Using Updated Climate Accounting to Slow Global Warming Before 2035

Abstract:

The current and projected worsening of climate impacts make clear the urgency of limiting the global mean temperature to 2°C over preindustrial levels. But while mitigation policy today may slow global warming at the end of the century, it will not keep global warming within these limits. This failure arises in large part from the climate accounting system used to inform this policy, which does not factor in several scientific findings from the last two decades, including:

• The urgent need to slow global warming before 2035. This can postpone the time the +1.5°C limit is passed, and is the only way to avoid the most serious long-term climate disruptions.
• That while it may mitigate warming by the end of the century, reducing emissions of CO₂ alone, according to UNEP/WMO[1], will do “little to mitigate warming over the next 20-30 years,” and “may temporarily enhance near-term warming as sulfate [cooling] is reduced.”
• That the only emissions reductions that can slow warming before 2035 are focused on short-lived climate pollutants. A small increase in current mitigation funding could fund these projects, the most promising of which target emissions in regional climate “hot spots” like the Arctic and India.[2]

To ensure policies can effectively slow global warming before 2035, a new climate accounting system is needed. Such an updated system is being standardized in the USA,[3] and has been proposed for use in ISO standards. The key features of this updated system are: consideration of all climate pollutants and their multi-faceted climate effects; use of time horizons which prioritize mitigation of near-term warming; a consistent and accurate accounting for “biogenic” CO₂; protocols ensuring that new scientific findings are incorporated; and a distinct accounting for emissions affecting regional “hot spots”. This accounting system also considers environmental impacts outside of climate change, a feature necessary to identify “win-win” projects with climate benefits but without environmental trade-offs.

[1] UNEP/WMO. Integrated Assessment of Black Carbon and Tropospheric Ozone. 2011.

[2] UNEP. Atmospheric Brown Clouds: A Regional Assessment Report with Focus on Asia. 2008.

[3] American National Standards Institute draft LEO-SCS-002 standard for life cycle assessment.

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