Sami Grover

With 1.4 million megawatts of coal plants planned, and some people questioning Germany's push for renewables, it sometimes feels like fossil fuels are staging a come back.

Even as the world's biggest investors urge rapid action on climate change, we hear naysayers claim that a near-term shift to clean energy will cost too much and/or is not yet technically feasible.

Others disagree.

In a letter published in Nature last month, three prominent experts on renewables called for an immediate moratorium on building new fossil fuel infrastructure. The three scientists—Keith Barnham, of the Physics Department at Imperial College London; Kaspar Knorr, of the Fraunhofer Institute for Wind Energy and Energy System Technology, in Kassel, Germany; and Massimo Mazzer of the CNR-IMEM, Parma, Italy—argued that the solar component of a global 100% renewable energy supply could be installed as early as 2020 using existing technology, little energy storage, and subsidies no higher than Germany's current Feed In Tariff scheme.