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Climate
Change - 2007
This is a faithful
summary of the IPCC Fourth Assessment Report.
(EnviroNews is grateful to Mr. Jacques de Selliers <[email protected]>,
founder & Vice-Chairman, GreenFacts for permitting us to
publish it)
Source: GreenFacts asbl/vzw,
Brussels, Belgium
(URL: http://www.greenfacts.org/)
Genesis of climate change
The Earth’s climate is
influenced by many factors, such as, the amount of energy coming from the sun,
but also by factors such as the amount of
greenhouse gases and
aerosols in the
atmosphere, and the
properties of the Earth’s surface, which determine how much of this solar energy
is retained or reflected back to space.
The
atmospheric
concentrations of
greenhouse gases
such as
carbon dioxide (CO2),
methane (CH4)
and
nitrous oxide (N2O)
have significantly increased since the beginning of the industrial revolution.
This is mainly due to human activities, such as the burning of
fossil fuels,
land use change,
and agriculture. For instance, the atmospheric concentration of carbon dioxide
is now far higher than in the last 650 000 years and has been growing faster in
the last ten years than it has been since the beginning of continuous
measurements around 1860.
Climate change in the past
The warming of global
climate is now unequivocal. There are many observations of increasing air and
ocean temperatures, widespread melting of snow and ice, and rising sea levels.
More specifically,
eleven of the last twelve years (1995-2006) rank among the 12 warmest years ever
recorded since global surface temperatures are measured (1860). Over the last
100 years (1906–2005), global temperature has increased by 0.74°C. Global sea
level has risen by 17 cm during the 20th century, because of the melting of snow
and ice from many mountains and in the polar regions. More regional changes have
also been observed, including changes in Arctic temperatures and ice, ocean
salinity, wind patterns, droughts,
precipitations, frequency of heat waves and intensity of tropical cyclones. The
temperatures of the last half century are unusual in comparison with those of at
least the previous 1300 years. The last time that the polar regions remained
significantly warmer than now for a very extended period (125 000 years ago),
the sea level rose by 4 to 6 meters.
Future Scenario
The global average
temperature is expected to increase by about 0.2°C per decade over the next two
decades. Continuing
greenhouse gas emissions at or above
current rates would cause a further increase in global temperatures and many
other climatic changes during the 21st century.
The best estimates for
projected global temperature increases from the 1980s to the end of the 21st
century range from 1.8°C (1.1 - 2.9°C) to 4°C (2.4 - 6.4°C) for the IPCC
scenarios that do not consider additional
mitigation measures apart from those already in place in 2000.
Global average sea level
is expected to rise by 18 to 59 cm by the end of the 21st century. Warming is
expected to be greatest over land and at high northern latitudes and smallest
over the Southern Ocean and parts of the North Atlantic Ocean. Other projected
changes include acidification of the oceans, reduced snow cover and
sea ice, more frequent heat waves and
heavy precipitation, more intense tropical cyclones, and slower oceanic
currents.
Warming and sea level
rise caused by human activities will continue for centuries, even if
greenhouse gas concentrations were to be
stabilized. If warming persists over many centuries, it could lead to a complete
melting of the
Greenland Ice sheet, increasing global sea
levels by about 7m.
Observed impacts of climate change
Regional
climate change is already affecting many
natural systems. For instance, it is increasingly being observed that snow and
ice are melting, and frozen ground is thawing, hydrological and biological
systems are changing and in some cases being disrupted, migrations are starting
earlier, and
species' geographic ranges are shifting
towards the poles.
Despite remaining gaps
in our knowledge, it is likely that these effects are linked to human influence
on climate. At the regional level, however, responses to natural variability are
difficult to separate from the effects of
climate change.
Some previously
unanticipated impacts of regional
climate change are just starting to become
apparent. For instance, melting
glaciers can threaten mountain settlements
and water resources, and damages associated with coastal flooding are
increasing.
Future impacts
Over the course of the
21st century, many impacts are expected to occur in natural systems. For
instance, changes in precipitation and the melting of ice and snow are expected
to increase flood risks in some areas while causing droughts in others. If there
is significant warming the capacity of
ecosystems to
adapt will be exceeded, with negative
consequences such as an increased risk of extinction of
species. The most vulnerable people are in
general the poor, since they have less capacity to
adapt, and their livelihoods are often
dependent on resources that are linked to climate. Africa is found to be
particularly vulnerable to
climate change, because of existing
pressures on its
ecosystems and its low capacity to
adapt. On all continents, water supply and
the threat to coastal areas will be an issue. Overall future impacts are
expected to be negative, although some positive effects are also expected
initially, such as an increase in agricultural
productivity at high latitudes
accompanying a moderate warming, or decreased heating needs in cold regions.
Impacts will depend on
the magnitude of the temperature increase. For instance, some crops at mid- to
high latitudes will have higher
productivity if local temperature
increases by 1-3°C, but will be negatively affected beyond that. If higher
temperatures persist after the 21st century it could result in very large
impacts. For instance, the large sea-level rise that would result from the
melting of the Greenland and Antarctic
ice sheets would have major repercussions
on coastal areas. The cost associated with the effects of
climate change is projected to increase
over time with rising temperatures.
A projected increase in
the severity and frequency of droughts, heat waves, and other extreme weather
events is expected to cause major impacts over the course of this century.
Human Adaptation to
climate change
Human’s stance through
technological solutions such as coastal defences and changes in consumption
habits. Humans are already adapting to climate change, and further
adaptation efforts will be necessary
during coming decades. However, adaptation alone is not expected to be able to
cope will all projected effects since the options diminish and the costs
increase with rising temperatures. Vulnerability of human
populations to
climate change and its consequences can be
affected by other factors, such as pollution, conflicts, or epidemics such as
AIDS. An emphasis on
sustainable development can help human
societies reduce their vulnerability to climate change. However, climate change
itself can become an impediment to their development.
Mitigation measures that
aim to reduce emissions can help avoid, reduce or delay impacts, and should be
implemented in order to ensure that
adaptation capacity is not exceeded.
Current trends in
greenhouse gas emissions
Global
greenhouse gas emissions have grown
markedly since pre-industrial times, with a 70% increase from 1970 to 2004
alone. Over this period, emissions from the transport and energy sectors have
more than doubled. Policies put in place in some countries have been effective
in reducing emissions in those countries to a certain degree, but not
sufficiently to counteract the global growth in emissions.
Without additional
measures to mitigate
climate change, global green house gas
emissions will continue to grow over the coming decades and beyond. Most of this
increase would come from developing countries, where per capita emissions are
still considerably lower than those in developed countries.
Measures needed to
reduce greenhouse gas emissions
Mitigation measures to
reduce
greenhouse gas emissions have a certain
cost. However, they also constitute an economic benefit by reducing the impacts
of
climate change, and the costs associated
with them. In addition, they can bring economic benefits by reducing local air
pollution and energy resource depletion.
If the benefits of
avoided
climate change are taken into account and
a “carbon price” is established for each unit of
greenhouse gas emissions, this could
create incentives for producers and consumers to significantly invest in
products, technologies and processes which emit less
greenhouse gases. The resulting mitigation
potential is substantial and could offset the projected growth of global
emissions over the coming decades or reduce emissions below current levels.
Mitigation measures
could contribute to stabilizing the concentration of
greenhouse gases in the
atmosphere by 2100 or later. To achieve
low stabilization levels, stringent mitigation efforts are needed in the coming
decades. This could reduce global
GDP by up to a few percent.
Changes in lifestyle and
behaviors that favor resource conservation can contribute to
climate change mitigation.
Mitigation measures can
also have other benefits for society, such as health cost savings resulting from
reduced air pollution. However, mitigation in one country or group of countries
could lead to higher emissions elsewhere or effects on the global economy.
No one sector or
technology can address the entire mitigation challenge. All sectors including
buildings, industry, energy
production, agriculture, transport,
forestry, and waste management could contribute to the overall mitigation
efforts, for instance through greater energy efficiency. Many technologies and
processes, which emit less
greenhouse gases are already commercially
available or will be in the coming decades.
In order to stabilize
the concentration of
greenhouse gases in the
atmosphere, emissions would have to stop
increasing and then decline. The lower the stabilization level aimed for, the
more quickly this decline would need to occur. Worldwide investments in
mitigation technologies, as well as research into new energy sources, will be
necessary to achieve stabilization. Delaying emission reduction measures limits
the opportunities to achieve low stabilization levels and increases the risk of
severe
climate change impacts.
Incentives for
mitigation
A wide variety of policy
tools can be applied by governments to create incentives for mitigation action,
such as regulation, taxation, tradable permit schemes,
subsidies and voluntary agreements. Past
experience shows that there are advantages and drawbacks for any given policy
instrument. For instance, while regulations and standards can provide some
certainty about emission levels, they may not encourage innovations and more
advanced technologies. Taxes and charges, however, can provide incentives, but
cannot guarantee a particular level of emissions. It is important to consider
the environmental impacts of policies and instruments, their cost effectiveness,
institutional feasibility and how costs and benefits are distributed.
Although the impact of
the Kyoto protocol’s first commitment period 2008-2012 on global carbon
emissions is expected to be limited, it has allowed the establishment of a
global response to the climate problem as well as the creation of an
international carbon market and other mechanisms that may provide the foundation
for future mitigation efforts.
Switching to more
sustainable development paths can make a
major contribution to
climate change mitigation. Policies that
contribute to both climate change mitigation and
sustainable development include those
related to energy efficiency, renewable energies, and conservation of natural
habitats. In general, sustainable development can increase the capacity for
adaptation and mitigation, and reduce
vulnerability to the impacts of climate change.
Conclusions
Current warming trends
are unequivocal. It is very likely that
greenhouse gases released by human
activities are responsible for most of the warming observed in the past fifty
years. The warming is projected to continue and to increase over the course of
the 21st century and beyond.
Climate change already has a measurable
impact on many natural and human systems. Effects are projected to increase in
the future and to be more severe with greater increases in temperature.
Adaptation measures are already being
implemented, and will be essential in order to address the projected
consequences. There is, however, a limit to adaptation; mitigation measures will
also be needed in order to reduce the severity of impacts.
Mitigation measures that
aim to reduce
greenhouse gas emissions can help avoid,
reduce or delay many impacts of
climate change. Policy instruments could
create incentives for producers and consumers to significantly invest in
products, technologies and processes which emit less
greenhouse gases. Without new mitigation
policies, global greenhouse gas emissions will continue to grow over the coming
decades and beyond. Rapid world-wide investments and deployment of mitigation
technologies, as well as research into new energy sources will be necessary to
achieve a stabilization of the concentration of greenhouse gases in the
atmosphere.
Additional research addressing gaps in knowledge would further reduce
uncertainties and thus facilitate decision-making related to climate change. | 
