do we know about global climate change?
|We know that the earth has become warmer over
the last century. The Intergovernmental Panel on Climate Change
(IPCC), a group established by the World Meteorological Organization
(WMO) and the United Nations Environment Programme (UNEP), reports
that the average surface temperature of the earth has increased
during the twentieth century by about 0.6° ± 0.2°C.
(The ± 0.2°C means that the increase might be as
small as 0.4°C or as great as 0.8°C.) This may seem
like a small shift, but although regional and short-term temperatures
do fluctuate over a wide range, global temperatures are generally
quite stable. In fact, the difference between todays average
global temperature and the average global temperature during
the last Ice Age is only about 5 degrees C. Indeed, its
warmer today around the world than at any time during the past
1000 years, and the warmest years of the previous century have
occurred within the past decade.
|You can think of this web site as a window into
the world of scientific research. In this primer, youll
find a general discussion of the physical processes underlying
the earths climate, an outline of the kinds of data that
may shed light on how the climate is changingand the role
of human activity in these changes and a description of
some of the questions and uncertainties that researchers continue
to explore. This primer is organized into four interconnected
sections: the Atmosphere; the Hydrosphere (the earths
oceans and water); the Cryosphere (the areas of the planet covered
by snow and ice); and the Biosphere (the living organisms inhabiting
all these domains).