The Great Lakes Basin plays an important role in the economy and society of the United States and Canada, and climate change in this region may affect many sectors. In this study, six GCM simulations were downscaled to resolve the Great Lakes using a regional climate model (RCM) with 25 km × 25 km resolution. This model was used to project changes in temperature and precipitation during the mid-century (2040–2069) and late-century (2070–2099) over the Great Lakes basin region with reference to a baseline of 1980–2009. The whole-basin annual mean temperature is projected to increase 2.1 °C to 4.0 °C above the baseline during the mid-century, and 3.3 °C to 6.0 °C during the late-century. Summer temperatures in the southern portion of the basin are projected to increase more than the temperatures in the northern portion of the basin; whereas winter temperatures are projected to increase more in the north than in the south. Estimates of the whole-basin annual precipitation with respect to the baseline vary from −3.0% to 16.5% during the mid-century and −2.9% to 21.6% during the late-century, respectively. Future summer precipitation in southwestern areas of this region is expected to decrease by 20%–30% compared to the baseline, but winter precipitation (mostly snow) is expected to increase by 11.6% and 15.4% during the mid-century and late-century. This study highlights the effects of the large expanses of water (such as the Great Lakes) on regional climate projections and the associated uncertainties of climate change.

Six bias correction (BC) methods; delta-method (DT), linear scaling (LS), power transformation of precipitation (PTR), empirical quantile mapping (EQM), gamma quantile mapping (GQM) and gamma-pareto quantile mapping (GPQM) were applied to adjust the biases of historical monthly precipitation outputs from five General Circulation Models (GCMs) dynamically downscaled by two Regional Climate Models (RCMs) for a total of seven different GCM-RCM pairs over Costa Rica. High-resolution gridded precipitation observations were used for the control period 1951-1980 and validated over the period 1981-1995. Results show that considerable biases exist between uncorrected GCM-RCM outputs and observations, which largely depend on GCM-RCM pair, seasonality, climatic region and spatial resolution. After the application of bias correction, substantial biases reductions and comparable performances among most BC methods were observed for most GCM-RCM pairs; withEQMand DT marginally outperforming the remaining methods. Consequently, EQM and DT were selectively applied to correct the biases of precipitation projections from each individual GCM-RCM pair for a near-future (2011-2040), mid-future (2041-2070) and far-future (2071-2100) period under Representative Concentration Pathways (RCPs) 2.6, 4.5 and 8.5 using the control period 1961-1990. Results from the bias-corrected future ensemble-mean anticipate a marked decreasing trend in precipitation from near to far-future periods during the dry season (December, January, February (DJF) and March, April, May (MAM) for RCP4.5 and 8.5; with pronounced drier conditions for those climatic regions draining towards the Pacific Ocean. In contrast, mostly wetter conditions are expected during the dry season under RCP2.6, particularly for the Caribbean region. In most of the country, the greatest decrease in precipitation is projected at the beginning of the rainy season (June, July, August (JJA) for the far-future period under RCP8.5, except for the Caribbean region where mostly wetter conditions are anticipated. Regardless of future period, slight increases in precipitation with higher radiative forcing are expected for SON excluding the Caribbean region, where precipitation is likely to increase with increasing radiative forcing and future period. This study demonstrates that bias correction should be considered before direct application of GCM-RCM precipitation projections over complex territories such as Costa Rica.

The Philippines is one of the most exposed countries in the world to tropical cyclones. In order to provide information to help the country build resilience and plan for a future under a warmer climate, we build on previous research to investigate implications of future climate change on tropical cyclone activity in the Philippines. Experiments were conducted using three regional climate models with horizontal resolutions of approximately 12 km (HadGEM3-RA) and 25 km (HadRM3P and RegCM4). The simulations are driven by boundary data from a subset of global climate model simulations from the CMIP5 ensemble. Here we present the experimental design, the methodology for selecting CMIP5 models, the results of the model validation, and future projections of changes to tropical cyclone frequency and intensity by the mid-21st century. The models used are shown to represent the key climatological features of tropical cyclones across the domain, including the seasonality and general distribution of intensities, but issues remain in resolving very intense tropical cyclones and simulating realistic trajectories across their life-cycles. Acknowledging model inadequacies and uncertainties associated with future climate model projections, the results show a range of plausible changes with a tendency for fewer but slightly more intense tropical cyclones. These results are consistent with the basin-wide results reported in the IPCC AR5 and provide clear evidence that the findings from these previous studies are applicable in the Philippines region.

The Laurentian Great Lakes Basin has been subject to increasingly extreme weather events in the past seven decades. This study uses a regional climate model spanning the region to project summer maximum temperature (Tmax), winter minimum temperature (Tmin), and seasonal extremes of precipitation for the mid-century (2030–2059) and late-century (2060–2089) relative to the baseline period (1980–2009). The basin's southern portion (US side) summer Tmax increases are projected to be greater than those in the northern portion of the basin (Canadian side), whereas Canadian side winter Tmin increases will be greater than those on the US side. The annual number of extremely hot days (Tmax ≥ 32 °C) in this region during mid-century and late century periods is projected to rise by 6.1–15.3 days and 10.0–32.1 days relative to the baseline period (1980–2009) values (0.1–21.5 days), respectively; whereas the annual number of extremely cold days (Tmin ≤ −18 °C) is projected to be reduced by 3.9–6.2 days (mid-century) and 5.5–9.9 days (late century) compared to the baseline period (2.6–60.5 days). The annual number of extremely cold days is projected to remain unchanged in 23%–61% of the area over the Lakes. The Basin's annual precipitation is projected to rise continuously but the degree of change will vary by season. Winter and spring precipitations are projected to rise greatly, autumn precipitation will rise to a lesser extent, but summer precipitation is projected to decline relative to the baseline period. The annual number of extremely wet days (≥40 mm/day) over the Lakes only is projected to increase by between 0.3 and 0.6 days (mid-century) and 0.5–0.8 days (late century). The annual number of extremely wet days over land areas is projected to increase by 0.2–0.6 days and 0.5–0.8 days, respectively. However, about 20% of the region will also experience a reduced number of extremely wet days, which implies that future precipitation changes in this region may be quite different at smaller scales (e.g. county to county) than over larger scales. We propose that lake and land differences, seasonal variations, and changed and unchanged areas should all be considered in climate studies of regions within which large inland water bodies reside, as these regions will have similarities with the Great Lakes basin.

The Great Lakes Basin is an important agricultural region for both the United States and Canada. The regional crop growths are affected by inter-annual climatic conditions and intra-seasonal variability. Consequently, monthly climate change projection data can provide more useful information for crop management than seasonal climate projections. However, very few studies undertaken for the Great Lakes Basin have focused on monthly timescales. In this study, we investigate the projected mid-century (2030-2059) monthly mean maximum temperature (Tmax) and minimum temperature changes of this region, relative to the baseline period (1980-2009). Future Tmax increases in this region are likely to be greater during the May to October period (coinciding with the region's growing season) than in other months. The order of magnitude of future Tmax and Tmin changes of the five Great Lakes sub-basins are Superior > Huron > Michigan > Erie and Ontario. Most future Tmax changes over land areas are higher than those over the lakes, whereas Tmin changes are likely to be higher over lakes than over the adjacent land areas in this region. The future number of extreme warm days (Tmax ≥ 29-32 °C) in this region will increase by between about 5 days (in the north) to 40 days (in southern parts of the basin), while the number of winter cold days (Tmax ≤ -5 °C ~ 0 °C) may decrease by between 3 days (south) and 35 days (north). This study furthermore identifies some fluctuations of latitudinal temperature gradients in the Great Lakes Basin, these areas covering the north latitude 40.5-41.5°, 43.5-44.0°, 45.5-46.5°, and 47.5-49.5°.