Dear Ermias Teferi,

For your assessment protocol, you can rely on future projections of Earth system / Climate models that have contributed to the Coupled Model Intercomparison Project Phase 5. All the forcing fields should be on the CMIP5 database.

For the question on the reliability, several recent studies have evaluated models against recent observations, and sometimes provided ranking of models for some parameters. For example:

Anav, A., Friedlingstein, P., Kidston, M., Bopp, L., Ciais, P., Cox, P., et al. (2013a). Evaluating the Land and Ocean Components of the Global Carbon Cycle in the CMIP5 Earth System Models. Journal of Climate, 26(18), 6801–6843. doi:10.1175/JCLI-D-12-00417.1

Anav, A., Murray-Tortarolo, G., Friedlingstein, P., Sitch, S., Piao, S., & Zhu, Z. (2013b). Evaluation of Land Surface Models in Reproducing Satellite Derived Leaf Area Index over the High-Latitude Northern Hemisphere. Part II: Earth System Models. Remote Sensing, 5(8), 3637–3661. doi:10.3390/rs5083637

Piao, S., Sitch, S., Ciais, P., Friedlingstein, P., Peylin, P., Wang, X., et al. (2013). Evaluation of terrestrial carbon cycle models for their response to climate variability and to CO2 trends. Global Change Biology, 19(7), 2117–2132. doi:10.1111/gcb.12187

And for a large overview of CMIP5 models:

Knutti, R., Masson, D., & Gettelman, A. (2013). Climate model genealogy: Generation CMIP5 and how we got there. Geophysical Research Letters, 40(6), 1194–1199. doi:10.1002/grl.50256

You can also found interesting information on the last IPCC report...

One major issue to use these model projections is that climate mean-state is more or less biased. If such biases are found in variables used to define ecosystems' tipping points, thresholds...(in temperature or precipitation for example), they can mix up the response of ecosystems to climate change.

Some bias-correction methods exist in the literature (e.g., Li et al., 2010) and are quite often used for impacts studies.

Li, H., Sheffield, J., & Wood, E. F. (2010). Bias correction of monthly precipitation and temperature fields from Intergovernmental Panel on Climate Change AR4 models using equidistant quantile matching. Journal of Geophysical Research, 115(D10), D10101. doi:10.1029/2009JD012882

I hope this helps.