Tokyo has enacted a measure to cut greenhouse gases. Governor Shintaro Ishihara created Japan's first emissions cap system, aiming to reduce greenhouse gas emission by a total of 25% by 2020 from the 2000 level. Tokyo is an example of an urban heat island, and the phenomenon is especially serious in its special wards. According to the Tokyo Metropolitan Government, the annual mean temperature has increased by about  over the past 100 years. Tokyo has been cited as a "convincing example of the relationship between urban growth and climate".