Japan has not warmed since 1989!
1989 is the year that Dr. James Hansen, then Director, NASA’s Goddard Institute for Space Studies, testified before a Senate subcommittee, its name too long to matter. Prior to the hearing, air conditioning was turned off in the room and the windows opened. They wanted people to be hot and uncomfortable. This was the hearing that introduced the world to the concept of Global Warming, later changed to Climate Change (probably to avoid the embarrassment of absence of warming).
This article shows three graphs, one each for Tokyo, the island of Hachijō-jima, and the entire island of Japan. Winters there have not warmed since 1987 (the entire island), and 1984 (Tokyo). The graph for Hachijō-jima goes all the way back to 1947. If anything it shows a slight cooling trend.



