• reanalysis;   • earth system  [1] Evaluation of
Reanalyses—Developing an Integrated Earth System Analysis (IESA)
Capability; Baltimore, Maryland, 1–3 November 2010;
Understanding how Earth system components and their interactions
are changing over time is crucial to developing national
strategies for managing climate risk. Despite vast improvements
in observational capabilities, observations alone are, and will
continue to be, insufficient to fully determine the present
state of the atmosphere, much less quantify the states of other
components of the Earth system such as the ocean, land surface,
cryosphere, and biosphere. Thus, a fundamental scientific
challenge remains: obtaining optimal estimates of past and
present climate and, more generally, of the full Earth system.
This will help researchers to determine how and why changes are
occurring and to assess the associated impacts.