deployed. Among the measures that might be used, there was high agreement and much evidence that policies that put a price on the cost of carbon emissions could provide incentives for consumers and producers. Carbon prices of 5 to 65 US$/t in 2030 and 15 to 130 US$/t by 2050 are envisaged for stabilization at around 550 ppm by 2100. Synthesis Report A draft version of the Synthesis Report, said to be subject to final copyedit, was published on 16 November 2007. The six topics addressed in the Synthesis Report are: Observed changes in climate and its effects (WGI and WGII). Causes of change (WGI and WGIII). Climate change and its impacts in the near and long term under different scenarios (WGI and WGIII). Adaptation and mitigation options and responses, and the inter-relationship with sustainable development, at global and regional levels (WGII and WGIII). The long term perspective: scientific and socio-economic aspects relevant to adaptation and mitigation, consistent with the objectives and provisions of the Convention [sic], and in the context of sustainable development (WGI and WGIII). Robust findings, key uncertainties (WGI, WGII and WGIII). The "Convention" mentioned in Topic 5 is the UN Framework Convention on Climate Change (UNFCCC). The key findings from the AR4 Synthesis Report will be discussed Wednesday 13 December 2007 at the United Nations Climate Change Conference (UNFCCC COP 13—CMP 3) in Bali, Indonesia, which takes place 3–14 December (see UNFCCC home page). Anthropogenic warming could lead to some impacts that are abrupt or irreversible The SPM states that "Anthropogenic warming could lead to some impacts that are abrupt or irreversible, depending upon the rate and magnitude of the climate change." "There is medium confidence that approximately 20–30% of species assessed so far are likely to be at increased risk of extinction if increases in global average warming exceed 1.5–2.5°C (relative to 1980–1999). As global average temperature increase exceeds about 3.5°C, model projections suggest significant extinctions (40–70% of species assessed) around the globe." "Partial loss of ice sheets on polar land could imply metres of sea level rise, major changes in coastlines and inundation of low-lying areas, with greatest effects in river deltas and low-lying islands. Such changes are projected to occur over millennial time scales, but more rapid sea level rise on century time scales cannot be excluded." Reception The Fourth Assessment Report has been the subject of criticism. Skeptics of anthropogenic global warming