Scientists unearth Australia’s early historical records of droughts and flooding rains
source: University of Melbourne
The first snowfall recorded in Sydney since European settlement was reported in the Sydney Herald on 30 June 1836, and a previously undescribed severe drought gripped southeastern Australia from 1837–1842.
These are two of the fascinating findings in a world-first study by University climate researchers of Australia’s early settlement climate history.
In the study, researchers from the School of Earth Sciences have uncovered historical weather records as far back as 1788 in southeastern Australia, completing our understanding of Australia’s natural climate variability before the beginning of official records in 1910.
The records rescued by the research team paint a picture of the natural weather occurrences such as warm, cool, dry and wet conditions in this early settlement period. Before now, this information has been missing from our climate records and our nation’s history.
Dr Linden Ashcroft from the School of Earth Sciences explains the study is the first consolidated instrumental climate record of Australia’s most populated region and closes an important gap in our meteorological past.
“This study adds an extra 70 years to help our understanding of weather patterns. The research team set out to examine year to year fluctuations in temperature, pressure and rainfall to understand how factors like El Nino events have affected Australia’s climate in the past.
“Learning more about how these features behaved in the 1800s helps us understand how they may behave in the future, which is crucial for water security,” she says.
In their research published in the Geoscience Data Journal, Dr Ashcroft, Dr Joelle Gergis and Professor David Karoly have analysed instrumental weather observations rescued from 3400 pages from 39 historical sources, to reconstruct the climate experienced in the first 72 years of European settlement in Australia.
The new research by the team has drawn on the earliest instrumental observations of historical daily and monthly temperature, atmospheric pressure and rainfall observations included in thousands of pages of government gazettes, newspapers, farm records, and even First Fleet log books.
Dr Ashcroft describes how the records were analysed by the team.
“The weather observations were not taken using modern methods so we are unable to determine the exact temperature or pressure value for a certain day or year. However, our detailed data control and homogenisation shows the records are of surprisingly good quality for their age and can provide useful information on relative climate variability in Australia’s past.”
The records have revealed Australia’s early settlers experienced patterns of dry, wet and cold conditions. A prolonged drought period was identified in New South Wales from 1837 to 1843, yet wet conditions dominated Tasmania in the same period from 1836 to 1838. The first snowfalls in Sydney and Melbourne since early settlement were recorded during two severe cold weather periods.
Dr Ashcroft’s study complements previous work done by the University of Melbourne research team led by Dr Gergis, which last year used documentary records to identify 24 new drought years and 19 new wet periods in south-eastern Australia from 1788–1860.
This study was conducted as part of Dr Gergis’s SEARCH (South-Eastern Australia Recent Climate History) project, which won the 2014 University of New South Wales Eureka Prize for Excellence in Interdisciplinary Scientific Research for their success in mapping a thousand years of Australia’s climate history.
“Long-term weather records give water managers a complete data set to understand natural climate variability, and this data could help to inform climate modelling studies looking at the future,” Dr Ashcroft says.
