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TitleModelling future climate change
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorFlato, G; Gillett, N; Arora, V; Cannon, A; Anstey, J
SourceCanada's changing climate report; by Bush, E (ed.); Lemmen, D S (ed.); 2019 p. 73-111, (Open Access)
LinksOnline - En ligne (interactive - interactif)
LinksCanada's Changing Climate Report - Additional Information
PublisherGovernment of Canada
Mediapaper; on-line; digital
RelatedThis publication is contained in Bush, E; Lemmen, D S; (2019). Canada's changing climate report
RelatedThis publication is a translation of ().
File formatpdf
ProvinceBritish Columbia; Alberta; Saskatchewan; Manitoba; Ontario; Quebec; New Brunswick; Nova Scotia; Prince Edward Island; Newfoundland and Labrador; Northwest Territories; Yukon; Nunavut; Northern offshore region; Eastern offshore region; Western offshore region
NTS1; 2; 3; 10; 11; 12; 13; 14; 15; 16; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 52; 53; 54; 55; 56; 57; 58; 59; 62; 63; 64; 65; 66; 67; 68; 69; 72; 73; 74; 75; 76; 77; 78; 79; 82; 83; 84; 85; 86; 87; 88; 89; 92; 93; 94; 95; 96; 97; 98; 99; 102; 103; 104; 105; 106; 107; 114O; 114P; 115; 116; 117; 120; 340; 560
Lat/Long WENS-141.0000 -50.0000 90.0000 41.7500
SubjectsNature and Environment; surficial geology/geomorphology; environmental geology; hydrogeology; climate; climatology; climate effects; snow; ice; permafrost; ground ice; sea ice; glaciers; surface waters; rivers; lakes; temperature; precipitation; ground temperatures; oceanography; climate, arctic; Canadian Cordillera; climate change; ice caps; fresh water; cumulative effects
Illustrationslocation maps; graphs; models; plots
ProgramClimate Change Impacts and Adaptation Program, Canada in a Changing Climate
Released2019 04 02; 2020 12 08
This chapter provides an overview of Earth system models and how they are used to simulate historical climate and to make projections of future climate. Historical simulations allow models to be evaluated via comparison with observations, and these show that models are able to reproduce many aspects of observed climate change and variability. They also allow experiments to be conducted in which human and natural causes of climate change can be identified and quantified. In order to make future projections, it is necessary to specify future emissions, or concentrations of greenhouse gases and aerosols, as well as future land-use change. Owing to uncertainty regarding future human activity (in particular, the extent to which ambitious emission reductions will be implemented), a range of future scenarios must be used. Results from future climate projections are discussed, along with sources of confidence and uncertainty. On average, the models project a future global mean temperature change (relative to the 1986-2005 reference period) of about 1ºC for the low emission scenario (Representative Concentration Pathway [RCP] 2.6) and 3.7ºC for the high emission scenario (RCP 8.5) by the late 21th century, with individual model results ranging about 1ºC above or below the multi-model average. This change is over and above the 0.6ºC change that had already occurred from 1850 to the reference period. The low emission scenario (RCP2.6) is consistent with limiting the global temperature increase to roughly 2ºC and is therefore roughly compatible with the global temperature goal agreed to in the Paris Agreement. This scenario requires global carbon emissions to peak almost immediately and reduce to near zero well before the end of the century. Regardless of the global mean surface temperature level attained when emissions become net zero, temperature will remain at about that level for centuries. In other words, global temperature change is effectively irreversible on multi-century timescales. The relationship between cumulative emissions of carbon dioxide (CO2) and global mean surface temperature provides a simple means of connecting emissions from fossil fuels - the main source of anthropogenic CO2 - to climate change. It also leads to the concept of a carbon emissions budget - the amount of carbon that can be emitted before temperatures exceed a certain value. The Intergovernmental Panel on Climate Change (IPCC, 2014) has assessed that, to have a 50% chance of keeping global warming to less than 2ºC above the pre-industrial value, CO2 emissions from 2011 onward would have to remain below 1300 billion tonnes of CO2 (GtCO2), roughly equal to what has already been emitted since the beginning of the Industrial Era. For a 50% chance of keeping the temperature increase to less than 1.5ºC, emissions from 2011 onward would have to be limited to 550 GtCO2. It must be noted that estimation of carbon budgets, especially for low temperature targets, is a rapidly developing area of research, and updated budgets will be assessed in the near future. The chapter concludes with a discussion of downscaling methods, that is, methods to transform global Earth system model results into more detailed, local information better suited to impact studies. Downscaled results are often used in impact studies, but users must keep in mind that the enhanced detail provided does not necessarily mean added value, and that uncertainty is larger at smaller spatial scales.
Summary(Plain Language Summary, not published)
This chapter describes what Earth system models are and how they are used. Model-based projections of climate change at a global scale are presented, along with a discussion of the global carbon budget and methods to downscale coarse resolution global model projections to finer spatial scales.

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