A Consideration on Dangerous Level of Global Warming

抄録

　To prevent global warming, as stated in Article 2 of the United Nations Framework Convention on Climate Change (UNFCCC), stabilization of greenhouse gas concentrations in the atmosphere and limitation of temperature increases to certain levels are required. Identification of the critical level of temperature increase (i.e., the level where danger occurs) in order to allow ecosystems to adapt, food to be produced and economies to develop is a fundamental issue, as is the implementation of reduction measures to ensure that temperatures do not exceed this level. However, to identify dangerous levels of temperature increase, we need to examine the factors that influence the target temperature so as to ensure it does not exceed the threshold, i.e., the border between danger and safety. For example, the European Union (EU) has accumulated scientific knowledge and decided that 550 ppm should be the stabilization concentration of greenhouse gases, and a temperature rise of 2°C or less should be the long-range target for preventing global warming. Examination has started of the framework stated in the Kyoto Protocol for beyond 2013. To set up a specific long-range target, scientific knowledge of related factors such as stabilization concentrations, level of temperature increase, and effect threshold plays an important role. On the basis of past impact studies, this paper considers levels of temperature rise and thresholds for the impacts caused by global warming.