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Louisiana
Climate Projections
Louisiana's climate has always been variable and sometimes extreme—and climate change may intensify this historical pattern. Average state temperatures have varied substantially over the past century, with a warming trend of about 1°F since the late 1960s. Extreme rainfall events, primarily thunderstorms, have increased during the 20th century. While rainfall totals have changed little, seasonal trends are apparent—winter average rainfall has increased slightly and summer totals have decreased somewhat. Louisiana's rate of relative sea-level rise is the highest in the United States. Water levels along the Louisiana coast—from Holly Beach to New Orleans to the Chandeleur Islands—have risen by up to 40 inches over the past 100 years due to a combination of globally rising seas and substantial local sinking of the land (subsidence).
Present Climate in Louisiana
- Louisiana has a warm and humid climate.
- Annual rainfall totals range from 40 to 70 inches, making rainfall an integral part of life in Louisiana.
- Rainfall is brought by extratropical storms in the winter, and thunderstorms and tropical storms in the summer and fall.
- Tropical storms strike the Louisiana coast nearly once every four years on average, but hurricane frequency varies by decade and is strongly influenced by the El Niño–La Niña cycle.
- Occasionally, Louisiana experiences substantial flooding, especially during hurricanes, but is also familiar with droughts, especially during La Niña events—such as the 25-month-long drought from 1998-2000.
| Projected Climate Changes in Louisiana |
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3-10°F rise in winter lows and 3-7°F rise in summer highs. July heat index-a measure combining temperature and humidity-could rise by 10-25°F. The freeze line is likely to move north.
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Rainfall is likely to decrease in the immediate coastal regions of Louisiana, resulting in drier conditions. Models also project significant summer soil moisture decreases in coastal regions. In upland areas, one model projects wetter conditions, while the other projects drier conditions.
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More frequent intense rainfall events are expected, with longer dry periods in between. Hurricane intensity (characterized by maximum wind speeds and rainfall totals) could increase slightly with global warming, although changes in future hurricane frequency are uncertain. Even if storm frequencies and intensities remain constant, the damages from coastal flooding and erosion will increase as sea level rises.
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Sea level will increase at a faster rate over the coming century. By 2100, ocean levels around Louisiana could be 24–47 inches higher than today, based on a continued average subsidence rate of 8–31 inches per century and a mid-range sea-level rise scenario. Even a relatively small vertical rise in sea level (a few inches to 1 foot) can move the shoreline inland by substantial distance (several tens of feet) along low-lying, flat coastal areas.
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Temperature and precipitation will continue to vary, in part related to the ENSO (El Niño / Southern Oscillation ) cycle.
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Photo Credits:
Brown Pelican - South Florida Water Management District.
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