EWB climate analysis

Climate Impacts on the Eastern WheatbeltTim Scanlon

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Contents• Nothing surprising in the analysis• Looked at two zones so far

• 16 sites in Westonia and Yilgarn• 69 sites in Mt Marshall to Narembeen

• Major changes in January and May-July rainfall• Significant changes in temperatures

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WA Rainfall Change Isohyets

Equivalent of moving 50 km

Something happening since 2000?

England, Ummenhoffer and Santosa, 2006

Something happening since 2000?

EWB Rainfall

Decadal Trends Since 1900

GSR Decile Changes

Changes in deciles

EWB Site Rainfall Ranges

EWB Temperature

EWB Monthly Temperature

EWB Change in Temperature

Westonia-Yilgarn Rainfall

Westonia-Yilgarn Temperature

Yields?

Summary

SummaryGrowing season rainfall has decreased 43.8mm (19%).

Mostly a loss in May and June rainfall.

Gains in summer rainfall, particularly January, of 32.5mm (60%).

Annual rainfall only declined 10.5mm as a result (3.5%).

Summer rainfall highly variable, one in three years.

The annual average temperature increases of 0.7 (maxima) and 0.26 (minima).

These are in line with current analyses and predictions from the literature.

Early (April-June) and late (Oct) season much hotter.

Mid season overnight colder (June-Sept).

Temperature increases and winter season dominance mean the summer gains of little value to plants.

The rainfall changes are the changes expected by mid-century. Mid-century figures will need a rethink.

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Projected rainfall changes for end of century

Supporting your success IOCI3 Technical Report, 2012

WA Rainfall Change Isohyets

Summary

SummaryGrowing season rainfall has decreased between 20 and 45mm.

Mostly a loss in May and June rainfall.

Gains in summer rainfall, particularly January, offset the annual rainfall figures.

Temperature increases and season winter season dominance mean the summer gains of little value to plants.

The temperature changes are in line with current analyses and predictions from the literature.

The rainfall changes are the changes expected by mid-century. Mid-century figures will need a rethink.

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2000 - 2013Yields from ABARES, and estimated from GIWA for 2013/14.

WA Wheat Production and Seasonal Rainfall

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Seasonal rainfall and productionYear MAM JJA ASO May-Oct Production 2000 B B B B 5.82001 B B N-A B 7.82002 B B B B 4.02003 A N-A A N-A 11.12004 B N-B N-A N-B 8.62005 A N-B A A 9.12006 B B N-B B 5.12007 B B N-B B 5.82008 N B N-A B 8.32009 B N-A N N-B 8.12010 B B B B 5.02011 B A A N-A 11.02012 B B B B 6.62013 A B A N-B 15.2

Indian Ocean Climate InitiativeKey findings include:

❖ Winter rainfall has decreased sharply and suddenly in the region since the mid

70s.

❖ The decline was not gradual but more of a switching to an alternative rainfall

regime.

❖ The rainfall decrease accompanied and was apparently associated with,

documented change in large scale atmospheric circulation at the time.

❖ The decrease in rainfall, and associated circulation changes, bear some

resemblance to model projections for an enhanced greenhouse effect (EGE) but

are not sufficiently similar to indicate, beyond doubt, that the EGE is responsible.

❖ Most likely both natural variability and the EGE have contributed to the rainfall

decrease.

1975 and 2000 “special dates”

2000 thought to be because of post 1998 El Nino ENSO phase with a greater

proportion of heat being accumulated in the oceans.

Climate changes for post 2000

Pre versus Post 2000?

Something happening since 2000

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Scan statistic for 5 year window by Karyn Reeves and Mario D’Antuono.

Scan statistic for pre versus post 2000

Thank youVisit agric.wa.gov.au

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