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2.  Global warming refers to
the rising average
temperature of Earth's
atmosphere and oceans
and its projected
continuation. In the last
100 years, Earth's
average surface
temperature increased by
about 0.8 °C (1.4 °F) with
about two thirds of the
increase occurring over
just the last three
decades.

3.  Warming of the climate system is unequivocal, and
scientists are more than 90% certain most of it is
caused by increasing concentrations of greenhouse
gases produced by human activities such as
deforestation and burning fossil fuel.
 These findings are recognized by the national
science academies of all the major industrialized
countries.

4.  Climate model projections
are summarized in the
2007 Fourth Assessment
Report (AR4) by the
Intergovernmental Panel
on Climate Change
(IPCC). They indicate that
during the 21st century the
global surface temperature
is likely to rise a further 1.1
to 2.9 °C (2 to 5.2 °F) for
their lowest emissions
scenario and 2.4 to 6.4 °C
(4.3 to 11.5 °F) for their
highest.

5.  An increase in global temperature will cause sea levels
to rise and will change the amount and pattern of
precipitation, and a probable expansion of subtropical
deserts. Warming is expected to be strongest in the
Arctic and would be associated with continuing retreat of
glaciers, permafrost and sea ice. Other likely effects of
the warming include more frequent occurrence of
extreme weather events including heatwaves, droughts
and heavy rainfall events, species extinctions due to
shifting temperature regimes, and changes in
agricultural yields.

6.  around the globe, though
the nature of these regional
changes is uncertain. In a 4
°C world, the limits for
human adaptation are
likely to be exceeded in
many parts of the world,
while the limits for
adaptation for natural
systems would largely be
exceeded throughout the
world. Hence, the
ecosystem services upon
which human livelihoods
depend would not be
preserved.

7.  Proposed responses to global warming include
mitigation to reduce emissions, adaptation to the
effects of global warming, and geoengineering to
remove greenhouse gases from the atmosphere or
reflect incoming solar radiation back to space. The
primary international effort to prevent dangerous
anthropogenic climate change ("mitigation") is
coordinated by the 194-nation UNFCCC

8.  The Kyoto Protocol is
their only legally binding
emissions agreement and
only limits emissions
through the year 2012.
Afghanistan and the USA
are the only nations in the
UNFCCC that have not
ratified the original
protocol, and as of
October 2011 several
others have refused to
extend the emissions
limits beyond 2012

9.  Nonetheless, in the 2010 Cancun Agreements, member
nations agreed that urgent action is needed to limit global
warming to no more than 2.0 °C (3.6 °F) above pre-
industrial levels. Current scientific evidence, however,
suggests that 2°C is the "threshold between ‘dangerous’
and ‘extremely dangerous’ climate change", that this
much warming is possible during the lifetimes of people
living today, and that steep reductions in global emissions
must be made by 2020 in order to have a 2-out-of-3
chance of avoiding global warming in excess of 2°C.

10. -presented by;
>Santiago salamanca Gómez
>Sandy Martínez
-presented to:
>OLGA LUCIA BEJARANO