IPCC Special Report on the Ocean and Cryosphere in a Changing Climate
"A total of 670 million people in high mountain regions and 680 million people in low-lying coastal zones depend directly on these systems. Four million people live permanently in the Arctic region, and small island developing states are home to 65 million people." (Source: IPCC Homepage) The report not only details the escalating costs as well as the risks of delayed action, but also the benefits of ambitious sustainable development.
The special report can be found here.