Does not fully characterize the climate impact
of nonradiative forcing, the indirect aerosol effect (other than the first), and the semidirect aerosol effect
Some types
of nonradiative forcing are not easily quantified in watts per square meter, thus it is not clear how to compare them to radiative forcing
However, this approach may not convey appropriately the impacts
of nonradiative forcings on societally relevant climate variables such as precipitation or ecosystem function.
Not exact matches
Other
nonradiative forcings modify the biological components
of the climate system by changing the fluxes
of trace gases and heat between vegetation, soils, and the atmosphere and by modifying the amount and types
of vegetation.
The atmosphere and oceans, through their general circulation, act as vast heat engines, compensating for this imbalance by providing
nonradiative mechanisms for the transfer
of heat from the Equator to the poles.
Nonradiative heat transfer again compensates for the imbalance, this time largely by vertical atmospheric motions involving the evaporation and condensation
of water.
Another important
nonradiative mechanism is the exchange
of heat that occurs when the temperature
of the air is different from that
of the surface.
These
nonradiative forcings generally have radiative impacts, but describing them only in terms
of this radiative impact does not convey fully their influence on climate variables
of societal relevance.
Nonetheless, the limitations call for broadening the concept to account for
nonradiative forcing, spatial and temporal heterogeneity
of forcing, and nonlinearities.
Several
nonradiative forcings involve the biological components
of the climate system.
Further work is needed to quantify links
of regional
nonradiative forcing to regional and global climate response
Another consideration in devising metrics for
nonradiative forcings is enabling direct comparison with radiative forcings, computed in units
of watts per square meter.
It needs to be expanded to account for the vertical and regional structure
of radiative forcing and also for
nonradiative climate forcings.
Finally, we examine ways to improve the application
of radiative and
nonradiative forcing metrics in policy analyses directed at climate change.