Science and policy characteristics of the Paris Agreement temperature goal

Journal name:
Nature Climate Change
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The Paris Agreement sets a long-term temperature goal of holding the global average temperature increase to well below 2 °C, and pursuing efforts to limit this to 1.5 °C above pre-industrial levels. Here, we present an overview of science and policy aspects related to this goal and analyse the implications for mitigation pathways. We show examples of discernible differences in impacts between 1.5 °C and 2 °C warming. At the same time, most available low emission scenarios at least temporarily exceed the 1.5 °C limit before 2100. The legacy of temperature overshoots and the feasibility of limiting warming to 1.5 °C, or below, thus become central elements of a post-Paris science agenda. The near-term mitigation targets set by countries for the 2020–2030 period are insufficient to secure the achievement of the temperature goal. An increase in mitigation ambition for this period will determine the Agreement's effectiveness in achieving its temperature goal.

At a glance


  1. Projected impacts at 1.5 [deg]C and 2 [deg]C GMT increase above pre-industrial levels for a selection of indicators and regions.
    Figure 1: Projected impacts at 1.5 °C and 2 °C GMT increase above pre-industrial levels for a selection of indicators and regions.

    a, Increase in global occurrence probability of pre-industrial 1-in-a-1000 day extreme temperature events17. b, Increase in extreme precipitation intensity (RX5Day) for the global land area below 66° N/S and South Asia21. c, Reduction in annual water availability in the Mediterranean21. d, Share of global tropical coral reefs at risk of long-term degradation37. e, Global sea-level rise commitment for persistent warming of 1.5 °C and 2 °C over 2000 years44. f, Changes in local crop yields for present-day tropical agricultural areas21 (below 30° N/S, model dependent implementation of present day management24). Dashed boxes: no increase in CO2 fertilization (No CO2). Panels b, c and f display median changes that are exceeded for over 50% of the respective land areas.

  2. GMT projections for emission scenarios assessed by the IPCC and UNEP.
    Figure 2: GMT projections for emission scenarios assessed by the IPCC54 and UNEP68.

    a, Probability of holding warming below 2 °C during the entire twenty-first century and below 1.5 °C by 2100 (allowing for overshoot any time before 2100, if probability by 2100 is at least 50%). b, Maximum median warming above 1.5 °C for scenarios that reach zero globally aggregated GHG emissions in the second half of the twenty-first century (horizontal axis). Empty (filled) circles indicate scenarios for which median warming returns below 1.5 °C before or by 2100 (after 2100). Scenarios have been extended beyond 2100 assuming constant 2100 emission levels. A list of all scenarios included in b is given in Supplementary Table 2.

  3. Absolute contribution of bioenergy to total primary energy supply in literature scenarios with below 3 [deg]C of warming relative to pre-industrial levels by 2100.
    Figure 3: Absolute contribution of bioenergy to total primary energy supply in literature scenarios with below 3 °C of warming relative to pre-industrial levels by 2100.

    a, Bioenergy contributions to primary energy in 2050 (black dots represent individual scenarios). Sustainable potentials highlighted in green and light green are based on ref. 63. b, As with a, but for the 2100 primary bioenergy contribution. A list of all scenarios included is given in Supplementary Table 2.

  4. Characteristics of below 2 [deg]C and 1.5 [deg]C pathways.
    Figure 4: Characteristics of below 2 °C and 1.5 °C pathways.

    a, Global emissions trajectories for likely below 2 °C warming scenarios70, and scenarios limiting warming to below 1.5 °C by the end of the century51, 68. Trajectories are based on integrated scenarios that simulate least-cost pathways for obtaining climate protection from 2020 onward. Current estimates of GHG levels implied by INDCs (orange, data from ref. 70) and current policies (purple, minimum–maximum range from ref. 99) by 2025 and 2030 are indicated. Differences in the historical emissions of both scenario sets are due to differences in the underlying models and arbitrary model sampling. b, Timing of globally aggregated emissions reaching zero for total Kyoto-GHG emissions, total CO2 emissions, and CO2 emissions from energy and industry, respectively. The colours of the ranges correspond to the scenarios shown in panel a. A list of all scenarios included is given in Supplementary Table 2.


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Author information


  1. Climate Analytics, 10969 Berlin, Germany

    • Carl-Friedrich Schleussner,
    • Michiel Schaeffer,
    • Tabea Lissner &
    • William Hare
  2. Potsdam Institute for Climate Impact Research, 14473 Potsdam, Germany

    • Carl-Friedrich Schleussner,
    • Tabea Lissner,
    • Anders Levermann,
    • Katja Frieler &
    • William Hare
  3. Energy Program, International Institute for Applied Systems Analysis, 2361 Laxenburg, Austria

    • Joeri Rogelj
  4. Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zürich, Switzerland

    • Joeri Rogelj,
    • Erich M. Fischer &
    • Reto Knutti
  5. Environmental Systems Analysis Group, Wageningen University and Research Centre, 6708 PB Wageningen, the Netherlands

    • Michiel Schaeffer
  6. Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, New Jersey 08544, USA

    • Rachel Licker
  7. Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany

    • Anders Levermann
  8. Lamont-Doherty Earth Observatory, Columbia University, New York 10964-1000, USA

    • Anders Levermann


C.F.S, J.R., M.S. and W.H. led the writing of the paper with significant contributions from all authors. C.F.S, J.R., M.S. and W.H. designed the manuscript structure and content. C.F.S., J.R. and M.S. carried out the analysis presented and produced the figures.

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