Integrated assessment models of climate change/global environment should:
One such model, IMAGE 2.0, is a process-based, geographically explicit model of the global system which integrates society, biosphere and climate. Applications of the model include providing scenarios for the Intergovernmental Panel on Climate Change (IPCC) working groups, the Core Project of the International Geosphere-Biosphere Programme, and others contemplating the impacts of global climate change.
The goal of the IMAGE 2.0 model is to present a balanced and integrated representation rather than to advance any of the particular areas of modeling. Economic calculations for driving forces are done on a regional basis; other calculations are done on a grid- cell basis. The size of a grid cell is half a degree latitude by half a degree longitude so cities do not show up. Even very large cities like Tokyo and New York do not cover more than 40% of any grid cell.
How might such a model be used to anticipate surprises? It can be helpful in seeing how nonlinear linkages of components of the system can produce surprises. Two potential surprises that emerge from the IMAGE 2.0 integrated assessment model are a change in the methane trend and a possible ocean circulation realignment.
Methane Trend Potential Surprise
Following water vapor and carbon dioxide, methane is the next most important gas contributing to radiative forcing. The counter- intuitive surprise scenario that emerges from the model is that even though methane emissions continue to increase, atmospheric concentrations of methane decrease after a peak in the year 2050 due to an increase in hydroxyl (OH) radical production and concentrations. This surprise scenario is a result of the coupled effects of land-cover changes, decreases in biomass burning, downward trends of carbon monoxide and methane emissions, and concentrations of hydroxyl radical and methane in the atmosphere.
Ocean Realignment Potential Surprise
This scenario assumes a slowing of the Gulf Stream and a 70% reduction of downwelling in the North Atlantic followed by stabilization. Thermohaline circulation is essentially switched off, resulting in reduced transport of heat from the tropics and a drop in surface air temperature of 2.5 degrees C in the Northern Hemisphere. Model runs indicate that this initial surprise then generates other surprises. The boreal forest is the major carbon sink in the year 2050, but ceases to be a carbon sink when the temperature cools by 2.5 degrees C, resulting in a net buildup of CO2 with uncertain consequences.
Changes in ocean circulation can significantly affect the pattern and amplitude of climate change, the global carbon cycle, and the extent of agricultural areas. The strongest effect on the carbon cycle is the indirect effect of climate on the terrestrial carbon sink. Integrated modeling permits a more complete assessment of the potential impacts of such changes. In response to the question: "What happens if you turn the deep-water formation back on?" It appears that the rate of temperature rise concentrated in high latitudes where the downwelling occurs increases about threefold.
Conclusions regarding surprises:
Conclusions regarding integrated models:
Integrated models can be tools to study and anticipate surprises:
How can we design policies and research robust to surprise?
In short, integrated assessment models are useful in that the couplings bring interesting nonlinearities (surprises) to the surface.
In the discussion which followed Alcamo's presentation, it was pointed out that the IMAGE 2.0 model, despite its Dutch lineage, fails to include sea level rise.
