General circulation models (GCMs or global climate models) have been designed to simulate the planet's future climate.  In the past 30 years climate modelers have been improving the GCMs' spatial resolution from the first assessment report (FAR-1995) to the fourth report (AR4-2007) for the IPCC (Intergovernmental Panel for Climate Change) to meet the needs of climate change impacts models simulating finer scale processes. The scale has changed from ~500 km x 500km grid cells to ~110 x 110 km grid cells (see figure to right; source of graphics: IPCC 2007).

Despite these advances, important questions remain about the scale at which spatial and temporal interpolations of GCM projections are reliable. GCM projections cannot be used directly for regional or local impact assessments because the models were designed to simulate the entire planet's climate and their accuracy declines at the local scale due to their inherent coarse spatial resolution. In complex terrain, such as cliffs, deep valleys, rugged mountains, the local climate may decouple from the regional climate and create local processes that are difficult to measure, let alone simulate. Cold air drainage in valleys, temperature inversions, fog banks along large bodies of water, all feed back to the atmosphere but their measurements and representations in models are far from simple.

Downscaling techniques are used to bring GCM results to the scale of interest. Several methods exist, the follwoing are the most commony used:

 The uncertainty of the original GCM projections result from the imperfect knowledge of:

New findings from on-going changes in climate constantly bring scientists back to the drawing board to improve existing models.

In order to influence decisions with climate information, conservation practitioners need to be asking relevant questions to the providers of climate scenarios. For example, work by Daly et al. (2008) suggests that conservation biologists and climatologists should jointly explore issues relevant to the location of the study area including:

There are several galleries in Data Basin that provide snapshots of GCM projections used by climate change impacts groups.

Examples of Climate Modeling Teams and GCM acronyms:

Reference:

Daly, C., Halbleib, M., Smith, J.I., Gibson, W.P., Doggett, M.K., Taylor, G.H., Curtis, J., and Pasteris, P.A. 2008. Physiographically-sensitive mapping of temperature and precipitation across the conterminous United States. International Journal of Climatology 28: 2031-2064.