The original Working Group I report was approved by the IPCC in December, 1995. Subsequent to that approval, IPCC has apparently allowed additional edits to the document. Some changes are editorial, serving to add clarification or to correct sentence structure. However, other changes appear to go beyond that and have the effect of changing the substance and tone of this chapter. The most significant edits are identified below.
New material is italicized, deleted material has a strike through it.
The claimed statistical detection of an anthropogenic signal in the observations must always be accompanied by the caveat that other explanations for the detected climate-change signal cannot be ruled out completely, unless a rigorous attempt has been made to do so. This distinction rests on the fact that scientists and policymakers have different perceptions of risk. Nevertheless , The process of quality-controlling paleoclimatic data, integrating information from different proxies, and improving spatial coverage should be encouraged. Unless paleoclimatic data can help us to 'constrain' the century time scale natural variability estimates obtained from CGCMs, it will be difficult to make a convincing case for the detection and attribution of an anthropogenic climate change signal. This, however, does not preclude the possibility that a significant part of the trend is due to natural forcing factors.