The ocean response to climate change guides both adaptation and mitigation efforts

The ocean’s thermal inertia is a major contributor to irreversible ocean changes exceeding time scales that matter to human society.This fact is a challenge to societies as they prepare for the consequences of climate change,especially with respect to the ocean.Here the authors review the requirements for human actions from the ocean’s perspective.In the near term(∼2030),goals such as the United Nations Sustainable Development Goals(SDGs)will be critical.Over longer times(∼2050–2060 and beyond),global carbon neutrality targets may be met as countries continue to work toward reducing emissions.Both adaptation and mitigation plans need to be fully implemented in the interim,and the Global Ocean Observation System should be sustained so that changes can be continuously monitored.In the longer-term(after∼2060),slow emerging changes such as deep ocean warming and sea level rise are committed to continue even in the scenario where net zero emissions are reached.Thus,climate actions have to extend to time scales of hundreds of years.At these time scales,preparation for“high impact,low probability”risks—such as an abrupt showdown of Atlantic Meridional Overturning Circulation,ecosystem change,or irreversible ice sheet loss—should be fully integrated into long-term planning.

在全球变化背景下,海洋的很多变化在人类社会发展的时间尺度上(百年至千年)具有不可逆转性,海洋巨大的热惯性是造成该不可逆性的主要原因.这个特征为人类和生态系统应对海洋变化提出一系列挑战.本文从海洋变化的角度总结了人类应对气候变化的要求,提出需要进行多时间尺度的规划和统筹.在近期(到2030年),实现联合国可持续发展目标至关重要.在中期(2050–2060年前后),全球需要逐步减排并实现碳中和目标.同时,适应和减缓气候变化的行动和措施必须同步施行;全球海洋观测系统需要得以维持并完善以持续监测海洋变化.在远期(在2060年之后),即使全球达到净零排放,包括深海变暖和海平面上升在内的海洋变化都将持续,因此应对全球变化的行动需持续数百年之久.在该时间尺度,应对“低概率,高影响”气候风险(即发生的可能性较低,但一旦发生影响极大的事件带来的风险,例如:大西洋经圈反转环流突然减弱,海洋生态系统跨过临界点,无可挽回的冰盖质量损失等)的准备应充分纳入长期规划.