Climate Change Impacts in the Gulf Coast Philip B. Bedient Civil & Environmental Engineering Rice University

Climate Change History n Earth’s climate has always been changing –Ice age (2 m.y.a.), glacial periods, polar ice caps –18,000 yrs ago: cold spell & continental glaciers n Last 100 yrs, surface has warmed about 0.6°C n In past 10,000 yrs, global temp. has never varied more than 1.5°C

Why has it been changing? n Various theories n Intricate & complex relationship b/w ocean, atmosphere, ice, and other elements n No climatic element in systems is isolated n Influences path of ocean currents, transport of heat, global wind system, and climates

Key Predictions for Future n Increased warming –5-9°F increase next 100 yrs n Differing regional impacts n Vulnerable ecosystems n Widespread water concerns n Secure food supply n Near-term forest growth increase n Damage in coastal/permafrost areas n Adaptation determines health

Greenhouse effect n Delicate balance of incoming & outgoing energy in earth-atmosphere n Atmosphere gases (water vapor, CO 2, CH 4, halocarbons, O 3 ) absorb Earth’s heat n Radiate some heat back to Earth, some passes through into space n Humans change atmosphere –burn coal, oil, natural gas, destroy forests –CO 2 risen 30%, CH 150% in past 100 yrs –CO 2 risen 30%, CH 4 150% in past 100 yrs n Heat energy can’t pass into space

Increasing Greenhouse Gases n Unusual rapid warming of 0.6°C in 20th century n Human activities major cause of warming n Carbon emissions have increased from 1 to over 7 billion metric tons/year n Lifetimes of gases last centuries n CO 2 Predicted to triple by 2100

Climate Assessment Tools n Historical records & climate simulations n General Circulation Model (GCM) –model Earth’s climate –incomplete, but still state-of-science n Two main models- Hadley & Canadian

Hadley & Canadian Models n Principles driving models are similar n Differ in representation of effects of important processes n Thus, different views of 21st century climate n Hadley predicts wetter climate n Canadian predicts greater temp increase n Uncertainties –how to represent clouds & precipitation –how emissions of greenhouse gases will change

Past & Future Temperature Change

Precipitation Change n Large increases in 20th century (5- 10%) n Due to frequency & intensity growth n Increasingly frequent heavy precipitation events in 21st century

Soil Moisture n Critical for agriculture & natural ecosystems n Levels set by precipitation, run-off, evaporation, soil drainage n Higher temp increases evaporation, removing moisture n Models differ due to different temp & precipitation predictions

Future Ecosystem Changes n Vegetation response to CO 2 concentrations double present levels

Multiple stresses n Climate only one of changes in global environment n Effects of climate & other environmental changes

Common Climate Changes n Predict increased warming, precipitation, evaporation Northwest West Midwest Pacific northwest Islands

Common Issues n Weather extreme increase n Natural ecosystem, species, and biodiversity changes n Water resource changes (lake levels, snow melting) n Public health and safety n Shifts in tourism and recreation n Sea-level variability

Southeast n Half of remaining wetlands located here n Rapid growth (30% population increase b/w 1970 & 1990) n Produces half of U.S. timber supplies n Warming and thus higher evaporation predicted n Lower soil moisture n Significant precipitation increase also predicted

Southeast: Future Climate Scenarios

Southeast: Impacts on Humans n Weather-related stresses –frequent weather disasters: drought, hurricane –flooding in Texas (low-lying coast counties) –high heat index & poor air-quality to increase death rate –southern heat wave & drought of 1998: $6 billion in damages & over 200 deaths –8 to 15° heat index increase for southernmost states

Southeast: Climate Effects n Crop and economy impact –will vary according to area and crop –adaptation: switch crops, vary planting dates, water usage, crop rotations, fertilizers n Water quality stresses –sewage, dead animals, fuel, chemicals from flooding –high temp- decrease dissolved oxygen

Southeast: Climate effects n Coastal area threats –sea-level rise will impact ecosystems –Obvious impacts on coastal flooding n Forest productivity shifts –greater CO 2 : production increase in north –Pine trees

Climate Change Summary n Warmer temp will lead to more vigorous hydrological cycle- severe droughts &/or floods n Uncertain predictions, especially in timing, magnitude, & regional patterns of climate change n Balance of evidence shows there is discernible human influence on global climate