<p>One of the hottest topics in the field of civil engineering and disaster mitigation technology is the management of the effects of the global warming and the intensified rainfall effects. This issue appears so urgent that many discussions and efforts are aiming at construction of a resilient community. Nevertheless, the author sometimes feels that what is going on today is not very logical and that some efforts are just affected by ‘common sense’ that does not doubt what people are doing. To shed light on this issue, the author collected meteorological and biological data and interpreted them. It was found that, in a long-term scope, the winter warming is evident but that summer warming is not clear. Next, from the viewpoint of disaster, a historical review was made of the rainfall-induced disasters since 1945 in Japan. Opposite from the common argument that rain disaster is aggravating, it was found that the size of the rain disasters has been smaller since 1990. The main reason for this is presumably the human efforts in the past to mitigate disasters. For a quantitative evaluation of the situation, a parameter called vulnerability index was defined and plotted against time. Accordingly, it became clear that this index has been decreasing with time consistently due to the long-term efforts of human. Finally, it is stressed that the disaster mitigation requires a persistent long-term effort, although it may not match the recent popular phrase of cost and time-performance benefit.</p>