FIGURE 3.1 Illustration of increasing complexity and diversity of elements incorporated into common models used in the Intergovernmental Panel on Climate Change (IPCC) process over the decades. Evolution of the resolution (left side) and physical complexity (right side) of climate models used to inform IPCC reports from the mid-1970s to the most recent IPCC report (IPCC, 2007a,b,c). The illustrations (left) are representative of the most detailed horizontal resolution used for short-term climate simulations. SOURCES: Figure 1.2 and 1.4 from IPCC (2007c). FAR, First Assessment Report, 1990; SAR, Second Assessment Report, 1995; TAR, Third Assessment Report, 2001; AR4, Fourth Assessment Report, 2007.
Although comprehensive climate models are becoming more complex, an increasing range of other models has helped to evaluate and understand their results and to address problems that require different tradeoffs between process complexity and grid resolution. Uncoupled component models, often run at higher resolution or with idealized configuration, allow a more controlled focus on individual processes such as clouds, vegetation feedbacks, or ocean mixing and enable the behaviors of the uncoupled components to be studied in more detail.