Hachijojima is rural and in the middle of the ocean – making a weather station there less prone to bad siting, such as airports, asphalt, concrete, steel and other heat absorbing infrastructure. There's no sign of man made climate change on the island !
What is apparent in the last graph is the peak in 1997-1998. It matches the original NOAA (US Commerce Department) data that showed 1997- 1998 much warmer than today's NOAA temperatures, including the 2016 El Nino, before they arbitrarily LOWERED their 1997 data.
Japan Meteorological Agency (JMA) data go back almost 80 years. There has been virtually no summer temperature trend. Winter temperatures since 1947 also show no long-term trend. The annual mean temperature data for Hachjojima seems to follow a cyclic behavior that resembles ocean surface temperature cycles we see around the globe, like the PDO or AMO.
