Warming and Cooling: The Medieval Climate Anomaly in Africa and Arabia

Abstract

The Medieval Climate Anomaly (MCA) is a well‐recognized climate perturbation in many parts of the world, with a core period of 1000–1200 Common Era. Here we present a palaeotemperature synthesis for the MCA in Africa and Arabia, based on 44 published localities. The data sets have been thoroughly correlated and the MCA trends palaeoclimatologically mapped. The vast majority of available Afro‐Arabian onshore sites suggest a warm MCA, with the exception of the southern Levant where the MCA appears to have been cold. MCA cooling has also been documented in many segments of the circum‐Africa‐Arabian upwelling systems, as a result of changes in the wind systems which were leading to an intensification of cold water upwelling. Offshore cores from outside upwelling systems mostly show warm MCA conditions. The most likely key drivers of the observed medieval climate change are solar forcing and ocean cycles. Conspicuous cold spikes during the earliest and latest MCA may help to discriminate between solar (Oort Minimum) and ocean cycle (Atlantic Multidecadal Oscillation, AMO) influence. Compared to its large share of nearly one quarter of the world's landmass, data from Africa and Arabia are significantly underrepresented in global temperature reconstructions of the past 2,000 years. Onshore data are still absent for most regions in Africa and Arabia, except for regional data clusters in Morocco, South Africa, the East African Rift, and the Levant coast. In order to reconstruct land palaeotemperatures more robustly over Africa and Arabia, a systematic research program is needed.

Vegetation and climate change during the Medieval Climate Anomaly and the Little Ice Age on the southern Cape coast of South Africa: Pollen evidence from Bo Langvlei

“…In terms of temperature, Stoebe-type pollen is present at minimum values from c. AD 900 to AD 950, increases slightly until ~AD 1180, and then declines as Afrotemperate forest pollen increases in abundance. This potential indication of slightly cooler conditions around this time runs counter to some other studies (Lüning et al, 2017;Tyson and Lindesay, 1992) rooting grass and thus drier conditions) and grey-scale records from Cold Air Cave (Holmgren et al, 2003;Lee-Thorp et al, 2001), this cooling may be associated with weakened tropical influence in eastern South Africa and the southern Cape. Concurrent indications of increased precipitation at Verlorenvlei in the Western Cape (Stager et al, 2012) and more humid conditions at nearby Seweweekspoort (Chase et al, 2013(Chase et al, , 2017 may suggest the increased influence of temperate circulation systems at this time, supporting the model of an coeval inverse relationship between temperate and tropical circulation systems in South Africa (Cockroft et al, 1987;Van Zinderen Bakker, 1976).…”

The Medieval Climate Anomaly in the Mediterranean Region

“…The cooling from 1300 CE may be a delayed response to the solar Wolf Minimum and/or the decline in the NAO and AMO (Figure ). MCA cooling recorded in the marine cores GeoB6008 (site AA5) and OC437‐7 (site AA7) reflects intensified upwelling in the Canary Current Upwelling System rather than a wider regional climatic response (Lüning et al, ). With the exception of the mentioned Moroccan sites, MCA palaeotemperature information in North Africa is lacking, which indicates the urgent need for more palaeoclimatological work here (Figures and ).…”

“…A total of 79 Mediterranean localities were identified (Figure 2 and Tables 1 and S1). This Mediterranean review forms part of an attempt to palaeoclimatically map the MCA on a global scale (Lüning et al, 2017(Lüning et al, , 2018Lüning, Gałka, Bamonte, et al, 2019;Lüning, Gałka, García-Rodríguez, et al, 2019).…”

“…In order to better assess the magnitude of recent Global Warming, the observed climatic change has to be placed in a longer‐term palaeotemperature context. Of particular interest is the Medieval Climate Anomaly (MCA), a recognized period of natural preindustrial climate change associated with marked temperature and hydroclimatic variability in many parts of the world (e.g., Graham et al, ; Lüning et al, , ; Lüning, Gałka, Bamonte, et al, ; Mann et al, ). The MCA represents the most recent natural warm phase, preceded in the Northern Hemisphere by the Dark Ages Cold Period (~400–800 CE, Helama et al, ) and followed by the Little Ice Age (LIA, 1300–1850, e.g., Shindell, ).…”

Impact of climate change on the ecology of the Kyambangunguru crater marsh in southwestern Tanzania during the Late Holocene

“…BP), is the only period of the investigating 4000 yr record when conditions were warm and wet at Kyambangunguru, suggesting that its origin may be different from the other recorded climatic changes. The MCA is described as warm and dry in most north-eastern Africa (Lüning et al, 2017;Nash et al, 2016;Nicholson et al, 2013) and humid in southern Africa (e.g. Nash et al, 2016;Tyson and Lindesay, 1992;Woodborne et al, 2015).…”