Title: On the Linearity of Local and Regional Temperature Changes from 1.5°C to 2°C of Global Warming

Abstract

Because of the Paris Agreement it is imperative there is greater understanding of the consequences of limiting global warming to the target 1.5° and 2°C levels above preindustrial conditions. It is challenging to quantify changes across a small increment of global warming, so a pattern-scaling approach may be considered. Here we investigate the validity of such an approach by comprehensively examining how well local temperatures and warming trends in a 1.5°C world predict local temperatures at global warming of 2°C. Ensembles of transient coupled climate simulations from multiple models under different scenarios were compared and individual model responses were analyzed. For many places, the multimodel forced response of seasonal-average temperatures is approximately linear with global warming between 1.5° and 2°C. Yet, individual model results vary and large contributions from nonlinear changes in unforced variability or the forced response cannot be ruled out. In some regions, such as East Asia, models simulate substantially greater warming than is expected from linear scaling. Examining East Asia during boreal summer, we find that increased warming in the simulated 2°C world relative to scaling up from 1.5°C is related to reduced anthropogenic aerosol emissions. Our results indicate that, where forcings other than those due tomore » greenhouse gas emissions change, the warming experienced in a 1.5°C world is a poor predictor for local climate at 2°C of global warming. In addition to the analysis of the linearity in the forced climate change signal, we find that natural variability remains a substantial contribution to uncertainty at these low-warming targets.« less

Authors:

King, Andrew D. ^[1]; Knutti, Reto ^[2]; Uhe, Peter ^[3]; Mitchell, Daniel M. ^[3]; Lewis, Sophie C. ^[4]; Arblaster, Julie M. ^[5]; Freychet, Nicolas ^[6]

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+ Show Author Affiliations

1. Univ. of Melbourne (Australia)
2. ETH Zurich (Switzerland)
3. Bristol Univ. (United Kingdom)
4. Univ. of New South Wales, Sydney, NSW (Australia)
5. Monash Univ., Melbourne, VIC (Australia); National Center for Atmospheric Research, Boulder, CO (United States)
6. Univ. of Edinburgh, Scotland (United Kingdom)

Publication Date:

Mon Aug 06 00:00:00 EDT 2018

Research Org.:

National Center for Atmospheric Research (NCAR), Boulder, CO (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER); National Science Foundation (NSF); Australian Research Council

OSTI Identifier:

1541846

Grant/Contract Number:  

FC02-97ER62402

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Climate

Additional Journal Information:

Journal Volume: 31; Journal Issue: 18; Journal ID: ISSN 0894-8755

Publisher:

American Meteorological Society

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Climate change; Temperature; Climate models; Model comparison