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Revised draft (BK/PQ Oct 7, 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 />Summary of Evidence <br />Our climate is changing, this is clear. Since 1950, many changes are unprecedented. <br />These include atmosphere and ocean warming, winter snow cover decreasing, Arctic sea <br />ice decreasing, sea level rising, increased melting of mountain glaciers, increased <br />atmospheric water vapor, and the timing of seasonal events (earlier thaws, later frosts). <br />Accompanying these changes are extreme rainfall events and more severe drought. <br />Average global surface temperature has risen about 1.5° F in the past 100 yrs. The <br />past decade was the warmest over the past measured 136 years. In the Northern <br />Hemisphere, 1983 -2012 appears to be the warmest 30 -year period over the last 1,400 yrs. <br />And, the past 15 consecutive months were the hottest on record — average temperature in <br />July 2016 was 1.5° F hotter than the average July for the years 1950 -1980. <br />Global average ocean surface temperatures have steadily increased since 1950, <br />causing the ocean to expand— contributing to sea level rise. Since 1950, sea level rise rates <br />have been greater than the average rate during the previous 2,000 years. Additionally, the <br />majority of glaciers on Earth continue to shrink. Over the last two decades the Greenland <br />and Antarctic ice sheets have melted significantly. If the Greenland ice sheet fully melts it <br />would cause global average sea level to rise about 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 (a follow -on article discussing how distant past climate changes <br />inform the current scientific community's opinions is being composed). GHGs have <br />increased to levels unseen in the last 800,000 yrs. GHGs are controlled by earth's orbit <br />