We never said biochar is a miracle cure

George Monbiot's implication that we believe biochar is a miracle solution to CO2 reduction is grossly misunderstood

It is unfortunate that George Monbiot has insinuated that one of us (Jim Hansen) is a believer in biochar as a "miracle" solution for the climate crisis. If he is basing this on our published papers, then he has grossly misunderstood them. An attentive reader would know his insinuation is false by simply examining our land use-related assumptions in our recently published peer-reviewed paper, Target atmospheric CO2: Where should humanity aim?

Broadly speaking, our climate change mitigation scenarios are strictly illustrative in nature, in other words, they serve to convey the types, magnitude and time frame of mitigation measures needed to reduce atmospheric carbon dioxide amounts. Although we do mention waste-derived biochar as a possible mitigation option, it certainly does not mean we are advocating that as the panacea. Indeed, as we very clearly outline in the paper, our scenarios assume waste-derived biochar provides only a very small fraction of the land use-related CO2 drawdown, with reforestation and curtailed deforestation providing a magnitude more. Nowhere do we assert or imply plantations should be grown specifically for biochar, or that reforestation should be at the expense of food crops, pristine ecosystems or substantially inhabited land. Furthermore, all relevant numbers used in our mitigation scenarios are derived from the peer-reviewed scientific literature.

On the issue of land use changes in general, our paper clearly states any biofuels approach must be very carefully designed, and we cite two major critiques of current biofuels approaches. We agree there are still fundamental uncertainties associated with biochar as a mitigation option, but the peer-reviewed papers we cite describe these uncertainties.

Monbiot's piece might leave readers with the impression that human-assisted reforestation is a lose-lose situation everywhere on the planet. However, there are numerous scientific assessments that indicate there are hundreds of millions of hectares of suitable, sparsely inhabited lands — lands degraded by human activities in the first place. Given that reforestation occurs on a large scale even in nature (for example natural succession), it makes perfect sense to promote sensible, anthropogenic reforestation, among other reasons to undo the damage caused by large-scale deforestation.

• Pushker Kharecha and Jim Hansen are at NASA's Goddard Institute for Space Studies and Columbia University's Earth Institute.

Link to article: http://www.guardian.co.uk/environment/2009/mar/25/hansen-biochar-monbiot-response