Holocene climatic change in Morocco: a quantitative reconstruction from pollen data

Annual precipitation, July and January temperatures were reconstructed from a continuous Holocene pollen sequence from the Middle Atlas, Morocco, using the best modern analogues method. The reconstructions show a clear difference between the early and late Holocene: from similar to 10 ka to similar to 6.5 ka the climate was drier and warmer than during the period since 6.5 ka. The average value of annual precipitation was similar to 870 mm until 6.5 ka, then rose to similar to 940 mm. Between 10 ka and 6.5 ka January and July temperatures were about 4 degrees C higher than the present. Both temperatures show a marked decrease between 7 ka and 6 ka. After 6.5 ka July and January temperatures fluctuated between 21 and 23 degrees C, and 2.5 and 5 degrees C respectively. January temperatures show a period of intermediate values ( similar to 3.5 degrees C) between 4 ka and 5.5 ka. The reconstructed climate values generally match palaeolimnological data from the same core, which show five intervals of low lake level during the Holocene. They are also consistent with regional-scale COHMAP simulated palaeoclimate that shows contrasting patterns of rainfall variation between the northwesternmost part of Africa and the intertropical band.