In their efforts to understand what constitutes natural climatic variation, climatologists are examining glaciers, tree rings and other sources for data on ancient climates. They are also applying modern technology to create models of the natural factors affecting climate. Unfortunately, "Natural factors are insufficient to explain the rise in global temperatures since the 1950s," says Liu Chung-ming, the former director of National Taiwan University's Global Change Research Center.
氣候學者參考冰河、樹輪等等地質史「信差」所遺留下的古氣候證據，加上現代科學以各種影響氣候的自然因素模擬實驗，「推算不出一九五○年代後的暖化趨勢，」台大大氣科學系教授、也是前台大全球變遷中心主任柳中明說，學界無法從自然變動中找到增溫原因。