World Needs a Backup Plan

Earth from space. CREDIT: NASA

World leaders need an emergency backup plan to stave off catastrophic climate change if cuts in greenhouse gas emissions don't work, says climate scientist Ken Caldeira of the Carnegie Institution in Washington, D.C.

"We need a climate engineering research and development plan, in addition to strong measures to reduce greenhouse gas emissions," Caldeira said in testimony to the British Parliament yesterday. "Prudence demands that we consider what we might do in the face of unacceptable climate damage, which could occur despite our best efforts to rein in greenhouse gas emissions."

Among the wild ideas that have been floated:

• Inject dust or sulfur into the atmosphere to scatter sunlight.
• Construct a "sun shade" with an artificial ring of small particles or a spacecraft that would block some of the sun's rays.
• Inject iron into oceans to stimulate the growth of plankton, which consume carbon dioxide.
• Bury carbon underground to sequester it for millennia.

Critics question the effectiveness of these schemes and worry that tampering with the Earth’s systems would create as many problems as they solve, according to a statement from the Carnegie Institution. "But others warn that currently accelerating carbon emissions may push the planet’s climate system to a tipping point, making drastic measures necessary to prevent an environmental calamity," it states.

"Science is needed to address critical questions, among them: How effective would various climate engineering proposals be at achieving their climate goals? What unintended outcomes might result? How might these unintended outcomes affect both human and natural systems?" Caldeira said. "Engineering is needed both to build deployable systems and to keep the science focused on what's technically feasible."

Caldeira thinks university researchers should drive the effort to make a backup plan.

"A climate engineering research plan should be built around important questions rather than preconceived answers," he advised the committee. "It should anticipate and embrace innovation and recognize that a portfolio of divergent but defensible paths is most likely to reveal a successful path forward; we should be wary of assuming that we've already thought of the most promising approaches or the most important unintended consequences."

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