What is needed to stay below a 2°C global temperature rise?

10/04/2010 - A new Information Reference Document “Scientific Perspectives after Copenhagen”, commissioned by the EU’s Climate Change Expert Group ‘Science’ (EGSci) , addresses key scientific and technical issues relevant to the international efforts to reach the 2°C target. This document includes an assessment of the overall emission reduction pledges under the Copenhagen Accord. The document has been released during a side event at the intersessional UNFCCC climate conference in Tianjin (China).
What is needed to stay below a 2°C global temperature rise?

The Copenhagen Accord sets a goal of limiting average global surface warming to 2°C, to achieve the ultimate objective of the UNFCCC: to prevent “dangerous anthropogenic interference” with the climate system. It further calls for Parties to submit their 2020 emission reduction Pledges in order to begin achieving this goal.

A number of scientists across the EU, among them scientists of the Potsdam Institute for Climate Impact Research (PIK), have assessed the most relevant studies, including the IPCC 4th Assessment Report and identified a set of conditions that could ensure a likely chance1 of achieving the 2°C target:

  • A peak in global emissions is likely to be required by approximately 2015. The later the peak occurs, the steeper the decline in emissions would need to be in the subsequent decades, potentially exceeding feasibility and raising the costs of mitigation.
  • A decrease in global emissions of 50-70% in comparison to 1990 is necessary by 2050. Continued emission reductions are thereafter required, well beyond 2050.
  • Reductions of long-lived greenhouse gases, such as carbon dioxide are essential.  In addition, reductions of the short-lived greenhouse gases, black carbon aerosols, tropospheric ozone, and aviation-induced cloudiness, could also make an important contribution.

However, even under the most optimistic interpretation of the current pledges, additional commitments would be necessary to ensure that the 2°C target remains achievable (with a likely chance). Without such stronger action now, post-2020 emission reduction rates will potentially become unfeasible.

To achieve such greenhouse gas reductions, credible, effective and fair policy instruments targeting as many emissions sources as possible will be required. 

The new Reference Document reinforces the evidence provided by the IPCC 4th Assessment Report that limiting warming to less than 2°C above pre-industrial temperatures considerably reduces the risk of triggering accelerated or irreversible changes in the climate system as well as of large scale adverse impacts.  

The scientific results clearly suggest that an ambitious political agreement is necessary because the window of opportunity is closing to avoid dangerous climate change.

Further information:

The Reference Document Scientific Perspectives after Copenhagen” [PDF; 715 KB] was initiated by the Spanish Presidency and finished during the Belgian Presidency. It can be downloaded at:


In order to obtain a hard copy, please contact secretariat_ssd@belspo.be.


(1): “likely chance“: means that with a given emission path, there is at least a 66% chance that the warming will be below the stated level, considering uncertainties in the response of the climate system.