Science, Ice Age

Ice ages are periods of cooler global temperatures and periodic expansion of glaciers, lasting hundreds of millions of years. An ice age is a long period (from millions to tens of millions of years) when global temperatures are relatively low and large areas of the planet are covered by continental ice sheets and alpine glaciers. Ice ages are periods of prolonged cooling of the Earth’s climate, resulting in the expansion of continental ice caps, polar ice caps, and mountain glaciers. The last million years of Earth’s history were marked by a series of ice ages interrupted by relatively short periods of warm temperatures.

The current ice age is the most studied and best studied, especially the last 400,000 years, since the last 400 years in particular is a period covered in ice cores that record the composition of the atmosphere and indicate the temperature and volume of ice. Ice core records also provide valuable information about changes in temperature and greenhouse gases over the past 800,000 years.

Over the past two decades, ice cores extracted from the Earth, two existing ice sheets, Greenland and Antarctica, have revealed the most detailed climate data to date. Evidence of dramatic climate change is easy to see in ice cores taken from Greenland and Antarctica. Ice cores provide hundreds of thousands of years of annual and even seasonal climate data, integrating millions of years of climate data into ocean sediment cores.

The most recent ice age occurred between 120,000 and 11,500 years ago, while the current interglacial period, the Holocene, is expected to last tens of thousands of years more (and human activity could inadvertently delay the onset of the next ice age). The researchers used Earth’s orbital data from the ice age to find the warmest interglacial historical period most similar to the current one, and from that predicted that the next ice age would typically begin within 1,500 years.

Since then, ice ages on Earth have undergone a cycle of glacial ages, with ice sheets advancing and retreating on timescales of 40,000 to 100,000 years, known as glacial ages, glacial or glacial advancement and interglacial, interglacial, or glacial retreat . All human settlements on Earth in the past 100,000 years are entirely possible because we were in an ice age at the time. Throughout the early stages of the Pleistocene, the rise and breakup of ice sheets followed a 41,000-year cycle (related to changes in Earth’s tilt).

For example, when the Earth was emerging from the last glacial cycle, the warming trend was halted 12,800 years ago when temperatures plummeted in just a few decades. During the Ice Ages, Earth’s climate changed repeatedly between very cold periods when glaciers covered most of the world (see map below) and very hot periods when many glaciers melted. Canada and the northern United States were completely covered in ice, as was all of northern Europe and northern Asia.

Long ago (though not much geological time has passed since the people of the Stone Age survived), the northern region was buried miles deep in continental ice sheets. Although scientists debate the extent of the ice sheets during these times, there is evidence that ice in the equatorial regions reached sea level. The next well-documented ice age, perhaps the most severe of the past billion years, occurred between 720 and 630 million years ago (a period of low temperature) and likely produced a Snowball Earth, in which ice sheets reached the equator [42 ]. ] could end the accumulation of greenhouse gases such as CO 2 from volcanoes. Compared with the situation of the earth 20,000 to 30,000 years ago, we are obviously not yet in an ice age, but judging from the long history of the earth, we are actually still in a global ice age called the Quaternary Ice Age, also known as the Quaternary Ice Age. It was the last ice age. 2.6 years. ten thousand years.

The 26,000-year precession, or wobble cycle, of Earth’s N pole in the sky is just one of the factors that influence the amount of sunlight entering the northern hemisphere and influence the coming and going of recent ice ages. The period of these changes is related to changes in the tilt of the Earth’s axis of rotation (41,000 years), changes in the orientation of the Earth’s elliptical orbit around the sun, called the “equinox precession” (23,000 years), and changes in the shape of the elliptical orbit (100,000 years) (more round or more). And 21 roughly corresponds to the time when the Earth’s axis oscillates, the deterministic (i.e. orbit) calculated by Serbian engineer Miyutin Milankovic. To track Earth’s temperature over the past 600,000 years, Serbian mathematician Milutin Milanković carefully calculated how orbital changes (such as eccentricity, precession, and axial tilt) affect solar radiation levels, and published in 1941 “The Sunshine Classic and Ice Ages” Issues of his work published in a book”.

Since astronomical theory was based on an increase in the amount of sunlight falling on one hemisphere, while decreasing on the other hemisphere, many experts considered the world model of ice ages a crushing refutation. These changes in the distribution of solar energy on the Earth’s surface are not enough to explain the dramatic climate changes during ice ages, especially beyond high latitudes. The figure below shows the results of Shakun et al., 2013, for various regions of the Earth, as well as the uncertainties in their estimates at various climatic points and time periods at the end of the last ice age. If CO2 contributed only about 35% warming at the end of the last ice age, and albedo change due to melting ice sheets played an important role, this would mean a climate sensitivity of about 3°C, much more in line with current model estimates. albeit with very large uncertainties given the limits of accuracy with which models simulate global changes over this period.

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