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Observed emergence of the climate change signal: from the familiar to the unknown
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  • Ed Hawkins,
  • David John Frame,
  • Luke James Harrington,
  • Manoj Joshi,
  • Andrew David King,
  • Maisa Rojas,
  • Rowan T Sutton
Ed Hawkins
University of Reading

Corresponding Author:e.hawkins@reading.ac.uk

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David John Frame
Victoria University of Wellington
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Luke James Harrington
Environmental Change Institute
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Manoj Joshi
University of East Anglia
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Andrew David King
University of Melbourne
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Maisa Rojas
Universidad de Chile
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Rowan T Sutton
National Centre for Atmospheric Science, University of Reading
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Changes in climate are usually considered in terms of trends or differences over time. However, for many impacts requiring adaptation, it is the amplitude of the change relative to the local amplitude of climate variability which is more relevant. Here, we develop the concept of ‘signal-to-noise’ in observations of local temperature, highlighting that many regions are already experiencing a climate which would be ‘unknown’ by late 19century standards. The emergence of observed temperature changes over both land and ocean is clearest in tropical regions, in contrast to the regions of largest change which are in the northern extra-tropics - broadly consistent with climate model simulations. Significant increases and decreases in rainfall have also already emerged in different regions with the UK experiencing a shift towards more extreme rainfall events, a signal which is emerging more clearly in some places than the changes in mean rainfall.
28 Mar 2020Published in Geophysical Research Letters volume 47 issue 6. 10.1029/2019GL086259