Twin cities Berlin and Tokyo want to further deepen their partnership and work together on 21st century problems such as climate change. “We are facing global challenges that we must tackle in our metropolises,” Berlin Mayor Kai Wegner said on Tuesday in Tokyo at the signing of a new communiqué with Tokyo Governor Yuriko Koike. The twinning of the two cities happened exactly 30 years ago. The past 30 years have been “very significant” for Tokyo and Berlin, Tokyo Governor Koike said at the ceremony. Wegner told an audience at the City Hall in the Japanese capital: “I believe that the next 30 ye…