Conclusions and the future of climate research - The Global Climate System: Patterns, Processes, and Teleconnections - page 322

the carbon cycle, atmospheric chemistry, and ocean circulation. Feedbacks
can involve all components of the atmospheric system. They affect the
sensitivity of climate processes and are not well understood. They may be
positive (enhancing) or negative (reducing). A controversial current example
is the role of infrared radiation absorption by greenhouse gases in global
temperature and moisture change. Incoming shortwave radiation is absorbed
by the Earth's surface, and re-released as longwave energy (see Chapter 1 ).
Increased greenhouse gas levels in the atmosphere lead to greater infrared
absorption, creating higher atmospheric temperatures. A warmer atmosphere
can hold more water vapor, and thus evaporation from surface water sources
is enhanced. The higher moisture levels in the atmosphere, enhanced by
increased tropospheric instability due to the warming, enhance cloud forma-
tion. The increased clouds (along with increased particle matter from human
sources) reduce incoming shortwave radiation through backscattering and
reflection. Theoretically, then, less longwave radiation becomes available
from a cooler Earth's surface. But the increased clouds are more efficient at
absorbing longwave radiation than the atmospheric gases, potentially increas-
ing atmospheric warming.
Within this very general feedback framework are a whole series of further
complexities and questions. What impacts do variations in atmospheric chem-
istry have on the feedback process? What is the role of dominant processes, such
as the ocean and the biosphere? How do the cloud processes work and why?
These kinds of questions are being addressed through projects such as SOLAS
and ILEAPS, which are studying biochemical feedbacks between surfaces and
the atmosphere and how transformation processes work. The IPCC ( 2001 )
acknowledges that of all the feedback components, it is the role of clouds that
is the least understood.
10.2.4 Climate variability and change at the extremes
of the Earth
Despite the advent of satellites, and major increases in research and knowledge
over the past 20 years, understanding of climate and its variability in the polar
regions is in many ways the last great climate frontier. Modeling results reported
by IPCC ( 2001 ), and also in Chapter 9 , plus a wide range of measurements, have
identified the potential for major climate change associated with warming in the
polar regions, especially in the Arctic. Chapter 5 and the essays by Wendler
highlight some important areas where information is lacking.
The polar ice caps are physically the most demanding, and logistically the
most difficult, environments on the globe in which to measure and assess
climate. CliC provides the major international research focus on the cryosphere
and climate. There are three main goals. The first is to enhance the observations
and monitoring to support accurate detection of climate change. Long-term data