Friday, 28 July 2017

Climate Change - Heading for 2 degrees rise in global temperatures

The highly respected Berkeley Earth project has reported that 2016 was the warmest year in the modern record.

This chart shows the annual average global temperatures up to 2015, 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.  

It's useful to look at average global temperatures by comparing decades.
This chart comes from the World Meteorological Organisation.

The high figures in the 1930s and 1940s were produced partly because there were strong El Ninos over a period from about 1939 to 1942.

Since the mid 20th century global temperatures have risen, decade by decade.

New research published June 2015 confirms this trend:

Over a longer term, it's obvious that the current situation is unusual.

A temperature rise of 2 degrees C above pre-industrial temperature has been agreed as a threshold beyond which climate change risks become unacceptably high.

However, there are major objections even to the "two-degree limit".
Many say the number is simply too high.

Archbishop Desmond Tutu has pointed out that a two-degree global average rise might result in Africa’s temperature rising as much as 3.5 degrees C —a potentially disastrous change.

The current rise in temperature has reversed all the natural trends.

Thursday, 27 July 2017

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.
melting of McCarty Glacier in Alaska


Embedded image permalink

Mount Lyell is in Yosemite National Park, California.

New research shows that glacier retreat is a global phenomenon and is "without precedent".

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.


Wednesday, 26 July 2017

Climate Change - The last 1,000 years of global temperatures

Average global temperature is now higher than it has been for a long time.


Graph by Klaus Bitterman.

Green dots show the 30-year average of the PAGES 2k reconstruction. 

The red curve shows the global mean temperature, based on HadCRUT4 data from 1850 onwards. 

In blue is the original "hockey stick" from paper by Mann, Bradley and Hughes (1999) with its uncertainty range (light blue). 

The green dots are calculated using data from many places around the world, using information from a range of temperature proxies, such as documents, ice, lakes, pollen, tree rings, corals, seabeds and speleothems.
78 researchers from 24 countries, together with many other colleagues, worked for seven years in the "PAGES 2k" Project on this climate reconstruction. 

Their study is based on 511 climate archives from around the world.

PAGES is the Past Global Changes programme launched in 1991. 

Tuesday, 25 July 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.

Monday, 24 July 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.

Sunday, 23 July 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.

Saturday, 22 July 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.

Friday, 21 July 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.

Thursday, 20 July 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.

Wednesday, 19 July 2017

Climate Change - The Pliocene Rebooted?

Atmospheric carbon dioxide concentration is now around 400 parts per million (ppm).

It last reached similar levels during the Pliocene, 5.3-2.6 million years ago.


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.

Of course, there were no modern humans at that time.



Hominids of the Pliocene

Nor was there a global system of food supply relying on stable climates for agriculture.

Tuesday, 18 July 2017

Climate Change - Permafrost and greenhouse gases

Arctic permafrost – ground that has been frozen for many thousands of years – is now thawing because of global climate change.

“The release of greenhouse gases resulting from thawing Arctic permafrost could have catastrophic global consequences,” said Dr. Max Holmes, a Senior Scientist at the Woods Hole Research Center (WHRC).


Greenhouse gases and permafrost.  

Thawing permafrost releases greenhouse gases (carbon dioxide and methane) into the atmosphere, which accelerate climate change, which in turn cause more thawing of the permafrost. 

This may be a fairly slow process, and there is a lot more research to be done in this area.

Monday, 17 July 2017

Climate Change - Oceania

Oceania is a region made up of thousands of islands throughout the Central and South Pacific Ocean. 

It includes Australia, the smallest continent in terms of total land area.


Many of the nations in Oceania are Small Island Developing States (SIDS).


Many scientists say that Oceania is more vulnerable than most parts of the Earth to climate change, because of its climate and geography. 

The heavily coastal populations of the continent’s small islands are vulnerable to flooding and erosion because of sea level rise. 


An international team of researchers has produced this graph of ocean levels, for a period of time going back to around 500 BC. 

Five of the Solomon Islands have been swallowed whole by rising sea levels between 1947 and 2014. 
"It’s a perfect storm,” says Simon Albert of the University of Queensland. “There’s the background level of global sea-level rise, and then the added pressure of a natural trade wind cycle that has been physically pushing water into the Western Pacific."
Albert and his colleagues analysed aerial and satellite images from 1947 to 2014 to study the effects of creeping sea levels on the coastlines of 33 reef islands in the Solomons.

Five islands present in 1947, ranging in size from 1 to 5 hectares, had completely disappeared by 2014.
Another six islands had shrunk by 20 to 62 per cent in the same period, confirming anecdotal reports of people living in the area.
Homes in Solomon Islands close to edge of sea
The most populated of these, Nuatambu Island, is home to 25 families, who have witnessed 11 houses wash into the sea since 2011.
Fiji’s shoreline has been receding about 15 centimetres per year over the last 90 years.

Samoa has lost about half a metre per year during that same time span. 

The global sea level graph is from this paper: 
"Temperature-driven global sea-level variability"

Sunday, 16 July 2017

Climate Change - Why isn't every year a record year?

Heat can affect things without causing a temperature rise.

Extra heat can be used in ‘changing state’ instead of raising temperature.
A change of state could be … a solid melting to a liquid
Or a liquid evaporating to a gas.

So heat is needed to change ice at zero degrees C to water at zero degrees C.
And to change water into water vapour….. without raising the temperature.
Scientists call the heat used to change state latent heat.
Also, there are natural variations in the global climate, El Nino events being the ones that affect world temperature the most.
The opposite to 'El Nino' is 'La Nina', a cooling effect.
If global temperatures are plotted on a graph in a way that shows these variations, it makes the overall warming trend very obvious.
Bar chart of temperature anomalies 1880-2015 indicating El NiƱe phase
Every La Nina year since 1998 has been warmer than every El Nino year before 1995.

As the Earth warms, each El Nino event 'rides' on a higher base-line global temperature:

Saturday, 15 July 2017

Climate Change - Deltas at risk

Deltas often form when rivers reach the sea.

The river can carry sand and mud when it is flowing fast.

As the water enters the sea, it slows down, and the sediment drops to make the delta.


Many deltas are at risk from climate change.   This map shows the levels of risk.



An estimated 80 percent of the world's megacities are located in fragile river deltas.   A megacity has a population of over 10 million people.

Over 500 million people live on deltas.

Why are deltas at risk?

One reason is rising sea level, which wears away the delta from the front.

Friday, 14 July 2017

Climate Change - Have humans caused climate change for 180 years?

An international research project has found human activity has been causing global warming for almost two centuries, according to a report in Phys.Org
Humans have caused climate change for 180 years
Australian National University researcher Associate Professor Nerilie Abram. Credit: Stuart Hay, ANU
Lead researcher Associate Professor Nerilie Abram from The Australian National University (ANU) said that their study found that warming began during the early stages of the Industrial Revolution.

Warming is first detectable in the Arctic and tropical oceans around the 1830s, much earlier than scientists had expected.
CO2 information from ice cores shows that atmospheric CO2 levels began to rise from around 280 ppm as the 19th century began.
Atmospheric CO2 concentration over the last millennium, as reconstructed from ice core data obtained by Etheridge et al. (1998) at Law Dome, Antarctica.

Thursday, 13 July 2017

Climate Change - The 8,200 year event

When the last glacial period ended about 11,500 years ago, the Earth's modern climate began to develop. 

The large continental ice sheets shrank, and sea level rose.


Around 8,200 years ago, however, a major cooling event occurred. 

The 8.2 ka event was first discovered in the Greenland ice core GISP2.

Over two decades temperature cooled about 3.3°C in Greenland.

Temperatures in Europe dropped by around 2°C.

The entire event lasted about 150 years.

Then temperatures warmed, returning to their previous levels. 

So what caused the 8.2 ka event?

As the large ice sheets in Canada were melting, a large meltwater lake formed south of the Hudson Bay. 

Geologists have named this Lake Agassiz, after the 19th century scientist Louis Agassiz.


It was dammed to the north by the Laurentide ice sheet.

Slowly, the ice melted further, and the lake emptied into the sea in a very short period of time.




The cold water flooding into the Atlantic caused cooling, and the rising sea level formed the North Sea and the English Channel, creating the familiar shape of Britain.

This event shows that the climate can react strongly to sudden changes.

Wednesday, 12 July 2017

Climate Change - The Atmosphere



Space is not very far away.

Aircraft on long-haul flights travel at a height of about 10 km.

The lowest layer of the atmosphere, the Troposphere, ends at about 15 km.

The air in the layers above the troposphere is very thin indeed.

Think of a place around 15 km (9 miles) from where you are.

That's pretty much how near you are to space.

All the waste gases people dump into the air are trapped in the thin layer of air around the Earth.


Molecules in the air include nitrogen and oxygen as well as water, carbon dioxide, ozone, and many other compounds in trace amounts, some created naturally, others the result of human activity.

In addition to gases, the atmosphere contains extras such as smoke, dust, acid droplets, and pollen.


Atmospheric concentrations of some greenhouse gases over the last 2,000 years.