Short statement on the relevance of the findings in IPCC AR4 chapter 14
(North America) to the United States, 21 September 2007

This is a statement prepared by Christopher Field and Linda Mortsch,
Coordinating Lead Authors of chapter 14, based on the chapter contents. 
It has not been separately evaluated or approved by the IPCC.

The major conclusions in the IPCC AR4 Working Group II chapter on North
America (chapter 14) all apply to the United States.  While each of the
issues has a spatial pattern that makes it more critical in some
locations than in others, all of the topics and impacts discussed in the
chapter are relevant to at least some locations in the United States.  

Chapter 14 presents a balanced assessment, based on existing research,
of key implications of climate change for North America.  The findings
on sensitivities, trends, impacts, adaptation and vulnerability
associated with climate variability and climate change were drawn from a
review and assessment of published references.  The findings were framed
for the North American context but they are also relevant at the
Canadian and the U.S. scale, as research results from both countries
were used to develop the conclusions. A wide range of examples documents
sensitivity, impacts, vulnerability and adaptation in the United States.
 Specifically, the U.S. has been affected by weather-related extreme
events, including hurricanes, floods, wildfires and drought.  Even
though the U.S. has high adaptive capacity, there are still vulnerable
people, places and sectors.   Trends in forest fires in the U.S. and
Canada illustrate sensitivity of forest ecosystems to climate
variability. The projected impacts of increasing numbers of wildfires
and a longer wildfire season are relevant to both countries.  The U.S.
has an extensive, populated and developed coastline with substantial
vulnerability to climate-related extreme events. In the future, impacts
from rising sea level, storms, and storm-surge flooding are likely to
increase; the Atlantic and Gulf coasts are vulnerable to more severe
storm impacts. Current trends and sensitivities, plus projected impacts
from climate-change scenarios, point to problems with water availability
and quality in the snowpack-dominated western mountains, where warming
will likely compound challenges from over-allocation of water resources.
 Hot temperatures and extreme weather are likely to cause increased
adverse health impacts, including heat-related mortality, pollution,
storm-related fatalities and injuries, and infectious diseases.  The
potential impacts and need for countermeasures to reduce impacts are
relevant to both countries.  The built environment is also vulnerable to
a changing climate, with impacts from, for example, more intense
precipitation and permafrost melt.  The long life spans of major
infrastructure and the extended planning required for replacing
infrastructure place a priority on incorporating climate change
information into infrastructure design as an adaptation strategy.   The
U.S., with its large population and widespread development, has many
people and extensive assets that may be exposed to potential impacts of
climate change.   

