Climate Change in California: Costly Damage Worsened by Fossil Fuel Companies’ Science Deception

Published Mar 29, 2016

California is suffering from the costly effects of climate change—damages that have been worsened by three decades of uncontrolled emissions and fossil fuel companies’ documented deception about climate change science. Californians’ health, property, economy and environment have all been harmed by the pollution and misinformation propagated by coal, oil and gas companies, particularly Chevron, ExxonMobil, BP and Shell. The National Academy of Sciences affirmed in March 2016 that it is possible to estimate the influence of climate change on some types of specific extreme events, in particular: heat waves, cold snaps, droughts and heavy precipitation. This UCS backgrounder summarizes official state assessments, research and other sources about climate change impacts in California.


  • The July 2006 heat wave caused 140 heat-related deaths in California. Heat-related illnesses—such as heat stroke, electrolyte imbalance, acute renal failure, kidney disease, diabetes and cardiovascular diseases—resulted in more than 16,000 excess emergency department visits (Indicators of Climate Change in California, pp. 124-26).
  • Mortality from cardiovascular conditions on extremely hot days is estimated to be up to 28 percent higher than normal. The elderly, infants and African Americans are at higher risk for hospitalization for stroke, diabetes, acute kidney failure, dehydration and pneumonia. Preterm delivery is more likely for all pregnant women (Our Changing Climate 2012, p. 4).
  • Residents of socioeconomically disadvantaged neighborhoods in the Los Angeles, Sacramento, San Diego and San Francisco metropolitan areas are at greater risk of heat-related illnesses due to the “urban heat island effect” (Indicators of Climate Change in California, p. 130).
  • The Asian tiger mosquito, which transmits dengue and chikungunya viruses, has recently been discovered in Los Angeles County. Mosquito-borne diseases may become established in California due to rising temperatures (Indicators of Climate Change in California, p. 121).
  • Higher temperatures increase ground-level ozone levels, and a longer and more severe wildfire season causes higher ozone and particulate pollution, which worsens respiratory health problems (Our Changing Climate 2012, p. 4).



  • Sea level along California’s coastline has risen about seven inches in the last century. It could be 10-18 inches higher in 2050 than in 2000, and 31-55 inches higher by the end of the century, affecting up to 32 million residents in coastal counties. This represents a four- to eightfold increase in the rate of sea-level rise over that observed in the last century (Our Changing Climate 2012, p. 9).
  • If population and development were kept at today’s levels, a 100-year flood in 2100, after a 55-inch sea-level rise, would put at risk 480,000 people and $100 billion of property (in 2000 dollars) along San Francisco Bay and the California coast (Our Changing Climate 2012, p. 9).
  • As early as 2050, today’s 100-year storm could occur once every year, given current projections of sea-level rise (Our Changing Climate 2012, p. 9).
  • Rising tides could also damage infrastructure, including water supply and delivery, energy, transportation, ports and fire-fighting systems (From Boom to Bust? Climate Risk in the Golden State, p. 4).



  • Climate change is strongly influencing biological systems. Some terrestrial species have shifted their range toward cooler regions (closer to the poles and/or higher altitudes) and changed timing of their growth stages (“phenology” or “spring creep”). Aquatic species have exhibited similar responses (Indicators of Climate Change in California, p. 119).
  • Many of California’s 121 native freshwater fish species—including commercially valuable coho salmon and steelhead trout—are already in decline and are particularly vulnerable to climate change, with 83 percent at high risk of extinction (Our Changing Climate 2012, p. 12).