Wednesday, 30 September 2015

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.

Tuesday, 29 September 2015

Climate Change - Farming, food & possible mass migrations

Farmers can put up with some bad weather, but climate change will make unusual events more likely.


20-30% of plant and animal species will be more likely to become extinct if the temperature rises by more than 1.5-2.5C.

There will be big effects on farming from droughts and floods.



The biggest effects will be seen first near the Equator.

Just being near the Equator makes it more difficult for countries to make economic progress.

Hotter conditions affect how crops grow.

Our agriculture is heavily reliant on grasses from the temperate regions.

Corn, wheat, and rice are all types of grass.



People will try to leave places where they cannot produce enough food.

Countries where food prices rise rapidly tend to become unstable, making conflicts more likely.





People who are struggling to cope with their food supply will move to cities, or aim to move to other countries, where they may not be welcome.

Farming developed in the stable climate of the Holocene.


Humans were around from over 200,000 years ago, and it is likely farming was not viable until the climate settled down.

Monday, 28 September 2015

Climate Change - Early steps in Climate Science


1800-1870 

Level of carbon dioxide gas (CO2) in the atmosphere, as later measured in ancient ice, was about 290 ppm (parts per million).



Global temperature for 1850-1870 was about 13.6°C.

1824
Jean-Baptiste Joseph Fourier calculated that the Earth would be far colder if it lacked an atmosphere. 



1859
John Tyndall discovered that some gases block infrared radiation. 



He suggested that changes in the concentration of the gases could bring climate change.





1930s 
Milutin Milankovitch proposed orbital changes as the cause of ice ages. 

1938 
Guy Callendar showed that global warming was underway, reviving interest in the question. 


1950s 
By accident, Russell Coope discovered that some past climate change events happened in just a few decades.


This came from his research into beetle fossils in 'Ice Age' layers.

1958 
Telescope studies showed a greenhouse effect raises temperature of the atmosphere of Venus far above the boiling point of water. 



1960 

Charles David Keeling accurately measured CO2 in the Earth's atmosphere.

He was not expecting to detect an annual rise.

The CO2 level was 315 parts per million (ppm)and global temperature (five-year average) was 13.9°C.

Keeling's measurements have been continued.

Current chart and data for atmospheric CO2

At the end of 2014 the level was around 400 ppm.

Global temperature in 2014 was 14.57°C.

Sunday, 27 September 2015

Climate Change - How the great ice sheets are melting

An ice sheet is a mass of glacial land ice extending more than 50,000 square kilometres. 

An ice cap is an area of land ice smaller than an ice sheet.

The two ice sheets on Earth today cover most of Greenland and Antarctica.

An example of an ice cap is Iceland’s Vatnaj√∂kull.


The ice sheets are now losing ice at the unprecedented rate of 500 cubic kilometres a year. 
Embedded image permalink

Scientists from the Alfred Wegener Institute (AWI) in Bremerhaven mapped changes in the height of the Greenland and Antarctic ice sheets.

They have found they are melting at record pace. 

“Since 2009, the volume loss in Greenland has increased by a factor of about 2, and in the West Antarctic Ice Sheet by a factor of 3,” 

says glaciologist Professor Dr. Angelika Humbert, one of the study’s authors.

A new NASA project called Oceans Melting Greenland (OMG) will observe changing water temperatures on the continental shelf surrounding Greenland, and how marine glaciers react to the presence of warm, salty Atlantic water.

Some people confuse ice sheets with sea ice, but they are not the same.

Arctic sea ice area is declining over time. 

Antarctic sea ice behaves in a more complex way.

Saturday, 26 September 2015

Climate Change - Ice in Antarctica

Some people say "The ice sheets in Antarctica are growing".

This is very misleading.


First, the Antarctic has ice on land and in the sea.


Antarctica is a continent covered by ice, unlike the ocean in the Arctic.


The sea ice surrounding Antarctica melts almost to the coast each summer.



The winter sea ice has increased by around 1% over the last few decades.

This is due to complex processes.

It is linked to melting of the land ice on Antarctica…..

Antarctica is losing very large amounts of ice from its ice sheets and glaciers.


The graph is from data collected by the GRACE satellites.

Here is an outline of what is happening in the seas around Antarctica......
  • Seawater does not freeze until around minus 2 degrees C because it is salty.
  • This effect of salt, of course, is used to help defrost roads.
  • The meltwater off Antarctica’s ice sheets is freshwater.
  • Freshwater has a low density, so it forms a layer on top of the sea.
  • Freshwater freezes (of course) at zero degrees C.
  • So the top layer freezes more easily.
  • Also windchill helps to freeze that top layer.

Here is a useful comparison of Antarctic and Arctic sea ice ……



The Earth's poles are warming faster than the rest of the planet.


For example, the largest ice shelf in the Antarctic peninsula is being thinned by warmer seas and warmer air. 

Between 1998 to 2012  the Larsen C ice shelf lost an average of four metres of ice. 
Tthe leading edge of the remaining part of the Larsen B ice shelf. A separate ice shelf, Larsen C, is thinning from above and below, scientists found.
The leading edge of the remaining part of the Larsen B ice shelf   Photograph: HO/REUTERS




Many ice shelves around Antarctica are getting thinner over time.


As the ocean warms, heat is reaching the bases of the ice shelves, melting them from below.

Friday, 25 September 2015

Climate Change - The long-lasting effects on sea life

An important scientific study reports that ocean life can take thousands of years to recover from climate change.

D8H_6787.jpeg

The team, led by Dr Sarah Moffitt, examined more than 5,400 fossils, from sea urchins to clams, found in a 30 metre sediment core from the ocean floor off Santa Barbara, California.

The tube-like sediment core is a slice of ocean life as it existed between 3,400 and 16,100 years ago.

An example of an ocean sediment core.

It provides a snapshot of what happened during the last major deglaciation.

It was a time of abrupt climate warming, melting polar ice caps, and expansion of low oxygen zones in the ocean.

The sediment core revealed a history of a well-oxygenated sea-floor full of life.

Then there was a period of oxygen loss and warming, that triggered a rapid collapse of life.

A typical view of the ocean floor
The study shows that fossils nearly vanish in layers formed when oxygen levels in the sea dropped.

In periods of less than 100 years, ocean oxygen levels decreased significantly.

Quite small changes in oxygen in seawater can cause big changes for seafloor life.

The study results suggest that future periods of global climate change may result in similar effects, with life taking thousands of years to recover.

"It’s not just about temperature," says Sarah Moffitt. 

               Dr Moffitt examining a fossil marine gastropod (sea-snail)
"It’s about disrupting fundamental earth processes that we as humans have understood to be very stable. They’re not stable." 

"These systems have the capacity to be very unstable when you poke the climate system with a sharp stick."

Thursday, 24 September 2015

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 were 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.

Wednesday, 23 September 2015

Climate Change - 2014 - Warmest Year in Modern Record

The year 2014 ranks as Earth’s warmest since records began in 1880.


9 of the 10 warmest years in the instrumental record have now occurred since the year 2000.



The exception was 1998, which was affected by a very strong El Nino event.

That means nobody born since 1976 has experienced a colder-than-average year.

2014 was not even affected by an El Nino, which has been the case for previous record years.



For a more complete picture of 2014, here is a link to a detailed report:


Tuesday, 22 September 2015

Climate Change - Volcanoes

Many people think volcanoes produce more carbon dioxide than humans.

In fact, volcanoes produce far less carbon dioxide than humans.





Geologists have checked this problem very carefully.


This chart compares the average yearly production of carbon dioxide by human activities and volcanoes......

This information comes from the United States Geological Survey.


Very large volcanic eruptions do affect global temperatures for a year or two.


The second-largest volcanic eruption of the 20th century occurred at Mount Pinatubo in the Philippines on June 15, 1991.


The volcano exploded in a cataclysmic eruption that ejected more than 5 cubic kilometres of material. 


The ash cloud from this eruption rose 35 kilometres into the air.


Nearly 20 million tons of sulphur dioxide were injected into the stratosphere in Pinatubo's 1991 eruptions.


Dispersal of this gas cloud around the world caused global temperatures to drop temporarily (1991 through 1993) by about 0.5°C.


In 1815,  Mount Tamboraan enormous volcano on a remote island in the Indian Ocean, erupted and threw enormous amounts of volcanic ash into the upper atmosphere.


The weather in 1816 was unprecedented. 

Spring arrived, but then everything seemed to turn backward, as cold temperatures returned. 

The sky seemed permanently overcast. 

1816 became known as "The year without a summer".

The lack of sunlight became so severe that farmers lost their crops.

Food shortages were reported in Ireland, France, England, and the United States.

The Year Without a Summer

It was over 100 years before anyone understood the reason for this weather disaster.

New research shows that volcanic events over the last 2,500 years can be linked to short periods of global cooling.

Monday, 21 September 2015

Climate Change - The last 22,000 years of global temperature change



This graph shows how temperatures have changed over the last 11,000 years, since the end of the last glacial stage.


The graph uses data from modern temperature records, plus information about the past from a research paper that combined data from over 70 different scientific studies.

The next graph adds data from even further back in time:


The green part covers the time as the last glacial stage was coming to an end, and the great ice sheets were melting.

The last glacial stage ended about 10,000 years ago. 

Then, for nearly 5,000 years, global temperature was surprisingly stable

In the next 5,000 years, up to about 1800, global temperature declined by about 0.7 deg.C.

There were some variations in that slow decline:


From 1800 until 2000, temperature rose by about 0.8 deg.C, according to the World Meteorological Organisation.




This chart shows the annual average global temperatures from NASA's Goddard Institute for Space Studies (GISS)

One thing to note ….. every La Nina ‘year’ since 1998 was warmer than every El Nino ‘year’ before 1995.  

Temperatures now are higher than during any part of the Holocene.
The United States National Atmospheric and Oceanic Administration has produced this graphic of the modern instrumental temperature record.

Global surface temperature anomaly for 2015 so far is in green - the 6 previous warmest years are in red.



The recent rise in temperature has happened as industrial societies have burned fossil fuels.

Sunday, 20 September 2015

Climate Change - The Experts

In the latest survey by Dr James Powell, 69,402 out of 69,406 climate change researchers accept human activity is the cause of global warming.

What do scientists who research climate change say?

Professor Tim Palmer FRS, Royal Society Research Professor in Climate Physics, University of Oxford:



“The threat of dangerous man-made changes to global climate is quite unequivocal. 
It follows that if we want to reduce this threat, we must cut our emissions of greenhouse gases."

Professor John Shepherd FRS, Ocean & Earth Science, University of Southampton:


“The evidence is very clear that the world is warming, and that human activities are the main cause. 
Natural changes and fluctuations do occur but they are relatively small."

Professor Joanna Haigh CBE FRS, Professor of Atmospheric Physics, Imperial College London:



The concentration of carbon dioxide in the Earth’s atmosphere now exceeds anything it has experienced in the past 3 million years and its continuing upward trend is almost certain to result in further global warming."

Professor Sir Brian Hoskins FRS, Director of the Grantham Institute for Climate Change at Imperial College London:




“The evidence of changes in many different aspects of the climate system, from the ice sheets to the deep ocean, shows that climate change is happening.   
To reduce the serious risks posed by increasing changes in the climate, we need to redouble our efforts globally to limit carbon dioxide and other greenhouse gas emissions.”

The Royal Society has also published a "Short Guide to Climate Change" 

Another organisation offering an important document is the Geological Society of London.

                                  
The Geological Society of London say -

This rate of increase of CO2 is unprecedented.....

even in comparison with the massive injection of carbon into the atmosphere 55 million years ago that led to the major PETM warming event....

and is likely to lead to a similar rise in both temperature and sea level. 

From.....

Climate Change: Evidence from the Geological Record

Another expert who is good at explaining climate change is