A small group of highly-respected climate-change and Earth systems scientists testified before the U.S. House of Representatives today in a hearing titled the hearing titled “Geoengineering: Assessing the Implications of Large-Scale Climate Intervention,” which explored the current lack of geoengineering research and the need for ramped up research efforts in this area.

“Geoengineering” is a catch‐all term, used to refer to a broad collection of strategies to diminish the amount of climate change resulting from greenhouse gas emissions. Ken Caldeira, a scientist at Stanford University, described three characteristics that define “geoengineering” strategies, namely: (1) intent to affect climate; (2) affecting climate at a regional to global scale; and, (3) novelty or lack of familiarity. In addition, Caldeira said geoengineering strategies fall into into one of two broad categories:

(1) Solar Radiation Management (SRM) strategies that seek to directly intervene in the climate system, without directly affecting atmospheric greenhouse gas concentrations

(2) Carbon Dioxide Removal (CDR) strategies that seek to diminish atmospheric greenhouse gas concentrations, after the gases have already been released to the atmosphere

The most promising SRM proposals appear to be inexpensive, can be deployed rapidly, and can cause the Earth to cool quickly. But they do not address the root causes of our climate problem or the problem of ocean acidification. Examples of SRM include injecting particles into the atmosphere or whitening clouds over the ocean to reflect incoming solar radiation. While SRM approaches may reduce overall climate risk, they may also create new environmental and political risks.

The most promising CDR approaches appear to be expensive  require long lead times to work.  Yet, they address the root cause of the problem – excess carbon dioxide in the atmosphere. Examples include biological approaches such as planting forests and chemical approaches that extract carbon dioxide from the atmosphere or from emissions sources and store it underground.

Caldeira compared geoengineering approaches to seatbelts in automobiles. “Just because we wear seatbelts, that does not mean we will drive more recklessly,” he said. “Seat belts can remind us that driving is a dangerous activity.”

He stressed the need for a research program to uncover the limitations and potential pitfalls of geoengineering. “We do not want our seat belts to be tested for the first time when we are in an automobile accident. If the seat belts are not going to work, it would be good to know that now. If there is something really wrong with thoughtfully intervening in the climate system, we should try to find that out now, so that if a crisis occurs, policy makers are not put in the position of having to decide whether to let people die or try to save their lives by deploying, at full scale, an untested system.

The U.S. House of Representative’s Committee on Science and Technology held the hearing titled “Geoengineering: Assessing the Implications of Large-Scale Climate Intervention” on November 5, 2009.