The history of past hydroclimatic extreme events, essential information for predicting future changes, is preserved in fluvial sediments. Here, we reconstruct changes in decadal-scale extreme flooding events over the period 7700–1700 cal yr BP from floodplain sediments in the middle reach of the Nakdong River, Korea, based on lithogenic elemental ratios (e.g., Zr/Ti and Sr/Si). For example, Nakdong extreme flooding (NEF) events frequently occurred at 7700, 7200, 6000, 5000, 3800, 3200, 2900, 2600, 2300, 2000, and 1700 cal yr BP, and were associated with higher sea-surface temperatures and strong El Niño-Southern Oscillation (ENSO) activity. Notably, we found a significant change in the frequency of extreme events ca. 3700 cal yr BP over East Asia. The hydroclimate fluctuated with dominant periodicities of 950 and 540 years in 7700–3700 cal yr BP and shorter centennial to decadal cycles (320, 110–120, and 60–75 years) in 3700–1700 cal yr BP. This 3.7-ka climatic shift is consistent with a marked southward shift of the intertropical convergence zone, intensified ENSO activity, increased frequency of recurving typhoons, and deep-ocean circulation changes in both the northern and southern hemispheres, demonstrating the urgent need for investigating the critical role of past deep-water circulation in hydroclimate changes.

Fossil pollen analyses from northern Lake Malawi, southeast Africa, provide a high-resolution record of vegetation change during the Pleistocene/Holocene transition (~ 18–9 ka). Recent studies of local vegetation from lowland sites have reported contrasting rainfall signals during the Younger Dryas (YD). The Lake Malawi record tracks regional vegetation changes and allows comparison with other tropical African records identifying vegetation opening and local forest maintenance during the YD. Our record shows a gradual decline of afromontane vegetation at 18 ka. Around 14.5 ka, tropical seasonal forest and Zambezian miombo woodland became established. At ~ 13 ka, drier, more open formations gradually became prevalent. Although tropical seasonal forest taxa were still present in the watershed during the YD, this drought-intolerant forest type was likely restricted to areas of favorable edaphic conditions along permanent waterways. The establishment of drought-tolerant vegetation followed the reinforcement of southeasterly tradewinds resulting in a more pronounced dry winter season after ~ 11.8 ka. The onset of the driest, most open vegetation type was coincident with a lake low stand at the beginning of the Holocene. This study demonstrates the importance of global climate forcing and local geomorphological conditions in controlling vegetation distribution.

Cave sediments collected from Reflection Cave on the Vaca Plateau, Belize show variations in the δ13C values of their fulvic acids (FAs), which indicate periods of vegetation change caused by climatic and Maya influences during the late Holocene. The δ13C values range from − 27.11‰ to − 21.52‰, a shift of ∼ 5.59‰, which suggests fluctuating contributions of C3 and C4 plants throughout the last 2.5 ka, with C4 plant input reflecting periods of Maya agriculture. Maya activity in the study area occurred at different intensities from ∼ 2600 cal yr BP until ∼ 1500 cal yr BP, after which agricultural practices waned as the Maya depopulated the area. These changes in plant assemblages were in response to changes in available water resources, with increased aridity leading to the eventual abandonment of agricultural areas. The Ix Chel archaeological site, located in the study area, is a highland site that would have been among the first agricultural settlements to be affected during periods of aridity. During these periods, minimal water resources would have been available in this highly karstified, well-drained area, and supplemental groundwater extraction would have been difficult due to the extreme depth of the water table.

Nannofossil assemblages from core MD02-2510 provide a ~ 22 ka record of past oceanographic variability in Alfonso Basin (Gulf of California, east subtropical Pacific). In this area, environmental conditions depend on a monsoonal system heavily influenced by changes in the location of the ITCZ and nearby atmospheric pressure centers. To reconstruct nutricline depth and ENSO-like variability, two ecological indexes were calculated based on the relative abundance of the three dominant coccolith species. The late glacial period is characterized by intensified wind-driven upwelling, high primary productivity and La Niña-like conditions. An environmental shift occurs during the glacial–interglacial transition, El Niño-like conditions intensify, nutricline deepens and surface productivity declines. The late Holocene is characterized by a persistent increase in nutricline depth and dominance of El Niño-like conditions. The fluctuations in the composition of the coccolith assemblages can be related to orbital-scale fluctuations in the average position of the ITCZ. However, while the ENSO-like signal that overprints the record varies in response to orbital forcing, on suborbital time scales the relation between ENSO-like conditions and the average position of the ITCZ and the North Pacific High changes, suggesting that the development of persistent El Niño-like conditions is strongly dependent on the specific climatic background.

This study investigates changes in precipitation patterns and variations in paleoproductivity in the tropical Pacific region associated with the North American Monsoon, Intertropical Convergence Zone (ITCZ) latitudinal migration, and changes in insolation during the middle and late Holocene. Major and trace element records (Al, Ba, C, K, Si and Ti) and Zr/Al and Ba/Al ratios in a core from Alfonso Basin, southern Gulf of California, are used as proxies of terrigenous input and bio-productivity. Records reveal an increase in precipitation and low bio-productivity ca. 6200 to 2400 cal yr BP, associated with the strengthening of monsoonal precipitation and northward shift of the ITCZ mean position in the eastern tropical Pacific. A multi-centennial drought from ca. 2400 to 1900 cal yr BP, and a dry and cold interval ca. 700 and 500 cal yr BP, are characterized by strong aeolian input and enhanced productivity, associated with diminution of the summer monsoonal precipitation and reduced insolation in the Northern Hemisphere and more southerly ITCZ position. Correlation of Alfonso Basin records with other records in the Gulf of California and the Pigmy and Cariaco basins in the Gulf of Mexico and central Atlantic provides constraints on NAM, ITCZ migration, and insolation-driven changes.

The third millennium BP crisis of the central African rainforest is not sufficiently understood. The low resolution of most pollen profiles and a large plateau of the calibration curve aggravate the exact dating of the event, and its causal climatic parameters are debated. We present a high-resolution pollen profile from the swamp site Nyabessan in the southern Cameroonian rainforest, covering the period 3100-2300 cal yr BP. Between 3100 and 2500 cal yr BP, the climate was favourable for a regional evergreen forest with Caesalpiniaceae and Lophira and a local Raphia swamp forest. Around 2500/2400 cal yr BP, a significant decrease of mature forest and swamp forest taxa and an increase of pioneers indicate that the rain forest was seriously disturbed and replaced by secondary formations. The dominance of Trema orientalis, a pioneer well adapted to seasonal desiccation, points to a much more accentuated seasonality after 2500 cal yr BP, which seems to be linked to a southwards shift of the ITCZ during the northern hemisphere winter months. We propose that the rain forest crisis between 2500 and 2200 cal BP created favourable conditions for farming and paved the way for a major expansion of Bantu speaking populations.

In the tropical Indian Ocean, the Maldive Islands lack surface freshwater, so are unsuitable for dragonfly reproduction. Nevertheless, millions of dragonflies (Insecta, Odonata; mostly globe skimmer, Pantala flavescens) appear suddenly every year starting in October. Arrival dates in the Maldives and India demonstrate that the dragonflies travel from southern India, a distance of some 500–1000 km. Dates of arrival and occurrence coincide with the southward passage of the Inter-tropical Convergence Zone (ITCZ). Circumstantial evidence suggests that the dragonflies fly with north-easterly tail winds, within and behind the ITCZ, at altitudes over 1000 m. It is proposed that this massive movement of dragonflies is part of an annual migration across the western Indian Ocean from India to East Africa. Arrival dates in the Seychelles support this hypothesis. Dragonflies also appear (in smaller numbers) in the Maldives in May, with the onset of the southwest monsoon, suggesting a possible return migration from Africa. These proposed migrations of dragonflies, regularly crossing 3500 km or more of open ocean, were previously unknown. It is known that these dragonflies exploit ephemeral rain pools for reproduction; the monsoons and ITCZ bring not only alternating, seasonal rains to India and Africa, but also appropriate winds for dragonflies to follow those rains. Several bird species migrate from India across the western Indian Ocean to wintering grounds in Africa. They do so at the same time as the dragonflies, presumably taking advantage of the same seasonal tail winds. Many of these birds also eat dragonflies; the possible significance of this was not previously appreciated.