Saturday, 23 September 2017

Climate Change - Evidence from Ice Cores

Ice cores are cylinders of ice, drilled from an ice sheet or a glacier. 


They are usually 10 centimetres in diameter, and can be taken from deep in the ice.

Ice cores provide trapped samples of ancient air.


"Air bubbles trapped in ice are like little time capsules that record the past atmospheric composition. 

"So we measure loads of different gases, and essentially we can measure greenhouse gases such as carbon dioxide and methane."

Most ice core records come from Antarctica and Greenland.


Law Dome is a location in Antarctica.

The evidence in Law Dome ice cores shows that since the 18th century, when the Industrial Revolution began, the level of carbon dioxide has risen.

Now it has reached around 400 ppm, a rise of 85 ppm in just 56 years.  

The longest ice cores are from 3km deep in ice. 

The oldest ice core records extend 123,000 years in Greenland, and now to 1 million years in Antarctica. 


The graph shows how carbon dioxide has increased and decreased over hundreds of  thousands of years.

During glacial stages, ice covered large areas of the Earth.

The most recent glacial stage occurred between about 120,000 and 11,500 years ago. 



Since then, the Earth has been in an interglacial period called the Holocene.

During glacial stages, CO2 levels were around 200 parts per million (ppm).

During the warmer interglacial periods, they hovered around 280 ppm. 

In 2013, CO2 levels passed 400 ppm for the first time in recorded history. 

A new study using evidence from a highly detailed ice core from West Antarctica shows a link between abrupt temperature changes on Greenland and Antarctica during the last ice age.

Friday, 22 September 2017

Autumn Equinox in the Northern Hemisphere

Today is the Autumn Equinox in the Northern Hemisphere, and the Spring Equinox in the Southern Hemisphere.

Every place on earth experiences 12 hours of daylight twice a year, around the Spring and Autumn Equinox.

At the Equinoxes, the Sun rises almost exactly in the east, travels through the sky for 12 hours, and sets almost exactly in the west.



The September equinox marks the moment the Sun appears to cross the celestial equator – the imaginary line in the sky above the Earth’s equator – from north to south. 

After the September equinox, northern days continue to shorten until the December solstice.

Thursday, 21 September 2017

Climate Change - The Iceman

In places which are not as frozen as they were, amazing discoveries have been made.


In 1991 two hikers in the Alps found a body.

They were shocked, and reported the find.

It was even more extraordinary when the investigation found that the body was thousands of years old.



The clothing, weapons and other items found with the body give a glimpse into life when metal was first being used.



Tests later confirmed the iceman dates back to 3,300 BC.

He probably died from a blow to the back of the head. 


His body was so well-preserved that scientists were able to determine that his last meal was red deer, herb bread, wheat bran, roots and fruit.


He lived at a time, over 5,000 years ago, when the Earth was starting to cool.



So when he died high in the mountains, his body became covered with snow.

Modern warming (shown by the red part of the graph) made it possible to find him.

Wednesday, 20 September 2017

Climate Change - The Greenhouse Effect

What do scientists mean by the "Greenhouse Effect"?

When the Sun's energy arrives at the Earth, it travels through the air.

Some is reflected back to space, but some hits the Earth and warms it.

The warm Earth gives off infrared radiation with various wavelengths.  


Some of those waves can pass back out of the air to space, but some are absorbed by certain gases in the air.


If there are more of those gases, less heat escapes into space.



Concentrated 'greenhouse gases' on Venus have caused the surface temperature to rise to 735 Kelvin (462 degrees C; around 900 degrees F)



Carbon dioxide levels in the atmosphere have risen quickly since people began burning large quantities of fossil fuels.

There was carbon dioxide in the air before that, at around 270 parts per million.

Without any carbon dioxide, the Earth would be very cold.

The temperature would be around -18 degrees C.

There have been times when most of the carbon dioxide was trapped in rocks.

The Earth cooled into a state called 'Snowball Earth'




These ancient events are unlikely to be repeated - they occurred when the Sun was producing less energy.

Tuesday, 19 September 2017

Climate Change - The Carbon Cycle

Carbon dioxide is always in the atmosphere as part of the Earth's carbon cycle.

The global carbon cycle transfers carbon through the Earth’s different parts - the atmosphere, oceans, soil, plants, and animals. 

So carbon moves around — it flows — from place to place.



Carbon dioxide (CO2) is the main greenhouse gas emitted through human activities. 

Human activities are changing the carbon cycle.

First, by adding more CO2 to the atmosphere, mainly by burning fossil fuels.

Also by changing the ability of natural sinks, like forests, to remove CO2 from the atmosphere. 

Human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution. 




The carbon sinks, on land and in the oceans, have responded by increasing the amount of carbon they absorb each year.

Carbon sinks cope with about half of human greenhouse gas emissions. 

The other half has accumulated in the atmosphere.

Monday, 18 September 2017

Climate Change - Iceland

Iceland lies on the Mid-Atlantic Ridge, which is why it has volcanic activity.





Iceland also has ice caps and glaciers.

Iceland is one of the fastest-warming places on the planet – as much as four times the Northern Hemisphere average. 
The glaciers that cover more than 10 percent of the island are losing an average of 11 billion tons of ice a year. 
              Iceland glacial meltwater - photo Tom Harding
The water melting from Iceland's glaciers would fill 50 of the world's largest trucks every minute.
Parts of Iceland are rising as the ice caps melt, reducing the weight on the Earth's crust.

The thinning of the ice caps reduces the pressure on the rocks.
Geologists know lower pressure from above makes volcanoes erupt more easily.
Lower pressure allows volcanic gases to expand, and mantle rocks melt more easily at lower pressure as well.


So more magma can rise into the volcanic systems.
As that happens, Iceland's volcanoes may get more active.

Sunday, 17 September 2017

Climate Change - 2016 - Warmest year in modern record

2016 was the warmest year in NOAA's 137-year series. 

This is the third consecutive year a new global annual temperature record has been set. 


All 16 years of the 21st century are included in the seventeen warmest years in the modern record (1998 is currently the eighth warmest.) 

The five warmest years have all occurred since 2010.

It is increasingly likely the Earth is now warmer than at any time since the Eemian Interglacial, over 115,000 years ago.

The Eemian was warmer than the Holocene because of higher insolation.

Insolation refers to the amount of solar energy received per unit time at any one location, and it was higher due to astronomical cycles.