Archive by date | May 2007


I wrote a longish feature for Nature this week on geoengineering. It goes into various details perhaps a little deeper than some accounts have, and of course also leaves out stuff that in an ideal world it would have got in. The bottom line is that lowering the earth’s average temperature by putting long-lived particles of some sort into the stratosphere is, as has long been known, technologically feasible, and would alter the course of, but not completely stop, climate change. Crucially, as yet we cannot predict with any confidence what the net changes under a warming+cooling regime would be, and though there are signs they might be a little smaller than was once thought they could easily be large enough to be complete showstoppers.  Read more

Solutions in the soil

As it happens we’ve a look at the subject in Nature this week, too — a commentary (pdf) from one of the field’s main men, Johannes Lehmann of Cornell, which takes things forward nicely, I think. One of the advantages he points out for biochar sequestration — as opposed, say, to sequestration of carbon in aquifers — is that once the carbon is in the soil “it is difficult to imagine any incident or change in practise that would cause a sudden loss of stored carbon”. And he also argues that this sort of practise could be carried out at a serious scale:

I have calculated emissions reductions for three separate biochar approaches that can each sequester about 10% of the annual US fossil-fuel emissions (1.6 billion tonnes of carbon in 2005). First, pyrolysis of forest residues (assuming 3.5 tonnes biomass per hectare per year) from 200 million hectares of US forests that are used for timber production; second, pyrolysis of fast-growing vegetation (20 tonnes biomass per hectare per year) grown on 30 million hectares of idle US cropland for this purpose; third, pyrolysis of crop residues (5.5 tonnes biomass per hectare per year) for 120 million hectares of harvested US cropland. In each case, the biochar generated by pyrolysis is returned to the soil and not burned to offset fossil-fuel use. Even greater emissions reductions are possible if pyrolysis gases are captured for bioenergy production.

Cities: key players in the climate change arena

Posted by Olive Heffernan on behalf of Paty Romero-Lankao Cities play key and diverse roles in the climate change arena. Regarding mitigation, a high proportion of energy, industrial and transportation emissions is generated by urban areas. Although most of the electricity and fuels are produced outside cities, they are aimed at satisfying cities’ “thirst” of energy. Therefore, urban areas place a huge burden not only on the absorptive capacity of the local environment; they also influence wide patterns of energy and land use in the surrounding and more distant areas, in the livelihoods and quality of life of people living  … Read more

The plant-methane link again

This week in Nature we have a news story on an attempt to follow up Frank Keppler’s work on methane produced aerobically by green plants which we published early last year (news story | paper). The Keppler piece, which suggested that methane emissions from green plants were a significant but previously unappreciated factor in global methane emissions, caused quit a lot of fuss, understandably, in the media — since methane is a greenhouse gas which, over short time horizons, is about 75 times more powerful than carbon dioxide — and quite a lot of befuddlement among plant scientists. If it were true, it would have significant implications for the way that people model methane production, and the levels of production that one might predict in a warming world. The debate rumbled on last year (another news report, this time by my colleague Quirin).  Read more

Meeting at the cost of climate

The week before last, I was one of an army of geoscientists travelling to Vienna from Europe and the world for the General Assembly of the European Geophysical Union (EGU). And of course, we are all aware of climate change. There was a talk on “The carbon footprint of academic travelling – assessing the sustainability of different ways of travelling to the EGU Assembly”. Too late, since most of us had already come by plane