Countdown to Zero?

It would be nice to be entirely convinced by Michael Mann's recent modelling, suggesting that, if (a big if?), the world rapidly achieves net zero emissions (of carbon dioxide), we should be able to curtail the climate disaster 'within a couple of decades' (https://www.theguardian.com/environment/2021/jan/07/global-heating-stabilize-net-zero-emissions). His optimism is based on factoring in 'the huge carbon absorption capacity' of natural systems including the oceans, wetlands and forests. These, Mann feels, can lower surface temperatures until technological fixes come in. I retain a number of concerns. Firstly, I don't think we are looking very well after our oceans, wetlands and forests (so their capacity might be reducing). Secondly, carbon dioxide is not the only 'greenhouse gas'. Methane (burped by cattle and released by the melting tundra) is much more potent and is not removed by natural systems. And, Thirdly, so much ice has melted, that the planet's solar gain is much increased (less is reflected back into space). The heating earth might be less bright. Mann's calculations also depend on politicians, who claim their countries will be net zero emitters by 2030, actually achieving this aim. As I have said repeatedly, many talk the talk but few (there are not many votes in it?) walk the walk.