It doesn’t have to turn the Earth into Venus for unusually-rapid climate shifts to destabilize geopolitics badly, exceed system tolerances in infrastructure, consume an ever-growing portion of the economy either by increased loss and waste or in efforts at mitigation, and thereby effectively amp up the power of many other forms of global X-risk (or just contribute directly to X-risk by numerous small factors, none of which would by itself be capable of overwhelming the system, but which collectively undermine it).
It doesn’t have to turn the Earth into Venus for unusually-rapid climate shifts to destabilize geopolitics badly, exceed system tolerances in infrastructure, consume an ever-growing portion of the economy either by increased loss and waste or in efforts at mitigation, and thereby effectively amp up the power of many other forms of global X-risk (or just contribute directly to X-risk by numerous small factors, none of which would by itself be capable of overwhelming the system, but which collectively undermine it).