Climate change, energy and environment ministers from Group of Seven (G7) countries concluded their Sapporo meeting Sunday with promises of massive renewable energy expansion, especially wind power, and continued nuclear power development.

But the lack of a clear timeline to end coal dependency raised questions as to whether the world can effectively negotiate further agreements to keep global warming to 1.5 degrees Celsius by midcentury and achieve net zero carbon emissions by 2050.

To reach this goal, the G7 promised to speed up the phaseout of unabated fossil fuels. Including the term “unabated,” however, leaves open the possibility of current coal plants employing hydrogen and ammonia cofired plants as well as carbon capture and storage in the years ahead, all of which are controversial new technologies.