Global warming is the rising average temperature of Earth's atmosphere and oceans since the late 19th century and its projected continuation. Since the early 20th century, Earth's average surface temperature has increased by about 0.8 °C, with about two thirds of the increase occurring since 1980. Warming of the climate system is unequivocal, and scientists are more than 90% certain that most of it is caused by increasing concentrations of greenhouse gases produced by human activities such as deforestation and the burning of fossil fuels.
Water vapor is the dominant greenhouse gas, the most important gaseous
source of infrared opacity in the atmosphere. As the concentrations of other greenhouse
gases, particularly carbon dioxide, increase because of human activity, it is centrally
important to predict howthewater vapor distribution will be affected. To the extent that
water vapor concentrations increase in a warmer world, the climatic effects of the other
greenhouse gases will be amplified.
Information about climate1 is used to make decisions every day. From farmers deciding
which crops to plant next season to mayors in large cities deciding how to prepare for future heat
waves, and from an insurance company assessing future flood risks to a national security planner
assessing future conflict risks from the impacts of drought, users of climate information span a
vast array of sectors in both the public and private spheres. Each of these communities has
different needs for climate data, with different time horizons (see Box 1) and different tolerances
China stands front and center in the congressional debate on climate change, due
to that nation’s contribution to global emissions and competitiveness in global trade.
With its large population, rapidly expanding economy, and heavy reliance on coal,
China now shares the lead in global greenhouse gas (GHG) emissions with the
United States. China’s GHG emissions are expected to continue growing in the years
ahead based on projections of continuing rapid economic growth.
The Animal Production and Health Section of the Joint FAO/IAEA Division of
Nuclear Techniques in Food and Agriculture recognises that the trend towards
intensification of livestock production in developing countries presents both opportunities
and challenges. The potential opportunities are the flow-on benefits to the
producers and local economy while the potential challenges are the flow-on costs
to the environment, animal health and welfare.
By inadvertently increasing the concentration of energy-trapping gases in the
lower atmosphere, human actions have begun to amplify Earth’s natural green-
house effect. The primary challenge facing the world community is to achieve
sufﬁcient reduction in greenhouse gas emissions so as to avoid dangerous inter-
ference in the climate system. National governments, via the UN Framework
Convention on Climate Change (UNFCC), are committed in principle to seeking