Observed coherent changes in climatic extremes during the second half of the twentieth century

Abstract

A new global dataset of derived indicators has been compiled to clarify whether frequency and/or severity of climatic extremes changed during the second half of the 20th century. This period provides the best spatial coverage of homogenous daily series, which can be used for calculating the proportion of global land area exhibiting a significant change in extreme or severe weather. The authors chose 10 indicators of extreme climatic events, defined from a larger selection, that could be applied to a large variety of climates. It was assumed that data producers were more inclined to release derived data in the form of annual indicator time series than releasing their original daily observations. The indicators are based on daily maximum and minimum temperature series, as well as daily totals of precipitation, and represent changes in all seasons of the year. Only time series which had 40 yr or more of almost complete records were used. A total of about 3000 indicator time series were extracted from national climate archives and collated into the unique dataset described here. Global maps showing significant changes from one multi-decadal period to another during the interval from 1946 to 1999 were produced. Coherent spatial patterns of statistically significant changes emerge, particularly an increase in warm summer nights, a decrease in the number of frost days and a decrease in intra-annual extreme temperature range. All but one of the temperaturebased indicators show a significant change. Indicators based on daily precipitation data show more mixed patterns of change but significant increases have been seen in the extreme amount derived from wet spells and number of heavy rainfall events. We can conclude that a significant proportion of the global land area was increasingly affected by a significant change in climatic extremes during the second half of the 20th century. These clear signs of change are very robust; however, large areas are still not represented, especially Africa and South America.

Assessment of Biological and Environmental Phenology at a Landscape Level from 30 Years of Fixed-Date Repeat Photography in Northern Sweden

“…Daily temperature data were used to calculate length of growing season in any given year using the method described by Frich et al (2002).…”

Recent Changes in Frost Days and the Frost-Free Season in the United States

“…Frich et al (2002) found evidence of longer growing seasons and fewer frost days in much of the mid-and high latitudes in the Northern Hemisphere in the last 50 years. Furthermore, Heino et al (1999) found decreasing frost days across northern Europe during the twentieth century, and similarly, Bonsai et al (2001) also found decreasing frost days in Canada.…”

Contributions of different bias‐correction methods and reference meteorological forcing data sets to uncertainty in projected temperature and precipitation extremes

“…Historical and future changes in the frequency, intensity, and duration of climate extremes have been increasingly studied in the last few decades using daily weather observation networks, global climate model (GCM) simulations [Frich et al, 2002;Alexander et al, 2006;Donat et al, 2013;Sillmann et al, 2013aSillmann et al, , 2013b, and regional climate model simulations [Iizumi et al, , 2012. At the global scale, GCM-projected climate extremes are translated into water scarcity, human health burden, food production loss, and degradation of ecosystem services using GCM output as the input of impact models (e.g., hydrologic and crop models).…”