The long lifetime of existing transportation and energy infrastructure means that continued emissions of CO2 from these sources are likely for a number of decades. This ‘infrastructural inertia’ alone is projected to produce a warming commitment of 1.3°C above the pre-industrial era. This result emphasizes that extraordinary measures will be required to limit emissions from new energy and transportation sources if global temperature is to be stabilized below 2°C.

Climate modeling has demonstrated that even if atmospheric composition was fixed at current levels, continued warming of the climate would occur due to inertia in the climate system. This form of climate change commitment has become widely recognized. Davis et al. focus attention on inertia in human systems, by asking ‘what CO2 levels and global mean temperature would be attained if no additional CO2-emitting devices (e.g., power plants, motor vehicles) were built but all the existing CO2-emitting devices were allowed to live out their normal lifetimes?”. Barring widespread retrofitting or early decommissioning of existing infrastructure, these committed emissions represent ‘infrastructural inertia’. The authors developed scenarios of global CO2 emissions from existing infrastructure directly emitting CO2 to the atmosphere for the period 2010 to 2060 (with emissions approaching zero at the end of this time period) and used the University of Victoria Earth System Climate Model to project the resulting changes in atmospheric CO2 and global mean temperature. Projections with low, mid and high emissions scenarios led to projected global average warming of 1.3°C (1.1° to 1.4°C) above the pre-industrial era. Since new sources of CO2 are bound to be built in the future in order to satisfy growing demands for energy and transportation, the committed warming from existing infrastructure makes clear that satisfying these demands and achieving the 2°C target of the Copenhagen Accord will be an enormous challenge.

Summary courtesy of Environment Canada

The promises countries have made to control carbon emissions will see temperatures rise by up to 4C during this century, a UN report concludes.

The report, from the UN Environment Programme (Unep), comes days before the opening of this year’s climate summit.

It concludes there is a significant gap between what science says is necessary to constrain temperature rise and what governments have pledged to achieve.

But with extra political will, it says, warming could be kept much lower.

On Sunday, scientists released data showing that the recession curbed emissions from fossil-fuel burning by only 1.3% during 2009, and that they are set to begin rising again as the global economy cranks up once more.

Unep’s analysis shows that even if governments implement all they have pledged to do, that would “…imply a temperature increase of between 2.5-5C [from pre-industrial times] before the end of the century”.

But for the two-degree scenario 2.8% is just the beginning; from 2020 to 2035 the rate of decarbonisation needs to double again, to 5.5%. Though they are unwilling to say it in public, the sheer improbability of such success has led many climate scientists, campaigners and policymakers to conclude that, in the words of Bob Watson, once the head of the IPCC and now the chief scientist at Britain’s Department for Environment, Food and Rural Affairs, “Two degrees is a wishful dream.”