Three Practical Pathways By Which We Can Get To 350ppm & Avert Climate Catastrophe sign copenhagen photo

photo: Matthew McDermott

With some new research on how even keeping global temperature rise to 2°C may not be enough to avoid some pretty catastrophic climate change effects, and the last round of international climate change talks prior to the year-ending COP16 summit in Mexico just opening in China, it's particularly apropos that the Center for Biological Diversity and have just released a short briefing on why we need to get CO2 levels back to 350ppm and, perhaps most importantly, how we can actually do that considering we're already about 40ppm above that with no global agreement on climate in sight. The 10-page briefing, Not Just a Number: Achieving a CO2 Concentration of 350ppm of Less to Avoid Catastrophic Climate Impacts [PDF], goes over fairly familiar territory for TreeHugger readers on why we need strong climate action to return us to 350ppm, in short:

Unlike higher targets, pathways to 350 ppm provide a reasonable chance of limiting temperature rise to 1.5°C above pre-industrial levels. Limiting warming to 1.5°C is called for by the Alliance of Small Island States, the Least Developed Countries, and Climate Action Network as the maximum level beyond which climate change must be considered dangerous. While limiting warming to 2°C may have seemed acceptable when first proposed by the European Union in 1996, the best available science now indicates that much smaller increases in global mean temperature will result in substantial environmental and socio-economic consequences.

Starkly, it says, "A 2°C temperature rise is simply no longer an acceptable target for climate policy." Something with which recent research examining the geological record concurs. But how do we get there? The briefing lists three pathways:

Pathway 1: Stringent near-term reductions, modest net-negative emissions after 2050 -- Reduce emissions 42% below 1990 levels by 2020, with net-zero emissions by 2050. Here emissions peak in 2011, with declines reaching 10% per year soon thereafter. Net-negative emissions are achieved through "very low fossil fuel emissions and sequestration through existing removal methods such as reforestation."

Pathway 2: Less stringent near-term reductions, high net-negative emissions after 2050 -- Emissions peak in 2012, reductions of 14% below 1990 levels by 2020, and 84% below 1990 levels by 2050. For those 2020 targets, developed nations' emissions have to be 45% below 1990 by 2020 and developing nations are 30% below business as usual; emissions from aviation and shipping have to be halved; deforestation must be halted; loopholes in the Kyoto Protocol allowing credits for dubious forestry and land-use management are closed. The high net-negative emissions past 2050 are achieved though "extensive use of biomass energy combined with carbon capture and storage." However, considering food security and biodiversity concerns, this last part "may not be feasible".

Pathway 3: Very stringent near-term reductions, no net-negative emissions -- To achieve a 350ppm target by 2100 without negative emissions, requires 97% reductions below 1990 levels by 2020 and 100% reductions by 2030. Temperature rise do this should peak around 1.9°C and fall back to 1.5°C above pre-industrial levels by 2220. If the time horizon is increased to 350ppm by 2200, we would need 47% reductions below 1990 levels by 2020, 79% lower by 2030, and 97% lower by 2050--temperature rise would peak around 2.1°C and fall back to 1.5°C by 2300. If that sounds more feasible than the first part of Pathway 3 consider that "extending the time horizon to reach 350ppm increases peak temperature and with it the risk of experiencing severe and irreversible climate impacts."

Frankly, considering the apparent deadlock in international talks, combined with the fact that much of the political talk is about 450ppm CO2 concentrations not the safer 350ppm, any of these pathways seem challenging. But, in terms of what is feasible should the political will be strengthened, all seem doable.

Which in light of the continued disheartening news about how bad things could get under a business-as-usual emissions scenario actually lifts my spirits. Here are three (four, really) alternate ways forward, let's just choose a path a start moving together. .

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More on Global Climate Change
Front-Line Climate Change Nations Stake Out Positions: 1.5°C Temp Rise, 350ppm, Request 1.5% GDP Aid
IPCC Chairman's Endorsement of 350ppm Goal a Big Boost in Fighting Climate Change: Bill McKibben
Least Developed Countries and Island Nations Endorese 350 PPM GoalThe Science of 350, the Most Important Number on the Planet

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