Alva Review-Courier -

BEIJING (AP) — Commercial development of the globe's huge reserves of a frozen fossil fuel known as "combustible ice" has moved closer to reality after Japan and China successfully extracted the material from the seafloor off their coastlines.

But experts said Friday that large-scale production remains many years away — and if not done properly could flood the atmosphere with climate-changing greenhouse gases.

Combustible ice is a frozen mixture of water and concentrated natural gas. Technically known as methane hydrate, it can be lit on fire in its frozen state and is believed to comprise one...