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Executive Summary
In
2006, Americans experienced a summer heat wave that broke records from coast to
coast and killed almost 200 people. The year ended and 2007 began with the
warmest winter on record globally. This unseasonably warm weather is part of a
long-term trend toward rising temperatures and extreme weather events resulting
from global warming.
Global
average surface temperatures have increased by more than 1.4°F since the second
half of the 19th century.
Earlier this year, the United Nations’ Intergovernmental Panel on Climate
Change (IPCC) concluded that the evidence of global warming is “unequivocal” and
that human activities are responsible for most of the rise in temperatures.
To
examine recent temperature patterns in the United
States, we compared temperature data for the years
2000-2006 from 255 weather stations located in all 50 states and Washington, DC
with temperatures averaged over the 30 years spanning 1971-2000. Overall, we
found that temperatures were above the 30-year average across the country, indicating
pervasive warming.
SUMMER 2006: RECORD-BREAKING HEAT
A
long-lasting summer heat wave hit most of the country in 2006, making it the
second warmest summer on record for the contiguous United States. Heat waves have
serious implications for human health, causing heat stroke, heat exhaustion,
and even death. Our analysis of climate data for June-August 2006 showed:
- During
the summer of 2006, the average temperature was at least 0.5°F above the 30-year
average at 82% of the locations studied. In Rapid City,
South Dakota and Helena, Montana,
average summertime temperatures were 5°F
above normal.
- The average
maximum temperature — the peak temperature on any given day — was at least
0.5°F above the 30-year average at two-thirds (67%) of the locations
studied. The Great Plains and Mountain
West suffered some of the most above-normal summer temperatures in 2006.
- The
summer heat wave produced a high number of dangerously hot days at or above
90°F across the country. Almost three-fourths (71%) of the locations examined
recorded more frequent (compared with the historical average) days with
peak temperatures of at least 90°F. Tupelo,
Mississippi experienced 40 more
90°F or warmer days than normal in 2006.
- The
2006 summer heat wave was marked by above-average minimum temperatures—
the lowest temperatures recorded on a given day, usually at night. The
average minimum temperature was at least 0.5°F above the 30-year average
at 81% of the locations studied and 9.7°F above normal in Reno, Nevada,
the highest in the country.
Warmer
nighttime temperatures exacerbate the public health effects of heat waves,
since people need cooler nighttime temperatures to recover from excessive heat
exposure during the day.
In
April 2007, the IPCC warned that North American cities that currently
experience heat waves are expected to face “an increased number, intensity, and
duration of heat waves,” threatening
public health, particularly that of elderly Americans and infants.
2006:
SECOND WARMEST YEAR ON RECORD
With
a scorching summer and mild start to winter,
the 2006 average temperature for the contiguous
United States was the second warmest on record, according to
the National Climatic
Data Center.
Every state in the Lower 48
experienced above normal temperatures
in 2006. Our analysis of 2006 climate
data showed:
- In
2006, the average temperature was at least 0.5°F above the 30-year average
at 87% of the locations examined. The Upper Midwest
and Mountain West in particular experienced warmer-than normal average
temperatures in 2006.
- The
average maximum temperature was at least 0.5°F above the 30-year average
at 81% of the stations examined. Warmerthan- average days hit Texas and the Great Plains the hardest in 2006, with
average peak temperatures soaring more than 5°F above normal in Oklahoma City, Oklahoma.
- The average
minimum temperature was at least 0.5°F above the 30-year average at 80% of
the stations examined. Minimum temperatures were particularly mild in the Upper
Midwest, where temperatures soared almost 5°F above the 30-year average in
Minneapolis-St. Paul, Duluth, and Rochester, Minnesota.
2000-2006:
TEMPERATURES RISING
The
above-average temperatures of 2006 are part of a broader warming trend since
2000. Our analysis of climate data for 2000-2006 showed:
- Between
2000 and 2006, the average temperature was at least 0.5°F above the 30-year
average at 87% of the locations studied. Average temperatures in Alaska were the most anomalous, with Talkeetna near Denali National Park averaging more than
4°F above the 30-year average.
- The
average maximum temperature was at least 0.5°F above the 30-year average
at more than two-thirds (68%) of the locations studied. Average maximum temperatures
in Pueblo and Alamosa, Colorado
were 2.6°F above normal.
- Overall,
temperatures are not dropping at night as much now as they did in the
past. Between 2000 and 2006, the
average minimum temperature was at least 0.5°F above the 30-year average
at 80% of the locations studied. Albuquerque,
New Mexico and Sault Ste. Marie, Michigan reported
average minimum temperatures of more than 3°F above normal.
Even
though the IPCC identified significant risks with continued global warming, the
panel also concluded that “many impacts can be avoided, reduced, or delayed” by
quickly and significantly reducing global warming pollution. To protect future
generations, the
United States
should:
Cap
global warming emissions. The United States should establish
mandatory, science based limits on carbon dioxide and other global warming
pollutants that reduce total emissions from today’s levels by the end of the decade,
by at least 15-20% by 2020, and by at least 80% by 2050.
Adopt
complementary clean energy policies to reduce global warming emissions.
Toachieve these reductions, the United States
should adopt strong policies and financial incentives
to improve energy efficiency and increase the use of clean, renewable energy.
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