We disagree with M.I. Hoffert et al.'s (Advanced technology paths to global climate stability: Energy for a greenhouse planet, Reviews, 1 Nov., p.981) characterization of the IPCC Third Assessment Report's conclusion that known technological options could achieve a broad range of atmospheric stabilization levels, such as 550 ppm, 450 ppm or below over the next hundred years or more, as a misperception of technological readiness."...