RECOMMENDATIONS:

Test and improve the ability of climate models to reproduce the observed vertical structure of forcing for a variety of locations and forcing conditions.

Undertake research to characterize the dependence of climate response on the vertical structure of radiative forcing.

Report global mean radiative forcing at both the surface and the top of the atmosphere in climate change assessments.

• Develop parameterizations for using surface forcing in integrated assessment and simple climate models.

Determine the Importance of Regional Variation in Radiative Forcing

The concept of a global mean radiative forcing is an approximation. Even forcings thought to be fairly uniform, such as solar variability and the well-mixed greenhouse gases, have seasonal and latitudinal variability. Other forcings, in particular tropospheric aerosols and landscape changes, have much more spatial and temporal heterogeneity in their distribution. Human modifications to landscape and vegetation dynamics have caused large regional changes in the surface distribution of net absorbed surface radiation into latent and sensible turbulent heat fluxes. To date, there are only limited observational and modeling studies of regional radiative forcing and response. Indeed, there is not yet a consensus on how best to diagnose a regional forcing and response in the observational record.

Regional variations in radiative forcing are likely important for understanding regional and global climate responses; however, the relationship between the two is not well understood. Regional climate responses can also be caused by global forcings, making it difficult to disentangle the effects of regional and global forcings. Regional diabatic heating can cause nonlinear, long-distance communication of convergence and divergence fields, often referred to as teleconnections. Thus, regionally concentrated diabatic heating can influence climate thousands of kilometers away from its source region. Improving societally relevant projections of regional impacts will require a better understanding of the magnitude of regional forcings and the associated climate response.

RECOMMENDATIONS:

Use climate records to investigate relationships between regional radiative forcing (e.g., land-use or aerosol changes) and climate response in the same region, other regions, and globally.

• Test and improve model simulations of regional radiative forcing and the surface energy budget using observations from aircraft campaigns, surface networks, and satellites.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement