History of climate modeling

Ferrel's three‐cell general circulation diagram.4

Atmosphere–ocean general circulation model (AOGCM) simulations of 20th century global mean surface temperature anomaly with (a) and without (b) anthropogenic forcing. Black line in both graphs represents observations. Thick red (a) and blue (b) lines represent the trend across all model simulations. Original caption: Comparison between global mean surface temperature anomalies (°C) from observations (black) and AOGCM simulations forced with (a) both anthropogenic and natural forcings and (b) natural forcings only. All data are shown as global mean temperature anomalies relative to the period 1901–1950, as observed (black, Hadley Centre/Climatic Research Unit gridded surface temperature data set (HadCRUT3); Brohan et al., 2006) and, in (a) as obtained from 58 simulations produced by 14 models with both anthropogenic and natural forcings. The multi‐model ensemble mean is shown as a thick red curve and individual simulations are shown as thin yellow curves. Vertical grey lines indicate the timing of major volcanic events. Those simulations that ended before 2005 were extended to 2005 by using the first few years of the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) A1B scenario simulations that continued from the respective 20th‐century simulations, where available. The simulated global mean temperature anomalies in (b) are from 19 simulations produced by five models with natural forcings only. The multi‐model ensemble mean is shown as a thick blue curve and individual simulations are shown as thin blue curves. Simulations are selected that do not exhibit excessive drift in their control simulations (no more than 0.2°C per century). Each simulation was sampled so that coverage corresponds to that of the observations. (Reprinted with permission from Ref 38. Copyright 2007 Cambridge University Press.)

The AGCM family tree.34 A Vast Machine: Computer Models, Climate Data, and the Politics of Global Warming (Cambridge: MIT Press, 2010), p. 168. Graphic by Trevor Burnham. Acronym expansions and further information is available at pne.people.si.umich.edu/vastmachine/agcm.html.

Spectral models handle horizontal motion in mathematical ‘wave space’ and vertical motions in physical grid space. Grid point values are computed by sampling the wave space. Graphic by Courtney Ritz and Trevor Burnham.

Processes incorporated in generations of GCMs from the mid‐1970s. Acronyms refer to the four assessment reports (AR) of the Intergovernmental Panel on Climate Change (IPCC), released in 1990 (FAR), 1995 (SAR), 2001 (TAR), and 2007 (AR4). (Reprinted with permission from Ref 38. Copyright 2007 Cambridge University Press.)

Schematic representation of the Cartesian grid structure used in finite‐difference GCMs. Graphic by Courtney Ritz and Trevor Burnham.