The Last Glacial Maximum was the coldest stretch of the last Ice Age, when the great ice sheets reached their limits. Between about 26 500 and 19 000 years ago ice lay over almost all of Canada and the north of Europe, the world averaged about 6 °C colder than today, and the sea stood about 120 to 130 m below its present level. It is among the best studied climates of the past, because it shows how the whole planet responds to lower greenhouse gases and vast sheets of ice.
Where the ice stopped
The largest sheet, the Laurentide, covered essentially all of Canada east of the Rocky Mountains and reached roughly to the Missouri and Ohio rivers and east to Manhattan. At its highest, around the Keewatin Dome, the surface stood 3.2 km above sea level, but near the edge it was far thinner: about 610 m over Manhattan.
In Europe, ice covered all of Iceland and Ireland and roughly the northern half of Britain. Its southern edge ran through Germany and Poland, and in the east it reached as far as the Taymyr Peninsula in Siberia. Far to the south, the Patagonian ice sheet ran along the Andes from about 35°S to 55°S.
The planet was not white from pole to pole. Alaska stayed mostly free of ice because its climate was too dry. The Arctic Ocean was not frozen throughout: sediment cores suggest shallow seasonal ice riddled with icebergs, with spells of open water. The cold reached further than the ice, with permafrost as far south as Szeged in Hungary and Beijing in China.
Dating the peak
A 2009 study led by Clark compiled 5 704 radiocarbon and other ages from ice sheets and mountain glaciers. It found the ice growing to its limits between 33 000 and 26 500 years ago and holding nearly all those positions until 19 000 to 20 000 years ago, when rising summer sunlight in the north started the melt.
The temperature comes from a 2020 reconstruction led by Tierney, which combined chemical signals in ocean plankton fossils with climate models: about 6 °C of global cooling, and about 14 °C in the Arctic.
A lower sea and a dustier sky
With so much water held in ice, the sea fell. The figure given by the US Geological Survey is about 125 m. A 2018 study led by Yokoyama used fossil corals from the edge of the Great Barrier Reef and found that sea level there dropped by about 20 m between 21 900 and 20 500 years ago, to 118 m below today’s. Allowing for the way the Earth responds to the weight of ice and water, the team calculated a global low of about 125 to 130 m. That gap between local and global sea level is one reason figures from about 120 to 130 m are all quoted.
The fall turned shelves into land. Beringia joined Asia to Alaska, Doggerland joined Britain to Europe, Sundaland tied Borneo and Bali to Asia, and Australia, New Guinea and Tasmania became a single land called Sahul.
The world was dry as well as cold. Ice cores show dust levels as much as 20 to 25 times today’s. The Sahara and other sandy deserts spread, shifting dunes covered half of Australia, and rainforest in West Africa shrank greatly. Savanna may have split the Amazon rainforest into two blocks, though how far that forest shrank is still debated.
Survivors in the south-west
Europe’s human population may have fallen by as much as 60 per cent. A 2023 study led by Posth compared 356 genomes of ancient hunter-gatherers and found that one ancestry came through the coldest millennia, about 25 000 to 19 000 years ago, in south-western Europe. It belonged to people of the Solutrean culture, known from sites in France, Spain and Portugal for finely worked flint points. The study found no sign that Italy had served as a refuge.
Oak and ash beside a warm spring
A few temperate trees held on in unlikely places. In the Vienna Basin in central Europe, a 2024 study led by Hošek reported leaves, wood and pollen dated to between 19 000 and 26 000 years ago, including oak, linden and common ash, in what was otherwise a periglacial desert. Springs at 15 to 35 °C kept a small area humid and mild. The authors call it the first unequivocal fossil proof that such trees survived the cold in central Europe.
