Argument: Solar shading is a just response to irreversible global warming
Molly Bentley. "Guns and sunshades to rescue climate". BBC. 2 Mar. 2006 - Any cook who has tasted a dish after tossing in too much salt or hot pepper knows the panic of trying to undo the damage.
You raid the spice rack to mask the glut of cayenne, but oops - now it is swimming in oregano. It is hard to restore the balance once you overdo it.
We have experienced this with the Earth's atmosphere for some time now; concentrations of greenhouse gases continue to grow even as we adopt international protocols and clean technologies in an attempt to bring them down.
It is apparent our energy-saving tricks are not enough to prevent perhaps catastrophic climate change. But there may be a "plan B"; and while scientists hope it will not be needed, they are considering it anyway.
It would be plucked from an array of bold and contentious proposals which go under the heading "geoengineering".
Fraser Cain. "Solar Shade to Reverse Global Warming". Universe Today. July 7th, 2006 - The overwhelming scientific consensus predicts that human emissions of carbon dioxide will warm the planet over the coming decades and centuries. By how much and how quickly is still up for dispute, but most agree it's time to take action. Reducing carbon dioxide emissions is the key, but what if it's already too late, and the temperature tipping point has already been reached? Dr. Roger Angel from the University of Arizona takes a page from the book of C. Mongomery Burns and suggests a gigantic sunshade placed in space above the Earth might help keep us cool.
Robert Roy Britt. "No Stopping it Now: Seas to Rise 4 Inches or More this Century". LiveScience. 17 Mar. 2005: Even if all industrial pollution and auto emissions suddenly ceased today, Earth's climate will warm at least 1 degree by the year 2100 and seas will rise 4 inches (11 centimeters), according to a new study.
The warming is likely to continue through 2400, another study forecasts.
The worst-case scenario projects the global average temperature rising 6.3 degrees Fahrenheit within this century and the sea level climbing a foot or more.
The outlook is based on greenhouse gases that were in the atmosphere in 2000, with no additional input of the chemicals, which serve as a global blanket to trap solar energy.
"Many people don't realize we are committed right now to a significant amount of global warming and sea level rise because of the greenhouse gases we have already put into the atmosphere," said Gerald Meehl, who led the study out of the National Center for Atmospheric Research (NCAR).
"Even if we stabilize greenhouse gas concentrations, the climate will continue to warm, and there will be proportionately even more sea level rise," Meehl said today. "The longer we wait, the more climate change we are committed to in the future."
Ken Caldeira at the Carnegie Institution of Washington, in California: "If this is the case [that global climate change is irreversible], then I am not clear on what the 'greenest' path is. Is it better to let the Greenland ice sheet collapse and let the polar bears drown their way to extinction, or to spray some sulphur particles in the stratosphere?"
Hansen's study suggests that only moderate additional warming is likely to trigger the disintegration of the west Antarctic and Arctic ice sheets - events which would be near-impossible to reverse.
"If this is the case, then I am not clear on what the 'greenest' path is," says Caldeira. "Is it better to let the Greenland ice sheet collapse and let the polar bears drown their way to extinction, or to spray some sulphur particles in the stratosphere?"
He says that if forced to consider deploying a solar shield, "we would need to be confident that we would not be creating bigger problems than we are solving. Therefore, it is important both to understand the mess we are in today - how close are we to making irreversible changes, how fast can we alter our energy system - and to understand what might happen should we try to avoid some of the worst outcomes by engineering our climate".
Caldeira and Matthews also found that a solar shield would not correct abnormalities in rainfall. Most notably, the tropics would receive less rain than in the absence of the greenhouse effect, as predicted by climate change models.