Westchester Action Plan, 2008 - Westchester County Government

The most recent assessment report was the work of over 2,500 scientific expert reviewers,
800 contributing authors, and 450 lead authors from over 130 countries. It was the result
of four review cycles, and it addressed 49,610 review comments.
The IPCC reports the following findings:
• Warming of the climate system is unequivocal, as is now evident from observations
of increases in global average air and ocean temperatures, widespread melting of snow
and ice, and rising global average sea level.
• Global GHG emissions due to human activities have grown since pre-industrial times,
with an increase of 70 percent between 1970 and 2004.
• CO 2 is the most important GHG caused by human activity. Its annual emissions
have grown by about 80 percent between 1970 and 2004.
• Atmospheric concentrations of CO 2 and methane in 2005 exceed by far the
natural range over the last 650,000 years.
• Eleven of the last twelve years (1995 – 2006) rank among the 12 warmest years of
record, with 2005 being the hottest year on record.
• Since 1961, the average temperature of the ocean has increased to depths of at
least 3,000 meters; the ocean has been absorbing more than 80 percent of the heat
added to the climate, causing seawater to expand, and contributing to sea level rise.
• Mountain glaciers and snow cover have declined in both hemispheres.
• Temperatures in the top layer of permafrost in the Arctic have generally increased
since the 1980s, with the maximum area covered by seasonally frozen ground
decreasing by about 7 percent in the Northern Hemisphere since 1900.
• The frequency of heavy precipitation events has increased, consistent with
warming and observed increases in atmospheric water vapor.
• Widespread changes in extreme temperatures have been observed over the last 50
years; with cold days, cold nights and frost less frequent, and hot days, hot nights and
heat waves increasingly frequent.
Increases in GHGs released to the atmosphere last from decades to centuries. Emissions
from previous years have impacts on the climate at this time, while today's emissions will
affect the climate well beyond the 21st century. As a result, the IPCC predicts that
continued GHG emissions are expected to cause further warming and induce many changes
in the global climate system during the 21st century that will very likely be larger than
those observed during the 20th century. Specifically, they project the following
consequences:
• Cities will be further challenged by an increased number, intensity and duration of
heat waves.
Attachment 1: Climate Change, Global Warming, and Westchester
Westchester Action Plan, 2008 1-2