Hawkins, Edward D. and Ortega, Pablo and Suckling, Emma and Schurer, Andrew and Hegerl, Gabi and Jones, Phil D. and Joshi, Manoj and Osborn, Timothy J. and Masson-Delmotte, Valerie and Mignot, Juliette and Thorne, Peter and van Oldenborgh, Geert Jan (2017) Estimating Changes in Global Temperature since the Preindustrial Period. Bulletin of the American Meteorological Society, 98 (9). pp. 1841-1856. ISSN 1520-0477

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Abstract

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 preindustrial? Somewhat 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 preindustrial 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 preindustrial using a range of approaches based on observations, radiative forcings, global climate model simulations, and proxy evidence. Our assessment is that this preindustrial 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 preindustrial levels. We provide some recommendations for how this assessment might be improved in the future and suggest that reframing temperature limits with a modern baseline would be inherently less uncertain and more policy relevant.

Item Type:	Article
Keywords:	Estimating Changes; Global Temperature; Preindustrial Period;
Academic Unit:	Faculty of Social Sciences > Geography Faculty of Social Sciences > Research Institutes > Irish Climate Analysis and Research Units, ICARUS
Item ID:	8958
Identification Number:	https://doi.org/10.1175/BAMS-D-16-0007.1
Depositing User:	Peter Thorne
Date Deposited:	06 Nov 2017 15:48
Journal or Publication Title:	Bulletin of the American Meteorological Society
Publisher:	American Meteorological Society
Refereed:	Yes
URI:	Publisher
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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