Climate Model Projections for Canada: A Comparison of CMIP5 and CMIP6

ABSTRACT Recent studies have identified stronger warming in the latest generation of climate model simulations globally, and the same is true for projected changes in Canada. This study examines differences for Canada and six sub-regions between simulations from the latest Sixth Coupled Model Intercomparison Project (CMIP6) and its predecessor CMIP5. Ensembles from both experiments are assessed using a set of derived indices calculated from daily precipitation and temperature, with projections compared at fixed future time intervals and fixed levels of global temperature change. For changes calculated at fixed time intervals most temperature indices display higher projected changes in CMIP6 than CMIP5 for most sub-regions, while greater precipitation changes in CMIP6 occur mainly in extreme precipitation indices. When future projections are calculated at fixed levels of global average temperature increase, the size and spread of differences for future projected changes between CMIP6 and CMIP5 are substantially reduced for most indices. Temperature scaling behaviour, or the regional response to increasing global temperatures, is similar in both ensembles, with annual temperature anomalies for Canada and its sub-regions increasing at between 1.5 and 2.5 times the rate of increase globally, depending on the region. The CMIP6 ensemble projections exhibit modestly stronger scaling behaviour for temperature anomalies in northern Canada, as well as for certain indices of moderate and extreme events. Such temperature scaling differences persist even if anomalously warm CMIP6 global climate models are omitted. Comparing the mean and variance of future projections for Canada in CMIP5 and CMIP6 simulations from the same modelling centre suggests CMIP6 models are significantly warmer in Canada than CMIP5 models at the same level of forcing, with some evidence that internal temperature variability in CMIP6 is reduced compared with CMIP5.

[1]  N. Gillett,et al.  Making climate projections conditional on historical observations , 2021, Science Advances.

[2]  F. Zwiers,et al.  Changes in Annual Extremes of Daily Temperature and Precipitation in CMIP6 Models , 2020, Journal of Climate.

[3]  G. Hegerl,et al.  Comparing Methods to Constrain Future European Climate Projections Using a Consistent Framework , 2020, Journal of Climate.

[4]  C. R. Rajulapati,et al.  Robustness of CMIP6 Historical Global Mean Temperature Simulations: Trends, Long‐Term Persistence, Autocorrelation, and Distributional Shape , 2020, Earth's Future.

[5]  S. Seneviratne,et al.  Regional Climate Sensitivity of Climate Extremes in CMIP6 Versus CMIP5 Multimodel Ensembles , 2020, Earth's future.

[6]  N. Gillett,et al.  Climate Model Projections of 21st Century Global Warming Constrained Using the Observed Warming Trend , 2020 .

[7]  R. Knutti,et al.  Reduced global warming from CMIP6 projections when weighting models by performance and independence , 2020, Earth System Dynamics.

[8]  Christopher J. Smith,et al.  Past warming trend constrains future warming in CMIP6 models , 2020, Science Advances.

[9]  K. Taylor,et al.  Causes of Higher Climate Sensitivity in CMIP6 Models , 2020, Geophysical Research Letters.

[10]  T. Mauritsen,et al.  Emergent constraints on Earth’s transient and equilibrium response to doubled CO2 from post-1970s global warming , 2019, Nature Geoscience.

[11]  N. Gillett,et al.  The Canadian Earth System Model version 5 (CanESM5.0.3) , 2019, Geoscientific Model Development.

[12]  K. Calvin,et al.  Global emissions pathways under different socioeconomic scenarios for use in CMIP6: a dataset of harmonized emissions trajectories through the end of the century , 2018, Geoscientific Model Development.

[13]  J. Rogelj,et al.  Characterizing half‐a‐degree difference: a review of methods for identifying regional climate responses to global warming targets , 2017 .

[14]  R. Moss,et al.  The Scenario Model Intercomparison Project (ScenarioMIP) for CMIP6 , 2016 .

[15]  S. Seneviratne,et al.  Allowable CO2 emissions based on regional and impact-related climate targets , 2016, Nature.

[16]  Veronika Eyring,et al.  Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) experimental design and organization , 2015 .

[17]  Hans von Storch,et al.  Testing ensembles of climate change scenarios for “statistical significance” , 2013, Climatic Change.

[18]  Karl E. Taylor,et al.  An overview of CMIP5 and the experiment design , 2012 .

[19]  G. Hegerl,et al.  Indices for monitoring changes in extremes based on daily temperature and precipitation data , 2011 .

[20]  A. Thomson,et al.  The representative concentration pathways: an overview , 2011 .

[21]  David E. Bernholdt,et al.  The earth system grid: enabling access to multimodel climate simulation data. , 2009 .

[22]  Reto Knutti,et al.  The use of the multi-model ensemble in probabilistic climate projections , 2007, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[23]  M. Allen,et al.  Constraints on future changes in climate and the hydrologic cycle , 2002, Nature.

[24]  S. Coles,et al.  An Introduction to Statistical Modeling of Extreme Values , 2001 .

[25]  Philip W. Jones.  First- and Second-Order Conservative Remapping Schemes for Grids in Spherical Coordinates , 1999 .