Zwiers (2002) asserts that more attention should be given to climate change scenarios of the next 10-20 years since there is reasonably good agreement among models over these time periods and these are the time periods of most interest to policy makers.
By putting projections in probabalistic terms, scientists can more effectively communicate recent results in a form that can be used by decision-makers. Recent studies (Knutti et al, 20023; Stott and Kettleborough, 2002) that put proababalistic limits on estimates of future changes indicate that increases of the global mean temperature by 2020-2030 are likely to be 0.4 to 1.2 K greater than the 1990-2000 average. This range represents the 5%-95% confidence limit of these projections. Knutti et al (2002) find that there is a 40% chance that warming over the next century will exceed the IPCC estimates and only a 5% chance that warming will fall below the IPCC range.
References
Knutti, R., T. F. Stocker, F. Joos, and G.-K. Plattner, 2002: Constraints on radiative forcing and future climate change from observations and climate model ensembles. Nature, 416, 719-723.
Stott, P. A., and J. A. Kettleborough, 2002: Origins and estimates of uncertainty in predictions of twenty-first century temperature rise. Nature, 416, 723-726.
Zwiers, F. W., 2002: The 20-year forecast. Nature, 416, 690-691.