本研究主要是整理分析過去觀測資料中全球氣候變遷的相關研究，其中包括了IPCC 第四次評估報告的部分重點、最新的研究報告和臺灣學者的研究，並且簡單地描述了IPCC第五次評估報告的原則和著重的地方。在平均氣候狀態的改變，地表氣溫的上升是最明顯且一致的氣候變遷，在過去百年中(1906～2005)地表溫度大約上升了0.74℃。其他相關的變化如海平面的上升和海冰的融化也都被觀測到，其中海平面在1961年至2003年間大約上升了77mm。至於降水和極端事件如颱風的改變，因為有著極高的不確定性，對於其變遷趨勢並無一致性的結論。在後IPCC 第四次評估報告時期（2007 年以後），對於全球水循環有了更多的研究，一般而言，全球總降水量在增加，但增加的速率仍有爭議。強降水的強度和頻率也有逐漸增加的趨勢，而且趨於兩極化，即雨季越濕、乾季越乾，但這些變化會隨著地區的改變而有所不同。至於颱風的變化，不確定性仍然非常高。IPCC 在第五次評估報告改為根據大氣輻射能量的改變來設定情境。另外，IPCC 在第五次評估報告中增加了強化不確定性的評估，區域氣候變遷的研究和近期氣候推估等重點。

This study is to summarize previous studies on observed global climate changes, which include a part of the IPCC 4th assessment report (AR4), the latest studies and some results from Taiwan scientists. The general criteria for the IPCC 5th assessment report is also discussed here. For changes in mean state, the most clear and consistent climate change is the increase of surface temperature, which is about 0.74℃ in the past century (1906-2005). Other changes, such as sea level rising and sea ice melting, are all observed. In the period of 1961-2003, sea level has risen about 77mm. Precipitation and extremes, such as typhoons, show strong uncertainties, so no clear and consistent tendency has been found. After the IPCC AR4 was published in 2007, there are a lot of studies on the global hydrological cycle. In general, global precipitation is increasing, but the magnitude is still an unsettled issue. Precipitation intensity and frequency also tend to increase. One robust feature is that wet gets wetter and dry gets drier, but with spatial variations. Changes in typhoons are highly uncertain. Unlike the previous IPCC scenarios, the next IPCC assessment report (AR5) will use radiative forcing to define scenarios. The evaluation of uncertainty, regional climate changes and a near-term projection will also be the focus in AR5.