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INSIDER: A Glossary to Understand the Different Proposals for a Long-term Goal at COP 21

The international community has adopted a goal to limit global warming below 2°C (3.6°F) above preindustrial levels (and consider 1.5 degrees C) in order to avoid some of the worst climate impacts. However, the 2°C goal does not easily guide every day decision-making because it does not state who needs to act, by how much and by when. So negotiators are considering a second, complementary goal which would operationalize the target to limit warming below 2°C.  Many have termed this a “long-term goal” which would aim to send a much clearer signal to the world what pathway key players need to follow to stay below 2°C.

There are a number of options for the long-term goal in the current draft1 of the international climate agreement to be finalized at COP 21 in Paris, but the devil is in the detail. The language is currently peppered with numerous wording choices, which could be interpreted differently. This blog aims to disentangle these terms and identify their implications for the 2°C goal.  An additional component in the draft text is that countries would develop long-term plans that would outline how the country is thinking about getting to whatever long-term goal is agreed.

  • Decarbonization of the global economy: Denotes decreasing average carbon intensity of primary energy production, while full decarbonization suggests zero unabated (not captured by CCS) CO2 emissions from energy and industrial processes. Stabilizing emissions of non-CO2 gases (e.g. methane) is sometimes included in a decarbonization goal. It is worth noting that full decarbonization need not imply no emissions. Emissions could theoretically be balanced by carbon sequestration to the extent substantial enough reductions or enhanced sinks exist.  If decarbonization were included in the agreement, it would need to clearly specify the emissions-reduction pathway embraced to effectively communicate the necessary system change (e.g. in technologies, behavior). 
  • Carbon neutrality: Means annual net zero anthropogenic CO2 emissions, balancing any CO2 released with an equivalent amount of CO2 uptake. In order to stay below a 2°C rise, global carbon neutrality should be achieved between 2055 and 2070.  But this term has on occasion been used differently. Costa Rica has a carbon neutrality pledge to “achieve Carbon Neutrality by 2021 with total net emissions comparable to total emissions in 2005.” Ethiopia has targets to “achieve carbon-neutral middle-income status before 2025” and “limit its net greenhouse gas (GHG) emissions in 2030 to 145 Mt CO2e or lower.” Instead of aiming at net zero emissions, some countries seem to interpret carbon neutrality as stabilizing GHG emissions at a certain level. Any carbon neutrality goal would need to be accompanied by a timeframe for reaching net zero carbon emissions.
  • Climate neutrality is the same concept as carbon neutrality but rather than focus on carbon dioxide emissions solely, it represents net zero anthropogenic GHG emissions. In order to stay below a 2°C rise, global climate neutrality should be achieved between 2080 and 2100.
  • Net zero carbon emissions: Usually considered a synonym for carbon neutrality, but is arguably clearer because it explicitly states that net emissions be brought to zero. The term can be confused with “zero emissions,” a goal calling for all emissions to decline to zero without carbon sequestration (or negative emissions through bioenergy and CCS, although it remains unproven at scale) balancing out emissions. Like many of the other framings, a net zero emissions goal can still lead to overshooting the carbon budget unless the term is coupled with other targets.
  • Net zero GHG emissions: Same concept as net zero carbon emissions but conveys a target of net zero emissions of both carbon dioxide and non-CO2 gases. 
  • Low-carbon or low GHG emissions transformation: The term is used to convey a message to transform our emissions-generating activities, which is necessary to limit warming to 2°C.  However, if such a goal is not complemented by quantified targets (such as for emissions reductions and renewable generation) with specific timelines, it will still be too vague to send the right signals to decision makers.
  • Sharing the remaining carbon budget: This term refers to sharing the estimated amount of CO2 that can be emitted cumulatively for a likely chance of achieving the 2°C goal. Only 1,000 Gt CO2 are left in the carbon budget. As opposed to a goal framed as a percentage emissions reduction by a certain date, a carbon budget goal constrains cumulative emissions over the entire time period, reducing risks of overshooting the 2°C goal. However, on its own, the framing may not adequately guide an emissions pathway with plausible decarbonization rates (e.g. we could exhaust the carbon budget quickly and require 6 percent annual emissions reduction rates in later decades). A few countries like the UK and Norway have adopted a carbon budget approach, but it is not common practice. If the agreement contained reference to a carbon budget, it will still be challenging to translate it to the national level given no agreement exists among counties on a fair allocation.
  • Percentage emissions reductions by a certain date: Another way of communicating what needs to be done and by when in a quantitative manner. The IPCC states that GHG emissions should reduce by 40 percent to 70 percent by 2050 below 2010 levels, and fall to near-zero or below by 2100 to have a likely chance of limiting warming to 2 °C.
  • Peaking emissions: Means that emissions reach a maximum level before they decline afterwards. To have a likely chance of meeting the 2°C goal, global GHG emissions peak in 2020 or before in around 85 percent of scenarios in the IPCC scenario database, and all regions peak by 2020. Although not a particularly “long-term” goal, the peaking language exists in the draft negotiating text in Article 3 about the long-term goal, given its relevance in determining the timeline and ambition of the global emissions trajectory.

Moving Forward with a Long-Term Goal

The above definitions of terms describe the relevant scientific literature’s assessment of what is needed in terms of global emissions reductions. The terms, however, do not differentiate which countries would need to do what by when.  Clearly, any final text will need to recognize the different capacities of countries to achieve the long-term goal and provide some flexibility for those countries. This goal will be achieved at the same time as the world is working to achieve zero poverty; the two must go very much together.

An operationalization of the 2°C target has the potential for more clearly communicating to countries, cities and the private sector necessary changes with a clear timeline. To be effective, the framing should:

  • First and foremost, be consistent with the most recent climate science;
  • Provide clarity on the level and timing of long-term emissions reductions;
  • Provide a clear limit on cumulative emissions; and
  • Communicate clearly a plausible annual rate of emissions reductions that allows for a      smooth transition, while considering flexibility for those countries with less capacity.

Provide clarity on the level and timing of long-term emissions reductions

What the science tells us needs to happen for a likely chance of limiting warming to 2 degrees C (least cost)


Would need further specification on timing of decarbonization

Reduce CO2 emissions to net zero between 2055 and 2070, and all GHGs by 2080 and 2100.

Carbon neutrality

Would need further specification on timing of carbon neutrality

Achieved between 2055-2070.

Climate neutrality

Would need further specification on timing of climate neutrality

Achieved between 2080 and 2100.

Net zero emissions

Would need further specification on timing of net zero emissions

Reduce CO2 emissions to net zero between 2055 and 2070, and all GHGs by 2080 and 2100.

Emissions transformation

Would need further specification on type, level and rate of transformation

Reduce CO2 emissions to net zero between 2055 and 2070, and all GHGs by 2080 and 2100.

Sharing the remaining carbon budget


Limit remaining budget to 1000 Gt CO2.

Percent emissions reduction by a certain date


40-70% below 1990 levels by 2050 and near zero or below by 2100


No, not unless accompanied by a long-term goal.

Global emissions peak by 2020

It is worth noting that these framings are not mutually exclusive and, given their relative strengths, ideally some framings will be combined in the final agreement.

By including the right signals, the new climate agreement can catalyze action leading up to 2030 and provide direction for long-term action to give the world a fighting chance of staying below 2°C.

[1] Article 3 of the current co-chairs text states:  [Parties aim [to achieve the global temperature goal], in accordance with the best available science [and the principles of the Convention], through [long-term global [low-[carbon][emission] transformation] [[climate][carbon] neutrality]], [and peaking their [net] emissions] [by 2030][20XX][as soon as possible], [with a [x]40-[y]70% net emission reduction below 2010 levels by 2050][according to the global carbon budget distribution based on climate justice], and [overall reductions][[net] zero emissions] [over the course of the century][by 2050][by 2100].2 ] Option 2: [Parties aim to reach long-term global low-emission transformation, in the context of sustainable development and equitable access to atmospheric space {placeholder for further elaboration of the context, including CBDR, comprehensiveness, distribution of global carbon budget based on climate justice and etc.}.] Option 3: [In pursuit of the objective of the Convention set out in its Article 2,][and][to achieve the long-term temperature goal set out in Article 2 of this Agreement,] Parties aim to reach [by X date] [as soon as possible] [a peaking of global greenhouse gas emissions] [and rapid reductions of global greenhouse gas emissions thereafter to at least] [40-70] [70-95] per cent below 2010 levels by 2050] [and zero net greenhouse gas emissions in the period 2060 - 2080] [[bearing in mind that peaking will vary for different countries and will be longer for developing countries] [[and] bearing in mind social and economic development and poverty eradication are the first and overriding priorities of developing country Parties]][[in pursuing [decarbonisation of the global economy over the course of this century] [global low - carbon transformation] [global low-emission transformation]] [in the sharing of the remaining global emission budget]].

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