Robinson will seek to "mobilize political will and action" ahead of the special summit of heads of state and government, called by Ban, to be held in New York on September 23, the UN said.
The United Nations is seeking to limit global warming to two degrees Celsius over pre-Industrial Revolution levels, but scientists say current emission trends could hike temperatures to more than twice that level by century's end.
Robinson, who served as UN high commissioner for human rights from 1997 to 2002, had until now served as the UN special envoy for Africa's Great Lakes region.