Friday, 31 July 2015

Climate Change - "The climate has always changed .......what is all the fuss about?"

The climate has changed before.


When people say "It's changed before without people, so people can't be involved this time" ....think of forest fires.



Fires happened throughout time, does that mean people can't start fires?

Ice ages, warm times ... the geological record in the rocks shows many events.

Even so, the current changes are very unusual.





Graph based on a paper published in 2013


The recent rise in temperature is very fast.



What other kinds of changes are happening?


Geologists have compared the past with the present.


This report -
Climate Change Evidence: The Geological Society of London


explains what they have discovered.

This is based on part of that report:

"Before the current warming trend began, temperatures were declining.

This cooling took Earth’s climate into the ‘Little Ice Age’ (1450 – 1850). 

Calculations indicate that this period of cool conditions should continue for about another 1,000 years. 

Nevertheless, after 1900 the overall decline in temperature sharply reversed." 

So the Earth should be cooling.

There's lots of evidence for human involvement in these changes.  
Atmospheric CO2 is now around 400 parts per million (ppm).
It last reached similar levels during the Pliocene, 5.3-2.6 million years ago.
Outcrop view

In the middle Pliocene, the concentration of carbon dioxide in the air ranged from about 380 to 450 parts per million. 

During this period, the area around the North Pole was much warmer and wetter than it is now.

Summer temperatures in the Arctic were around 15 degrees C, which is about 8 degrees C warmer than they are now.
Global average temperatures were 2-3°C warmer than today.

Sea level rose by up to 20 metres in places.

What are the risks?
This source gives examples relating mainly to the USA ..........

but applicable more widely too.

For more interesting information, see -

Fact Sheets produced by 

Thursday, 30 July 2015

Climate Change - 2015 temperatures

The Earth is going through an extraordinary process.... the planet is warming, the ice is melting, and the climate is changing.


In 2015, the warming trend continued.

The year 2015 ranks as Earth’s warmest year since records began in 1880.


This is reported by scientists from NASA and the National Oceanic and Atmospheric Administration. 

The average surface temperature has risen about 1.0 degree Celsius since the late-19th century.

Fig A2


Globally-averaged temperatures in 2015 beat the previous record set in 2014 by 0.13 degrees Celsius

NASA analysis estimates 2015 was the warmest year with 94% certainty.



2015 was the first time the global average temperature was 1 degree Celsius or more above the 1880-1899 average.

Global annual average temperature relative to 1961-1990 based on the three major global temperature datasets (HadCrut4, NASA GisTEMP and NOAA). 


 Source: World Meteorological Oroganisation

9 of the 10 warmest years in the record have occurred in the 21st century.

From earlier years, only 1998, affected by the strongest El Nino event, makes fifth place.


Wednesday, 29 July 2015

Climate Change - Greenland

The invention of the name Greenland may mark the start of the advertising industry.

saga tells how Erik the Red, the Icelandic Viking who wanted to get people to join his planned settlement, called it Greenland because a pleasant name would attract more settlers:

He called the land which he had found Greenland, because, quoth he, "people will be attracted thither, if the land has a good name." 

The ice sheet on Greenland covers most of this huge island.




Greenland is losing ice, and the mass of ice lost is measured by satellites called GRACE.

Embedded image permalink

A survey of Greenland's glaciers has shown they are speeding up.

The speed has increased by about 30% in 10 years.

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.

Updates about Greenland's ice sheet are regularly posted by the National Snow and Ice Data Center.

Tuesday, 28 July 2015

Climate Change - The link with mass extinctions

What is the worst-case scenario for climate change?

The geological record shows that when the atmosphere suddenly changes, there are big effects on living things.


Five major mass extinction events are recorded in the rock record of the last 600 million years.
The biggest extinction was at the end of the Permian, around 252 million years ago.

It is called the End-Permian mass extinction.


Only about 8% of species survived to live on in the Triassic Period.


This photo shows geologists investigating tilted sedimentary rocks at Shangsi in South China.

Triassic rocks (at the top right) lie over the older Permian rocks.

Each mass extinction in the rocks matches with a change in the chemistry of the rocks called a 'carbon excursion'.

Some of the carbon excursions are 'negative CEs' and some are 'positive CEs'.

Negative CEs indicate that lots of gaseous carbon compounds escaped into the air, causing warming.

These are sometimes called hyperthermal events, meaning 'extreme warming'.

An example of a Negative CE is 



Ecosystems recovered from the PETM ..... it 'only' took 100,000 years.

In the PETM link above, see Section 9 ..Conclusions... last sentence.....

"the PETM is a natural analogue for increases in atmospheric COdue to fossil fuel burning over the next century, and implies a relatively high climate sensitivity."


Positive CEs involve the opposite effect ..... the Earth absorbs those gases and cooling follows.

Examples of positive CEs include 

The 'Snowball Earth' events.



Earth Systems simply react to the chemistry.

The changes were caused by natural processes in the past.

This time human activity is involved in producing something similar.

Currently CO2 is rising at 20 ppm per decade.


Nothing like this has happened in the time of Homo sapiens.

Uncontrolled addition of CO2 to the atmosphere is dangerous and will have serious consequences.


Photographs of ice cores being collected by drilling

Monday, 27 July 2015

Climate Change - What share of warming is caused by human activity, and what is the risk?

Scientists at the Geological Society of London say -
Here is the key part of the statement from GeolSoc:

Before the current warming trend began, temperatures in the Holocene (the last 11,000 years) were declining. 
Astronomical calculations indicate that this period of low insolation and associated cool conditions should continue for about another 1,000 years. 
Nevertheless, after 1900 the overall decline in temperature sharply reversed. 
There is now greater confidence than in 2010 that the only plausible explanation for the rate and extent of temperature increase since 1900 is the exponential rise in CO2 and other greenhouse gases in the atmosphere since the Industrial Revolution.


How can has this be proved?
The key is found in looking at the evidence of the Ice Age.
The last major glacial stage of the "Ice Age" ended thousands of years ago.

Since then, temperatures have changed, but the recent rise is very different.
The graph shows that as the ice melted, temperatures continued to rise for a few thousand years.
Around 10,000 years ago the global temperature became mainly stable.
Then around 5,000 years ago the Earth began to slowly cool, and that continued until modern times, with some variations.
So left to itself the Earth would be cooling, which would have led to a new glacial stage after thousands of years.


Glacial stages are linked to regular patterns in the movements of the Earth.

















The ice would start to return in around 1,500 years.

So the current rise in temperatures is not part of a natural cycle.



The natural cooling trend has been reversed.

This temperature rise is the effect of extra carbon dioxide.

The carbon dioxide has been produced mainly by burning fossil fuels.

(In the graph, Law Dome is a site in Antarctica where ice cores have been drilled to discover the ancient CO2 values - Mauna Loa is a site in Hawaii where the CO2 value has been measured in the air since the 1950s)

Sunday, 26 July 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.

Saturday, 25 July 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.

Friday, 24 July 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.

Thursday, 23 July 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 Vatnajökull.


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.

Wednesday, 22 July 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.

Tuesday, 21 July 2015

Climate Change - 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.

Monday, 20 July 2015

Climate Change - The long-lasting effects on sea life

new 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 the 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."