Publications Library

Droughts, one of the most significant natural hazards, are complex in nature with varying definitions typically tailored to the timing and/or duration of the episode along with associated impacts. Although previous investigations have assessed future drought occurrence across Canada, none have comprehensively and collectively assessed changes to meteorological, agricultural, and hydrological drought indicators using CMIP6 GCM projections. The main objective of this study was to assess future drought conditions across Canada at various temporal scales using standardized indices representing meteorological, agricultural, and hydrological droughts under multiple shared socio-economic pathways for the near (2041–2060) and far (2081–2100) future. On an annual basis, projected changes to all three drought indicators signify increased drying across the Prairies, portions of interior British Columbia, and most of Ontario. This drying is greater and covers more of the country during the warm season (April to September), while in summer and to a lesser extent autumn, widespread changes are only projected for meteorological and agricultural indicators. In spring, increased dry conditions are only prevalent in meteorological and hydrological indices. The cold season of October to March essentially shows little to no drying in any type of drought. Changes in all drought indices are amplified for higher SSPs and during the late century. This study improves an understanding of the spatial and temporal variations in projected changes to various drought types across Canada in response to human-induced warming. While results from this analysis are applicable for nation-wide drought assessments and drought management plans, they are less suitable for application at local scales where more detailed modelling may be required.

Geospatial climate change projections are critical for assessing climate change impacts and adaptations across a wide range of disciplines. Here we present monthly-based grids of climate change projections at a 2-km resolution covering Canada and the United States. These data products are based on outputs from the 6th Coupled Model Intercomparison Project (CMIP6) and include projections for 13 General Circulation Models (GCMs), three Shared Socio-economic Pathways (SSP1 2.6, SSP2 4.5, and SSP5 8.5), four 30-year time periods (2011–2040, 2021–2050, 2041–2070, and 2071–2100), and a suite of climate variables, including monthly maximum and minimum temperature, precipitation, climate moisture index, and various bioclimatic summaries. The products employ a delta downscaling method, which combines historical normal values at climate stations with broad-scale change projections (or deltas) from GCMs, followed by spatial interpolation using ANUSPLIN. Various quality control efforts, described herein, were undertaken to ensure that the final products provided reasonable estimates of future climate.

In 2023, wildfires burned 15 million hectares in Canada, more than doubling the previous record. These wildfires caused a record number of evacuations, unprecedented air quality impacts across Canada and the northeastern United States, and substantial strain on fire management resources. Using climate models, we show that human-induced climate change significantly increased the likelihood of area burned at least as large as in 2023 across most of Canada, with more than two-fold increases in the east and southwest. The long fire season was more than five times as likely and the large areas across Canada experiencing synchronous extreme fire weather were also much more likely due to human influence on the climate. Simulated emissions from the 2023 wildfire season were eight times their 1985-2022 mean. With continued warming, the likelihood of extreme fire seasons is projected to increase further in the future, driving additional impacts on health, society, and ecosystems.

This edition of the PCIC Update contains the following stories: 2023 and the Transition to 2024: A Record-Breaking Year Globally and for BC, Salmon Climate Impacts Portal Released, Development of High-resolution Climate Change Freshwater Hazard Data for BC, Updates to Plan2Adapt and PCIC Climate Explorer and The Pacific Climate Data Set Surpasses One Billion Observations, along with updates on staff changes and the Pacific Climate Seminar Series. The staff issue in this profile is on Quintin Sparks.

This Science Brief covers a recent paper in the Journal of Advances in Modeling Earth Systems that examines to what extent shared components and computer code between models affects their simulated climate sensitivities, feedbacks and resulting projections of surface air temperature. It finds that models with shared code tend to have greater similarity in their climate sensitivities, strengths of feedbacks, and therefore in their projected surface temperatures. The authors also demonstrated that weighting ensembles of models according to their family resemblance resulted in a lower equilibrium climate sensitivity than when using a simple ensemble mean, and also reduced differences in climate sensitivity between the two most recent generations of climate models.

The Earth’s climate system is warming, and signs of climate change are becoming evident across the planet. The capital region, located on Southern Vancouver Island and Gulf Islands of British Columbia (BC), is no exception. The Capital Regional District (CRD) has partnered with the Pacific Climate Impacts Consortium (PCIC) to produce high-resolution regional projections for temperature, precipitation, and related indices of extremes. These projections use the most up-to-date global modeling data (i.e., the Sixth Coupled Model Intercomparison Project, CMIP6) to illustrate how the region’s climate may change by the middle of this century. Information provided by this report and the accompanying data is intended to support decision makers and community partners in the region with an improved understanding of projected local climate change and related impacts.

Rare precipitation events with return periods of multiple decades to hundreds of years are particularly damaging to natural and societal systems. Projections of such rare, damaging precipitation events in the future climate are, however, subject to large inter-model variations. We show that a substantial portion of these differences can be ascribed to the projected warming uncertainty, and can be robustly reduced by using the warming observed during recent decades as an observational constraint, implemented either by directly constraining the projections with the observed warming or by conditioning them on constrained warming projections, as verified by extensive model-based cross-validation. The temperature constraint reduces >40% of the warming-induced uncertainty in the projected intensification of future rare daily precipitation events for a climate that is 2°C warmer than preindustrial across most regions. This uncertainty reduction together with validation of the reliability of the projections should permit more confident adaptation planning at regional levels.

Weighting models according to their performance has been used to produce multimodel climate change projections. But the added value of model weighting for future projection is not always examined. Here we apply an imperfect model framework to evaluate the added value of model weighting in projecting summer temperature changes over China. Members of large-ensemble simulations by three climate models of different climate sensitivities are used as pseudo-observations for the past and the future. Performance of the models participating in the phase 6 of the Coupled Model Intercomparison Project (CMIP6) are evaluated against the pseudo-observations based on simulated historical climatology and trends in global, regional, and local temperatures to determine the model weights for future projection. The weighted projections are then compared with the pseudo-observations in the future period. We find that regional trend as a metric of model performance yields generally better skill for future projection, while past climatology as performance metric does not lead to a significant improvement to projection. Trend at the grid-box scale is also not a good performance indicator as small-scale trend is highly uncertain. For the model weighting to be effective, the metric for evaluating the model’s performance must be relatable to future changes, with the response signal separable from internal variability. Projected summer warming based on model weighting is similar to that of unweighted projection but the 5th–95th-percentile uncertainty range of the weighted projection is 38% smaller with the reduction mainly in the upper bound, with the largest reduction appearing in southeast China.

Water regulation has contributed to the decline in Pacific salmon in British Columbia (Canada) despite attempts to manage reservoir operations to achieve operational requirements while meeting environmental needs to limit fish thermal stress. The ability of reservoir managers to meet these trade-offs in a changing climate is unknown. Here, we examine the reliability and vulnerability of the Nechako Reservoir to meet hydropower production commitments and fisheries needs under two projected Shared Socioeconomic Pathway scenarios (SSP2-4.5 and SSP5-8.5). While our findings are specific to the operation of the Nechako Reservoir, the issues that emerge are likely common to many reservoirs in areas where reservoir inflow regimes are currently snow-storage dominated. We found that projected changes in the timing of water availability have little to no influence on hydropower generation commitments. However, larger water releases will be required to avoid compromising reservoir safety, possibly endangering downstream fish habitat through scouring. Furthermore, the temperature of water released from the reservoir is projected to more frequently exceed a level, 20°C, that is detrimental to migrating sockeye salmon. Water released is subject to further warming as it travels towards the lower reaches of the Nechako River used by migrating salmon. Hence, there is a need to adapt reservoir operations to ensure reservoir safety and mitigate adverse effects on salmon habitat.