Climate Driver Update history
Climate drivers in the Pacific, Indian and Southern oceans and the Tropics

Sea surface temperatures (SSTs) for January 2024 were warmer than average across the tropical Pacific Ocean. Between 10°S and 10°N, SST anomalies were more than1. warmer than the long-term (1961–1990) average in most areas along the equator.

The extent and magnitude of warm anomalies across the equatorial Pacific has decreased east of the Date Line compared to December 2023, while warm anomalies increased west of the Date Line.

Warm SST anomalies also continued off most of the eastern Australian coast from central Queensland southwards and around Tasmania and include the Tasman Sea. When compared to December 2023, SST anomalies have increased over the Coral Sea region off the Queensland coast. Warm anomalies were also present through parts of the Southern Ocean south of Western Australia and have warmed further compared to December 2023. Small regions of cool than normal anomalies up to 1.2 °C were present in the Great Australian Bight.

In the Indian Ocean, cool anomalies were present off the Pilbara coast in Western Australia, with SST anomalies in a narrow band of along most the Western Australian coast having cooled when compared to December 2023. Warm anomalies persist in the Maritime Continent, particularly in the north of that region, with significant increase in warm SST anomalies occurring in a small region off the Sumatra coast, where anomalies were more than 2 °C warmer than they were compared to the previous month; this warming is in line with the decay of the 2023 positive IOD event.

The Bureau's long-range forecasts indicate warmer than average SSTs (reaching 1.2 °C warmer than average) will likely continue off the coast of northern and eastern Australia through till at least March.

For the week ending 4 February 2024, sea surface temperatures (SSTs) were warmer than average across the equatorial region of the tropical Pacific Ocean, with anomalies more than 1.2 °C warmer than average east of 160 °E along the equator. Large regions of warm anomalies between 0.8 °C and 2 °C extended across much of the off-equatorial South Pacific eastwards from Australia to French Polynesia at 160 °W.

Closer to Australia, warm SST anomalies of 1.2 °C to 2 °C extend across much of the western Pacific Ocean around Australia's eastern coastline, and patches of the Maritime Continent. SST anomalies more than 2 °C above average were also present in the Tasman Sea and south of Tasmania, and were also present off the coast of south-west Australia. Small regions close to the coast of the Great Australian Bight and off the western Pilbara coast have cool SST anomalies, up to 0.8 °C below average.

Compared to last fortnight, SSTs anomalies in the Great Australian Bight have warmed, while SST's off the north and west of the Australian coast and around much of the Maritime Continent have cooled. Warm anomalies in the South Pacific east of the Date Line and New Zealand have warmed further over the past fortnight.

The latest values of the three NINO indices for the week ending 4 February 2024 were: NINO3, +1.41 °C; NINO3.4, +1.40 °C; and NINO4, +1.32 °C.

Persistent NINO3 or NINO3.4 values warmer than +0.8 °C are typical of El Niño, while persistent values cooler than –0.8 °C typically indicate La Niña.

The 30–, 60– and 90-day Southern Oscillation Index (SOI) values for the period ending 4 February 2024 were +0.7, −1.2 and −2.7, respectively. All SOI values have declined compared to two weeks ago. This follows more frequent periods of low pressure anomalies over northern Australia over the last few weeks, with pressure patterns being close to normal over Tahiti recently following a period of higher than average pressure.

Trade winds for the 5 days ending 4 February 2024 were generally close to average over the western Pacific while trade winds were weaker than average over the central Pacific. Currently, the Madden–Julian Oscillation (MJO) is likely influencing winds across the central Pacific, as it is passes across the Pacific, leading to a region of weakened winds to the east of the Date Line.

During an El Niño event, there is typically a sustained weakening, or even reversal, of trade winds across much of the tropical Pacific.

The Madden–Julian Oscillation (MJO) is currently over the central Pacific Ocean. International climate models suggest it is likely to remain in the Pacific in the coming fortnight. At this time of year, when the MJO is over the central Pacific region, it may also weaken trade winds in the central to western Pacific. At this time of year, when the MJO is over the Western Pacific, the chance of above average rainfall typically reduces across northern Australia.

The Indian Ocean Dipole (IOD) index is +0.3 °C for the week ending 4 February 2024.

IOD events typically break down at the end of spring as the monsoon trough shifts south into the southern hemisphere. The breakdown this year has been later than usual, likely due to the strength of this event and the active El Niño. The IOD index has fallen below the +0.4 °C threshold at a weekly timescale for two consecutive weeks indicating the event has come to an end. International climate models surveyed by the Bureau suggest the IOD values will remain neutral until at least April.

Sea surface temperatures (SSTs) for the week ending 4 February were warmer than average across much of the western half of the tropical Indian Ocean, with warm anomalies extending in a band off the Horn of Africa coast south-eastward to waters south of Australia. Weaker warm anomalies were also present over much of the north-east part of the basin. Waters off the coast of Java, Indonesia have warmed steadily over the past two months,weakening the temperature gradient between the west and east of the tropical Indian Ocean that is characteristic of a positive IOD.

Outgoing Longwave Radiation (OLR) around the equatorial Date Line is currently below average (indicating increased cloudiness). OLR had been mostly below average since mid-September 2023, but has tended more positive since the start of 2024. This suggests that the atmospheric impacts of El Niño are weakening in the tropical Pacific.

Equatorial cloudiness near the Date Line typically increases during El Niño (negative OLR anomalies).

The 4-month sequence of equatorial Pacific sub-surface temperature anomalies (to 31 January 2024) shows warm anomalies across most of the top 50 m of the equatorial Pacific during January, with areas of cooler than average water between 100 and 200 m depth, extending across the basin to 100°W. Warm anomalies are greatest in magnitude, exceeding 3 °C warmer than average, in the far eastern Pacific between 130°W and 110°W. Cool anomalies reached more than 2 °C cooler than average across much of their extent.

Warm anomalies have persisted in the central and eastern Pacific between the surface and 200 m depth during October to December 2023, with patterns remaining similar. The depth of these warm anomalies has also slowly decreased over this period, and extend to only around 100 m depth during January. The magnitude and extent of cool anomalies has increased across the past few months. This sub-surface pattern of a layer of warmer than average waters above a layer of cooler than average waters is typical of the declining phase of El Niño.

For the 5 days ending 4 February 2024, sub-surface temperatures were more than 2 °C warmer than average across the top 50 m of the equatorial Pacific east of 140°W. Elsewhere, anomalies in the western and central Pacific were generally within 1 °C of average. An area of cool anomalies were present between around 100 and 200 m depth in the central equatorial Pacific, reaching more than 2 °C cooler than average.

Compared to last fortnight, the magnitude of warm anomalies in the central and eastern Pacific has decreased, while the area of cool anomalies below 100 m has moved slightly eastwards.

El Niño continues in the tropical Pacific Ocean. Model forecasts and observations indicate sea surface temperatures in the central tropical Pacific have peaked and are now declining. Sea surface temperatures in the tropical Pacific are expected to return to neutral El Niño–Southern Oscillation (ENSO) levels in the southern hemisphere autumn 2024. Most atmospheric indicators are close to normal levels, although trade winds have temporarily weakened in line with the passage of the Madden-Julian Oscillation through the region (see below).   

The Indian Ocean Dipole (IOD) has returned to neutral, with the latest weekly IOD index (to 4 February 2024) being below +0.4 °C (the positive IOD threshold) for the second consecutive week. IOD events typically break down as the monsoon trough shifts south into the southern hemisphere. Due to the strength of the positive IOD in 2023, the event decay has been later than usual. The majority of model forecasts indicate the IOD will be neutral until at least April, consistent with the annual cycle of the IOD.

The Southern Annular Mode (SAM) is currently neutral. Forecasts suggest it will remain mostly neutral over the coming fortnight. Neutral SAM has little influence on Australian rainfall patterns.

The Madden–Julian Oscillation (MJO) is currently over the central Pacific. International climate models suggest the MJO is likely to remain in the central Pacific during the coming fortnight. When the MJO is in the central Pacific region, it may also weaken trade winds in the central to western Pacific, which is likely to temporarily stall cooling SSTs associated with El Nino decline; SSTs across parts of the Pacific have indeed increased slightly over the past week.  

The World Meteorological Organization (WMO) has confirmed that 2023 was the warmest year on record. The WMO estimated global temperatures in 2023 were 1.45 ± 0.12 °C above the 1850–1900 average, exceeding the previous record warm years of 2016 and 2020, with 1.29 ± 0.12 °C and 1.27 ± 0.12°C respectively.

Global sea surface temperatures (SSTs) were highest on record for all respective months between April 2023 and January 2024.

Australia's climate has warmed by 1.48 ± 0.23 °C between 1910 and 2022, leading to an increase in the frequency of extreme heat events. In recent decades, there has also been a trend towards a greater proportion of rainfall from high intensity, short duration rainfall events, especially across northern Australia during the wet season.  

The Southern Annular Mode (SAM) is currently neutral. It is expected to become briefly positive in early February before returning to neutral. SAM has been positive for much of December 2023 and January 2024. During summer, positive SAM increases the chance of above average rainfall for parts of eastern NSW, south-eastern Queensland, eastern Victoria, and north-eastern Tasmania, but increases the chance of below average rainfall for western Tasmania. Rainfall increases are due to the positive SAM shifting westerly winds further south, increasing onshore flow over south-east Australia. Neutral SAM has little influence on Australian rainfall patterns.

International model forecasts and observations indicate warming of the equatorial Pacific has peaked and is now declining. Sea surface temperatures in the tropical Pacific are expected to return to neutral levels (neither El Niño nor La Niña) in the southern hemisphere autumn 2024. Six of seven models indicate a return to neutral by May, with the seventh model returning to neutral in June.