The widening gap between present emissions and the two-degree target

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The 2012 global carbon emission summary released today shows an ever-widening gap between rising emissions and the steps necessary to keep global temperatures within the generally agreed – but increasingly difficult – 2°C safe limit above pre-industrial levels.

The summary, published in Nature Climate Change and generated by the Global Carbon Project, clearly illustrates the fact that the necessary reductions in carbon dioxide emissions are becoming a receding goal.

Carbon dioxide emissions into the atmosphere are set to reach 36 billion tonnes of carbon dioxide this year, which is 58% above 1990. Growth rates of about 3% per year have been the norm since the beginning of the 2000s, except for a small drop in emissions during the Global Financial Crisis in 2009. Average annual growth rates in the decade of the 1990s were around 1%.

When current trends are aligned to the emission scenarios used to project future climate change by the Intergovernmental Panel on Climate Change (IPCC), it is clear that limiting global warming to 2°C above pre-industrial levels requires an immediate, large, and sustained global mitigation effort.

Long-term emissions scenarios are designed to represent a range of plausible future emission trajectories as input for climate change projections. The IPCC process has resulted in four generations of emissions scenarios including:

1. Scientific Assessment 1990 (SA90)
2. IPCC Scenarios 1992 (IS92)
3. Special Report on Emissions Scenarios (SRES)
4. the evolving Representative Concentration Pathways (RCPs) to be used in the upcoming IPCC Fifth Assessment Report.

Comparing observed decadal emission trends with emission scenarios helps inform the prospect of different scenarios being realised, enables the feasibility of desired changes in the current emission trajectory to be explored, and helps to identify whether new scenarios may be needed.

Emissions trends over the past ten years are tracking consistently with the most carbon-intensive pathways of the four families of scenarios, leading to 4 to 6°C warming over pre-industrial times by the end of this century.

Perhaps the most immediate critical challenge to meet the 2°C target is the need to curb global fossil fuel emissions within the next ten years. This would require annual emission mitigation rates to around 3%. Some integrated assessment models show that this is possible globally without causing economic damage.

The challenge lies in the fact that although emissions from the European Union have been declining for almost two decades, and more recently for the US as well, emissions growth in emerging economies such as China and India were 10% and 8% in 2011, respectively. It is difficult to envision how such high rates can be curbed any time soon, with China’s urbanisation not peaking until 2030, and India with half a billion people below the poverty line requiring increased per capita energy consumption to achieve desirable standards of life quality.

To put in perspective the drivers behind current emissions, China alone was responsible for 80% of the overall growth in global carbon emissions during 2011 and accounted for 28% of the global carbon emissions that year. This is well ahead of the US, which was at the top of the emissions tally until recently but now accounts for 16% of the total global carbon emissions. The European Union was responsible for 11%, and the Russian Federation 5.1% of global carbon emissions in that same year. The rest of the countries contributed 3% each or less.

However, there are examples in the recent historical records that show rapid transformation of energy systems for some countries, which have led to emissions reduction of 2-4%, consistent with the mitigation rates required to meet the 2°C target.

For instance, the oil crisis of 1973 led to a decrease in the share of fossil fuels (oil shifted to nuclear) for energy production in Belgium, France, and Sweden, with emission reductions of 4-5% per year sustained over ten or more years. A continuous shift to natural gas, partially substituting coal and oil, led to sustained mitigation rates of 1-2% per year in the UK in the 1970s and again in the 2000s, 2% per year in Denmark in the 1990-2000s, and 1.4% per year since 2005 in the USA.

These examples show that for individual countries, it has been technically and economically feasible to achieve rapid transformation of energy systems. The challenge is whether these examples for single countries, lasting each no more than a decade, can be applied globally and sustained for many decades. It is clear that the type of transformation needed would required the world to wake up tomorrow and embrace a new green industrial revolution whereby new economic development is focused on establishing a large and rapidly growing non-polluting energy sector as the vehicle to meet new energy and jobs demand.

Early action and coordinated mitigation from the largest emitters such as China, the United States, the European Union, and India would make a large impact in curbing emissions, as they together account for more than half of the global emissions. In all cases, there is the need for high levels of technological, social, and political innovation, and the increasing likelihood of the need to rely on net negative emissions in future.

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