SRM techniques act by reflecting the sun's energy away from Earth, meaning they lower temperatures rapidly, but do not affect CO2 levels. They therefore fail to address the wider effects of rising CO2, such as ocean acidification, and would need to be deployed for a very long time. Although they are relatively cheap to deploy, there are considerable uncertainties about their regional consequences, and they only reduce some, but not all, of the effects of climate change, while possibly creating other problems. The report concludes that SRM techniques could be useful if a threshold is reached where action to reduce temperatures must be taken rapidly, but that they are not an alternative to emissions reductions or CDR techniques.
"If we are confronted with a climate emergency and decide we cannot tolerate any more warming, engineering some system to deflect more sunlight back to space would likely be the primary option available to cool the Earth quickly," said Caldeira. "Of course, we need to make sure that tinkering with our environment in this way would not just cause bigger problems. We need to study these options now so that we can understand the pluses and minuses in case we need to deploy them."
Professor Shepherd added, "None of the geoengineering technologies so far suggested is a magic bullet, and all have risks and uncertainties associated with them. It is essential that we strive to cut emissions now, but we
|Contact: Ken Caldeira|