The timing of anthropogenic emergence in climate extremes

Andrew King, Markus Donat, Erich Fischer, Ed Hawkins, Lisa Alexander, David Karoly, Andrea Dittus, Sophie

Lewis and Sarah Perkins

Illustration

Time

Time of Anthropogenic Emergence (TAE)

Motivation

• No previous global study of emergence in temperature and precipitation extremes.

• Previous studies use modern baseline period.

Methodology

• For TAE to have occurred:

– A 20-year moving window must be significantly different (p < 0.05) from a 51-year quasi-natural period (1860-1910).

– AND all subsequent 20-year windows must remain significantly different from the quasi-natural period.

Data

• Multiple runs (23 in total) from six CMIP5 models.

• Historical (1860-2005) and RCP8.5 (2005-2099).

Data

• Apply our methodology to mean and extreme temperature and precipitation indices.

Name of index Definition

Tas Mean temperature

Pr Total precipitation

TXx Highest daily maximum temperature

TXn Lowest daily maximum temperature

TNx Highest daily minimum temperature

TNn Lowest daily minimum temperature

RX1D Maximum 1-day precipitation

RX5D Maximum consecutive 5-day precipitation

TAE temperature maps

TAE precipitation maps

The global picture

Where can we attribute changes in climate to anthropogenic influences?

Where can we attribute changes in climate to anthropogenic influences?

Conclusions

• First study to look at Time of Emergence of extremes on a global scale.

• Climate extremes tend to emerge later than means.

• Spatial aggregation brings forward TAE.

• High uncertainty in TAE values.

• Results can be used as a guide for attribution studies.

Thank you

E: andrew.king@unimelb.edu.au W: andrewdking.weebly.com