IPCC AR6报告解读：气候系统对二氧化碳移除响应

doi:10.12006/j.issn.1673-1719.2021.169

摘要/Abstract

摘要：

IPCC AR6报告中控温1.5℃和2℃的低排放情景需要在21世纪中叶以后实现净负CO₂排放,这需要在很大程度上依赖CO₂移除措施。AR6对CO₂移除的主要评估结论如下：CO₂移除有潜力从大气中去除CO₂（高信度);如果CO₂移除量超过CO₂排放量,将实现净负CO₂排放,降低大气CO₂浓度,减缓海洋酸化（高信度);通过CO₂移除方法从大气中去除的CO₂会部分被海洋和陆地释放的CO₂抵消（非常高信度);如果净负CO₂排放可以实现并且持续,CO₂引起的全球升温趋势将会逐渐扭转,但是气候系统的其他变化（例如海平面升高）仍会在未来的几十年到千年尺度上持续（高信度);不同CO₂移除方法会对生物化学循环和气候产生广泛的影响,这些影响会加强或减弱CO₂移除的降温潜力,并且影响水资源、食物生产和生物多样性（高信度）。

关键词: CO₂移除(CDR), 气候变化, 气候系统响应, 碳循环

Abstract:

The IPCC recently released the Six Assessment Report (AR6), addressing the most up-to-date physical understanding of the climate system and climate change. Climate system and the carbon cycle response to carbon dioxide removal is assessed in this report. Carbon dioxide removal (CDR) is a necessary component of the IPCC low emissions scenarios of SSP1-1.9 and SSP1-2.6 that keeps global warming from preventing 1.5℃ or 2.0℃. AR6 key assessment relevant to CDR are: CDR has the potential to removal CO₂ from the atmosphere and durably store it in reservoirs (high confidence); If the amount of CO₂removed from the atmosphere exceeds anthropogenic CO₂ emission, CDR would lead to net negative emissions, lowering atmospheric CO₂ concentration and reversing surface ocean acidification (high confidence); CO₂sequestered from the atmosphere by CDR would be partially compensated by CO₂ release from land and ocean carbon stores (very high confidence); If global net negative CO₂ emissions were to be achieved and be sustained, the global CO₂-induced surface temperature increase would be gradually reversed but other climate changes (such as sea level rise) would continue in their current direction for decades to millennia (high confidence). CDR methods can have potentially wide-ranging effects on biogeochemical cycles and climate, which can either weaken or strengthen the potential of these methods to remove CO₂ and reduce warming, and can also influence water availability and quality, food production and biodiversity (high confidence).

Key words: Carbon dioxide removal (CDR), Climate change, Climate system response, Carbon cycle

曹龙. IPCC AR6报告解读：气候系统对二氧化碳移除响应[J]. 气候变化研究进展, 2021, 17(6): 664-670.

CAO Long. Climate system response to carbon dioxide removal[J]. Climate Change Research, 2021, 17(6): 664-670.

图/表 2

图1 8个地球系统模式模拟的碳循环对一次性从大气中移除100 Pg C的CO2的响应[1] (a)大气CO2浓度,(b)陆地碳储量变化,(c)海洋碳储量变化注：模式模拟的碳循环对100 Pg C的CO2一次性从工业革命前的大气中移除的响应。陆地和海洋碳储量的变化为相对于工业革命前的值。模拟结果来自7个参加CO2移除模拟比较计划（Carbon Dioxide Removal Model Intercomparison Project,CDRMIP）的CMIP6模式和UVic模式。本图来源于AR6第五章图5.32。

Fig. 1 Carbon cycle response to instantaneous carbon dioxide (CO2) removal from the atmosphere. (a) Atmospheric CO2 concentration, (b) change in land carbon reservoir, (c) change in ocean carbon reservoir. (Results are shown for simulations with seven CMIP6 Earth system models and the UVic ESCM model of intermediate complexity forced with 100 Pg C instantaneously removed from the atmosphere)

图2 气候系统对CO2移除引起的净负CO2排放的响应[1] (a)标准化后的多模式平均的不同变量的变化,(b)多模式模拟的GSAT,(c)全球平均降水,(d)北冰洋9月海冰面积,(e)大西洋经向翻转环流（AMOC),(f)热膨胀造成的全球平均海平面高度变化注：模拟试验中,大气CO2从工业革命前的浓度以每年1%的增长至4倍的浓度,然后再以每年1%的速度下降到工业革命前的浓度,随后保持在工业革命前的浓度水平。图(b)~(f),红色线条代表CO2上升段,蓝色线条代表CO2下降段,指CO2移除引起净负CO2排放,棕色线条代表CO2稳定在工业革命前浓度的时间段;黑色的粗线代表多模式的平均值;实线代表CMIP6模式,虚线代表CMIP5模式或其他模式。参加CMIP6的模式数目标注在每一个小图中。垂直的虚线一条代表大气CO2达到4倍浓度的时间,另一条代表大气CO2又回到工业革命前浓度的时间。本图来源于AR6 第四章图4.37。

Fig. 2 Delayed climate response to CDR-caused net negative CO2 emissions[1]. (a) Normalized ensemble mean anomaly of key variables, (b) global surface air temperature, (c) precipitation, (d) September Arctic sea-ice area, (e) Atlantic meridional overturning circulation (AMOC), (f) thermostatic sea level. (In (a), the key variables include atmospheric CO2, surface air temperature, precipitation, thermosteric sea-level rise, global sea-ice area, Northern Hemisphere sea-ice area in September, and AMOC. In (b)-(f), red lines represent the phase of CO2 ramp-up, blue lines represent the phase of CO2 ramp-down, brown lines represent the period after CO2 has returned to pre-industrial level, and black lines represent the multi-model mean. For all of the segments in (b)-(f), the solid colored lines are CMIP6 models, and the dashed lines are other models. Vertical dashed lines indicate peak CO2 and when CO2 again reaches pre-industrial value. The number of CMIP6 and non-CMIP6 models used is indicated in each panel)

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