Climate Models

A reference to a climate model can refer to a global climate model (GCM) or a regional climate model (RCM).

GCMs can be divided into three groups, atmospheric GCMs (AGCM), oceanic GCMs (OGCM), or coupled atmospheric and oceanic GCMs (AOGCM).

It is important to note that GCMs are run independent of temperature measurements ref. Thus, changes to a temperature record will not affect GCM output. However, the GCM trends are often compared to measured temperature and other trends; if the trends were found to be sufficiently divergent, the GCM would require retooling until it became reasonably in line with actual recorded temperatures. In light of this, although recorded temperatures are not inputs into GCMs, they can and do affect model validation.

Furthermore, Kevin Trenberth states:

None of the models used by IPCC are initialized to the observed state and none of the climate states in the models correspond even remotely to the current observed climate. In particular, the state of the oceans, sea ice, and soil moisture has no relationship to the observed state at any recent time in any of the IPCC models. There is neither an El Niño sequence nor any Pacific Decadal Oscillation that replicates the recent past; yet these are critical modes of variability that affect Pacific rim countries and beyond. The Atlantic Multidecadal Oscillation, that may depend on the thermohaline circulation and thus ocean currents in the Atlantic, is not set up to match today’s state, but it is a critical component of the Atlantic hurricanes and it undoubtedly affects forecasts for the next decade from Brazil to Europe. Moreover, the starting climate state in several of the models may depart significantly from the real climate owing to model errors. I postulate that regional climate change is impossible to deal with properly unless the models are initialized.ref

IPCC 2001 Chapter 8 discusses model evaluation. Armstrong & Green (2007) evaluated the forecasting skill of the IPCC models and said "We have been unable to identify any scientific forecasts to support global warming. Claims that the Earth will get warmer have no more credence than saying that it will get colder." this paper was briefly discussed on CA.

CA posts on GCMs

CA has a section on modeling

Hansen in Antarctica: Compares Hansen et al. (1988)'s model projections with actual temperature observations in Antarctica.

RSS Corrects 2007 Error: The error correction is discussed in relation to Hansen et al. (1988), along with some new information regarding comparing satellite and surface temperatures provided by J Christy.

Hansen Scenarios A and B - Revised is a further look at Hansen et al. (1988) scenarios, breaking down each forcing prediction (CO2, CH4, etc) and how well they held up over time.

Pielke Comparison of Trends 1990-2007 is a discussion thread based on Pielke's post comparing Hansen et al. (1988), and all IPCC model accuracy with temperatures from different sources to 2007.

Hansen Scenarios A and B - Original: The original post on Hansen et al. (1988) scenarios, this post was updated and the newer revision should be consulted here.

Hansen GHG Concentration Projections: is a first look at various Hansen et al. (1988) and IPCC forcing predictions and how well they've held up.

Thoughts on Hansen et al 1988: Takes an initial look at Hansen et al. (1988) and its scenarios' relations to current temperatures. The Hansen model seems to predict a larger temperature increase than occurred.

Pielke Jr on IPCC Predictions is a discussion thread based upon Pielke Jr's post showing that 1990-92 IPCC GCMs have overestimated temperature increase due to global warming through 2007 when compared to surface and satellite temperature records.

AR4: “ad hoc tuning of radiative parameters” discusses the unscientific tuning of some (4?) AR4 IPCC GCMs.

AR4: “Now-Classic” Results on Cloud Uncertainty are “Unsettling” explores the statement that "They produced global average surface temperature changes (due to doubled atmospheric CO2 concentration) ranging from 1.9°C to 5.4°C, simply by altering the way that cloud radiative properties were treated in the model."

IPCC and Radiative Forcing #2: 1992-AR2

IPCC on Radiative Forcing #1: AR1(1990)

In Kiehl (2007) on Tuning GCMs CA summarizes and discusses some key points of the paper including; that there are no standard datasets for ozone, aerosols or natural forcing factors (all prominent features of modern models), the magnitude of applied anthropogenic total forcing compensates for the model sensitivity, and GCMs may do little more than embody certain key assumptions.

Hansen and Model Reliability - Compares recent temperatures with older model predictions from Hansen et al. (1988).
backtested a Hansen and Gavin Schmidt model
complexity of the Navier-Stokes equations behind some models.

many more exist but are not entered yet.