Publication Abstracts

Del Genio 1993

Del Genio, A., 1993: Accuracy requirements. In Long-Term Monitoring of Global Climate Forcings and Feedbacks, NASA CP-3234. J. Hansen, W. Rossow, and I. Fung, Eds. National Aeronautics and Space Administration, pp. 13-19.

Satellite and surface measurements, if they are to serve as a climate monitoring system, must be accurate enough to permit detection of changes of climate parameters on decadal time scales. The accuracy requirements are difficult to define a priori since they depend on unknown future changes of climate forcings and feedbacks. As a framework for evaluation of candidate Climsat instruments and orbits, we estimate the accuracies that would be needed to measure changes expected over two decades based on theoretical considerations including GCM simulations and on observational evidence in cases where data are available for rates of change.

One major climate forcing known with reasonable accuracy is that caused by the anthropogenic homogeneously mixed greenhouse gases (CO2, CFCs, CH4 and N2O). Their net forcing since the industrial revolution began is about 2 W/m2, and it is presently increasing at a rate of about 1 W/m2 per 20 years. Thus for a competing forcing or feedback to be important, it needs to be of the order of 0.25 W/m2 or larger on this time scale.

The significance of most climate feedbacks depends on their sensitivity to temperature change. Therefore we begin with an estimate of decadal temperature change. Figure 3.1 shows the transient temperature trends simulated by the GISS GCM when subjected to various scenarios of trace gas concentration increases. Scenario B, which represents the most plausible near-term emission rates and includes intermittent forcing by volcanic aerosols, yields a global mean surface air temperature increase ΔTs = 0.7°C over the time period 1995-2015. This is consistent with the IPCC projection of about 0.3°C/decade global warming. Several of our estimates below are based on this assumed rate of warming.

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BibTeX Citation

@inproceedings{de00400a,
  author={Del Genio, A.},
  editor={Hansen, J. and Rossow, W. and Fung, I.},
  title={Accuracy requirements},
  booktitle={Long-Term Monitoring of Global Climate Forcings and Feedbacks},
  year={1993},
  pages={13--19},
  publisher={National Aeronautics and Space Administration},
  address={Washington, D.C.},
}

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RIS Citation

TY  - CPAPER
ID  - de00400a
AU  - Del Genio, A.
ED  - Hansen, J.
ED  - Rossow, W.
ED  - Fung, I.
PY  - 1993
TI  - Accuracy requirements
BT  - Long-Term Monitoring of Global Climate Forcings and Feedbacks
SP  - 13
EP  - 19
PB  - National Aeronautics and Space Administration
CY  - Washington, D.C.
ER  -

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