Karmalkar Ambarish V, Bradley Raymond S
Northeast Climate Science Center and Climate System Research Center, Department of Geosciences, University of Massachusetts Amherst, Amherst, Massachusetts, United States of America.
PLoS One. 2017 Jan 11;12(1):e0168697. doi: 10.1371/journal.pone.0168697. eCollection 2017.
The differential warming of land and ocean leads to many continental regions in the Northern Hemisphere warming at rates higher than the global mean temperature. Adaptation and conservation efforts will, therefore, benefit from understanding regional consequences of limiting the global mean temperature increase to well below 2°C above pre-industrial levels, a limit agreed upon at the United Nations Climate Summit in Paris in December 2015. Here, we analyze climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to determine the timing and magnitude of regional temperature and precipitation changes across the contiguous United States (US) for global warming of 1.5 and 2°C and highlight consensus and uncertainties in model projections and their implications for making decisions. The regional warming rates differ considerably across the contiguous US, but all regions are projected to reach 2°C about 10-20 years before the global mean temperature. Although there is uncertainty in the timing of exactly when the 1.5 and 2°C thresholds will be crossed regionally, over 80% of the models project at least 2°C warming by 2050 for all regions for the high emissions scenario. This threshold-based approach also highlights regional variations in the rate of warming across the US. The fastest warming region in the contiguous US is the Northeast, which is projected to warm by 3°C when global warming reaches 2°C. The signal-to-noise ratio calculations indicate that the regional warming estimates remain outside the envelope of uncertainty throughout the twenty-first century, making them potentially useful to planners. The regional precipitation projections for global warming of 1.5°C and 2°C are uncertain, but the eastern US is projected to experience wetter winters and the Great Plains and the Northwest US are projected to experience drier summers in the future. The impact of different scenarios on regional precipitation projections is negligible throughout the twenty-first century compared to uncertainties associated with internal variability and model diversity.
陆地和海洋的差异变暖导致北半球许多大陆地区的升温速度高于全球平均气温。因此，适应和保护工作将受益于了解将全球平均气温升幅限制在比工业化前水平高2°C以下的区域影响，这是2015年12月在巴黎举行的联合国气候峰会上商定的一个限制目标。在此，我们分析了耦合模式比较计划第5阶段（CMIP5）的气候模型模拟结果，以确定美国本土在全球升温1.5°C和2°C时区域温度和降水变化的时间和幅度，并突出模型预测中的共识和不确定性及其对决策的影响。美国本土各地区的区域变暖速度差异很大，但预计所有地区在全球平均气温达到2°C之前约10 - 20年就会达到2°C。尽管各地区确切何时跨越1.5°C和2°C阈值存在不确定性，但在高排放情景下，超过80%的模型预测到2050年所有地区至少升温2°C。这种基于阈值的方法还突出了美国各地升温速度的区域差异。美国本土升温最快的地区是东北部，预计在全球变暖达到2°C时将升温3°C。信噪比计算表明，整个21世纪区域变暖估计值都处于不确定性范围之外，这使其对规划者可能有用。全球升温1.5°C和2°C时的区域降水预测存在不确定性，但预计美国东部冬季将更湿润，大平原和美国西北部预计未来夏季将更干燥。与内部变率和模型多样性相关的不确定性相比，不同情景对21世纪区域降水预测的影响可以忽略不计。
