temperatures 2–3 °C warmer than now. Research indicates that the Arctic had less sea ice than now. In the southwestern Iberian Peninsula, forest cover reached its peak between 9,760 and 7,360 years BP as a result of high moisture availability and warm temperatures during the HCO. Current desert regions of Central Asia were extensively forested because of higher rainfall, and the warm temperate forest belts in China and Japan were extended northwards. West African sediments additionally record the African humid period, an interval between 16,000 and 6,000 years ago during which Africa was much wetter than now. That was caused by a strengthening of the African monsoon by changes in summer radiation, which resulted from long-term variations in the Earth's orbit around the Sun. The "Green Sahara" was dotted with numerous lakes, containing typical African lake crocodile and hippopotamus fauna. A curious discovery from the marine sediments is that the transitions into and out of the wet period occurred within decades, not the previously-thought extended periods. It is hypothesized that humans played a role in altering the vegetation structure of North Africa at some point after 8,000 years ago by introducing domesticated animals, which contributed to the rapid transition to the arid conditions that are now found in many locations in the Sahara. Sea levels in the Sea of Japan were 2-6 metres higher than in the present, with sea surface temperatures being 1-2 °C higher. The East Korea Warm Current reached as far as Primorye and pushed cold water off of the cooler Primorsky Current to the northeast. The Tsushima Current warmed the northern shores of Hokkaido penetrated into the Sea of Okhotsk. Northwestern Patagonia, in a region known as the Arid Diagonal, was significantly drier during the Early and Middle Holocene, with the region becoming more humid during the Late Holocene following the end of the climatic optimum. In the far Southern Hemisphere (New Zealand and Antarctica), the warmest period during the Holocene appears to have been roughly 10,500 to 8,000 years ago, immediately after the end of the last ice age. The Amery Ice Shlf retreated approximately 80 kilometres landward during this warm interval. By 6,000 years ago, which is normally associated with the Holocene Climatic Optimum in the Northern Hemisphere, those regions had reached temperatures similar to today, and they did not participate in the temperature changes of the north. However, some authors have used the