"On the specific issue of climate change, Mercer, an actuarial consultancy, recently issued a report that argues, “Investors cannot assume that economic growth will continue to be heavily reliant on an energy sector powered predominantly by fossil fuels.” If climate change begins to cause economic and social havoc, governments will have to act, either by restricting energy use or by taxing carbon emissions. In such circumstances, Mercer contends, it will not be possible for energy companies to exploit all their known reserves: some will become “stranded assets”. The average annual returns from coal could fall by anywhere between 18% and 74% over the next 35 years, the report concludes. If such estimates are right, then eliminating exposure to the sector would be perfectly compatible with fiduciary duty."