| Abstract/Description or Keywords |
This document was developed to assist the Columbia Basin Trust’s Communities Adapting to Climate Change Initiative, a pilot project focused on selected communities in the basin. Climate affects many aspects of communities, including local ecosystems, tourism, forestry, energy and infrastructure. To consider climate in planning, the local climate must be well understood, including recent conditions, past trends, and projected changes to future climate. This document provides additional information that was not available during the previous regional assessment (Murdock et al. 2007). It draws heavily on a subsequent province-wide analysis (Rodenhuis et al. 2009) and on climate model projections prepared for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC 2007). Climate consists of components that function at different scales, superimposed to create the actual climate record observed at a given location. In this report, information is provided on historical averages, year-toyear variability, decadal oscillations, long-term trends, and also future projected changes to average climate. a) Climate Variability In the Canadian Columbia Basin, year-to-year variability is heavily influenced by the El NiĖo/Southern Oscillation (ENSO). For example, an El NiĖo winter is typically 1.0°C to 1.8°C warmer than an average winter in the basin. Conversely, La NiĖa years are usually colder than normal. On the scale of decades, the Pacific Decadal Oscillation (PDO) displays additional warming or cooling during its positive and negative phases, respectively. Precipitation is more complex than temperature. For example, both ENSO and PDO can influence precipitation by 20% in the region, but the effect varies depending on the season and can differ considerably over relatively short distances. Most of the basin receives less precipitation in winter during El NiĖo years and during the positive phase of the PDO. b) Temperature Temperatures have been increasing in the basin over the past century. In particular, the rate of increase in annual average temperatures in the area is 0.7°C to 1.7°C per century over the 1901-2004 period. Rates of warming are larger in the West Kootenays than the East Kootenays, for nighttime low (minimum) temperatures than daytime high (maximum) temperatures, and in winter than other seasons. The rate of temperature increase over the last century has been accelerating in most of the province but has remained quite constant in this area. The Canadian Columbia Basin is projected to be 1.2°C to 2.7°C warmer by the 2050s according to the 10th to 90th percentile of an ensemble of 30 Global Climate Model (GCM) projections, compared to the baseline (1961-1990) temperature. This projected warming is more rapid than past trends. c) Precipitation Precipitation has been changing over the past century, but unlike temperature, the details and even the direction of the trend depend on the time period of analysis. Over the 20th century, precipitation increased in all seasons in the basin, but in some seasons and locations the increase was not statistically significant. Future precipitation is projected to increase by up to 15% in winter and decrease by as much as 14% in summer for the basin as a whole according to an ensemble of GCMs, with large regional differences within the basin indicated by a Regional Climate Model. |
