Drought · Amazon basin
The Amazon runs low
The Amazon's rivers rise and fall every year by ten metres and more: high water in the middle of the year, low water in October and November. In 2023 the low water came early and went far lower than ever. The dry season brought only about a third of its usual rain, and record heat dried the forest and the rivers further. On 26 October the Rio Negro at Manaus stood at 12.70 m, the lowest since the gauge was installed in 1902, almost a metre below the previous record of 2010. [S1]
July – November 2023 · Central Amazon, Brazil · ERA5
12.70m
The Rio Negro at Manaus, 26 October
The lowest since records began in 1902; the previous record was 13.63 m in 2010.S1
31%
Of normal rain at Manaus, July–October
162 mm in ERA5 against a 1991–2020 normal of 526 mm.
+1.8°C
October at Manaus
ERA5's monthly mean, 29.5 °C against a normal of 27.7 °C.
30×
More likely with climate change
For the drought as farmers and forests feel it, rain and heat together.S2
What happened
From July the rain over the central and northern Amazon fell far below normal, month after month. With little rain and strong sun, the heat built: across the basin the temperature reached records from September to November. The rivers fell fast. Boats that carry food, fuel and medicine to towns without roads ran aground; communities along the rivers were cut off, and fish died in shrinking, overheated lakes.S1S2
An El Niño was developing in the Pacific, which usually dries the Amazon. But World Weather Attribution found that climate change was the main driver: El Niño and warming each cut the rain by similar amounts, while the extreme heat that dried the land came almost entirely from warming. Together, they made a drought this severe about 30 times more likely.S2
| Month | Rain, mm | Normal, mm | Mean, °C | Normal, °C |
|---|---|---|---|---|
| July | 34 | 120 | 27.9 | 26.5 |
| August | 43 | 107 | 28.8 | 27.2 |
| September | 40 | 131 | 29.4 | 27.7 |
| October | 46 | 168 | 29.5 | 27.7 |
The missing rain
At Manaus the year has a long wet season from December to May and a drier season from June to November. In 2023 even the dry season's usual rain failed: ERA5 puts 162 mm from July to October against 526 mm in a normal year. The seasonal map shows the deficit across the whole centre of the basin.
Heat and dry ground
37.0°C
ERA5's highest temperature at Manaus on 28 October 2023. Every month from July to October was 1.4–1.8 °C warmer than normal; October's mean was the highest, 1.8 °C above.
Heat and drought feed each other. Dry soil cannot cool itself by evaporating water, so more of the sun's energy goes into heating the air; hotter air draws more water from the remaining soil and the leaves. In the rainforest this matters doubly: a large part of the Amazon's rain is water recycled by the forest itself.S1
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References
News
Studies and guidelines
- S1Espinoza, J.-C., et al. (2024). The new record of drought and warmth in the Amazon in 2023 related to regional and global climatic features. Scientific Reports, 14, 8107.The record low of the Rio Negro, the rain and the record warmth.
- S2World Weather Attribution (2024). Climate change, not El Niño, main driver of exceptional drought in highly vulnerable Amazon River Basin. 24 January 2024.How much climate change and El Niño contributed.