COP21 Glossary of Terms Guiding the Long-term Emissions-Reduction Goal

This guide by the World Resources Institute provides a glossary of terms used in COP21 climate negotiations to define long-term emissions-reduction goals. It distinguishes between various technical terms such as decarbonization, carbon neutrality, and climate neutrality, while outlining the requirements for these goals to effectively operationalize the target of limiting warming to below 2°C or 1.5°C.

• The document distinguishes between several 'neutrality' and 'zero' terms: 'Net zero carbon emissions' and 'carbon neutrality' are often synonyms, though carbon neutrality can be achieved via offsets from other jurisdictions. 'Net zero GHG emissions' and 'climate neutrality' extend these concepts to include all greenhouse gases beyond just carbon dioxide.
• Decarbonization refers to reducing the ratio of CO2 or all greenhouse gas emissions from primary energy production. Full decarbonization requires zero unabated CO2 emissions from industrial processes and energy generation, though emissions can be balanced by carbon sequestration.
• Peaking emissions occurs when emissions reach a maximum level by a specific date before declining. The document notes that delaying the peak date increases the risk of failing to meet the 2°C goal and necessitates more aggressive future reduction targets.
• A carbon budget is the total amount of CO2 the world can emit to likely limit warming to 2°C. The 2014 IPCC Fifth Assessment Report estimated that two-thirds of this budget has already been used; WRI estimates the remainder could be exhausted in two decades if emissions are unabated.
• To be effective, complementary long-term goals must be consistent with climate science, limit both long-term and cumulative emissions, specify clear dates and gases, and provide a plausible reduction pathway.

APA

Levin, K. (2015). COP21 Glossary of Terms Guiding the Long-term Emissions-Reduction Goal. World Resources Institute. https://www.wri.org/insights/cop21-glossary-terms-guiding-long-term-emissions-reduction-goal

Chicago

Levin, Kelly. COP21 Glossary of Terms Guiding the Long-term Emissions-Reduction Goal. World Resources Institute, 2015. https://www.wri.org/insights/cop21-glossary-terms-guiding-long-term-emissions-reduction-goal.

Wikipedia

{{cite report |last1=Levin |first1=Kelly |title=COP21 Glossary of Terms Guiding the Long-term Emissions-Reduction Goal |publisher=World Resources Institute |date=2 December 2015 |url=https://www.wri.org/insights/cop21-glossary-terms-guiding-long-term-emissions-reduction-goal |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{levin2015cop21, author = {Levin, Kelly}, title = {{COP21 Glossary of Terms Guiding the Long-term Emissions-Reduction Goal}}, institution = {World Resources Institute}, year = {2015}, month = dec, url = {https://www.wri.org/insights/cop21-glossary-terms-guiding-long-term-emissions-reduction-goal}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }