Saturday, 24 March 2018

Climate Change - Repeat photography of melting glaciers

Glaciers are melting quickly in many places.

Grinnel Glacier- at the top, 1940, compared with the lower image from 2006. Repeat photography reveals this process.

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Mount Lyell is in Yosemite National Park, California.

New research shows that glacier retreat is a global phenomenon and is being caused by climate change: many places, the centennial-scale retreat of the local glaciers does indeed constitute categorical evidence of climate change.
In 2014Exit Glacier in Alaska melted and retreated 57 metres toward the Harding ice field, which itself has lost 10 per cent of its mass since 1950.

Friday, 23 March 2018

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.

Thursday, 22 March 2018

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) - this is not going to happen on Earth.

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.

Wednesday, 21 March 2018

Climate Change - 2017 global temperature report

According to the US National Oceanic and Atmospheric Administration, 2017 was the warmest year in the modern record without an El Niño present in the tropical Pacific Ocean.

The 2017 average global temperature across land and ocean surface areas was:

..... 0.84°C above the 20th century average of 13.9°C, behind the record year 2016 (+0.94°C) and 2015 (+0.90°C, the second warmest year on record). 

2015 and 2016 were both influenced by a strong El Niño episode. 

The chart above comes from State of Climate in 2017, a report from the World Meteorological Organisation.

Tuesday, 20 March 2018

Spring Equinox in the Northern Hemisphere

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

The Sun is at its lowest path in the sky on the Winter Solstice

After that day, the Sun follows a higher and higher path through the sky each day, until it is in the sky for exactly 12 hours. 

On the Spring Equinox, the Sun rises almost exactly in the east, travels through the sky for 12 hours, and sets almost exactly in the west. 

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

After the March equinox, northern days continue to lengthen until the June solstice.

Monday, 19 March 2018

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.

Daniel Rothman, Professor of geophysics in the MIT Department of Earth, Atmospheric and Planetary Sciences and co-director of MIT’s Lorenz Center, has identified “thresholds of catastrophe” in the carbon cycle that, if exceeded, would lead to an unstable environment, and ultimately, mass extinction.

Sunday, 18 March 2018

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.