Recently I read an article in Nature that highlighted major issues with the IPCC report. This article is titled Dangerous Assumptions and written by Roger Pielke, Tom Wigley, and Christopher Green. The main argument put forward by the authors is that the Intergovernmental Panel on Climate Change (IPCC) assumes a large amount of spontaneous technological advancement which is unrealistic and dangerous. For example, 2/3 of the improvements required to stabilize the atmosphere is already built into the IPCC AR4 (4th Assessment) report, their most recent report. The authors argue that the IPCC estimates are optimistic at best and unachievable at worst.
In addition, the reference scenarios used for the AR4 report have not been updated since 1994. These scenarios are discussed in the 2000 Special Report on Emission Scenarios (SRES). In response, climate scientists state that these details do not effect the results published in the IPCC AR4 report because the scenarios are ran for long periods of time, collecting data on averages not deviations from the mean. Secondly, many scenarios are ran to cover a wide range of future emission situations, which in turn requires policy action from the government. I have included links to some graphs from the IPCC SRES report to help explain the various scenarios.
The first graph is a basic break down of the various IPCC scenarios. Moving the bottom of the tree to the top means the scenarios are changing from low to high economic growth. Moving from the left of the tree to the right means the scenarios are changing low to high population growth. For more details on each scenario please see the SRES report.
The second graph shows projections for the various SRES scenarios. In the IPCC report the CO2 emission drivers include Population, Economic Activity (GDP) per capita, Energy Intensity (energy consumption per unit of GDP) and Carbon Intensity (CO2 emission per unit of energy). These same drivers were used by the authors analysis of assumptions in the IPCC AR4 report.
The authors of this article analyzed the spontaneous technology portion of each scenario to understand how much of the future carbon emissions was already accounted for in the baseline assumptions. They approached this problem by implementing a frozen technology baseline, thus eliminating spontaneous decarbonization. This revealed that a huge amount of emission-reducing technology is already built into the SRES scenarios.
Figure 1 in the article highlights how a large amount of projected decrease in carbon dioxide production is due to spontaneous technological development. The bar graph has three colors, blue, red and yellow. Blue indicates the reduction in carbon dioxide due to spontaneous technological development, Red indicates reduction due to climate policy and Yellow is where atmospheric carbon dioxide would be considered stabilized (500 p.p.m). One can immediately see that the blue section of the bars on the graph are larger than the red section, for all scenarios. For some scenarios this difference is quite large. Figure 2 in the article hits upon our current problem, that many past predictions can not keep up with the current observations. All of the IPCC AR4 scenarios are too conservative, thus predicting changes in Energy Intensity and Carbon Intensity that are lower than observations between 2000-2005.
These IPCC predictions indicate a decline in Energy Intensity exceeding 1.0% per year, this is unrealistic. One can only hope for approximately a 20% (+/- 10%) decrease in Global Energy Intensity due to sectoral shifts over a century. The observed rise in Global Energy and Carbon Intensities is due to developing worlds like China and India. In these countries many of the rural populations are moving to cities, where consumption of energy and energy-intensive materials is higher. This is obviously not accounted for in the IPCC scenarios. For example, China’s carbon dioxide emissions have risen by 11%-13% each year from 2000-2010 but the SRES Scenarios only assume a 2.6%-4.8% increase.
From these results the authors conclude that the IPCC report assumes most technological advances will occur automatically. Instead of pushing an overly optimistic future they should be using their report to shake things up and create conditions for the innovations assumed in the IPCC report to occur. These reports have a large effect on US Science Policy, thus all assumptions need to be stated clearly. Policy makers need to be fully informed, thus they need to know that the assumed technological transformations would take decades to complete, even if we started now. Fortunately the IPCC panel plans on updating the SRES in it’s next report, due in 2013 or later, but in the meantime policy makers need to be aware of how conservative the IPCC report really is.