GCOS Implementation Plan - WMO

Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC
(2010 Update)
ECV – Earth Radiation Budget
The Earth Radiation Budget (ERB) measures the overall balance between the incoming energy from
the sun and the outgoing thermal (longwave) and reflected (shortwave) energy from the Earth. It can
only be measured from space, and continuity of observations is an essential issue. The radiation
balance at the top of the atmosphere is the basic radiative forcing of the climate system. Measuring its
variability in space and time over the globe provides insight into the overall response of the system to
this forcing. The satellite measurements include solar irradiance observations as well as the
broadband directional measurements of reflected solar and outgoing longwave radiation. At least one
dedicated satellite ERB mission should be operating at any one time. Satellite observations should be
continued without interruption, and operational plans should provide for overlap so that accuracy and
resolution issues are resolved to meet climate requirements. This should be a continuing priority for
CEOS and CGMS in their planning process. The requirement for this overlap is demonstrated in
Figure 6 below.
Action A25 [IP-04 A24]
Action: Ensure continuation of Earth Radiation Budget observations, with at least one dedicated
satellite mission operating at any one time.
Who: Space agencies.
Time-Frame: Ongoing.
Performance Indicator: Long-term data availability at archives.
Annual Cost Implications: 30-100M US$ (Mainly by Annex-I Parties).
Figure 6: Observations of total solar irradiance (TSI) from a series of different instruments on satellites
as indicated, along with monthly sunspot number. The vertical bar in the upper right corner shows a
relative variation of 0.1% in TSI. Absolute values are uncertain and differ in the past by as much as 9
Wm -2 , and more recently systematically by around 4 Wm -2 so that continuous time series are only made
possible by overlapping measurements from different satellites. (Source:
http://spot.colorado.edu/~koppg/TSI accessed 24 September 2009).
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