The non-marginal nature of the climate problem and the importance of technological change

Allowing Earth's global mean temperature to rise by more than 1–2 degrees Celsius above its current level carries significant risk of triggering positive feedbacks that further raise temperature and lead to catastrophic climatic changes (Hansen, Sato et al. 2006; Lenton, Held et al. 2008). To limit warming to such a small rise in temperature, when current greenhouse gas (GHG) concentrations already commit us to an increase of 0.3–0.9 degrees Celsius above a reference level equal to global average temperatures over the period 1980–1999 (IPCC 2007a), will require massive cuts in carbon dioxide (CO2) emissions by the middle of the century. The climate problem cannot be tackled by tinkering at the margins.

Eliminating CO2 emissions is difficult for the simple reason that it is cheaper to obtain energy by burning coal, oil, and gas than by harnessing the sun, the wind, or atomic nuclei. The 2007 report of the Intergovernmental Panel on Climate Change reviewed the scientific literature and concluded that there are currently available, low-cost or even profitable opportunities for reducing CO2 emissions, mainly through the installation of energy-conserving equipment and techniques in industry, building, and transport. However, tapping low-cost reduction opportunities can achieve at most a cut of a few percentage points below business-as-usual (BAU) emissions (IPCC 2007). With current technologies, deeper cuts can come only by raising the cost of energy.