Why reduce your greenhouse gas emissions when you can just engineer the whole planet to prevent global warming? The idea of ‘geo-engineering’ is hugely attractive.

“The world has not been able to get carbon emissions under control. We should look at other options,” Margaret Leinin, chief science officer of geo-engineering company Climos says in a sizeable Reuters story on the topic.

But there are a number of different suggestions for schemes, ranging from pouring iron into the seas (to lock carbon up in plankton) to spraying water droplets up into clouds. In a new paper in Nature Geoscience, Philip Boyd of the University of Otago in New Zealand calls for geo-engineering schemes to be ranked according to their efficacy, cost, risk and impact on climate.

“The ideas for how to change our climate keep getting pumped out. They get lots of column inches,” says Boyd (New Scientist). “My concern is that we will reach a tipping point, people will ask what are we doing about it, and none of the schemes will have been tested.”

While he doesn’t back one technology over another, Boyd does come up with this comparison chart (more colour means a higher ranking). I’m not sure it’s going to please information design people, but it gets the point across.

“In the near future, we must decide the relative importance of time, cost, risk and efficacy in tackling climate change if it is decided to press ahead with a geo-engineering approach,” Boyd writes in his paper. “Of course, it could transpire after such an analysis that climate mitigation strategies with a very low risk but apparently higher costs, such as direct carbon capture and storage, are the best approach.”