Issued 8 December 2020

Introduction

Using data from 1 January to 30 November 2020, we can summarise the year-to-date status of Australia's climate and water resources and provide an indication of the possible end of year values and rankings for Australia's mean annual temperature and area averaged rainfall.

What has the temperature been like?

Australia's maximum temperature for January to November was the fifth warmest on record. Maximum temperatures have been very much above average or above average across most of Australia except parts of the south-east of the mainland and northern Tasmania.

Australia's minimum temperature for January to November was the fourth warmest on record, with above average minimum temperatures generally across the same regions as for maximum temperature. Minimum temperatures were close to or below average for eastern South Australia, western Victoria and south-west New South Wales.

Mean temperatures for January to November were third-warmest on record for Australia as a whole. Most of the country saw very much above average mean temperatures, although parts of South Australia, Victoria and New South Wales had mean temperatures that were close to average.

The year started with large bushfires continuing across Victoria and New South Wales and extreme heat across eastern Australia in January. Temperatures were much cooler across the south-east in February and into autumn when several cold fronts brought cooler air over the region. May was the first month since October 2016 where Australia's mean temperature was below average. Winter saw a return to warm daytime temperatures. However, clear night skies and generally dry and settled conditions saw below average minimum temperatures over much of south-eastern Australia.

It was very warm across northern Australia during August and into spring. Australian mean spring temperature was +2.03 °C above average, the previous warmest spring was 2014, at +1.81 °C above average. Spring minimum temperatures were the warmest on record, at +1.91 °C above average, exceeding the previous warmest spring (1998) by 0.45 °C. Spring ended with a severe to extreme heatwave across much of eastern Australia.

Where has it rained?

For Australia as a whole, the January to November rainfall was 7 per cent below average. However, the distribution of the rain in 2020 was highly variable. Much of New South Wales, Victoria and eastern South Australia experienced above average rainfall. Most of south-west Western Australia, north-east New South Wales and south-east Queensland saw below average rainfall.

2020 started with long term rainfall deficiencies across much of southern Australia. February saw heavy rainfall, flooding and coastal erosion in New South Wales. Seven tropical cyclones affected the Australian region from January to April, with three crossing the coast (Blake, Damien and Esther). Tropical cyclone Esther made landfall in the Gulf Country near the Northern Territory and Queensland border at the end of February. Remnants of tropical cyclone Esther also brought flooding to Queensland and had impacts as far south as Victoria.

A succession of cold fronts continued to bring rain across southern Australia during autumn. Autumn rainfall for the Murray–Darling Basin was 22 per cent above average, and long-term rainfall deficiencies eased significantly across much of the Basin. However, early winter was relatively dry, with June being the third driest on record for Australia as a whole. South-west Western Australia saw very little rain during this period, adding to the multi-year rainfall deficiencies the region was already experiencing.

Dry conditions persisted over Australia for much of the April to October cool season period. However, there were several complex low-pressure systems in the Tasman Sea from July to October. These brought severe storms, flooding, and coastal erosion along parts of the New South Wales coast.

What does this mean for water storage?

The major water storages in the Murray–Darling Basin have seen some recovery in 2020 but remain low across most of the northern Basin. Following a record dry 2019, the total water storage across the Murray–Darling Basin was only 34% at the beginning of 2020, the lowest level since the end of the Millennium Drought. Total storage levels further declined to 31% in early February. Higher than average rainfall since February, particularly in the southern Basin where most of the water is stored, has resulted in an increase of more than 30% to 61% across Murray–Darling Basin at the end of November.

The total water storage level in the northern Murray–Darling Basin was extremely low at only 5.6% at the start of 2020. Levels have since risen to 25% by the end of November. Apart from Burrendong at 43.5% full, all of the larger storages in the northern Basin remain at less than 30%, with Split Rock in the Namoi valley at only 4.5%.

Water storage levels in northern Western Australia and the Northern Territory continued to fall in 2020. Water levels in Lake Argyle, the largest water supply storage in Australia, have been decreasing since September 2017. The past three wet seasons have not delivered significant inflows to the storage, reducing the water level to 25% of the accessible storage at the end of November 2020. The lack of wet season filling is also reflected at Darwin, with the Darwin River storage at the end of November 2020 at its lowest level in 10 years.

The Sydney water supply system saw water storage levels falling to 42% in January and filling to near capacity in August. They were at 94% in at the end of November 2020.

What is the outlook for the calendar year?

For Australia as a whole, January to November mean temperature was +1.24 °C above the 1961–1990 average, the third warmest on record. The outlook for December indicates maximum temperatures are likely to be above average in eastern Australia and along the coast, and below average in central Western Australia. Minimum temperatures are likely to be above average for almost all of Australia in December. Using year-to-date observations and climate outlooks for December, the 2020 calendar year will likely be in Australia's warmest five years on record.

Rainfall averaged across Australia is likely to be close to the 1961–1990 average (the United Nations World Meteorological Organization's standard reference period) for the calendar year. January to November rainfall was 7 per cent below average. The Outlook for December is for likely above rainfall in central Western Australia, northern Queensland and across the Top End of the Northern Territory.

What about the global climate?

Sea-surface temperatures in eastern the tropical Pacific Ocean cooled over 2020, with the Bureau declaring an active La Niña on 29 September. While La Niña can bring cooler and wetter conditions to Australia, the impact of each event is different. The 2020 La Niña so far has been of moderate strength and saw winter-spring rainfall exceed that of recent years. However, the exceptionally warm spring is somewhat unusual for a La Niña period, similar only to that experienced in the 1988–1989 event; October 1988 remains the second warmest October on record behind 2015.

Indian Ocean conditions have been neutral throughout much of 2020, following one of the strongest positive India Ocean Dipole events on record in 2019. The neutral Indian Ocean conditions in 2020 contrasts with the last La Niña event, in 2010-11, where a strong negative Indian Ocean Dipole contributed to heavy rainfall and widespread flooding in the spring/summer period.

On 2 December 2020 the World Meteorological Organization (WMO) released its provisional report on the State of the Global Climate in 2020. The WMO reported that 2020 is likely to be one of the three warmest years on record for the globe, with the warmest six years (including 2020) all being since 2015. The average global temperature in 2020 is likely to be around 1.2 degrees above the pre-industrial (1850–1900) level. Temperatures over land have been warming faster than over the ocean. The State of the Climate 2020 report, released by the Bureau and CSIRO in November, found that Australia’s climate has warmed on average by 1.44 ± 0.24 °C since national records began in 1910.