Republican Riber Basin Water and Drought Portal

ENSO Outlooks and Climate Change

El Niņo-Southern Oscillation (ENSO)

Atmospheric and oceanic conditions cause El Niño and La Niña episodes. El Niño episodes reflect periods of exceptionally warm sea surface temperatures across the eastern tropical Pacific while La Niña episodes represent periods of below-average sea surface temperatures across the eastern tropical Pacific. For residents in the Republican River Basin this typically means that during an El Niño event there are wetter conditions and during a La Niña event the conditions are drier.  However, that isn’t always the case, as the events can vary depending on local climate variability too.  That is why it can be so difficult to predict these events.

An El Niño event occurs when the temperature stays +0.5 degrees C for at least 3 months.  La Niña events are the opposite; temperatures have to stay at -0.5 degrees C for three months to be considered a real La Niña event.  These events typically last approximately 9 to 12 months. They often begin to form during June through August, reach peak strength during December through April, and then dissipate during May through July of the next year. However, some prolonged episodes have lasted 2 years or even as long as 3 to 4 years. While their periodicity can be quite irregular, El Niño and La Niña events occur every 3 to 5 years on average. Improved knowledge of climate dynamics has resulted in improvements in long-term forecast capabilities of dynamic climate models. Such forecast information can assist water resource managers (NOAA, 2008).

Qi Hu and Song Feng have written papers in regard to the interannual variation in summer rainfall in the central United States.  They have looked at how interannual variations of the summer rainfall in the central U.S. correlates with the sea surface temperature in the Pacific Ocean and the southerly flow from the Gulf of Mexico.  Click on the links below to see the full paper.

Hu, Q, Feng, S. 2000. Variations of Teleconnection of ENSO and Internanual Variation in Summer Rainfall in the Central United States.  American Meteorological Society.

Hu, Q, Feng, S. 2000. Climatic Role of the Southerly Flow from the Gulf of Mexico in Interannual Variations in Summer Rainfall in the Central United States.  American Meteorological Society.
  
More detailed descriptions about El Niño and La Niña events can be found on the NOAA website. The Climate Predication Center also has a list of current El Niño effects on all U.S. states. The site shows historical El Niño-related precipitation effects on each state as well as graphics related to the events.

El Niño/La Niña Links

Water Resources and Climate Change

Although we don’t know exactly how climate change will affect regional water resources, it is clear that water resources are already stressed and any additional stress from climate change or increased variability will only intensify the competition for water resources. Observations since 1961 show that the average temperature of the global ocean has increased to depths of at least 3,000 meters and that the ocean has been absorbing more than 80 percent of the heat that has been added to the climate system. Overall the U.S. has warmed but the exact change varies by each region. Based on information from a report put together by the U.S Climate Change Science Program, historical documents show that 1995 to 2004 was the warmest decade worldwide in the last 1,000 to 2,000 years.

No matter what region, weather and climate factors (water availability, temperature, precipitation, and concentrations of carbon dioxide) impact the health of livestock, plants, and land.  Variation in yield between years is related to the weather during the growing season.  The weather also influences insects, weeds, and diseases, which all have an effect on agricultural production.

In all likelihood, the direct impacts of climate change on water resources will be hidden beneath natural climate variability. With a warmer climate, droughts and floods could become more frequent, severe, and longer-lasting. The potential increase in these hazards is a great concern given the stresses being placed on water resources and the high costs resulting from recent hazards. From 1980 to 2009, losses from 16 drought and wildfire events in the United States totaled $186 billion (NCDC, 2010). On the other hand, thirteen flood events totaled $70 billion. Regardless of which disaster occurs, extreme events could end up being more cause for concern than the long-term change in temperature and precipitation averages.

U.S. water management practices are quite advanced, but the reliance on past conditions as the foundation for future planning will not be as tenable since climate change creates conditions outside of historical parameters.  The best advice to water resource managers regarding climate change is to start addressing current stresses on water supplies and build flexibility and robustness into any system as well as incorporating conservation measures and techniques. Flexibility helps to ensure a quick response to changing conditions, while robustness helps people prepare for and survive the worst conditions. With this approach to planning, water system managers will be better able to adapt to the impacts of climate change, whatever they may be, and will also be better equipped for the climate variability we have now (NDMC, 2008).

References Cited

National Climatic Data Center. (n.d.). Billion Dollar U.S. Weather Disasters. Retrieved from http://www.ncdc.noaa.gov/oa/reports/billionz.html#narrative

National Drought Mitigation Center. (n.d.). Retrieved from http://www.drought.unl.edu/

National Weather Service Climate Prediction Center. (n.d.). El Nino/La Nina Home. Retrieved from http://www.cpc.noaa.gov/products/analysis_monitoring/lanina/

Other Climate Change Links