– Scientists are calling for tests to find ways to cool the planet — a step toward exploration of the controversial field of geoengineering, which aims to change the climate by blocking the sun’s rays.

It might be necessary if society can’t agree on how to stop carbon emissions that are heating up Earth, experts said at a meeting of the American Association for the Advancement of Science.

The call for small-scale tests represents a profound shift in thinking among the scientific community, which has resisted conversations about deliberate, large-scale manipulation of the planet.

“We have to know through research ... what the benefits and risks might be,” said climate scientist Alan Robock of Rutgers University.

Scientists say the proposals to study sun blocking are spurred by this reality: Even if we stopped carbon emissions today, the Earth would keep warming for several decades.

A geoengineering test, opposed by some environmentalists, could involve wafting sea-salt particles toward low clouds off California’s Central Coast to try to fend off sunlight. They argue it’s dangerous to tinker with the environment rather than stop the problem’s source.

Another might measure the cooling haze-inducing effect of emissions from Pacific cargo ships.

Some environmental groups oppose geoengineering tests because they may suggest an easy fix.

“Research into geoengineering is a distraction from the hard work of reducing carbon emissions,” said Richard Heinberg of the Santa Rosa-based Post Carbon Institute.

San Jose Mercury News