Kavli Institute
Coastal Morphology Group • Scripps Institution of Oceanography

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The Past

he state of our beaches is one of many systems dependent on southern California's climate.

Recent history
Weather records, available since about 1850, show annual fluctuations in rainfall.

Graph of rainfall in San Diego, 1851-2002.
Upper: Historical rainfall in San Diego, 1851-2002.
Lower: Cumulative residual rainfall in San Diego, for the same period, highlighting decadal scale rainfall trends.
* Definition of water year.
** Definition of cumulative residual.

Trend analysis of this record reveals wet and dry periods that may persist for several decades. From 1946 to 1977 there was a major dry period. The period between 1978-1998 experienced a wet trend. What will happen now? Perhaps another dry period beginning in 1999 as indicated by the PDO index (Click here to learn more about PDO).

Long-term climate cycles
Beyond the historic record, proxy records extend our knowledge of climatic conditions hundreds and thousands of years into the past.

  • California has experienced "megadroughts" lasting 200 years.
  • Megafloods hit southern California within the last 600 years -- floods 8 to 40 times larger than the biggest recorded flood.
  • El Niño frequency has increased in the last 5,000 years.
  • Globally, climate has switched abruptly from warm conditions to glacial conditions within a decade or two.
To learn more about past climates:
   • Paleoclimatology, NOAA
     This site provides "the paleoclimatic data and information needed to understand the
     climate of the past, in order to assess the current and potential future climate
     in the context of natural climate variability."

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Coastal Morphology Group • Scripps Institution of Oceanography

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