IPCC SROCC和AR6对高山区气候变化的评估表明，近期全球山地增暖速率提高，1980年代以来亚洲高山区增暖速率明显高于全球平均和其他高山区同期水平。各山地增暖普遍具有海拔依赖性，但机制复杂且区域差异大，除落基山脉未来气温增幅随海拔降低外，其余山地均随海拔有不同程度的升高。全球山地年降水在过去几十年没有明显趋势；预计未来北半球许多山地年降水将增加5%～20%，但极端降水变化的区域和季节差异较大，其中青藏高原喜马拉雅山脉极端降水频次和强度都将增大。山地年最大雪水当量的减少在固-液态降水转化的海拔高度带更强，未来山地降雪和积雪变化不仅与排放情景有关，而且与海拔高度密切相关。2010—2019年全球山地冰川物质亏损较有观测记录以来的任何一个10年都多，亚洲高山区虽然冰川物质亏损速率较小，但每年亏损的冰量在全球四大高山区中仅次于安第斯山脉南段。预计山地冰川将持续退缩数十年或数百年，未来亚洲高山区冰川退缩对海平面上升的贡献将居全球四大高山区之首。山地多年冻土温度升高、厚度减薄，预计未来多年冻土将加速退化，即使在低温室气体排放情景下，21世纪末青藏高原多年冻土面积预计也将减少13.4%～27....

气候反馈反映了气候系统内部对外界干扰的适应过程,在很大程度上影响对未来气候变化的预估。本文对政府间气候变化专门委员会（IPCC）第六次评估报告（AR6）中有关气候反馈的内容进行了梳理。相比第五次评估报告（AR5）,AR6对云反馈的认识有了较大提高,尤其是副热带海洋上空低云的反馈。AR6认为在高信度上云反馈参数为正值,即对气候变化起到一种放大效应。不过,云反馈的不确定范围在所有反馈机制中依然是最大的。除了普朗克反馈外,其他反馈机制（包括水汽、温度直减率、地表反照率、云、生物地球物理和非CO2生物地球化学反馈）均在正值区间或零附近,总体上对气候变化起到放大效应。AR6对总的气候反馈的估计值为-1.16 W·m-2·℃-1,5%～95%的置信区间为[-1.81,-0.51] W·m-2·℃-1。随着气候平均态的增暖,气候反馈参数很可能会更靠近正值。

IPCC第六次评估报告(AR6)第一工作组报告对气候系统各要素的可预测性(predictability)、不可逆性(irreversibility)和深度不确定性(deep uncertainty)给出了新认识。文中基于此对全球冰冻圈变化的上述三方面加以总结和归纳。总体来看,无论何种排放情景,半球和全球尺度上冰冻圈各要素于21世纪均具有一定的可预测性,即均向融化或退化方向变化,且具有不可逆性;但在区域尺度、短时间尺度和百年以上时间尺度上,不同冰冻圈要素或因内部变率大、或因响应机制复杂而存在可逆、可预测性差乃至深度不确定性难题。

This study estimates direct radiative forcing by tropospheric ozone and all aerosols between the years 1850 and 2000, using the new IPCC AR5 (the Intergovernmental Panel on Climate Change Fifth Assessment Report) emissions inventories and a fully coupled chemistry-aerosol general circulation model. As compared to the previous Global Emissions Inventory Activity (GEIA) data, that have been commonly used for forcing estimates since 1990, the IPCC AR5 emissions inventories report lower anthropogenic emissions of organic carbon and black carbon aerosols and higher sulfur and NOx emissions. The simulated global and annual mean burdens of sulfate, nitrate, black carbon (BC), primary organic aerosol (POA), secondary organic aerosol (SOA), and ozone were 0.79, 0.35, 0.05, 0.49, 0.34, and 269 Tg, respectively, in the year 1850, and 1.90, 0.90, 0.11, 0.71, 0.32, and 377 Tg, respectively, in the year 2000. The estimated annual mean top of the atmosphere (TOA) direct radiative forcing of all anthropogenic aerosols based on the AR5 emissions inventories is -0.60 W m(-2) on a global mean basis from 1850 to 2000. However, this is -2.40 W m(-2) when forcing values are averaged over eastern China (18-45 degrees N and 95-125 degrees E). The value for tropospheric ozone is 0.17 W m(-2) on a global mean basis and 0.24 W m(-2) over eastern China. Forcing values indicate that the climatic effect of aerosols over eastern China is much more significant than the globally averaged effect.

A spatially distributed, physically based, hydrologic modeling system (MIKE SHE) was applied to quantify intra- and inter-annual discharge from the snow and glacierized Zackenberg River drainage basin (512 km 2; 20% glacier cover) in northeast Greenland. Evolution of snow accumulation, distribution by wind-blown snow, blowing-snow sublimation, and snow and ice surface melt were simulated by a spatially distributed, physically based, snow-evolution modelling system (SnowModel) and used as input to MIKE SHE. Discharge simulations were performed for three periods 1997-2001 (calibration period), 2001-2005 (validation period), and 2071-2100 (scenario period). The combination of SnowModel and MIKE SHE shows promising results; the timing and magnitude of simulated discharge were generally in accordance with observations (R-2 = 0.58); however, discrepancies between simulated and observed discharge hydrographs do occur (maximum daily difference up to 44.6 m(3) s(-1) and up to 9% difference between observed and simulated cumulative discharge). The model does not perform well when a sudden outburst of glacial dammed water occurs, like the 2005 extreme flood event. The modelling study showed that soil processes related to yearly change in active layer depth and glacial processes (such as changes in yearly glacier area, seasonal changes in the internal glacier drainage system, and the sudden release of glacial bulk water storage) need to be determined, for example, from field studies and incorporated in the models before basin runoff can be quantified more precisely. The SnowModel and MIKE SHE model only include first-order effects of climate change. For the period 2071-2100, future IPCC A2 and B2 climate scenarios based on the HIRHAM regional climate model and HadCM3 atmosphere-ocean general circulation model simulations indicated a mean annual Zackenberg runoff about 1.5 orders of magnitude greater (around 650 mmWE year(-1)) than from today 1997-2005 (around 430 mmWE year(-1)), mainly based on changes in negative glacier net mass balance. Copyright (c) 2007 John Wiley & Sons, Ltd.