Renewable Energy Sources and Climate Change Mitigation (2011) covers alternatives to fossil fuels:
https://www.ipcc.ch/report/renewable-energy-sources-and-clim...
AR5 Climate Change 2014: Mitigation of Climate Change
https://www.ipcc.ch/report/ar5/wg3/
This also addresses the question of alternatives and mitigations in part. An updated report is due next year.