In this dashboard we present global indices of moderate temperature and precipitation extremes calculated from historical observations of temperature and rainfall. The HadEX3 indices were developed in collaboration between the Met Office, ARC Centre of Excellence for Climate Extremes at the University of New South Wales, Environment and Climate Change Canada and Barcelona Supercomputing Center. For a full list of contributors, please see the journal article and the main dataset webpage for HadEX3.
As the planet warms, the intensity, frequency and duration of extreme weather events such as heatwaves and heavy rainfall are expected to increase. Corresponding decreases in cool weather events are also expected.
Looking at the changing climate by studying the frequency, duration and intensity of extreme weather events provides a different perspective on climate change, complementing other metrics such as annual average temperature rise. It is often through extreme weather events that impacts from climate change first affect us, and these kinds of events also present the greatest shocks to human health and well-being, economies and the biosphere.
One of the indices showing the most dramatic change over time is the increase in the number of warm days, which is derived from changes in the daily maximum temperature. At the same time, the number of cold nights has decreased, marking a shift in the whole distribution of daily temperatures.
The variability of rainfall over space and time tends to be greater than that of temperature - a cloudburst might fall on a single village and last twenty minutes; a heatwave will typically affect the whole region - so the trends are perhaps less clear. However, there is a trend of an increasing contribution to total annual rainfall from very wet days, with an extra two per cent of precipitation falling on these days compared to 1961-90.
These extremes indices are based on daily measurements of temperature and precipitation made at weather stations around the world. Temperature and precipitation are measured using standardised scientific equipment to ensure that the readings are as accurate as possible.
One of the difficulties of assessing these kinds of extremes is getting hold of the data. The calculations use daily data, which is not freely shared by all countries because it has commercial value which some Meteorological services use to defray the costs of maintaining their national measuring networks. Initiatives led by the former WMO Expert Team on Climate Change Detection and Indices have worked with countries to calculate and share the indices.