increase in the average temperature of the
earth's atmosphere, especially a sustained increase
sufficient to cause climatic change.
gradual increase in the overall temperature of
the earth's atmosphere generally attributed to the
greenhouse effect caused by increased levels of
carbon dioxide, CFCs, and other pollutants.
warming is the rise in the average
temperature of oceans also
the early 20th century, Earth's mean surface
temperature has increased by about 0.8 °C
(1.4 °F), with about two-thirds of the increase
occurring since 1980.
of the climate system is unequivocal,
and scientists are 95-100% certain that it is
primarily caused by increasing concentrations
of greenhouse gases produced by human activities
such as the burning of fossil
fuels and deforestation.
Sea level rise is accelerating. The planet's temperature
The number of large wildfires is growing.
Dangerous heat waves are becoming more common.
Extreme storm events are increasing in many areas.
More severe droughts are occurring in others.
These are having significant and harmful effects on our
health, our environment, and our communities.
Global warming is primarily a problem of too much
carbon dioxide (CO2) in the atmosphere—which acts
as a blanket, trapping heat and warming the planet.
As we burn fossil fuels like coal, oil and natural gas
for energy or cut down and burn forests to create
pastures and plantations, carbon accumulates and
overloads our atmosphere.
Certain waste management and agricultural practices
aggravate the problem by releasing other potent global
warming gases, such as methane and nitrous oxide.
The greenhouse effect is the process by
which absorption and emission of infrared radiation by
gases in the atmosphere warm a planet's lower
atmosphere and surface.
Naturally occurring amounts of greenhouse gases have
a mean warming effect of about 33 °C (59 °F).Without
the earth's atmosphere the temperature across almost
the entire surface of the earth would be below freezing.
The major greenhouse gases are water vapor, which
causes about 36–70% of the greenhouse effect; carbon
dioxide (CO2), which causes 9–26%; methane (CH4),
which causes 4–9%; and ozone (O3), which causes 3–
7%. Clouds also affect the radiation balance
through cloud forcings similar to greenhouse gases.
Human activity since the Industrial Revolution has
increased the amount of greenhouse gases in the
atmosphere, leading to increased radiative forcing from
CO2, methane, tropospheric ozone, CFCs and nitrous
Reducing the amount of future climate change is
called mitigation of climate change.
The IPCC defines mitigation as activities that reduce
greenhouse gas (GHG) emissions, or enhance the capacity
of carbon sinks to absorb GHGs from the atmosphere.
Studies indicate substantial potential for future reductions in
emissions by a combination of emission-reducing activities
such as energy conservation, increased energy efficiency,
and satisfying more of society's power demands
with renewable energy and nuclear energy sources. Climate
mitigation also includes acts to enhance natural sinks, such
to climate change may be planned, either in
reaction to or anticipation of climate change, or
spontaneous, i.e., without government intervention.
A concept related to adaptation is "adaptive capacity",
which is the ability of a system (human, natural or
managed) to adjust to climate change (including climate
variability and extremes) to moderate potential damages,
to take advantage of opportunities, or to cope with
consequences. Unmitigated climate change (i.e., future
climate change without efforts to limit greenhouse gas
emissions) would, in the long term, be likely to exceed the
capacity of natural, managed and human systems to adapt.