Climate data and scenarios: synthesis of recent observation and modelling results, chapter 3.2


3.2 Precipitation

In this section, multi-model climate change projections (relative to the 1986-2005 reference period) are shown for precipitation in Canada. The format of these figures is as consistent as possible with the analogous figures in the IPCC AR5 Atlas (IPCC, 2013--Annex I) referred to earlier so as to allow direct comparison.

Time series of precipitation anomaly (as a percentage relative to the 1986-2005 mean), averaged over Canada and covering the historical period (as simulated by the CMIP5 models) and the future (to year 2100), are shown in Figure 8. Results for three future forcing scenarios, RCP2.6, RCP4.5, and RCP8.5, are provided. The individual thin lines are the results of the individual models listed in Table 2, and the heavy line represents the multi-model ensemble average. The range of values, quantified by the box and whisker plots to the right of each panel, results from both natural climate variability (as simulated by the models) and the differences in the detailed representation of physical processes in each model.

Figure 8

Figure 8 - Time series of historical and projected precipitation change for December-February (left) and June-August (right) average, as simulated by the CMIP5 multi-model ensemble. As in Annex I of the IPCC AR5 (IPCC, 2013), the individual curves represent the simulation results for individual models, while the heavy lines indicate the ensemble average. Results are shown for Canadian land areas only. Change is computed as a percentage relative to the 1986-2005 period. The spread amongst models, evident in the thin curves, is quantified by the box and whisker plots to the right of each panel. They show, for the 2081-2100 period, the 5th, 25th, 50th (median), 75th and 95th percentile values.

Long description of Figure 8

This figure has two graphs. The left graph represents a time series of historic and projected precipitation changes for the winter (December, January, and February) as simulated by CMIP5 multi-model ensemble for grids covering Canada. A solid line represents the historic change from 1900 to 2005 and shows an increase from around -2% to around 0%. The RCP2.6 line then continues to increase until it reaches around 10% in 2100. The RCP4.5 line continues on from 2005 to 2100 with an end point of around 18%. The RCP8.5 projection shows a change of around 37% by 2100. The right graph represents a time series of historic and projected precipitation change for the summer (June, July, and August) as simulated by CMIP5 multi-model ensemble for grids covering Canada. A solid line represents the historic change from 1900 to 2005 and shows almost no change, at around 0%. The RCP2.6 line then continues to increase until it reaches around 5%. The RCP4.5 line is almost identical to the RCP2.6 line. The RCP8.5 projection shows a change of around 8% by 2100.

As was shown for temperature in Figures 6 and 7, Figures 9 and 10 show maps of precipitation change from the CMIP5 multi-model ensemble, based on the RCP4.5 scenario. Similar maps for the other RCP scenarios are available from the Canadian Climate Data and Scenarios website. RCP4.5 is used here for illustration purposes (as in the IPCC Atlas) and its use here does not imply that it is more probable than the other RCPs.

Figure 9

Figure 9 - Maps of winter precipitation change projected by the CMIP5 multi-model ensemble for the RCP4.5 scenario, averaged over December-February. Change is computed relative to the 1986-2005 baseline period. As in the IPCC Atlas (IPCC, 2013), the top row shows results for the period 2016-2035, the middle row for 2046-2065, and the bottom row for 2081-2100. For each row the left panel shows the 25th percentile, the middle panel the 50th percentile (median), and the right panel the 75th percentile. The colour scale indicates precipitation change in % with positive change (increased precipitation) indicated by green colours and decrease by yellow to brown colours, consistent with the colour scale used in the IPCC AR5 Annex I (IPCC, 2013).

Long description of Figure 9

This figure consists of 9 maps of Canada showing projected changes in precipitation, driven by RCP4.5, for the winter (December, January, and February), organized in a 3 by 3 grid, with the 25th (left column), 50th (middle column) and 75th (right column) percentiles across the top of each column and the years 2016-2035 (first row), 2046-2065 (second row), and 2081-2100 (third row) down the side to indicate the years for each row. Each map shows most of the country with a projected increase in precipitation, with the 2016-2035/25th percentile map showing some slight drying over the southern parts of the country. The greatest increase in the precipitation is in the north and over Hudson Bay. As the percentiles go up, the changes in percent of precipitation increase. The same is true for time, the further into the future the projection represents, there is an increase in the amount of precipitation represented in the maps, so the map in the top left (25th percentile for 2016-2035), has the least amount of change in precipitation, whereas the bottom right map (75th percentile for 2081-2100), shows the greatest increase in precipitation.

Figure 1

Figure 10 - Maps of summer precipitation change projected by the CMIP5 multi-model ensemble for the RCP4.5 scenario, averaged over June-August. Change is computed relative to the 1986-2005 baseline period. As in the IPCC Atlas (IPCC, 2013), the top row shows results for the period 2016-2035, the middle row for 2046-2065, and the bottom row for 2081-2100. For each row the left panel shows the 25th percentile, the middle panel the 50th percentile (median), and the right panel the 75th percentile. The colour scale indicates precipitation change in % with positive change (increased precipitation) indicated by green colours and decrease by yellow to brown colours, consistent with the colour scale used in the IPCC AR5 Annex I (IPCC, 2013).

Long description of Figure 10

This figure consists of 9 maps of Canada showing projected changes in precipitation, driven by RCP4.5, for the summer (June, July and August), organized in a 3 by 3 grid, with the 25th (left column), 50th (middle column) and 75th (right column) percentiles across the top of each column and the years 2016-2035 (first row), 2046-2065 (second row), and 2081-2100 (third row) down the side to indicate the years for each row. Each of the three 25th percentile maps (2016-2035, 2046-2065, and 2081-2100) shows some decrease in precipitation over most of the country, with the 2016-2035 map showing almost all the country in the 0-10% decrease category. By 2081-2100, only the provinces from Ontario westward are in that category, and the east and the north are in the 0-10% increasing precipitation category. Again the highest percentile map for the most distant future projection shows the greatest change, with areas in the Arctic projected to increase by 20-30%, and with southern Canada only expected to have a 0-10% increase by 2100.

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