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Revised draft (BK Dec 5, 2016 <br />This is another in a series of articles by the Orange County Commission for the Environment <br />(CFE). Each article highlights an environmental issue of interest to the residents of Orange <br />County. The CFE is a volunteer advisory board to the Board of County Commissioners. <br />Additional information can be found in the Orange County State of the Environment 2014 report <br />at r /commission for the environment.php <br />Climate Change (Part 1 of 2) <br />Orange County Commission for the Environment <br />Evidence <br />Our climate is changing say 98% of climate scientists. Since 1950, many observed <br />changes are unprecedented. These include atmosphere and ocean warming, winter snow <br />cover decreasing, Arctic sea ice decreasing, sea level rising, increased melting of Alpine <br />glaciers, increased atmospheric water vapor, and timing of seasonal events (earlier thaws, <br />later frosts). Accompanying these changes are extreme rainfall events and more severe <br />drought. <br />Average global surface temperature has risen about 1.5° F in the past century. The <br />past decade was the warmest over the past 136 years. In the Northern Hemisphere, 1983- <br />2012 appears to be the warmest 30 -year period over the last 1,400 yrs. Sixteen of the past <br />18 months were the hottest on record —where the average temperature in July 2016 was <br />1.5° F hotter than the average July for the years 1950 -1980. These temperatures could be <br />the new normal in a decade. <br />Global ocean temperatures have steadily increased since 1950, causing the ocean to <br />expand— contributing to sea level rise. Over this period rates of sea level rise have been <br />greater than the average rate during the previous 2,000 years. Over the last two decades <br />the Greenland and Antarctic ice sheets have been melting as have most Alpine glaciers. If <br />the Greenland ice sheet fully melts, it would cause a global average sea level rise of about <br />23 feet. <br />Cause and Effect <br />Human influence on climate change is clear. Recent anthropogenic emissions of <br />greenhouse gases (GHGs) are the highest in history —they are the reason for the recent <br />rapid rate of change. GHGs have increased to levels unseen in the last 800,000 yrs. During <br />