need to do is look at the risks that the resources face.

Figure 29 shows one example of that: water resource vulnerability. How can we reduce our vulnerability to problems with water quality and water quantity? Obviously in the west that is a major issue. There are a variety of threats: natural landscape change, land management changes, long-term weather variability and change, human population demands, animal and insect dynamics, industrial and vehicular emissions and so forth, and they all interact with each other. We should look at our vulnerability to risk with today’s society and what we anticipate the society might be ten, twenty, or thirty years from now and try to make our system more robust to these resources. We should make our system robust to risk from the environment and from human activity, rather than relying on these IPCC models to tell us what is going to happen to the future and assuming that we can actually control climate, which I think is hubris. We can’t say that we have to prevent human intervention in the climate system; we are already intervening in the climate system.”

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