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Ice Age average global temperature '11°F colder than today'

The average global temperature during the last Ice Age 20,000 years ago was 46°F (7.7°C) — 11°F (6°C) colder than today — a study has reported.

Researchers from the US combined data from tiny marine fossils with climate models to forecast the weather during the so-called Last Glacial Maximum (LGM).

During this chilly period, the Earth’s ice sheets and glaciers had spread to cover around half of Europe, North America and South America — and much of Asia.

According to the researchers, the difference in the average temperatures between the last Ice Age and now represents a ‘huge change’.

The findings will help experts understand the link between changes in atmospheric carbon levels and global temperature shifts — and predict future climate change. 

The average global temperature during the last Ice Age 20,000 years ago was 46°F (7.7°C) ¿ 11°F (6°C) colder than today ¿ a study has reported. Pictured, a map of air temperatures during the last glacial maximum in comparison with those of before the industrial period

The average global temperature during the last Ice Age 20,000 years ago was 46°F (7.7°C) — 11°F (6°C) colder than today — a study has reported. Pictured, a map of air temperatures during the last glacial maximum in comparison with those of before the industrial period

‘We have a lot of data about this time period because it has been studied for so long,’ said paper author and geoscientist Jessica Tierney of the University of Arizona.

‘But one question science has long wanted answers to is simple: How cold was the ice age?’

To answer this question, Professor Tierney and colleagues analysed the fossilised remains of tiny ocean plankton — which preserve evidence of sea-surface temperatures at the times at which they were alive.

They then combined this data with climate simulations of the Last Glacial Maximum using a technique also employed by weather forecasters, called ‘data assimilation’.

‘What happens in a weather office is they measure the temperature, pressure, humidity and use these measurements to update a forecasting model and predict the weather,’ Professor Tierney said. 

The team, she added, used a National Center for Atmospheric Research, Colorado, model ‘to produce a hindcast [or historical forecast] of the LGM, and then we update this hindcast with the actual data to predict what the climate was like.’

Researchers from the US combined data from tiny marine fossils with climate models to forecast the weather during the so-called Last Glacial Maximum (LGM). During this chilly period, the Earth's ice sheets and glaciers (like that pictured) had spread to cover around half of Europe, North America and South America ¿ and much of Asia

Researchers from the US combined data from tiny marine fossils with climate models to forecast the weather during the so-called Last Glacial Maximum (LGM). During this chilly period, the Earth’s ice sheets and glaciers (like that pictured) had spread to cover around half of Europe, North America and South America — and much of Asia

As well as predicting the average global temperatures, the researchers also created  maps to show how figures varies in different regions of the world.

She and her team also created maps to illustrate how temperature differences varied in specific regions across the globe. 

‘In North America and Europe, the most northern parts were covered in ice and were extremely cold. Even here in Arizona, there was big cooling,’ Professor Tierney said.

‘But the biggest cooling was in high latitudes, such as the Arctic, where it was about 14°C (25°F) colder than today.’

‘Climate models predict that the high latitudes will get warmer faster than low latitudes,’ Professor Tierney added.

‘When you look at future projections, it gets really warm over the Arctic. That’s referred to as polar amplification.’

‘Similarly, during the LGM, we find the reverse pattern. Higher latitudes are just more sensitive to climate change and will remain so going forward.’

With their initial study complete, the team are looking to apply a similar hindcast technique to recreate the conditions experienced in Earth’s warmer periods.

‘If we can reconstruct past warm climates then we can start to answer important questions about how the Earth reacts to really high carbon dioxide levels,’ explained Professor Tierney.

This, she added, could ‘improve our understanding of what future climate change might hold.’

Knowing the temperatures of the Earth during the Last Glacial Maximum allows researchers to get a better idea of the climate sensitivity — or, in other words, how much the global temperature changes in response to atmospheric carbon. 

The team concluded that, for every doubling of the level of carbon in the atmosphere, the global temperature is liable to rise by 6.1°F (3.4°C) — a figure roughly in the middle of the range predicted by the latest climate models.

During the last ice age, atmospheric carbon dioxide levels were at around 180 parts per million — but today they have increased to 415 parts per million.

‘The Paris Agreement wanted to keep global warming to no larger than 2.7°F (1.5°C) over pre-industrial levels,’ said Professor Tierney.

‘But with carbon dioxide levels increasing the way they are, it would be extremely difficult to avoid more than 3.6°F (2°C) of warming.’

‘We already have about 2°F (1.1°C) under our belt, but the less warm we get the better, because the Earth system really does respond to changes in carbon dioxide.’

The full findings of the study were published in the journal Nature.

BRITAIN DURING THE LAST ICE AGE

The last Glacial Maximum was around 22,000 years ago when much of Europe was covered in ice.

During the ice age, which ended about 11,500 years ago, ice covered about 30 per cent of the land in the world.

In Britain, glacial ice and waterflows spread as far south as the Bristol Channel.

Average temperatures were 5°C (8°F) colder than they are today, allowing a one-kilometre-thick sheet of ice to cover much of the country.

The temperature remained below 0°C all year round in northern regions, particularly Scotland, allowing the sheet to remain on the land all year.

Ice connected Britain with Scandinavia, allowing a host of large wildlife to roam free between the UK and mainland Europe.

During this period Britain would have seen the likes of woolly mammoths, giant deer and wolves roaming its icy planes.

Large glacial lakes covered Manchester, Doncaster, Newcastle and Peterborough and much of the country was uninhabitable for humans.

Corridors of fast flowing ice, known as ice streams, flowed toward the east over Edinburgh and toward the west of Glasgow.

All of Ireland was covered in ice, which was flowing through the Irish sea where it met Welsh ice and then flowed south toward the Isles of Scilly.

Much of Scotland, Wales, the midlands and northern England was covered in perpetual ice.

Cambridge, which was covered by a huge glacial lake, was the most southern region to be heavily affected by the icy climate.

Over time the ice and its hefty waterflows carved out the land of Britain, forming geological scars that can still be seen today.

These include glacial ridges sculpted by moving ice and winding flows of rock that travelled for miles across the country.

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