Atmospheric circulation and hydroclimate impacts of alternative warming scenarios for the Eocene
Atmospheric circulation and hydroclimate impacts of alternative warming scenarios for the Eocene
复制标题
DOI：
10.5194/cp-13-1037-2017
复制
发表时间：
2017-08
影响因子：
4.3
通讯作者：
Henrik Carlson;R. Caballero
中科院分区：
文献类型：
--
作者：
Henrik Carlson;R. Caballero
抽象的。最近在模拟始新世早期温暖气候方面的工作表明，有可能在模型表面温度和代用品重建之间获得合理的全球匹配，但只有通过使用极高的大气CO2浓度或更适度的CO2水平，并辅之以减少全球云CO2。了解引起始新世温暖的辐射强迫的混合对约束地球的气候敏感性具有重要意义，但由于缺乏对云特性的直接代理约束，这一方向的进展受到阻碍。在这里，我们探索的潜力，区分不同的辐射强迫情景，通过它们对区域气候变化的影响。我们通过比较两种端元情景的气候模型模拟来做到这一点：一种是气候完全由CO2变暖（我们称之为温室气体（GHG）情景），另一种是气候完全由减少云的CO2变暖（我们称之为低CO2-薄云或LCTC情景）。这两种模拟具有几乎相同的全球平均表面温度和赤道到极点的温差，但LCTC情景的全球平均降水量比GHG情景高出11%。与温室气体情景相比，LCTC情景也有较冷的中纬度大陆和较温暖的海洋，热带气候更像厄尔尼诺。在LCTC情景中，亚热带极高的暖季温度得到缓解，而所有纬度的冷季温度都较低。这些变化看起来足够大，足以激励使用其他气候模型和一套更现实的建模假设进行进一步的更详细的研究。
Abstract. Recent work in modelling the warm climates of the early Eocene shows that it is possible to obtain a reasonable global match between model surface temperature and proxy reconstructions, but only by using extremely high atmospheric CO2 concentrations or more modest CO2 levels complemented by a reduction in global cloud albedo. Understanding the mix of radiative forcing that gave rise to Eocene warmth has important implications for constraining Earth's climate sensitivity, but progress in this direction is hampered by the lack of direct proxy constraints on cloud properties. Here, we explore the potential for distinguishing among different radiative forcing scenarios via their impact on regional climate changes. We do this by comparing climate model simulations of two end-member scenarios: one in which the climate is warmed entirely by CO2 (which we refer to as the greenhouse gas (GHG) scenario) and another in which it is warmed entirely by reduced cloud albedo (which we refer to as the low CO2–thin clouds or LCTC scenario) . The two simulations have an almost identical global-mean surface temperature and equator-to-pole temperature difference, but the LCTC scenario has ∼ 11 % greater global-mean precipitation than the GHG scenario. The LCTC scenario also has cooler midlatitude continents and warmer oceans than the GHG scenario and a tropical climate which is significantly more El Nino-like. Extremely high warm-season temperatures in the subtropics are mitigated in the LCTC scenario, while cool-season temperatures are lower at all latitudes. These changes appear large enough to motivate further, more detailed study using other climate models and a more realistic set of modelling assumptions.