Science magazine recently published (11 May 2007, p.829) a short but stunning letter about a new kind of overshoot connected with climate change. This overshoot has little to do with carrying capacity (see Catton's essential book ""Overshoot") but much to with avoiding taking any tough action now to reduce fossil-fuel burning and off-loading that responsibility onto later generations. Here is the letter in full:

"Overshoot" Scenarios and Climate Change

If it is desirable to remain beneath low levels of atmospheric carbon dioxide concentrations, and if Broecker (9 March, Science) is correct that this will be difficult to achieve by systematic emission reductions alone, then radical thinking across a broad range of options is required.

So far, the scientific community has considered climate change under plausible scenarios of technical and economic futures without any explicit action to curb emissions. However, if followed, such a scenario could take us into the territory of dangerous climate change [Schellnhuber et al, 'Avoiding Dangerous Climate Change' 2006], to which society would need to adapt. The community has also considered what emissions pathways would be needed to avoid crossing unacceptable or "dangerous" levels. These lead to the eventual stabilization of climate, but invariably require massive reductions in fossil fuel burning, starting soon. The latter places a burden on the current and next few generations, while the former leaves the potentially huge problem of dealing with the adverse effects of climate change to future generations. The balance of taking action now and the consequences of no action are an area of active debate [e.g., N. Stern, The Economics of Climate Change: The Stern Review].

It is against this dilemma that the concept of "overshoot" scenarios is emerging in which atmospheric concentrations and/or associated temperature increases could temporarily exceed target levels (such as the 2°C warming favored by the European Union) before declining to stabilization. In this scenario, emissions would be reduced less severely in the short term, but more severely later on (possibly using carbon capture technology), when compared to a nonovershooting scenario. As such, "overshoot" could be a conscious policy that removes some of the burden of mitigation from the present generations while protecting future generations from exposure to the most severe impacts. However, it comes with the inherent risk that the climate might enter a state from which recovery becomes impossible. The risks associated with "overshooting" and reversibility in climate change on practical time scales remain an open research question requiring urgent attention.

If emissions targets are not met, or if the impacts of climate change are greater than expected, we might well find ourselves in the position of having a greenhouse gas level that is "dangerous," thus accidentally following an overshoot scenario. In this case, the capability to draw CO₂ from the atmosphere might be highly desirable.

The letter's authors (Huntingford & Lowe) are sounding an alarm bell that may have been missed so far. Once elected and unelected power-brokers become satisfied that there is a way of wriggling out of system change (for 50 - 80% CO2 by 2050 can mean only that), then we can look forward to a new wave of climate-washing in which the baseline is moved and the debate reframed so that we avidly discuss how much CO2 overshoot we think we can get away with.

However, it may turn out that peak oil will force us to be honest about reacting seriously and at scale to climate change, while climate change and other ecological debacles may serve the same function for those who accept the coming oil decline but suggest options that take no heed of climate change and the environment.

Radical thinking across a broad range of options is required: this is the truth of the matter. There is no sign of that yet as the world works its way through a round of exquisitely hyped so-called solutions, which are then quietly dropped. Hydrogen and the 'dash for (natural) gas' have largely left the headlines to be replaced currently by a form of energy laundering called corn ethanol (in the USA) and rain-forest wrecking palm oil biodiesel (in Europe), while the ludicrously named 'green' nuclear and 'clean' coal are also making a good show in the 'technology will save us' sweepstake.

Every human alive needs and uses some kind of technology, it is true, but we are going to need to reframe our understanding of technology and think about structural changes before we have a chance of building systems that will see us (and our descendants) through energy decline and climate chaos.