Claim ledger — el_nino.md

Effort tier: T2 (briefing). Ledger built during research; verbatim snippets captured at the point of reading. Class A = load-bearing (headline, table, chart or conclusion). Class B = supporting context. Class C = common knowledge.

Derived rows (D-prefixed) show inputs, operation and result rather than a source snippet, per the research standard for numbers computed rather than quoted.

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Sourced claims

ID	Claim as it appears in the draft	Verbatim source snippet	Source	URL	Accessed	Tier	Class
C1	CPC has carried an El Niño Advisory since 9 July 2026	“ENSO Alert System Status: El Niño Advisory” (header, issued 9 July 2026)	NOAA CPC ENSO Diagnostic Discussion	https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf	2026-08-01	1	A
C2	97% chance the event persists through early spring 2027	“El Niño continues and will strengthen through the end of the year, with a 97% chance it will persist through early spring 2027.”	NOAA CPC ENSO Diagnostic Discussion, 9 Jul 2026	as C1	2026-08-01	1	A
C3	81% chance of a very strong El Niño in Oct–Dec, ranking among the largest since 1950	“There is an 81% chance of a very strong El Niño during October-December (Fig. 8) that would rank among the largest El Niño events in the historical record going back to 1950.”	NOAA CPC ENSO Diagnostic Discussion, 9 Jul 2026	as C1	2026-08-01	1	A
C4	CPC quotes relative Niño 3.4 +1.2 °C, Niño-4 +0.5 °C, Niño-1+2 +2.7 °C	“The latest weekly Niño-3.4 index value was +1.2°C, with the westernmost (Niño-4) and easternmost (Niño-1+2) indices at +0.5°C and +2.7°C, respectively (Fig. 2).”	NOAA CPC ENSO Diagnostic Discussion, 9 Jul 2026	as C1	2026-08-01	1	A
C5	These are relative indices (tropical mean removed)	“Time series of area-averaged relative sea surface temperature (SST) anomalies (°C) in the Niño regions … minus tropical mean (20°N-20°S). The relative indices are re-scaled to match the variance of traditional indices.”	NOAA CPC ENSO Diagnostic Discussion, Fig. 2 caption	as C1	2026-08-01	1	A
C6	Conventional weekly Niño indices, week centred 22 Jul 2026: 1+2 +3.8, 3 +2.5, 3.4 +2.2, 4 +1.0	22JUL2026 25.4 3.8 28.1 2.5 29.3 2.2 29.8 1.0	NOAA CPC weekly SST data file (wksst9120.for)	https://www.cpc.ncep.noaa.gov/data/indices/wksst9120.for	2026-08-01	1	A
C7	Coupling supports high confidence in persistence	“a strong coupling of the atmospheric and oceanic circulation across the Pacific contributes to very high confidence that El Niño will continue through early 2027”	NOAA CPC ENSO Diagnostic Discussion, 9 Jul 2026	as C1	2026-08-01	1	A
C8	SOI significantly negative; convection displaced east, suppressed over Indonesia	“Convection was enhanced over the central and east-central equatorial Pacific and was suppressed over Indonesia (Fig. 5). The traditional and equatorial Southern Oscillation indices were significantly negative.”	NOAA CPC ENSO Diagnostic Discussion, 9 Jul 2026	as C1	2026-08-01	1	A
C9	Next CPC discussion 13 August 2026	“The next ENSO Diagnostics Discussion is scheduled for 13 August 2026.”	NOAA CPC ENSO Diagnostic Discussion, 9 Jul 2026	as C1	2026-08-01	1	B
C10	BoM: El Niño underway since mid-June	“El Niño has been underway since mid-June and continues to strengthen, with further intensification likely in the coming months.”	BoM Southern hemisphere monitoring, 28 Jul 2026	https://www.bom.gov.au/climate/enso/	2026-08-01	1	A
C11	BoM: most models put the peak among or above the highest since 1950	“The majority of models indicate this event is likely to peak at levels among, or above, the highest observed since 1950.”	BoM Southern hemisphere monitoring, 28 Jul 2026	as C10	2026-08-01	1	A
C12	BoM Relative Niño 3.4 +1.94 °C, week ending 26 July 2026 (threshold +0.8 °C)	“The latest Relative Niño3.4 index value for the week ending 26 July 2026 is +1.94 °C, well above the El Niño threshold (+0.80 °C).”	BoM Southern hemisphere monitoring	as C10	2026-08-01	1	A
C13	IOD index +0.44 °C, first week at the positive threshold	“As of 26 July 2026, the weekly IOD index is +0.44 °C, which is the first week that the index has reached the positive IOD threshold (+0.4 °C), with sustained values above this threshold required before an event is considered established.”	BoM Southern hemisphere monitoring	as C10	2026-08-01	1	A
C14	Models favour a positive IOD developing in winter, persisting into spring	“Models suggest a positive IOD may develop during the southern hemisphere winter and persist into spring, although there remains some variation in timing and strength.”	BoM Southern hemisphere monitoring	as C10	2026-08-01	1	A
C15	30-day SOI −28.0 to 26 July	“30-day SOI to 26 July at –28.0”	BoM Southern hemisphere monitoring	as C10	2026-08-01	1	A
C16	SAM index negative, forecast to remain so to early August	“The Southern Annular Mode index is negative and forecast to remain so until at least early August.”	BoM Southern hemisphere monitoring	as C10	2026-08-01	1	B
C17	BoM caveat: strong Niño 3.4 signal does not necessarily mean strong Australian impacts	“A strong El Niño signal in the Niño 3.4 region does not necessarily mean strong impacts on Australia’s climate; ENSO is only one of many factors.”	BoM Southern hemisphere monitoring	as C10	2026-08-01	1	A
C18	BoM Aug–Oct 2026 rainfall outlook	“Below average August to October rainfall likely across the south-west and east; above average in the north-west” (issued 30 July 2026)	BoM Australian long-range forecast	https://www.bom.gov.au/climate/ahead/outlooks/	2026-08-01	1	A
C19	BoM Aug–Oct 2026 temperature outlook	“Above average temperatures likely across much of Australia”	BoM Australian long-range forecast	as C18	2026-08-01	1	A
C20	>80% chance of unusually hot maxima in western WA and the south-east	“with strongest signals (over 80%) in western Western Australia and southeastern areas”	BoM Australian long-range forecast	as C18	2026-08-01	1	B
C21	Winter crop production forecast −21% to 54.5 Mt in 2026–27	“National winter crop production is forecast to decrease 21% to 54.5 million tonnes in 2026–27, reflecting an expected fall in the total area planted and lower yields.”	ABARES Australian Crop Report June 2026 No. 218	https://www.agriculture.gov.au/abares/research-topics/agricultural-outlook/australian-crop-report/june-2026	2026-08-01	1	A
C22	Wheat −26% to 26.7 Mt; barley −15% to 14.1 Mt; canola −20% to 6.2 Mt	“Wheat production is forecast to fall by 26% to 26.7 million tonnes in 2026–27 … Barley production is forecast to fall by 15% to 14.1 million tonnes … Canola production is forecast to fall by 20% to 6.2 million tonnes”	ABARES Crop Report June 2026	as C21	2026-08-01	1	A
C23	NSW winter crop −37% to 11.7 Mt	“Winter crop production in New South Wales is forecast to decrease by 37% to 11.7 million tonnes in 2026–27”	ABARES Crop Report June 2026	as C21	2026-08-01	1	A
C24	Queensland winter crop −38% to 2.4 Mt	“Winter crop production in Queensland is forecast to fall by 38% to 2.4 million tonnes in 2026–27.”	ABARES Crop Report June 2026	as C21	2026-08-01	1	A
C25	WA winter crop −21% to 21.5 Mt	“Winter crop production in Western Australia is forecast to fall by 21% to 21.5 million tonnes in 2026–27, compared to the record production levels achieved in 2025–26.”	ABARES Crop Report June 2026	as C21	2026-08-01	1	A
C26	Victoria −4% to 9.7 Mt; SA stable at 9.1 Mt	“Winter crop production in Victoria is forecast to reach 9.7 million tonnes in 2026–27, down by 4% from 2025–26” / “Winter crop production in South Australia is forecast to remain stable at 9.1 million tonnes in 2026–27”	ABARES Crop Report June 2026	as C21	2026-08-01	1	A
C27	Northern NSW / southern Qld extremely dry to mid-May; below 20th percentile	“Extremely dry conditions across northern New South Wales and southern Queensland up until mid-May had resulted in very low soil moisture levels.” / “Rainfall across the Northwest, Northern Tablelands, Central West and northern parts of the Riverina around Griffith has been below the 20th percentile in the year to mid-May”	ABARES Crop Report June 2026	as C21	2026-08-01	1	A
C28	Southern cropping regions had average to very much above average Feb–Apr rain	“average to very much above average February to April rainfall across major cropping regions of southern Western Australia, South Australia and Victoria has incentivised growers to go ahead with winter cropping programs”	ABARES Crop Report June 2026	as C21	2026-08-01	1	A
C29	ABARES forecast built on the BoM outlook issued 21 May 2026 (60–80% chance of below-average winter rain)	“According to the three-month outlook (June to August), issued by the Bureau of Meteorology on 21 May 2026, there is a 60% to 80% chance that winter rainfall will be below average across cropping regions in Queensland, New South Wales, Victoria, South Australia and Western Australia.”	ABARES Crop Report June 2026	as C21	2026-08-01	1	A
C30	ABARES noted only an “increasing chance” of El Niño/pIOD at time of writing	“there is below-average winter rainfall forecast and an increasing chance of an El Nino and/or positive IOD event emerging throughout 2026”	ABARES Crop Report June 2026	as C21	2026-08-01	1	A
C31	Wheat area −12% to 10.9 Mha, smallest since 2019–20	“Area planted to wheat is forecast to fall by 12% to 10.9 million hectares, the smallest area planted since 2019–20”	ABARES Crop Report June 2026	as C21	2026-08-01	1	B
C32	2002–03: farm GDP −24.8%, ~0.9pp off GDP growth	“Farm Gross Domestic Product fell by 24.8 percent, directly subtracting 0.9 of a percentage point from overall GDP growth”	Australian Treasury, Economic Roundup Autumn 2004	https://treasury.gov.au/publication/economic-roundup-autumn-2004/the-impact-of-the-2002-drought-on-the-economy-and-agricultural-employment	2026-08-01	1	A
C33	2006–07: wheat, barley, canola down >60%; growth impact 0.5–0.75pp	“The nation’s wheat, barley and canola production were expected to fall by over 60% in 2006-07” / “believed to contract economic growth in the country by 0.75 percentage points”	Secondary reporting of ABARE/ABS estimates	—	2026-08-01	3	B
C34	Black Summer: 33 direct deaths, ~417 smoke-attributable deaths, >3,000 homes, ~24 Mha	“As many as 417 people died from bush fire smoke-induced health impacts and thousands more hospitalized”	Grattan Institute submission to the Royal Commission	https://grattan.edu.au/wp-content/uploads/2020/04/Grattan-Institute-submission-to-Royal-Commission.pdf	2026-08-01	2	A
C35	Monsoon onset 2–6 weeks later in El Niño years; fewer cyclones, later first crossing	“the date of the monsoon onset in tropical Australia is generally 2–6 weeks later during El Niño years than in La Niña years” / “during El Niño, the number of tropical cyclones is often below average, and the first coastal crossing can occur as late as mid-January”	BoM, What is El Niño and what might it mean for Australia?	https://www.bom.gov.au/climate/updates/articles/a008-el-nino-and-australia.shtml	2026-08-01	1	A
C36	SAM: positive phase drier southern Australia in winter, wetter east coast in summer	“During a positive SAM phase, there is higher chance of southern Australia experiencing dry conditions in winter, and a possibility for increased rainfall along the east coast in winter and summer.”	BoM, Southern Annular Mode	https://www.bom.gov.au/climate/sam/	2026-08-01	1	A
C37	2015–16 El Niño triggered the worst GBR bleaching recorded at that time	“In 2015/16, unusually high ocean temperatures associated with one of the strongest El Niño events on record triggered an unprecedented global coral reef crisis, initiating what would become the third documented global mass bleaching event.”	AIMS, coral bleaching events	https://www.aims.gov.au/research-topics/environmental-issues/coral-bleaching/coral-bleaching-events	2026-08-01	2	B
C38	AFAC Winter 2026 outlook: increased risk in northern Great Sandy Desert (WA) and central/northern NSW	“AFAC predicted an increased risk of fire across the northern parts of the Great Sandy Desert and surrounds in Western Australia, and parts of central and northern New South Wales”	AFAC Seasonal Bushfire Outlook Winter 2026	https://www.afac.com.au/public-resources/seasonal-bushfire-outlook-winter-2026	2026-08-01	2	B
C39	Menindee 33%, Blowering 25%, Wyangala 61%; SA opening allocation projection 62%	“The Menindee Lakes system … is at 33 per cent and falling. Blowering Dam … is at 25 per cent. Wyangala Dam … is steady at 61 per cent.” / “The projected opening allocation of 62 per cent assumes South Australia will receive 1,246 gigalitres”	Australian Rural & Regional News, 25 May 2026	https://arr.news/2026/05/25/murray-darling-water-allocations-where-things-stand-heading-into-winter-2026/	2026-08-01	3	B
C40	CP (Modoki) events historically drier for eastern Australia per unit Niño 3.4	Established finding in the cited literature; note relies on the papers’ central result rather than a single quoted sentence	Wang & Hendon (2007) J. Climate 20:4211; Taschetto & England (2009) J. Climate 22:3167	doi:10.1175/JCLI4228.1; doi:10.1175/2008JCLI2589.1	2026-08-01	2	B

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Derived figures (author calculations)

All computed from BoM area-averaged series, NOAA CPC ONI, NOAA PSL DMI, CPC AAO and GPCC v2020. Scripts: fetch_bom.py, analyse2.py, analyse3.py, gridded.py.

ID	Claim	Computation	Class
D1	24 El Niño events 1951–2023; 5 very strong	CPC rule (≥5 consecutive overlapping seasons with ONI ≥ +0.5) applied to oni.ascii.txt; very strong = peak ONI ≥ 2.0 → 1972, 1982, 1997, 2015, 2023	A
D2	Australian spring rainfall composite 73% of baseline; below normal in 92% of events	Mean over 24 onset years of (SON rainfall ÷ 31-yr centred rolling mean × 100) for region aus = 72.76; share of those years < 100 = 22/24 = 91.7%	A
D3	Regional spring composites: NT 64, Qld 65, SA 74, MDB 75, NSW 76, WA 80, Vic 83, Tas 91	Same operation per BoM region; values 64.03, 65.21, 73.62, 75.01, 76.14, 79.68, 82.65, 90.64	A
D4	Winter composites: Qld 64, NT 68, MDB 81, NSW 82, Vic 92, SA 93, WA 94, Tas 97	Same for JJA (period code 0608); values 63.85, 67.86, 81.47, 81.82, 92.18, 93.07, 94.22, 96.64	A
D5	Summer composites: WA 77 (88% of events dry), SA 83, NT 85, Qld 91, NSW 94, MDB 95, Vic 95, Tas 98	Same for DJF (period code 1202); WA = 77.39, share dry 21/24 = 87.5%	A
D6	corr(spring Niño 3.4, Australian spring rainfall) = −0.04, r² 0.00	Pearson correlation over 24 events of SON ONI against detrended aus SON rainfall %; eastern Australia −0.03, MDB −0.01	A
D7	corr(spring Niño 3.4, Australian spring Tmax) = +0.42, r² 0.18	Pearson correlation over the same 24 events against detrended aus SON Tmax anomaly	A
D8	Spring Tmax detrended composite: Aus +0.41, MDB +0.63, NSW +0.62 °C	Mean over 24 onset years of (SON Tmax − 31-yr centred rolling mean)	A
D9	Very strong events, spring Tmax vs 1961–90: NSW +2.07, MDB +2.07, Vic +1.71, SA +1.60, WA +1.46, Qld +0.97, Tas +0.96, NT +0.73 °C	Mean over 1972/1982/1997/2015/2023 of (SON Tmax − mean of 1961–90)	A
D10	ENSO share of that total ranges 29% (NT) to 75% (Tas)	D8 very-strong subset ÷ D9, per region: NT 0.21/0.73 = 29%; Tas 0.73/0.96 = 76%; NSW 1.29/2.07 = 62%	A
D11	IOD interaction table (Section 3.3), all cells — corrected 2026-08-03	Mean detrended SON rainfall % by (El Niño year? × SON DMI ≥ +0.4 °C?), 1950–2025; n = 8 / 16 / 52. Values as [El Niño+pIOD, El Niño no pIOD, gap, no El Niño]: Vic [68, 90, −22, 110]; SA [60, 81, −21, 114]; Tas [82, 95, −13, 105]; MDB [68, 78, −10, 114]; NSW [73, 78, −5, 113]; WA [78, 81, −3, 109]; NT [62, 65, −3, 119]; Qld [65, 65, −1, 117]. pIOD springs: 1972, 1982, 1994, 1997, 2006, 2018, 2019, 2023	A
D11f	Robustness of D11 at a +0.25 °C threshold (n=11 vs 13)	Vic 68 vs 95 (−27); SA 56 vs 89 (−33); MDB 67 vs 82 (−15); Qld 60 vs 69 (−9). Same ordering, larger southern gaps	A
D11g	Superseded values from the tercile split (do not reuse)	Vic 72 vs 104; MDB 67 vs 92; Qld 61 vs 74; threshold −0.06 °C. Retained here only so the correction is auditable	—
D11b	Gridded box table (Section 5), all cells — recomputed from AGCD 2026-08-03	Cosine-weighted, land-masked box means of the per-cell median: [rainfall % of average, share of events below normal, spring Tmax anomaly °C]. NE Aus [43, 90, +0.17]; N Aus [55, 83, +0.16]; E Aus [59, 79, +0.51]; NW WA [63, 75, +0.35]; S Aus [70, 73, +0.53]; SE Aus [72, 74, +0.41]; SW WA [84, 65, +0.46]. Prior GPCC values (49, 56, 61, 61, 71, 72, 83) agree within 2–6 pp — an independent cross-check, both retained in the working files	A
D11c	Very-strong-event spring rainfall column (Section 4.4)	Mean over 1972/1982/1997/2015/2023 of detrended SON rainfall %: NT 65, Qld 76, SA 68, MDB 78, NSW 84, WA 83, Vic 70, Tas 71, Australia 75	A
D11d	Selected-event table (Section 4.3)	Spring Niño 3.4 / Australian spring rainfall %: 1997–98 2.33/98; 2015–16 2.47/65; 1982–83 1.97/63; 2023–24 1.83/72; 2002–03 1.21/52; 2006–07 0.77/52; 2019–20 0.39/35; 1976–77 0.81/126	A
D11e	Share-of-events-below-normal column (Section 4.4)	NT 88%, Qld 92%, SA 79%, MDB 79%, NSW 75%, WA 79%, Vic 79%, Tas 75%, Australia 92%	A
D12	corr(SON ONI, SON DMI) = +0.55 (n=76); corr(SON ONI, SON SAM) = −0.25 (n=47)	Pearson correlations, 1950–2025 and 1979–2025 respectively	A
D13	SAM spring spread: Australia 121% (upper tercile) vs 81% (lower); non-El Niño years 128% vs 92%	Mean detrended SON rainfall % by SON AAO tercile, 1979–2025, n = 16/15/16 all years and 14/10/10 excluding El Niño years. NSW all years 125 vs 75; non-El Niño 131 vs 83. Tasmania reversed: all years 94 vs 108; non-El Niño 99 vs 114	A
D14	Gridded boxes: NE Aus 49% and 89% of events dry; SW WA 83% and 66%	Cosine-latitude-weighted mean over each box of the per-cell median (23 events) and per-cell share below 100	A
D15	Flavour split 17 EP / 7 CP; CP winter Qld 54% vs EP 68%	Classified by whether SON Niño 3 > SON Niño 4 anomaly (PSL ERSSTv6); composites as D4 restricted to each subset	B
D16	2019 had the highest SON DMI in the sample (+0.90) and the driest Australian spring (35%)	From elnino_events_full.csv and D2 series	A
D17	Southern states supply 40.3 Mt of the 54.5 Mt national crop forecast	WA 21.5 + Vic 9.7 + SA 9.1 = 40.3 Mt (C25, C26)	B
D18	The IOD shift is worth ~10pp of MDB and ~22pp of Victorian spring rainfall — corrected 2026-08-03	From D11: MDB 78 − 68 = 10pp; Vic 90 − 68 = 22pp. Superseded figures were 25pp and 32pp, from the tercile split (D11g)	A

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Additional claims — el_nino_treasurer_brief.md

ID	Claim as it appears in the draft	Verbatim source snippet	Source	URL	Accessed	Tier	Class
T1	Gross value of agricultural production forecast −5% to $98.3bn in 2026–27	“Gross value of agricultural production to fall by 5% to $98.3 billion in 2026–27.”	ABARES Agricultural Commodities Report, June Quarter 2026	https://www.agriculture.gov.au/abares/research-topics/agricultural-outlook/june-2026	2026-08-01	1	A
T2	Agricultural export value −9% to $74.8bn	“Agricultural export value to fall by 9% to $74.8 billion driven by lower livestock product and crop exports.”	ABARES Ag Commodities June 2026	as T1	2026-08-01	1	A
T3	Average broadacre farm business profit −70%	“Average broadacre farm business profit to fall by 70% driven by lower revenue and higher input prices.”	ABARES Ag Commodities June 2026	as T1	2026-08-01	1	A
T4	Crop production value −8% to $50.9bn; crop exports −10% to $37.0bn, volumes offset by higher prices	“Total value of Australian crop production to fall by 8% in 2026–27 to $50.9 billion. Value of crop exports to fall by 10% to $37.0 billion as lower volumes are expected to offset higher prices. Domestic grain prices to rise in 2026–27”	ABARES Ag Commodities June 2026	as T1	2026-08-01	1	A
T5	Livestock and livestock product value −2% to $47bn; exports −7% to $38bn	“Gross value of livestock and livestock product production to fall by 2% to $47 billion in 2026–27.” / “Value of livestock and livestock product exports to fall by 7% in 2026–27 to $38 billion.”	ABARES Ag Commodities June 2026	as T1	2026-08-01	1	B
T6	Global grains and oilseeds production at a record high in 2025–26	“Total global grains and oilseeds production is expected to reach a new record high in 2025–26.”	ABARES Ag Commodities June 2026	as T1	2026-08-01	1	B
T7	Current crop forecast is 4% above the 10-year average and the 7th largest on record	“winter crop production is expected to remain 4% higher than the 10-year average in 2026–27 and would be the 7th largest winter crop on record”	ABARES Crop Report June 2026	see C21	2026-08-01	1	A
T8	National Bushfire Recovery Fund $2bn, plus $691.2m through existing disaster support mechanisms	“On 6 January 2020, the Prime Minister announced the establishment of the National Bushfire Recovery Agency (NBRA) and the $2 billion National Bushfire Recovery Fund.” / “As well as the commitment of $2 billion for the Fund, the Australian Government has also provided an additional $691.2 million in funding through other existing disaster support funding mechanisms (for example, disaster recovery payments and allowances for individuals).”	ANAO, Administration of the National Bushfire Recovery Agency	https://www.anao.gov.au/work/performance-audit/administration-the-national-bushfire-recovery-agency	2026-08-01	1	A
T9	Future Drought Fund $519.1m over 8 years	“invested a record $519.1 million in Future Drought Fund programs”	Prime Minister of Australia media release	https://www.pm.gov.au/media/519-million-boost-help-farmers-mitigate-impacts-drought	2026-08-01	1	A
T10	2018–19 response included $297m Drought Communities Programme Extension and $148.5m household support round	“$297 million was provided over four years from 2018-19 for the Drought Communities Programme Extension” / “$148.5 million for Round 2 of the Drought Community Support Initiative”	Commonwealth drought programme documentation	https://www.infrastructure.gov.au/territories-regions-cities/regional-australia/regional-and-community-programs/drought-programs	2026-08-01	2	B
T11	Farm Management Deposits are deductible when made, assessable when withdrawn; drought triggers early access	“If any FMDs that you have previously claimed as a tax deduction are repaid, they are treated as assessable income in the income year they’re made.” / “Funds must be held for at least 12 months unless extraordinary circumstances—like drought, natural disaster or severe personal hardship—require early access.”	Australian Taxation Office, FMD scheme	https://www.ato.gov.au/businesses-and-organisations/income-deductions-and-concessions/primary-producers/managing-varying-income/farm-management-deposits-scheme	2026-08-01	1	A
T12	Agriculture value added is around 2% of GDP	“The latest value from 2024 is 2.04 percent” (agriculture share of GDP); World Bank reports 2.22% for agriculture, forestry and fishing in 2024	World Bank via TheGlobalEconomy	https://www.theglobaleconomy.com/Australia/share_of_agriculture/	2026-08-01	2	A

Derived — Treasurer brief

ID	Claim	Computation	Class
TD1	Southern states supply 40.3 Mt of the 54.5 Mt national forecast	WA 21.5 + Vic 9.7 + SA 9.1 = 40.3 Mt (C25, C26)	A
TD2	Scenario B: a 20% southern haircut takes the national crop to ~46–48 Mt	40.3 × 0.20 = 8.1 Mt; 54.5 − 8.1 = 46.4 Mt	A (judgement — the 15–25% yield-loss range is an assumption, not a modelled elasticity)
TD3	Scenario C: a 35% southern haircut takes it below 40 Mt	40.3 × 0.35 = 14.1 Mt; 54.5 − 14.1 = 40.4 Mt, before further northern losses	A (judgement, as TD2)
TD4	Farm GDP was ~3.6% of GDP in 2002–03	Treasury: farm GDP −24.8% subtracted 0.9pp from growth → 0.9 ÷ 0.248 = 3.63%	A
TD5	The same proportional collapse today would subtract ~0.5pp	0.248 × 2.04% = 0.51pp, using the 2024 agriculture share (T12)	A
TD6	The Black Summer response was roughly five times the Future Drought Fund commitment	(2,000 + 691.2) ÷ 519.1 = 5.2×	B
TD7	Scenario weights 45 / 40 / 15	Judgement. Anchored on: 16 of 24 historical El Niño events fell in the top IOD tercile (D11), BoM’s statement that models favour a positive IOD, and the historical frequency of 2002/2006-severity outcomes (roughly 3 of 24 events). Not a model output.	A (judgement)
TD9	El Niño adds a further ~15% from here; more than half the peak-to-trough loss is already booked	Implied 2025–26 base = 54.5 ÷ (1 − 0.21) = 69.0 Mt. Scenario B = 46.4 Mt (TD2). Incremental fall from 54.5 = 14.8%. Peak-to-trough = (69.0 − 46.4) ÷ 69.0 = 32.7%; the booked 21% is 64% of that.	A
TD8	Incremental GDP effect of 0.1–0.3pp (Scenario B), 0.3–0.5pp (Scenario C)	Scaled from TD5: Scenario C approximates a 2002-magnitude farm-sector collapse at today’s sector share (~0.5pp); Scenario B is roughly half that. Order-of-magnitude only.	A (judgement)

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Deviation log

Check	Result
CPC Niño 3.4 value	Deviation found and corrected. An initial automated extraction of the CPC discussion returned “+1.2 °C” without noting it was a relative index, while a secondary source reported “+2.1 °C” for the same period. Both were correct against different definitions. Resolved by reading the source PDF directly (C4, C5) and cross-checking the raw weekly data file (C6). The distinction is now explained in Section 1.2 rather than buried.
IRI/CPC model plume probabilities	Claim dropped. An automated read of the IRI Quick Look returned 100% El Niño probabilities for six consecutive seasons and “23 of 26 models”. These could not be confirmed against the source and are not used. Probability statements rest on C2 and C3 (CPC) and C11 (BoM) instead.
Gridded temperature composite	Dataset excluded. GHCN-CAMS SON temperature composites gave a negative anomaly for northern Australia, contradicting the BoM station-based series (D8). Attributed to sparse station density; the gridded temperature product is not used for any quoted figure or chart.
Arid-cell skew in gridded rainfall	Method changed. Composite mean of percent-of-baseline gave northern Australia 63% with only 42% of events below normal — internally inconsistent, caused by right-skew in low-rainfall cells and by NaN cells counting as “not dry”. Switched to per-cell median and explicit NaN masking; results (56%, 83%) then agree with the BoM state series.
IOD threshold	Method changed, then corrected. The conventional +0.4 °C threshold applied to the HadISST long DMI selected only 9 of 76 spring seasons, leaving n=1 in the “positive IOD, no El Niño” cell. The first version switched to terciles to fill that cell. That was an error: the series is centred at −0.17 °C, so the upper tercile begins at −0.06 °C, and a group labelled “upper-third IOD” was in substance “IOD above about zero” — which a reader would take to mean a positive IOD event. Reverted to the +0.4 °C threshold on 2026-08-03, with the unusable cell omitted rather than estimated, and a robustness check added at +0.25 °C. Direction of the finding unchanged; southern magnitudes fall (Victoria 32 pp → 22 pp; Murray-Darling 25 pp → 10 pp) and Queensland’s small gap becomes no gap (13 pp → 1 pp), which sharpens the north-south contrast. Discovered while building the gridded maps.
Gridded IOD map	Figure dropped. A three-panel map splitting the spring composite by IOD state was built and discarded: AGCD ends at 2020, leaving only 7 positive-IOD events, and the per-cell difference field was dominated by noise in the arid interior. The area-averaged signal is consistent (Victoria −19 pp, SW WA −15 pp on the same data), so the finding stands — the map was simply the wrong instrument for it, and the bar chart is retained instead.
Gridded product	Upgraded. The first version mapped GPCC v2020 at 1°. Replaced on 2026-08-03 with BoM AGCD v1 at 5 km (aggregated to 0.25°), which is the authoritative Australian analysis and carries temperature as well as rainfall. GPCC retained as an independent cross-check; the two agree within 2–6 pp on every region box. AGCD interpolates over ocean rather than masking it — an ocean-coloured first draft caught this — so a Natural Earth land mask is now applied before any plotting or averaging.
Chart title accuracy	Corrected. A draft figure title read “Most of the heat in a modern El Niño spring is not the El Niño”. D10 shows the ENSO share exceeds half in 6 of 8 regions, so the claim was false for most of the country. Title changed to state the size of the baseline shift instead.
BoM source access	www.bom.gov.au returns HTTP 403 to non-browser clients. All BoM material retrieved from reg.bom.gov.au, which serves identical files. Noted in Section 10.

Outstanding

• C33 (2006–07 economic impact) rests on secondary reporting of ABARE/ABS estimates rather than the primary documents. Class B; worth replacing with the ABARE Australian Commodities issue or the ABS national accounts release before any of this is republished.
• C39 (storage percentages) is a Tier 3 source. Primary data are available at mdbwip.bom.gov.au and should be substituted if these numbers become load-bearing.
• No blind claim audit has been run. At T2 this is required for Class A claims; it has not yet been done for this note.