Conserving Freshwater and Coastal Resources in a Changing Climate

Courtesy of Union of Concerned Scientists (UCS 2006)
climate patterns continues to grow (Alley, 2007).
Recent reports have used advances in modeling technology
to create predictions for the United States’
Northeast, Mid-Atlantic and Great Lakes regions
(UCS, 2006; Najjar, 2000, Kling, 2003). This report summarizes
these projections. The ranges used are based
on low and high greenhouse gas emission scenarios for
conditions at the end of the century, unless otherwise
noted.
Temperature:
• Annual average temperatures are expected to
increase by 3.5° - 12.5° F (1.9° - 6.9° C) for the
Northeast (UCS 2006), and 4.9°- 9.5° F (2.7°-
5.3° C) in the Mid-Atlantic (Najjar, 2000), with
most of the warming occurring in winter
months.
Figure 2. Projected changes in duration of low streamflow in summer
and fall months
• A rise in winter temperatures of 6° - 14°F (3° -
8°C) and a rise in summer temperatures of
11° - 16°F (6° - 9°C) in the Great Lakes region.
• In the Northeast, the number of days above 90° F
(32.2°C) is anticipated to increase from a current
average of 10-15 days per year to an average of
30-60 days per year by the mid-21st century.
Similarly, the current average of 2-3 days per year
over 100°F (37.8°C) may rise to up to 28 days per
year (UCS 2006).
Sea Temperatures and Sea Level Rise:
• Sea surface temperature is expected to warm by
5° - 8° F (2.2°- 4.4°C) by the end of the century
(UCS 2006).
• Globally, sea level is predicted to rise 2.5 - 13
inches by mid-century and 4 - 33 inches by the
end of the century (UCS 2006).
Precipitation and Water Flows:
• Annual precipitation is anticipated to increase
by 10% (about 4 inches) in the Northeast
(UCS 2006), by 15% (about 6 inches) in the
mid-Atlantic (Najjar 2000) and by 10 – 20%
(about 3 to 6 inches) in the Great Lakes region
(Kling 2003).
• Winter precipitation is expected to increase even
more, up to 11-16 % by the middle of this century
and 20-30% by the end of the century for the
Northeast (UCS 2006).
• The intensity of precipitation (i.e. the average
amount of rain that falls on any given rainy day)
is expected to increase by up to 15% in the
Northeast by the end of the century (UCS 2006)
and the frequency of heavy rainstorms may
double by the end of the century in the Great
Lakes Region (Kling 2003).
• Droughts are predicted to become more frequent
with short-term droughts that occur in the
Northeast now once every 2 to 3 years occurring
as often as once per year by the end of the
century (UCS 2006).
• In the Northeast, the number of snow-covered
days (days on which land is covered with snow)
is predicted to decrease by 4-15 days by the end
of the century (UCS 2006).
• The duration of the Northeast’s low flow period
for rivers and streams is expected to arrive a
week earlier and extend several weeks longer
into the fall (UCS 2006). Predictions of stream
flow changes in the Mid-Atlantic region are less
certain, flow could decrease by 4% or increase
by 27% (Najjar 2000).
• The Northeast will see an increase in evaporation
rates and a decrease in soil moisture in the
summer and fall while experiencing an increase
in soil moisture in winter and spring (UCS 2006).
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Conserving Freshwater and Coastal Resources in a Changing Climate