UN chief Ban Ki-moon announced Monday the appointment of two special envoys on climate change.

Former president of Ghana John Kufuor and former prime minister of Norway Jens Stoltenberg have been asked to mobilize the "political will and action" of governments and heads of state.

This will lead up to a 2015 global agreement to curb climate-altering greenhouse gas emissions and they will work to raise awareness before a UN climate summit next September in New York.

"The summit will be an important milestone to mobilize political commitment for the conclusion of a global agreement by 2015," Ban's office said in a statement.