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This summary represents the formally agreed
statement of the IPCC concerning the sensitivity, adaptive capacity, and
vulnerability of natural and human systems to climate change, and the
potential consequences of climate change. |
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Factors such as land-use change and
pollution also act on these physical and biological systems, making it
difficult to attribute changes to particular causes in some specific cases. |
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There is emerging evidence that some social and
economic systems have been affected by the recent increasing frequency of
floods and droughts in some areas. |
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However, such systems are also affected by
changes in socioeconomic factors such as demographic shifts and land-use
changes. |
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The relative impact of climatic and
socioeconomic factors are generally difficult to quantify. |
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Sensitivity is the degree to which a system is
affected, either adversely or beneficially, by climate-related stimuli. |
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Climate-related stimuli encompass all the
elements of climate change, including mean climate characteristics, climate
variability, and the frequency and magnitude of extremes. |
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The effect may be direct (e.g., a change in crop
yield in response to a change in the mean, range, or variability of
temperature) or indirect (e.g., damages caused by an increase in the
frequency of coastal flooding due to sea-level rise). |
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Adaptive capacity is the ability of a system to
adjust to climate change (including climate variability and extremes) to
moderate potential damages, to take advantage of opportunities, or to cope
with the consequences. |
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Vulnerability is the degree to which a system is
susceptible to, or unable to cope with, adverse effects of climate change,
including climate variability and extremes. |
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Vulnerability is a function of the character,
magnitude, and rate of climate change and variation to which a system is
exposed, its sensitivity, and its adaptive capacity. |
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Natural systems are vulnerable to climate
change, and some will be irreversibly damaged. |
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Natural systems at risk include glaciers, coral
reefs and atolls, mangroves, boreal and tropical forests, polar and alpine
ecosystems, prairie wetlands, and remnant native grasslands. |
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It is well-established that the geographical
extent of the damage or loss, and the number of systems affected, will
increase with the magnitude and rate of climate change. |
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Many human systems are sensitive to climate
change, and some are vulnerable. |
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Human systems that are sensitive to climate
change include mainly water resources; agriculture (especially food
security) and forestry; coastal zones and marine systems (fisheries); human
settlements, energy, and industry; insurance and other financial services;
and human health. |
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The vulnerability of these systems varies with
geographic location, time, and social, economic, and environmental
conditions. |
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A general reduction, with some variation, in
potential crop yields in most regions in mid-latitudes for increases in
annual-average temperature of more than a few °C. |
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Decreased water availability for populations in
many water-scarce regions, particularly in the sub-tropics. |
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An increase in the number of people exposed to
vectorborne (e.g., malaria) and water-borne diseases (e.g., cholera), and
an increase in heat stress mortality. |
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A widespread increase in the risk of flooding
for many human settlements (tens of millions of inhabitants in settlements
studied) from both increased heavy precipitation events and sea-level rise. |
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Increased energy demand for space cooling due to
higher summer temperatures. |
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Increased potential crop yields in some regions
at mid-latitudes for increases in temperature of less than a few °C. |
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A potential increase in global timber supply
from appropriately managed forests. |
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Increased water availability for populations in
some water-scarce regions—for example, in parts of southeast Asia |
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Reduced winter mortality in mid- and
high-latitudes. |
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Reduced energy demand for space heating due to
higher winter temperatures. |
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Those with the Least Resources (i.e, wealth,
technology, education, information, skills, infrastructure, access to
resources, and management capabilities) have the Least Capacity to Adapt
and are the Most Vulnerable. |
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Based on experimental research, crop yield
responses to climate change vary widely, depending upon species and
cultivar; soil properties; pests, and pathogens; the direct effects of
carbon dioxide (CO2) on plants; and interactions between CO2, air
temperature, water stress, mineral nutrition, air quality, and adaptive
responses. |
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Even though increased CO2 concentration can
stimulate crop growth and yield, that benefit may not always overcome the
adverse effects of excessive heat and drought. |
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Most studies indicate that global mean annual
temperature increases of a few °C or greater would prompt food prices to
increase due to a slowing in the expansion of global food supply relative
to growth in global food demand. |
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It is established, though incompletely, that climate
change, mainly through increased extremes and temporal spatial shifts, will
worsen food security in Africa. |
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Vegetation modeling studies continue to show the
potential for significant disruption of ecosystems under climate change. |
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The results of these changes will lag behind the
changes in climate by years to decades to centuries. |
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Under climate change scenarios, there would be a
net increase in the geographic range of potential transmission of malaria
and dengue–two vector-borne infections each of which currently impinge on
40-50% of the world population. |
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Extensive experience makes clear that any
increase in flooding will increase the risk of drowning, diarrhoeal and
respiratory diseases, and, in developing countries, hunger and
malnutrition. |
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