IMPACTS
THAT HAVE ALREADY BEEN OBSERVED
Climate Change has already affected
many physical, biological and human systems. Impacts of regional climate change
observed throughout the world include:
- Shrinking glaciers
- Thawing permafrost
- Late freezing
and early break-up of ice on rivers and lakes
- Poleward shifts
of plant and animal ranges
- Declines of
some plant and animal populations
- Earlier flowering
of trees
- Earlier emergence
of insects and egg-laying in birds
- Preliminary
evidence shows that humans have been affected by recent increases in floods
and droughts
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Vulnarable
Natural Systems
"Natural
systems are vulnerable to climate change and some will be irreversibly damaged."
Among the most vulnerable natural systems are:
- Glaciers,
particularly alpine glaciers in temperate and tropical regions
- Coral reefs and atolls, which
are home to more than 1/3 of all known marine species
- Mangroves,
integral buffers against coastal erosion and habitats for a huge number
of species.
- Boreal
and tropical forests,
including the forests of North America Polar and alpine ecosystems, which
are inherently vulnerable and are expected to experience the most extreme
warming Prairie wetlands, crucial breeding grounds for waterfowl Remnant
native grasslands
Greater climate change will mean
greater loss of biodiversity - both in geographical range and intensity.
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Vulnarable
Human Systems
"Many
human systems are sensitive to climate change, and some are vulnerable."
Impacts on agriculture are expected
to be dominantly negative. Although in a few areas there may be minor increases
in crop yields in the short term, as climate change
deepens agriculture is expected to suffer almost everywhere.
Human settlements
in low-lying regions are particularly vulnerable to flooding.
The expected 21st century sea level rise, coupled with increased heavy precipitation
events and strong storm surges, threatens hundreds of millions of people in
densely populated areas (e.g. Bangladesh, Egypt's Nile Delta). This
will cause loss of life and property as well as large scale migration.
Other vulnerable
human systems include:
- forestry coastal zones and fisheries
- energy and industry insurance
and other financial services
- human health water resources
(see Water Impacts in North America)
- Extreme climatic events like
droughts, floods and windstorms can be devastating to human societies.
Most
of these events are projected to increase in frequency and intensity during
the 21st century. The economic and societal impacts of intensifying extremes
are expected to fall disproportionately on the poor.
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Catastrophic
surprises are possible
The potential
for large scale, irreversible impacts presents severe, but poorly understood
risks.
Projected climate change could prompt sudden reorganizations in Earth systems
with catastrophic ramifications. Unfortunately, our understanding of these
possible impacts is too rudimentary to allow us to judge their likelihood.
Because of this, they are not included in IPCC projections.
Plausible, but poorly understood
possibilities include:
- Slowing of the ocean circulation
that warms the North Atlantic. This would cause a sudden
cooling of Northern Europe and drastically rearrange the global heat budget.
- Collapse of the Greenland or
West Antarctic Ice Sheet. The rapid melting of either
one of these ice sheets would cause 3m to 5m of global sea level rise.
- Accelerated greenhouse effects
due to carbon cycle feedback. A snowball-effect
could result if Earth systems react to warming by releasing more greenhouse
gases from reservoirs such as permafrost.
- Massive
release of methane from hydrates in coastal sediments. Hydrates
contain vast amounts of methane gas in a relatively unstable form. Changes
in ocean temperature or circulation could release this methane to the atmosphere,
contributing to a "runaway greenhouse".
Any one of these would have massive,
global impacts beyond those already outlined in the Report.
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Adaptation
is necessary
Even if strong steps toward mitigation
are taken immediately, climate changes to come will require adaptation by
human and natural systems. These adaptations will invariably incur costs.
It will be crucial to consider climate change effects in long term planning
in order to prevent as much damage as possible.
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The
poorest people are the most vulnerable.
Industrialized nations have many
resources at their disposal to help them adapt to changing climate, while
developing nations are generally inequipped for large scale adaptation. As
a result, loss of life andeconomic
impacts are expected to be greater in developing nations.
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Back to climate change
Back to impacts
of climate change
PROJECTED
CHANGES IN EXTREME CLIMATE EVENTS DURING THE 21ST CENTURY
Simple
Extremes:
- Higher
maximum temperatures; more hot days and heat waves over nearly all areas.Examples
of impacts:
- Increased incidence
of death and serious illness in older age groups and urban poor
- Increased heat
stres in livestock and wildlife
- Shift in tourist
destinations
- Increased risk
of damage to a number of crops
- Increased electric
cooling demand and reduced energy supply reliability
- Higher
minimum temperatures; fewer cold days,frost days and cold waves.Examples
of impacts:
- Decreased cold-related
human morbidity and mortality
- Decreased risk
of damage to a number of crops, increased risk to others
- Extended range
and activity of some pests and disease vectors, impacting forests and
agriculture
- Reduced heating
energy demand
- More
intense precipitation events.Examples of impacts:
- Increased flood,
landslide,avalanche and mudslide damage
- Increased soil
erosion
- Increased flood
runoff could increase recharge of some floodplain aquifers
- Increased pressure
on government and private flood insurance and disaster relief
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COMPLEX
EXTREMES
- Increased
summer drying in mid-lititudes and associated risk of drought. Examples
of impacts:
- Decreased crop
yields
- Increased damage
to building foundations caused by ground shrinkage
- Decreased water
source quantity and quality
- Increased risk
of forest fire
- Increase
in tropical cyclone peak wind intensity,mean and peak precipitation intensities.Examples
of impacts:
- Increased risks
to human life, risk of infectious disease epidemics and many other risks
- Increased coastal
erosion and damage to coastal buildings and other infrastructure
- Increased damage
to coastal ecosystems such as coral reefs and mangroves
- Intensified
droughts and floods associated with El Nino events in many different regions.Examples
of impacts:
- Decreased agricultural
and rangeland productivity in drought-and flood-prone regions
- Decreased hydro-power
potential in drought-prone regions
- Increased
Asian summer mansoon variability.Examples of impacts:
- Increased flood
and drought magnitude and damages in temperate and tropical Asia
- Increased
intensity of mid latitude storms.Examples of impacts:
**The
content of these pages are taken from www.davidsuzuki.org, an excellent website
about the environmental issues founded by Dr.
David Suzuki Foundation from Canada.
