Hydroclimatology of the U.S. Gulf Coast Under Global Climate Change Scenarios

Abstract

The historical climate record and climate change scenarios of the north-central Gulf of Mexico Coast (roughly from Houston, Texas to Mobile, Alabama) was examined to assess past and future temperature and hydrology of the region. Historical temperature data show an annual temperature pattern with high values in the 1920s-1940s, a drop in annual temperatures in late 1950s, persisting through the 1970s, and then an increase over the past two-plus decades. However, recent temperatures have mostly not reached the highs of previous decades. Annual precipitation is generally increasing, with some climate divisions, in particular those in Mississippi and Alabama, having significant long-term trends. 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. To assess future extremes in regional hydroclimatology, the A1B and B1 emission scenarios were examined for the region. Output from an ensemble of 21 global climate models run with the two emission scenarios indicates a wide range of possible climates in the mid-21st century, centered on the year 2050. The models suggest a warmer Gulf Coast region of about 1.5°C ± 1°C. Precipitation projections are more uncertain, with conflicting increases and decreases projected by the various models, although most suggest a decrease in annual rainfall across the Gulf Coast. By compounding changing precipitation with increasing temperatures, overall 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. Impacts to the natural landscape (geomorphology and ecology) would likely be negligible.