Background
The authors write that "the north-central Gulf Coast of the United States was selected by the United States Department of Transportation as a test case for planning in the face of climate change," with the region selected running roughly from Houston, Texas to Mobile, Alabama, which area is important to the nation for its "oil and gas industry, strategic port facilities, abundant fisheries and tourism," as well as the fact that the bulk of the region's infrastructure "rests within dynamic and biologically productive wetland environments."

What was done
As their contribution to this activity, Keim et al. assessed changes in the hydroclimatology of the region "over the instrumental climate record, as well as how the regional climate may change in the future according to an ensemble of state-of-the-art general circulation models" that were "used in the latest Intergovernmental Panel on Climate Change (IPCC) report for future projections at global and regional scales (Christensen et al., 2007; IPCC, 2007; Meehl et al., 2007)." More specifically, in this latter instance, they say they used the IPCC A1B and B1 emission scenarios to drive the output from an ensemble of 21 global climate models to calculate results for the mid-21st century, centered on the year 2050.

What was learned
The four researchers found that "the historical record shows this region as cooling and getting wetter," noting that "recent temperatures have mostly not reached the highs of previous decades," and stating that "annual precipitation is generally increasing, with some climate divisions, in particular those in Mississippi and Alabama, having significant long-term trends." Thus, as they continue, "over the entire record since 1919, there was an increase in rainfall, and that, combined with relatively cool temperatures, led to a 36% increase in runoff." As for the future, they report that "the models suggest a warmer Gulf Coast region of about 1.5°C ± 1°C," while "precipitation projections are more uncertain, with conflicting increases and decreases projected by the various models."

What it means
"Overall," as Keim et al. conclude, "runoff is likely to remain the same or decrease, while deficits (or droughts) could become less severe because of possible increases in summer and autumn precipitation," as observed by certain of the models, such that in the final analysis, "impacts to the natural landscape (geomorphology and ecology) would likely be negligible."

References
Christensen, J.H., Hewitson, B., Bisuioc, A., Chen, A., Gao, X., Held, I., Jones, R., Kolli, R.K., Kwon, W.-T., Laprise, R., Magana-Rueda, V., Mearns, L., Menendez, C.G., Raisanen, J., Rinke, A., Saar, A. and Whetton, P. 2007. Regional climate projections. In: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Avery, K.B., Tignor, M. and Miller, H.L. (Eds.). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge University Press, Cambridge, United Kingdom/New York, New York, USA, pp. 847-940.

Intergovernmental Panel on Climate Change (IPPC). 2007. Climate Change 2007 - Synthesis Report. Cambridge University Press, Cambridge, United Kingdom/New York, New York, USA.

Meehl, G.A., Stocker, T.F., Collins, W.D., Friedlingstein, P., Gaye, A.T., Gregory, J.M., Kitoh, A., Knutti, R., Murphy, J.M., Noda, A., Raper, S.C.B., Watterson, I.G., Weaver, A.J. and Zhao, Z.-C. 2007. Global climate projections. In: IPCC Climate Change 2007: The Physical Science Basis: Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M. and Miller, H.L., Eds.), Cambridge University Press, Cambridge, United Kingdom/New York, New York, USA, pp. 747-846.