Thursday, October 1, 2015

How Should Countries Take Responsibility for Climate Change for Both Past and Future GHG Emissions?

Allocating a 2°C cumulative carbon budget to countries (10 page pdf, Renaud Gignac and H Damon Matthews, Environ. Res. Lett., Jun. 19, 2015)

Today we review a very timely analysis and proposition concerning the equitable sharing of the carbon debt that needs to be paid off in order for the world to meet the objective of limiting climate warming to 2 deg C or 450 ppme by 2050 which is the objective of the climate conference to be held in Paris in December 2015. The authors estimated past CO2 emissions from the nations of the world, noting the top ten emitters were United States, China, Russia, Brazil, India, Germany, United Kingdom, France, Indonesia and Canada (where the roles of USA and Russia stand out). The turning to the carbon debt as a result of future emissions projected with climate modeling from now to 2050 (where the current peak emissions from the USA and China stand out). Commitments stated by some countries in advance of the conference fall well short of the combined carbon debt but the approach presents the benefit of an objective sharing of responsibility for reaching the target. Further refinement is needed to move beyond CO2 emissions to include other greenhouse gases. resp for cl ch  

Key Quotes:

“contraction and convergence (C&C) framework can be applied to the division of a global carbon budget among nations, in a manner that both maintains total emissions below a level consistent with 2 °C, and also adheres to the principle of attaining equal per capitaCO2 emissions within the coming decades”

“historical differences in responsibility for climate warming can be quantified via a cumulative carbon debt (or credit), which represents the amount by which a given country’s historical emissions have exceeded (or fallen short of) the emissions that would have been consistent with their share of world population over time.”

“The accumulated difference over time between actual and hypothetical equal per capita emissions therefore represents a country’s carbon debt (in the case of larger than equal per capita emissions) or credit (in the case of smaller than equal per capita emissions)”

“As expected, developed countries with high present-day per capita emissions see a dramatic decrease in their annual allowable emissions. This pattern holds also for China, whose per capita emissions are currently higher than the global average.”

“By contrast, India, Brazil and Indonesia maintain near-constant per capita emissions throughout the convergence phase, whereas much less developed regions such as Africa show large increases in their share of world emissions.”

“At the end of the year 2013, all developed countries carry substantial carbon debts, ranging here from 3.1 Gt CO2 for France, to more than 100 Gt CO2 for the United States.”

“Countries in the European Union have committed to a 40% reduction by 2030 relative to 1990 levels, Russia has announced a 25–30% cut by 2030 relative to 1990, Canada has targeted 30% below 2005 levels by 2030, and the United States have pledged to decrease emissions by 26–28% by 2025 relative to 2005 levels…China has announced that their emissions will peak by 2030. All of these commitments are clearly less ambitious than the values plotted”

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