The six scenarios considered in the report are:

• Baseline. A scenario in which energy efficiency improves in line with trends of the last 25 years, with no change in fuel mix by country. PWC uses this BAU scenario as the benchmark against which to assess the need for change.

• Scorched Earth. This scenario assumes energy efficiency improvements 1% less per annum than in the BAU scenario, with no change in fuel mix. This scenario might be associated with major technological advances leading to significantly lower fossil-fuel extraction costs and associated reductions in energy prices that eradicate economic incentives for efficiency improvements and substitution.

• Constrained Growth. This scenario maintains energy assumptions as in the baseline, but uses lower GDP growth, especially in the E7 countries.

• Greener Fuel Mix. Assumptions in this scenario are similar to those of the baseline, with the ex exception of a significant shift from fossil fuels to nuclear and renewables energy by 2050.

• Green Growth. This scenario combines the Greener Fuel Mix assumptions with energy efficiency improvements 1% per annum greater than in the baseline.

• Green Growth + CCS. This scenario adds carbon capture and sequestration to the Green Growth strategy.

PwC finds that both the Greener Fuel Mix and the Constrained Growth scenarios results in atmospheric CO₂ concentrations rising to more than 500 ppm by 2050, with the rate of increase only slightly decelerating.

...the majority of scientists would probably now see [500 ppm] as the maximum level consistent with avoiding severe risks of adverse climate change affects (and many now argue for a lower maximum at 450 ppm or even 400 ppm).

This suggests that the Green Growth scenario might be a more prudent target to aim for, implying a gradual reduction in global carbon emissions from a peak of around 8.5 GtC in 2025 to around 7.5 GtC in 2050, only slightly above current levels. However...this would still imply atmospheric CO₂ levels of around 475 ppm by 2050 and these would still be rising at around 2 ppm at that time according to our model, similar to the estimated rate of increase at present.

...plausible extrapolations from our Green Growth scenario without CCS would suggest that atmospheric CO₂ levels might reach 500 ppm by 2075 without clearly stabilizing.

So this scenario would seem to be at best minimally acceptable and would ideally need to be complemented by a combination of carbon capture and storage to reduce emissions to the atmosphere up to 2050 and further measures to cut emissions at a faster rate beyond that date.

PwC concludes that the G7 economies—the US, Japan, Germany, UK, France, Italy and Canada—may need to take the lead in reducing their carbon emissions, given that emissions from the faster-growing emerging economies will almost certainly continue to rise over the next few decades.

Our analysis suggests that there are technologically feasible and relatively low-cost options for controlling carbon emissions to the atmosphere. Estimates suggest that the level of GDP might be reduced by no more than around 2-3% in 2050 if this strategy was followed, equivalent to sacrificing only around a year of economic growth for the sake of reducing carbon emissions in 2050 by around 60% compared to our baseline scenario.

But if this is to be achieved, it will take further concerted action by governments, businesses and individuals over a broad range of measures to boost energy efficiency, adopt a greener fuel mix, and introduce carbon capture and storage technologies in power plants and other major industrial facilities.

—John Hawksworth, report author

This latest PwC report follows on from one published in March 2006 which highlighted the rapid growth potential of the E7 emerging economies—China, India, Brazil, Russia, Mexico, Indonesia and Turkey—leading up to 2050.

Resources:

• The World in 2050; The Impact of Global Growth for Carbon Emissions and Climate Change Policy