A Plan B to engineer climate

BERLIN, Germany (AFP) — Dismissed a decade ago as far-fetched and dangerous, schemes to tame global warming by engineering the climate have migrated from the margins of policy debate towards center stage.

“Plan A” remains tackling the problem at its source. But efforts to sharply reduce greenhouse gas emissions have fallen woefully short and cannot, most scientists agree, avert catastrophic climate change on their own.

Here is a “Plan B” menu of geoengineering solutions that can be broken down into two categories: dimming the sun, which remains highly controversial, and capturing carbon dioxide (CO2).

The goal is simple: prevent some of the sun’s rays from hitting the planet’s surface, forcing them instead back up into space.

One idea worthy of a “Star Wars” sequel would assemble giant orbiting mirrors to deflect a bit of Earth-bound radiation.

A more feasible scheme – experiments are scheduled for next fall in Arizona – would inject tiny reflective particles into the stratosphere.

Nature sometimes does the same: Debris from the 1991 eruption of Mount Pinatubo in thePhilippines lowered the planet’s average surface temperature for a year or two afterwards.

Scientists have also calculated ways to alter clouds that could help beat the heat.

One is to brighten the white, billowy ocean clouds that rebound sunlight back up. Another would thin cirrus clouds, which unlike other types absorb more heat than they reflect.

Even if it works as intended, solar radiation management would do nothing to reduce atmospheric CO2, which is making oceans too acidic. There is also the danger of knock-on consequences, including changes in rainfall patterns, and what scientists call “termination shock” – a sudden warming if the system were to fail.