These images illustrate the typical spatial resolution used in
state-of-the-art climate models around the times of each of the
four IPCC Assessment Reports. Around the time of the First
Assessment Report (FAR) in 1990, many climate models used a grid
with cells of about 500 km (311 miles) on a side (upper left
image). By the time of the the Second Assessment Report (SAR) in
1996, resolution had improved by a factor of two, producing grid
cells 250 km (155 miles) on a side. Models references in the
Third Assessment Report (TAR) in 2001 generally had reduced grid
cells sizes to about 180 km (112 miles), while Fourth Assessment
Report (AR4) models typically used a 110 km (68 mile) wide grid
cell, further improving resolution. Vertical resolution is not
depicted in these images, but has also improved over the years.
Typical FAR models had a single-layer "slab ocean" and 10
atmospheric layers; AR4 models often include 30 layers in the
oceans and another 30 in the atmosphere. Notice how elements of
topography, such