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On the linear additivity of climate forcing-response relationships at global and continental scales

  1. Hideo Shiogama1,*,
  2. Dáithí A. Stone2,3,†,
  3. Tatsuya Nagashima4,
  4. Toru Nozawa1,
  5. Seita Emori1

Article first published online: 17 OCT 2012

DOI: 10.1002/joc.3607

Additional Information

How to Cite

Shiogama, H., Stone, D. A., Nagashima, T., Nozawa, T. and Emori, S. (2012), On the linear additivity of climate forcing-response relationships at global and continental scales. Int. J. Climatol.. doi: 10.1002/joc.3607

Author Information

  1. 1

    Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba, Japan

  2. 2

    Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK

  3. 3

    Tyndall Centre for Climate Change Research, Oxford University Centre for the Environment, Oxford, UK

  4. 4

    Center for Regional Environmental Research, National Institute for Environmental Studies, Tsukuba, Japan

  1. †

    Present address: Lawrence Berkeley National Laboratory, Berkeley, CA, USA

*Correspondence to: H. Shiogama, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan. E–mail: shiogama.hideo@nies.go.jp

  • †

    Present address: Lawrence Berkeley National Laboratory, Berkeley, CA, USA

Publication History

  1. Article first published online: 17 OCT 2012
  2. Manuscript Accepted: 24 SEP 2012
  3. Manuscript Revised: 1 AUG 2012
  4. Manuscript Received: 16 JAN 2012

Funded by

  • Global Environment Research Fund (S-5) of the Ministry of the Environment of Japan
  • Innovative Program of Climate Change Projection for the 21st century
  • Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan. Grant Number: 23310014

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Keywords:

  • additivity;
  • climate change;
  • climate model;
  • detection and attribution;
  • future projection

ABSTRACT

Within the context of the prediction, detection and attribution of climate change, a number of studies have explicitly or implicitly assumed that individual climate responses to individual forcing agents can be linearly added to obtain the total climate response to the sum of the forcing agents. This assumption of the ‘linear additivity of forcing-response relationships’ has been tested by previous studies, but it remains controversial whether linear additivity holds with all combinations of forcing agents, such as ‘greenhouse gases plus indirect effects of anthropogenic aerosols’ or ‘greenhouse gases plus solar irradiance’. This study explored whether linear additivity holds in 5-year mean temperature/precipitation responses to various combinations of forcing agents in the 20th century and in a future-emissions scenario at global and continental scales. We used Model for Interdisciplinary Research on Climate version 3, which includes the first and second indirect effects of aerosols. The forcing factors considered were well-mixed greenhouse gases, the direct and indirect effects of sulphate and carbon aerosols, ozone, land-use changes, solar irradiance and volcanic aerosols (the latter three factors were specified only in the 20th-century runs). By performing and analysing an enormous matrix of forcing runs, we concluded that linear additivity holds in temperature responses for all of the combinations of forcing agents at the global and continental scales, but it breaks down for precipitation responses in certain cases of future projections.

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