Temperature and precipitation trends in Canada during the 20th century

Abstract

Trends in Canadian temperature and precipitation during the 20th century are analyzed using recently updated and adjusted station data. Six elements, maximum, minimum and mean temperatures along with diurnal temperature range (DTR), precipitation totals and ratio of snowfall to total precipitation are investigated. Anomalies from the IntroductionRecent analyses of climate trends indicate that the global mean surface temperature has increased by about 0.3 to 0.68C since the late 19th century, and by about 0.2 to 0.38C over the last 40 years (e.g., Nicholls et al., 1996). These studies have also shown that daily minimum temperatures have often increased at a greater rate than maximum temperatures, resulting in a decrease in the diurnal temperature range (DTR) for several regions of the world. There has been a small positive trend in global precipitation, of about 1% during the 20th century over land, with a greater increase in the high latitudes of the Northern Hemisphere, especially during the cold season. Considerable spatial and temporal variations have occurred over the past 100 years, and these tendencies of warming, increased precipitation and reduction of DTR have not been globally uniform. For example, Nicholls et al. (1996) showed warming in the mid-latitude Northern Hemisphere continents in winter and spring, and year-round cooling in the northwest North Atlantic and mid-latitudes over the North Pacific in the past four decades. Understanding the observed climate trends

Temporal and spatial temperature variability and change over Spain during 1850–2005

“…Temperature change, explained by a linear trend fit over the entire period and several subperiods of rising and falling temperatures, has been calculated on an annual and a seasonal basis by adapting Sen's [1968] estimator of the slope. Our application of this method is similar to that undertaken by Zhang et al [2000] in a study of annual temperature and precipitation change over Canada and in extreme wave heights over Northern Hemisphere oceans [Wang and Swail, 2001]. All trends are tested for statistical significance at the 0.01 level unless otherwise stated.…”

“…This was performed using the RClimDex software package [Zhang and Yang, 2004] on an annual basis that uses a robust method of estimating trends, following the methods of estimation of Zhang et al [2000] and Wang and Swail [2001]. Analysis on a seasonal basis has also been carried out by employing the EMULATE extreme indices software http://www.cru.uea.ac.uk/cru/projects/emulate/public/) developed by Walther [2004].…”

Changes in daily climate extremes in the eastern and central Tibetan Plateau during 1961–2005

“…The 95% confidence intervals are calculated from tabulated values [Kendall, 1955]. The significance of the trends is determined using an iterative procedure [Wang and Swail, 2001;X. Zhang et al, 2000] to compute the trends and to test the trends significance taking account of a lag-1 autocorrelation effect.…”

“…[12] In this study, linear trends for indices are calculated using a nonparametric approach, a Kendall's t-based Sen's robust slope estimator [Sen, 1968], which is adapted and applied in a study of annual temperature and precipitation change over Canada [ X Zhang et al, 2000], and in extreme wave heights over Northern Hemisphere oceans [Wang and Swail, 2001]. Annual missing value is excluded from the analysis when calculating the linear trend.…”

Trends in Seasonal Precipitation over China during 1961-2007

“…This method has been frequently used (Kunkel et al, 1999;Zhang et al, 2001). We used an iterative procedure, originally proposed by Zhang et al (2000) and later refined by Wang and Swail (2001), to calculate the trend and to test the significance at the 0.05 level, while taking into account autocorrelation effects in the series. To allow for comparison of trend magnitudes between stations with different mean climate, the trend is expressed by percentage changes relevant to the mean climatology during 1971−2000.…”