What initiative or group is responsible for the most reviewed and widely accepted reports that we have on climate change?

IPCC

Explanation:

IPCC is an acronym for Intergovernmental Panel on Climate Change. It was founded by Bert Bolin in 1988 and its headquarters is in Geneva, Switzerland.

The IPCC is a United Nations organization that is responsible for the most reviewed and widely accepted reports that we have on climate change.

The Intergovernmental Panel on Climate Change( IPCC)

Explanation:

This is an international panel under the United Nations which was founded in 1988.The United Nations members are also the active members of the panel .It assesses thoroughly published literatures by specialists on climate changes and takes a stand on how the environment and atmosphere should be treated.

The panel then further assesses how the climate change will influence the various habitats and the economy of the given area.