The association between the Siberian Traps,the largest continental flood basalt province,and the largest-known mass extinction event at the end of the Permian period,has been strengthened by re-cently-published high-precision 40Ar/39Ar dates from widespread localities across the Siberian prov-ince[1]. We argue that the impact of the volcanism was amplified by the prevailing late Permian envi-ronmental conditions―in particular,the hothouse climate,with sluggish oceanic circulation,that was leading to widespread oceanic anoxia. Volcanism released large masses of sulphate aerosols and carbon dioxide,the former triggering short-duration volcanic winters,the latter leading to long-term warming. Whilst the mass of CO2 released from individual eruptions was small compared with the total mass of carbon in the atmosphere-ocean system,the long ‘mean lifetime’ of atmospheric CO2,com-pared with the eruption flux and duration,meant that significant accumulation could occur over periods of 105 years. Compromise of the carbon sequestration systems (by curtailment of photosynthesis,de-struction of biomass,and warming and acidification of the oceans) probably led to rapid atmospheric CO2 build-up,warming,and shallow-water anoxia,leading ultimately to mass extinction. The association between the Siberian Traps, the largest continental flood basalt province, and the largest-known mass extinction event at the end of the Permian period, has been strengthened by re-cently-published high-precision 40Ar / 39Ar dates from widespread localities the Siberian prov-ince [1]. We argue that the impact of the volcanism was amplified by the prevailing late Permian envi-ronmental conditions-in particular, the hothouse climate, with sluggish oceanic circulation, that was leading to widespread oceanic anoxia. Volcanism released large masses of sulphate aerosols and carbon dioxide, the former triggering short-duration volcanic winters, the latter leading to long-term warming. Whilst the mass of CO2 released from individual eruptions was small compared with the total mass of carbon in the atmosphere- ocean system, the long ’mean lifetime’ of atmospheric CO2, com-pared with the eruption flux and duration, meaning that significant accumulation could occur over periods of 105 years. Compromise of the carbon sequestration systems (by curtailment of photosynthesis, de-struction of biomass, and warming and acidification of the oceans) probably led to rapid atmospheric CO2 build-up, warming, and shallow-water anoxia, leading ultimately to mass extinction.