The end of the last glacial period, which was about 10,000 years ago, is often called the end of the ice age, although extensive year-round ice persists in Antarctica and Greenland.
The Pleistocene epoch is a geological time period that includes the last ice age, when glaciers covered huge parts of the globe. Also called the Pleistocene era, or simply the Pleistocene, this epoch began about 2.6 million years ago and ended 11,700 years ago, according to the International Commission on Stratigraphy.
The overall trigger for the end of the last ice age came as Earth's orientation toward the sun shifted, about 20,000 years ago, melting the northern hemisphere's large ice sheets.
The Ice Ages began 2.4 million years ago and lasted until 11,500 years ago. During this time, the earth's climate repeatedly changed between very cold periods, during which glaciers covered large parts of the world (see map below), and very warm periods during which many of the glaciers melted.
The last cold episode of the Last Glacial Period ended about 10,000 years ago. Earth is currently in an interglacial period of the Quaternary, called the Holocene.
Yes, people just like us lived through the ice age. Since our species, Homo sapiens, emerged about 300,000 years ago in Africa, we have spread around the world. During the ice age, some populations remained in Africa and did not experience the full effects of the cold.
It might seem completely off-base to imagine that the heat-trapping gases emitted by humans could cause “global freezing” rather than “global warming.” But in fact, scientists have long hypothesized that greenhouse gases could cause cooling in some places and warming in others due to changes in ocean circulation.
New University of Melbourne research has revealed that ice ages over the last million years ended when the tilt angle of the Earth's axis was approaching higher values.
Will we enter into a new ice age? No. Even if the amount of radiation coming from the Sun were to decrease as it has before, it would not significantly affect the global warming coming from long-lived, human-emitted greenhouse gases.
When less sunlight reaches the northern latitudes, temperatures drop and more water freezes into ice, starting an ice age. When more sunlight reaches the northern latitudes, temperatures rise, ice sheets melt, and the ice age ends.
Genetic studies of modern human DNA tell us that at some point during this period, human populations plummeted from more than 10,000 breeding individuals to as few as 600.
Currently, we are in a warm interglacial that began about 11,000 years ago. The last period of glaciation, which is often informally called the “Ice Age,” peaked about 20,000 years ago. At that time, the world was on average probably about 10°F (5°C) colder than today, and locally as much as 40°F (22°C) colder.
Like all the others, the most recent ice age brought a series of glacial advances and retreats. In fact, we are technically still in an ice age. We're just living out our lives during an interglacial.
In general, it is felt that ice ages are caused by a chain reaction of positive feedbacks triggered by periodic changes in the Earth's orbit around the Sun. These feedbacks, involving the spread of ice and the release of greenhouse gases, work in reverse to warm the Earth up again when the orbital cycle shifts back.
During the last ice age glaciers covered almost one-third of Earth's land mass, with the result being that the oceans were about 400 feet (122 meters) lower than today. During the last global "warm spell," about 125,000 years ago, the seas were about 18 feet (5.5. meters) higher than they are now.
Flora and Fauna in the Last Ice Age
Most of Canada and Northern Europe was covered with large ice sheets. The U.S. was a mix of ice sheets, alpine deserts, snow forests, semi-arid scrubland and temperate grasslands. Areas that are deserts today—like the Mojave—were filled with lakes.
Humans during the Ice Age first survived through foraging and gathering nuts, berries, and other plants as food. Humans began hunting herds of animals because it provided a reliable source of food.
Is global warming real? Scientific consensus is overwhelming: The planet is getting warmer, and humans are behind it. The climate is certainly changing. But what is causing this change?
In fact, more than a million species may be at risk of future extinction due to global warming, and we're already seeing the first extinctions. The Center's Global Warming and Endangered Species Initiative is aimed at minimizing species loss from climate change.
Roughly 20,000 years ago the great ice sheets that buried much of Asia, Europe and North America stopped their creeping advance. Within a few hundred years sea levels in some places had risen by as much as 10 meters—more than if the ice sheet that still covers Greenland were to melt today.
The glaciations that occurred during this glacial period covered many areas, mainly in the Northern Hemisphere and to a lesser extent in the Southern Hemisphere.
While there is a clear relationship between CO2 and temperature over the past million years, it is difficult to extrapolate to future changes to the Earth's climate. For example, at the end of the last ice age atmospheric CO2 concentrations increased by around 50% while global temperatures increased by around 4C.
Now, in a study published in Nature this week, lead author Tierney and her team have successfully projected the average global temperature during the Last Glacial Maximum. Based on their models, the researchers found that the global average temperature from 19,000 to 23,000 years ago was about 46 degrees Fahrenheit.
No models predict an abrupt shutdown in North Atlantic circulation in the near future. Some predict an intensified current and accelerated warming instead of cooling. Even if the North Atlantic Current is deflected by a thickening lens of fresh water, only a modest change in circulation is predicted by other models.
While the effects of human activities on Earth's climate to date are irreversible on the timescale of humans alive today, every little bit of avoided future temperature increases results in less warming that would otherwise persist for essentially forever.