Salter S. 2021 Note for COP 26 on Marine Cloud Brightening

Present policies of most Governments, with a few predictable exceptions, concentrate on the desperate need to get to zero carbon emissions as soon as possible. This is a necessary but not sufficient objective. There is strong evidence from the Keeling curve below, about the difficulty. But if we could reduce carbon emissions to zero the concentration of atmospheric greenhouse gases will be what we have now plus what we will be emitting between now and the zero-emission date minus the amount taken up by the oceans. This means that typhoons, floods, droughts, bushfires, sea-level rise, Arctic ice loss and damage to coral will all be worse, perhaps much worse than now. If you think that present conditions are not acceptable you have to conclude that zero is not low enough. As well as reducing emissions we will HAVE TO remove greenhouse gases, probably with help from phytoplankton, and also do direct cooling a soon as we can and hopefully ramp it down as emissions reduce.除却少数可预见的例外，当前绝大多数国家的政策均将尽快实现零碳排放作为核心要务。这一目标虽属必要，却并非充分条件。下述基林曲线（Keeling Curve）已提供充分证据，表明实现该目标的艰巨性。但即便我们能够将碳排放降至零，大气温室气体浓度仍将等于当前浓度，加上从当下至实现零碳排放期间的排放量，再减去海洋所吸收的温室气体量。这意味着台风、洪涝、干旱、丛林山火、海平面上升、北极海冰消融以及珊瑚礁受损等灾害均会加剧，甚至可能比当前状况严峻得多。倘若你认为当前的气候状况尚且无法接受，那么必然会得出结论：零碳排放的目标仍不够低。除削减碳排放之外，我们还必须清除温室气体——这或许需要借助浮游植物（phytoplankton）的助力——同时需尽快开展直接降温操作，并有望随着碳排放的减少逐步降低降温规模。