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首页> 外文期刊>Atmospheric chemistry and physics >Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous
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Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous

机译：冰融化，海平面上升和超级暴风雨：来自古气候数据，气候模拟和现代观测的证据表明2°C的全球变暖可能是危险的

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We use numerical climate simulations, paleoclimate data, and modern observations to study the effect of growing ice melt from Antarctica and Greenland. Meltwater tends to stabilize the ocean column, inducing amplifying feedbacks that increase subsurface ocean warming and ice shelf melting. Cold meltwater and induced dynamical effects cause ocean surface cooling in the Southern Ocean and North Atlantic, thus increasing Earth's energy imbalance and heat flux into most of the global ocean's surface. Southern Ocean surface cooling, while lower latitudes are warming, increases precipitation on the Southern Ocean, increasing ocean stratification, slowing deepwater formation, and increasing ice sheet mass loss. These feedbacks make ice sheets in contact with the ocean vulnerable to accelerating disintegration. We hypothesize that ice mass loss from the most vulnerable ice, sufficient to raise sea level several meters, is better approximated as exponential than by a more linear response. Doubling times of 10, 20 or 40?years yield multi-meter sea level rise in about 50, 100 or 200?years. Recent ice melt doubling times are near the lower end of the 10–40-year range, but the record is too short to confirm the nature of the response. The feedbacks, including subsurface ocean warming, help explain paleoclimate data and point to a dominant Southern Ocean role in controlling atmospheric COsub2/sub, which in turn exercised tight control on global temperature and sea level. The millennial (500–2000-year) timescale of deep-ocean ventilation affects the timescale for natural COsub2/sub change and thus the timescale for paleo-global climate, ice sheet, and sea level changes, but this paleo-millennial timescale should not be misinterpreted as the timescale for ice sheet response to a rapid, large, human-made climate forcing. These climate feedbacks aid interpretation of events late in the prior interglacial, when sea level rose to +6–9 m with evidence of extreme storms while Earth was less than 1 °C warmer than today. Ice melt cooling of the North Atlantic and Southern oceans increases atmospheric temperature gradients, eddy kinetic energy and baroclinicity, thus driving more powerful storms. The modeling, paleoclimate evidence, and ongoing observations together imply that 2 °C global warming above the preindustrial level could be dangerous. Continued high fossil fuel emissions this century are predicted to yield (1)?cooling of the Southern Ocean, especially in the Western Hemisphere; (2)?slowing of the Southern Ocean overturning circulation, warming of the ice shelves, and growing ice sheet mass loss; (3)?slowdown and eventual shutdown of the Atlantic overturning circulation with cooling of the North Atlantic region; (4)?increasingly powerful storms; and (5)?nonlinearly growing sea level rise, reaching several meters over a timescale of 50–150?years. These predictions, especially the cooling in the Southern Ocean and North Atlantic with markedly reduced warming or even cooling in Europe, differ fundamentally from existing climate change assessments. We discuss observations and modeling studies needed to refute or clarify these assertions.
机译：我们使用数值气候模拟，古气候数据和现代观测资料来研究南极洲和格陵兰岛融化冰的影响。融水倾向于稳定海柱，引起放大的反馈，从而增加地下海洋变暖和冰架融化。冷融水和诱发的动力效应导致南大洋和北大西洋的海洋表面冷却，从而加剧了地球的能量失衡和热能通向全球大部分海洋表面。在低纬度地区变暖的同时，南大洋地表降温会增加南大洋的降水，增加海洋分层，减缓深水形成，并增加冰盖的质量损失。这些反馈使与海洋接触的冰盖容易加速崩解。我们假设，最脆弱的冰块足以使海平面升高几米的冰块损失，与线性响应相比，可以更好地近似为指数。 10、20或40年的倍增会导致大约50、100或200年的多米海平面上升。最近的冰融化时间接近10-40年范围的下限，但记录太短，无法确定响应的性质。这些反馈，包括地下海洋变暖，有助于解释古气候数据，并指出南大洋在控制大气中CO 2 方面的主导作用，进而对全球温度和海平面进行了严格控制。深海通风的千年（500-2000年）时间尺度会影响自然CO 2 变化的时间尺度，从而影响古全球气候，冰盖和海平面变化的时间尺度，但这古千年的时间尺度不应被误解为冰盖对快速，巨大的人为气候强迫做出反应的时间尺度。这些气候反馈有助于解释前一次冰期间的事件，当时海平面上升至+ 6–9 m，并有极端风暴的迹象，而地球的温度比今天低了1°C。北大西洋和南大洋的冰融化冷却增加了大气温度梯度，涡动能和斜压度，从而引发了更强烈的风暴。建模，古气候证据和持续的观测结果共同表明，高于工业化前水平2°C的全球变暖可能是危险的。预计本世纪持续的高化石燃料排放量将导致（1）南大洋的降温，特别是在西半球; （2）南大洋慢转，环流增加，冰架变暖，冰盖质量损失增加; （3）随着北大西洋区域的冷却，大西洋的倾覆环流的减速和最终停止; （4）越来越强大的风暴; （5）非线性增长的海平面上升，在50-150年的时间内达到几米。这些预测，特别是南大洋和北大西洋的降温，以及欧洲变暖甚至降温明显减少的预测，与现有的气候变化评估有着根本的不同。我们讨论了反驳或澄清这些主张所需的观察和建模研究。

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