Former New York City Mayor Michael Bloomberg has been chosen by United Nations Secretary-General Ban Ki-moon to be the U.N. special envoy for cities and climate change.

Reuters reported that the appointment was expected early Friday morning. U.N. deputy spokesman Farhan Haq made the official announcement Friday afternoon.

#UNSG appoints @ of the US as his Special Envoy for Cities & #ClimateChange
Former NYC Mayor Michael Bloomberg Appointed U.N. Special Envoy for Cities and Climate Change
@UN_Spokesperson
UN Spokesperson

In his new role, Bloomberg will “raise political will and mobilize action among cities as part of his longer-term strategy to advance efforts on climate change,” Haq said.

Combating climate change has long been a top issue of Bloomberg’s, who cited it as his reason for endorsing President Barack Obama for re-election in 2012.