Even if the world also has sustained success eliminating deforestation, reducing emissions of non-CO2 greenhouse gasses and improving energy efficiency, new investment in fossil fuel infrastructure can’t occur much beyond 2015 in order to maintain a 50% chance of limiting temperature increase to 2°C in 2100. Having a higher probability of achieving the 2°C goal or keeping these even odds of meeting the goal but delaying the end of the era of fossil fuel investment would require additional measures such as shutting down already-constructed fossil-fuel-using infrastructure before the end of its useful lifetime, further reducing energy demand, or achieving so called negative emissions, where CO2 is removed from the atmosphere and sequestered.
The goal of the Copenhagen Accord – to limit temperature increase to 2°C is still in reach – but the actions to get there are far beyond what we see being implemented around us today.
A thought experiment with our En-ROADS global energy model makes this clear.
What if, in 2015, we eliminated any new investment in fossil-fuel-using infrastructure, anywhere in the world? En-ROADS shows a surge in creation of new low-carbon energy sources, and an improvement in the global temperature by 2100 compared to ‘business as usual’. Rather than the 4.5°C of temperature increase under ‘business as usual’, the scenario results instead in 3.2°C of warming.

In this thought experiment using the global energy system model En-ROADS, there is no new investment in fossil fuel using infrastructure after 2015, but the long lifetime of the existing infrastructure means that fossil fuel use continues well into the century.
Eliminating new fossil-fuel-using power plants, automobiles, and factories just a few years from now sounds very drastic, of course, so why don’t we see more impact on the global temperature? The figure to the left helps explain why: even though no new infrastructure is built after 2015, the existing infrastructure lives on (and continues to produce CO2 emissions throughout its lifetime), only fading away in the second half of the century. (See the black wedge of energy from coal and the red wedge from oil in the figure).
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