Estimating changes in global temperature since the pre-industrial period

Bulletin of the American Meteorological Society: Abstract of Early Release Paper

Screen Shot AMS LogoOnline  —  Better defining (or altogether avoiding) the term ‘pre-industrial’ would aid interpretation of internationally agreed global temperature limits and estimation of the required constraints to avoid reaching those limits.

The United Nations Framework Convention on Climate Change (UNFCCC) process agreed in Paris to limit global surface temperature rise to ‘well below 2 °C above pre-industrial levels’. But what period is ‘pre-industrial’?

Some-what remarkably, this is not defined within the UNFCCC’s many agreements and protocols. Nor is it defined in the IPCC’s Fifth Assessment Report (AR5) in the evaluation of when particular temperature levels might be reached because no robust definition of the period exists.

Here we discuss the important factors to consider when defining a pre-industrial period, based on estimates of historical radiative forcings and the availability of climate observations. There is no perfect period, but we suggest that 1720-1800 is the most suitable choice when discussing global temperature limits.

We then estimate the change in global average temperature since pre-industrial using a range of approaches based on observations, radiative forcings, global climate model simulations and proxy evidence.

Our assessment is that this pre-industrial period was likely 0.55–0.80 °C cooler than 1986-2005 and that 2015 was likely the first year in which global average temperature was more than 1 °C above pre-industrial levels.

We provide some recommendations for how this assessment might be improved in future and suggest that reframing temperature limits with a modern baseline would be inherently less uncertain and more policy-relevant.
*Corresponding author address: Ed Hawkins, Department of Meteorology, University of Reading, Reading, UK. RG6 6BB, E-mail: e.hawkins@reading.ac.uk

Authors:

Ed Hawkins*, Pablo Ortega, and Emma Suckling
NCAS-Climate, Department of Meteorology, University of Reading, Reading, UK

Andrew Schurer and Gabi Hegerl
School of GeoSciences, Grant Institute, University of Edinburgh, Edinburgh, UK

Phil Jones
School of Environmental Sciences, University of East Anglia, Norwich, UK and Center of Excellence for Climate Change Research, Department of Meteorology, King Abdulaziz, University, Jeddah, Saudi Arabia

Manoj Joshi and Timothy J. Osborn
School of Environmental Sciences and Climatic Research Unit, University of East Anglia, Norwich, UK

Valérie Masson-Delmotte
Institut Pierre Simon Laplace, Laboratoire des Sciences du Climat et de l’Environnement (CEA-CNRS-UVSQ), Gif-sur-Yvette, France

Juliette Mignot
Climate and Environmental Physics, Physics Institute & Oeschger Center for Climate Change Research, University of Bern, Switzerland and LOCEAN/IPSL (Sorbonne Universités, UPMC-CNRS-IRD-MNHN), France

Peter Thorne
Department of Geography, Maynooth University, Maynooth, County Kildare, Ireland Geert

Jan van Oldenborgh
Koninklijk Nederlands Meteorologisch Instituut, De Bilt, Netherlands

Published Online: 24 January 2017
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Ed. Note: This abstract and author list is a modified format from the originalt o make it easier to read onlinef, but the words are unchanged.

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