globally averaged radiative forcing over the timescale of the averaging period. Ocean heat storage changes have been shown to be an essential metric that climate model simulations must skillfully reproduce. The accurate assessment of concurrent heat storage changes in the atmosphere, land, and continental glaciers and sea ice would permit the averaging time to be shorter. Measurements of moist enthalpy can be used to characterize the heat content in surface air, providing more information about the surface energy budget than given by surface air temperature alone. A network of surface stations intended to characterize the surface energy budget could help better understand and monitor nonradiative forcings, although care would be needed in determining the siting and density of stations to appropriately account for the impact of landscape heterogeneity.

RECOMMENDATIONS:

Continue observations of climate forcings and variables without interruption for the future in a manner consistent with established climate monitoring principles (e.g., adequate cross-calibration of successive, overlapping datasets).

Develop the capability to obtain benchmark measurements (i.e., with uncertainty significantly smaller than the change to be detected) of key parameters (e.g., sea level altimetry, solar irradiance, and spectrally resolved, absolute radiance to space).

• Continuously monitor key radiative forcing parameters with high spectral resolution in order to isolate and understand the physical processes (e.g., solar spectral irradiance; surface, ocean, and atmosphere radiance to space), and ensure continuity and radiometric compatibility with existing and future broadband satellite measurements of shortwave and longwave irradiance.

• Conduct a comprehensive review and documentation of current and historical surface observation sites that are used in long-term temperature monitoring.

Conduct highly accurate measurements of global ocean heat content and its change over time.

• Explore the value of creating a network of surface sites that provide representative monitoring of the surface energy budget.

ADDRESSING POLICY NEEDS

The concept of radiative forcing has clear policy applications. It has been used by the policy community to compare different forcings and as input to simple climate models used to consider policy options. Control strategies designed to address other environmental issues, such as air pollution or land-use changes, can also impact radiative forcings, a consequence



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