Seasonal conditions: September quarter 2020
Emma Pearce and Matthew Miller
Late forming La Niña emerges as key global climate influence of 2020–21
Climate conditions for global agriculture are correlated at different times of year with changes in leading indicators such as the El Niño–Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and the Southern Annular Mode (SAM). Both the ENSO and IOD are currently neutral. However, almost all models surveyed by the Bureau of Meteorology suggest the possibility of La Niña developing from September 2020.
La Niña conditions in the tropical Pacific are known to shift rainfall patterns in many different parts of the world. Although they vary somewhat from one La Niña to the next, the strongest shifts remain fairly consistent across regions and seasons (Figure 1).
La Niña has often been associated with wetter than average rainfall conditions in Australia, northern India, Indonesia, northern South America and parts of northern and southern Africa. Drier than average rainfall conditions are more likely in the southern United States and parts of east Africa, southern India, west Asia and southern and western South America.
La Niña is normally associated with higher than average winter, spring and early summer rainfall over much of Australia. Typically, across the southern hemisphere, La Niña events tend to begin in autumn, mature during winter, spring and early summer, and then begin to decay in late summer.
La Niña events that form in autumn have a more significant effect on agriculture in southern Australia than events that form later in the year. If a La Niña event were to establish during spring 2020 it is likely to benefit crop and pasture growth during the summer growing season across the northern half of Australia. This is supported by rainfall patterns seen across Australia during previous late forming La Niña events (2008–09 and 2011–12).
In addition to the enhanced likelihood of La Niña, there are warmer than average sea surface temperatures across large parts of the Indian Ocean. Of the 6 models surveyed by the Bureau of Meteorology, 4 suggest the possibility of a negative IOD developing in the Indian Ocean during spring. The IOD index has recently surpassed the negative IOD threshold but IOD values at or below –0.4 must be sustained for 8 weeks for this to be considered a negative IOD event. A negative IOD typically brings above average rainfall to southern Australia during spring. Although more than half of the models show that a negative IOD is possible, the individual models show a broad spread of likely scenarios covering both the neutral and negative IOD range.
Rainfall variable to date
Crop production is highly sensitive to climate. It is affected by long-term trends in average rainfall and temperature, inter-annual climate variability, shocks during specific growth stages, and extreme weather events (IPCC 2012). Some crops are more tolerant than others to certain types of stress. At each growth stage, different stresses affect each crop in different ways.
The rainfall anomalies and outlooks presented in this note give an indication of the current and future state of production conditions for major grain and oilseed-producing countries. These countries are responsible for over 80% of global production.
Rainfall from June to August tends to affect winter crop development and yield prospects across the southern hemisphere and starting soil moisture conditions for summer crops. In the northern hemisphere, June to August rainfall affects the development and yield prospects of spring wheat, canola crops and summer crops. It also influences farmers' planting intentions and opportunities for winter wheat and canola crops.
Rainfall over the 3 months to 31 August 2020 was variable for the world's major grain-producing and oilseed-producing regions. In the northern hemisphere, June to August 2020 rainfall was generally below the 1979 to 2000 average across parts of the European Union and Ukraine and in parts of the western plains of the United States. In contrast, rainfall was above average across the south-east of the United States, parts of Russia, India and west Asia. Dryness during May reduced soil moisture for winter grain and oilseed crops across many key growing areas surrounding the Black Sea, as well as across the European Union and the United Kingdom.
In the southern hemisphere, June to August 2020 rainfall was generally below the 1979 to 2000 average in southern Brazil, Central America and parts of eastern and western Australia.
Persistent dryness has limited the yield potential of second-crop maize in southern Brazil, but conditions were favourable in key production areas farther north. In Argentina, a dry May adversely affected winter grain crops in most major production areas and the reproductive development of soybeans. For Australia, above average rainfall during the first half of the year increased soil moisture levels and allowed timely planting of wheat, barley and canola.
Crop conditions mostly favourable
Global crop production conditions continue to be favourable despite mixed climatic conditions persisting across parts of the European Union, the United Kingdom, Ukraine, Argentina, Vietnam, China and the south of the Russian Federation. World production of wheat, maize, rice and soybean is expected to reach record levels in 2020–21.
In the southern hemisphere, conditions for wheat crops were generally favourable for Australia. As a result, production is expected to be average to above average. In Argentina, conditions remain mixed for crops leading up to harvest towards the end of 2020.
Production conditions have been more variable in the northern hemisphere. Dryness led to decreased winter wheat yields in the United Kingdom, the European Union, and southern growing regions of Ukraine and the Russian Federation. Conditions were generally favourable for winter wheat harvesting and spring wheat growth in Kazakhstan, Canada and the United States and spring wheat harvesting in China.
Global maize production is expected to reach record levels in 2020–21. Growing conditions for maize were generally favourable for harvest of the autumn–winter crop and for sowing of the spring–summer crop in Mexico. Harvest of the summer-planted crop was well underway in Brazil under mainly exceptional conditions, except for in the south where dry conditions have impacted crop development. Conditions were generally favourable for the United States, Canada, the European Union and India, although there were some mixed conditions due to dryness in parts of the United States, France, Ukraine and the Russian Federation and flooding in China.
Rice production is expected to reach a record level in 2020–21. Conditions were generally favourable for wet-season rice in Thailand, Japan and the Philippines and for the growth of single-season and late-season rice in China. In the United States, conditions were also favourable. The majority of rice transplanting in India was completed under favourable conditions. In Vietnam, conditions are generally favourable as planting continues in the north and harvest continues in the south. Yields in the south will be slightly reduced due to dry conditions. In Indonesia, the harvest of dry-season crops is ongoing. Yields have reduced due to a delayed rainfall onset. At the same time, dry-season crop sowing continues due to unusually high dry-season rainfall delaying planting.
Growing conditions for soybeans were generally favourable in the United States, Canada, Ukraine, China and India for crops due to be harvested in the northern hemisphere autumn, with some mixed conditions due to dryness in the United States and Ukraine. In Australia, growing conditions have been favourable for canola. Production is expected to rise to 3.4 million tonnes, slightly above the 10-year average to 2019–20.
Global climate outlook positive
The climate outlook for world agriculture is for average to above average rainfall between September and November 2020 for most of the world's major grain-producing and oilseed-producing regions. If realised, this is likely to benefit winter wheat and canola planting in the northern hemisphere and winter wheat and canola production in the southern hemisphere. Similarly, this is likely to benefit corn, soybeans, sunflower, millet, cotton, rice, peanut and sorghum production in the northern hemisphere and grain sorghum and cotton planting in the southern hemisphere.
The June to August rainfall percentiles and current production conditions show a marginal improvement from global conditions seen from March to May, which were used to formulate ABARES forecasts of global grain supplies and the impact on world prices in its June 2020 edition of Agricultural commodities. For country-by-country assessments of the climate outlook and potential impact on production conditions, see ABARES Weekly Australian climate, water and agricultural update–20 August 2020.
Australian production prospects good at the start of spring
The rainfall percentile, current production conditions and climate outlook data presented here were used to update ABARES forecasts of Australian food and fibre production for 2020–21.
Following above average rainfall during the January to April period, much of southern Australia recorded below average falls from May to July. Despite variable rainfall in June and July, close to average pasture growth rates and winter crop yield potentials were preserved across most southern Australian growing regions due to a drawdown of soil moisture reserves built up during late summer and autumn. Rainfall in August 2020 was average to above average across much of Australia. Substantial August rainfall improved soil moisture across much of Australia, supporting the final stages of winter crop development and providing a reliable base for the early planting of summer crops.
Reservoir storage levels have improved significantly in the Murray–Darling Basin water supply system. As at 3 September 2020 the current volume of water held in storage is 13,834 GL, which represents 55% of total capacity. This is 32% or 3,316 GL more than at the same time last year.
Nationally, plant growth conditions were generally average during the 2020 winter. Average to above average rainfall during August particularly benefited plant growth across southern Australia. Production prospects for winter crops are average to above average in most cropping regions at the beginning of spring. The area planted to summer crops is forecast to increase significantly in 2020–21 thanks to a favourable rainfall outlook for the spring–summer period.
For a more comprehensive assessment of the recent agricultural production conditions, the climate outlook and potential impact on production, see ABARES Weekly Australian climate, water and agricultural update–3 September 2020.
Australian agriculture – climate outlook
Early onset of the 2020–21 northern wet season is more likely
The Bureau of Meteorology's outlook (released on 27 August 2020) is for an early onset of the 2020–21 northern wet season. This reflects the potential development of a La Niña and a negative IOD during spring. The onset occurs when the total rainfall after 1 September reaches 50 millimetres, approximately the amount of rainfall required to stimulate plant growth. The onsets of the past two northern wet seasons were significantly delayed, reducing the summer growing season and recharge of water storages. An early onset of the 2020–21 northern wet season is likely to boost soil moisture and water storages, and benefit summer crop production and northern pasture growth.
Average or better rainfall likely for eastern cropping regions
The Bureau of Meteorology's climate outlook for September to November 2020 (released on 3 September 2020) suggests that the chance of exceeding the median spring rainfall is greater than 70% in most regions across the eastern half of Australia. In contrast, the chance of exceeding the median spring rainfall is less than 40% across parts of Western Australia. There are roughly equal chances of wetter or drier than average spring rainfall for the remainder of Western Australia.
The Bureau of Meteorology's forecast indicates a 75% chance of receiving between 50 and 200 millimetres across much of eastern Australia and parts of central, northern and far southern Australia. Lower rainfall totals between 25 and 50 millimetres are likely across parts of southern Western Australia and the remainder of central and northern Australia. These totals indicate that the onset of the northern wet season may occur in parts of central and eastern Queensland and much of the Northern Territory during October and November.
In many areas where soil moisture is close to average or better for this time of year, there is a high chance of recording September to November rainfall totals sufficient to sustain above average crop and pasture production through spring. There is a 75% chance of receiving between 100 and 200 millimetres of rainfall across most cropping regions in Queensland and between 50 and 200 millimetres across cropping regions in New South Wales, Victoria and South Australia.
The forecast indicates that Western Australia has a 75% chance of receiving rainfall of between 25 millimetres in the northern and central wheat belt and 100 millimetres in the eastern and southern wheat belt. These expected low 3-month rainfall totals in parts of the northern and central wheat belt are unlikely to sustain average crop production.
Except for parts of Western Australia, there is a high chance that spring 2020 rainfall will be around the seasonal median (between 1990 and 2012). If realised, this would deliver an excellent finish to the 2020 winter growing season across southern Australia and start of the summer growing season.
IPCC 2012, Managing the risks of extreme events and disasters to advance climate change adaptation, Intergovernmental Panel on Climate Change, Cambridge University Press, United Kingdom.
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