Saturday, 31 October 2015

Climate Change - Oceania


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

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. 

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"

Friday, 30 October 2015

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.
Every La Nina year since 1998 has been warmer than every El Nino year before 1995.

Thursday, 29 October 2015

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.

Wednesday, 28 October 2015

Climate Change - The Warmest Winter

The northern hemisphere winter , December 2014 to February 2015, was the warmest in the records, according to NASA.
The average temperature, taken for northern land and ocean surfaces, was 
0.79°C above the 20th century average. 

This was the highest for December, January and February in the 1880–2015 record, passing the previous record of 2007 by 0.03°C.


It is interesting to note that there were some 'cold spots'.

Eastern North America was colder than average, and there is an obvious 'blue blob' in the North Atlantic.


In 2015, Boston’s month of snow was a 1-in-26,315 year occurrence.

Tuesday, 27 October 2015

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.

Monday, 26 October 2015

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. 

Increases since about 1750 are due to human activities in the industrial era. 

Concentration units are parts per million (ppm) or parts per billion (ppb), indicating the number of molecules of the greenhouse gas per million or billion air molecules in an atmospheric sample.

Sunday, 25 October 2015

Climate Change - Can climate change increase earthquakes and volcanic eruptions?

Between about 20,000 and 5,000 years ago, Earth slowly changed from the frigid conditions of an Ice Age, to the world on which our civilization has developed.

As the ice sheets melted, colossal volumes of water flowed back into the oceans.



The pressures acting on the Earth's crust changed as a result. 

The weight of ice on the continents was reduced, and the rising seas put extra water pressure on the seafloors.

In response, the crust moved up and bent, creating extra volcanic activity, increased seismic shocks and giant landslides.



So if we continue to allow greenhouse gas emissions to rise unchecked, causing serious warming, will our planet's crust react once again?

In Alaska, climate change has pushed temperatures up by more than 3 degrees Celsius in the last half century, and glaciers are melting at a staggering rate, some losing up to 1 kilometre in thickness in the last 100 years. 



The reduced weight on the crust beneath is allowing faults to slide more easily, promoting increased earthquake activity in recent decades. 

The crust beneath the Greenland ice sheet is already rebounding in response to rapid melting, providing the potential for future earthquakes, as faults beneath the ice are relieved of their confining load. 



The possibility exists that these could trigger submarine landslides, making tsunamis capable of threatening North Atlantic coastlines. 

Eastern Iceland is bouncing back as its Vatnajökull ice cap melts. Research predicts a response from the volcanoes beneath. 

A rise in landslide activity will happen in the Andes, Himalayas, European Alps, and elsewhere, as the ice and permafrost that covers many mountain slopes melts away. 

As sea levels rise, the bending of the crust around the margins of the oceans might unlock coastal faults such as California's San Andreas, allowing them to move more easily.

At the same time, the extra weight of seawater could act to squeeze magma out of undersea volcanoes.



This post is based on the work of Bill McGuire, professor of geophysical and climate hazards at University College London.

Saturday, 24 October 2015

Climate Change - Tropical storms

Hurricanes, cyclones, and typhoons are all the same weather phenomenon.

We use those different names for these tropical storms in different places. 

In the Atlantic and North-East Pacific, the term “hurricane” is used.

So far, Hurricane Patricia is the strongest hurricane recorded at landfall. 

Embedded image permalink
Image of Hurricane Patricia tweeted by astronaut Scott Kelly.

In the North-West Pacific a tropical storm is called a “typhoon”, and “cyclones” occur in the South Pacific and Indian Ocean.

Three strong tropical storms (KiloIgnacio, and Jimena), formed in the Pacific in 2015. On Sunday 30th August, all of them were a category 4. 

This was the first time the north-eastern Pacific had seen three category 4 hurricanes at the same time.

Picture hurricanes in Pacific Ocean




Tropical storms can’t form outside the tropics - water temperatures are too cold.

Sea surface temperature must be at least 27°C, and this temperature is actually required to a depth of at least 50 m

The warm tropical atmosphere heats up the water at the ocean surface and begins to evaporate it. 

The trapped water vapour in the air rises up through the atmosphere. 



When the rising air cools, and the water vapour condenses into liquid water, the heat is released back into the atmosphere.

The warm air rushes upward, because it has a lower density than its surroundings. 

This then draws air up from below, and speeds up the rising air near the surface. 

Surface air around the growing disturbance rushes in to replace it. 


A satellite image from the National Oceanographic and Atmospheric Administration shows Hurricane Katrina bearing down on the Gulf Coast on Aug. 28, 2005.

As this cycle continues, more warm, moist air is drawn into the developing storm, and more heat is transferred from the surface of the ocean to the atmosphere. 

This continuing heat exchange creates a wind pattern that spirals around a relatively calm centre, or eye, like water swirling down a drain.



Friday, 23 October 2015

Climate Change - Oceans Are Losing Oxygen



Marlin can hunt in water a half mile down, and sailfish often dive deep too.

In more and more places around the world, ocean predators are sticking near the surface.

Why?

Warming temperatures are sucking oxygen out of waters even far out at sea, making enormous stretches of deep ocean hostile to marine life.



Vast stretches of the ocean interior suddenly lost oxygen during the transition out of the last glacial stage, between 17,000 and 10,000 years ago. 

This event was the most recent example of large-scale global warming.

Thursday, 22 October 2015

Climate Change - September 2015 - another record breaker

According to the US National Atmospheric and Oceanic Administration (NOAA) September 2015 was the warmest September in the modern record, which began in 1880.

September 2015 was 0.90°C (1.62°F) warmer than the 20th century average of 15.0°C (59.0°F), surpassing the previous record set in 2014 by 0.12°C (0.19°F). 


September 2015 was the fifth consecutive month a monthly high temperature record has been set.

The temperature for September 2015 shows the highest departure from average for any month among all 1629 months in the record that began in January 1880.

Wednesday, 21 October 2015

Climate Change - The Last Interglacial

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


The low readings match with times called 'glacial stages'.

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

The peaks in the graph show times when carbon dioxide was high, matching times called 'interglacial stages'.

The most recent glacial stage occurred between about 115,000 and 11,500 years ago. 

The last interglacial period occurred before it, from around 130,000 to 115,000 years ago.

It's official international name is the Eemian, but it has other names in specific places.
Climate information from that time is particularly useful.
During that time, temperatures on earth were higher at the poles than they are now. 
The sea level was between five and nine metres higher than current levels, because of the melting of ice in Greenland and Antarctica.
In the UK, this last interglacial period is called the 'Ipswichian'.
Pleistocene, Ipswichian raised beach deposits at Hope's Nose, Torquay, Devon, seen from the sea, 6th January 2012, photograph by Nikolett Csorvasi
Above, an interglacial 'raised beach' deposit at 9 metres above sea-level
This pebble, shell and sand accumulation is "Ipswichian" in age.
The warming during the last interglacial period was due to natural causes.

These were basically changes in solar radiation hitting the earth, due to the tilt of the earth on its axis. 
This earlier warm period is useful to estimate what the future has in store.
We can use past climates as a natural experiment on the Earth’s systems, to consider the way it reacts to warming. 

The Eemian began when the previous glacial stage ended.

New research has helped to explain that event.

Tuesday, 20 October 2015

Climate Change - July 2015

July 2015 was the warmest month in the modern temperature record.

The average temperature for July 2015 across global land and ocean surfaces was 1.46°F (0.81°C) above the 20th century average, according to the United States National Oceanic and Atmospheric Administration.

They say: "As July is climatologically the warmest month for the year, this was also the all-time highest monthly temperature in the 1880–2015 record, at 16.61°C, surpassing the previous record set in 1998 by 0.08°C."





Previous months in 2015 have also shown a warming trend is continuing, following the record-breaking year 2014.

Monday, 19 October 2015

Climate Change - 1816: The "Year Without a Summer"

The climate can react to sudden shocks.

The weather in 1816 was very strange. 

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

The sky seemed permanently overcast. 


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

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

1816 became known as "The Year without a Summer" or "18-hundred-and-frozen-to-death".

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

The eruption of an enormous volcano on a remote island in the Indian Ocean a year earlier had thrown enormous amounts of volcanic ash into the upper atmosphere.

The dust from Mount Tambora, which had erupted in early April 1815, had shrouded the globe. 

With sunlight blocked, 1816 did not have a normal summer.

In Switzerland, the dismal summer of 1816 led to the writing of a famous story. 

A group of writers, including Lord Byron, Percy Bysshe Shelley, and his future wife Mary, challenged each other to write dark tales, inspired by the gloomy and chilly weather.

During the miserable weather Mary Shelley wrote her classic novel Frankenstein.

This event was not unique.

A new study has found that 15 of the 16 coldest summers recorded between 500 B.C. and A.D. 1,000 followed large volcanic eruptions.

Volcanic events can cool the Earth for a few years.

The large eruption of Mount Pinatubo caused a dip in temperatures in the early 1990s:



Sunday, 18 October 2015

Climate Change - Oil geology

Oil is a fossil fuel.

It was formed from chemicals from ancient living things.

To make the chemicals in oil, the temperatures and pressures needed to be just right.

The oil (and gas) will only stay in the reservoir if there are suitable structures in the rocks:



The carbon compounds from the plants and animals have been trapped for hundreds of millions of years.

They have been burned to make carbon dioxide in a very short time.

The amount of carbon dioxide in the air has changed very quickly.

Diagram of how oil is made
Source: Library and Archives Canada
© Library and Archives Canada

Saturday, 17 October 2015

Climate Change - The Paleocene-Eocene Thermal Maximum

Yes, global warming has happened before.

Scott L. Wing is a research scientist and curator at the Smithsonian’s Museum of Natural History.


One of Scott's major research interests is the PETM.


"The Paleocene-Eocene Thermal Maximum (PETM) was an abrupt global warming event.

It occurred at the beginning of the Eocene Epoch, about 55.8 million years ago. 

At the start of the event something like 5-10,000 gigatons of carbon were released into the ocean and atmosphere in less than 10,000 years. 

As a result of the carbon release, temperatures rose 5-9˚C globally. 

The PETM is widely recognized by scientists as the best geologic analogy for the human-induced global warming that is happening now."



However, the current production of greenhouse gases by humans is far faster than the events that caused the PETM.


PETM versus modern greenhouse gas emissions
It took around 150,000 years for ecosystems to recover from this event.

Friday, 16 October 2015

Climate Change - El Nino

El Niño is an oscillation of the ocean-atmosphere system in the tropical Pacific, and has important consequences for weather around the world.

El Niño happens every three to seven years.

“El Niño” is Spanish for “The Christ Child”.

Peruvian fishermen named the event many years ago.

They noticed that every few years around Christmas, virtually no fish could be found in the unusually warm waters. 
El Niño is marked by unusually warm ocean temperatures in the Equatorial Pacific.

The opposite conditions are called La Nina, characterized by unusually cold ocean temperatures in the Equatorial Pacific. 

El Nino clearly affects global temperatures.

One piece of evidence that world temperatures are rising is that every La Nina ‘year’ since 1998 was warmer than every El Nino ‘year’ before 1995:  



Information about El Nino is provided in bulletins produced by the US National Weather Service and the Australian Bureau of Meteorology.

Thursday, 15 October 2015

Climate Change - What does 'climate' actually mean?

Lots of people discuss 'climate change'.

Some people confuse 'climate' with 'weather'.

If 'climate' and 'weather' are the same, why would there be two words?

Other people say "We call climate change 'winter' and 'summer'...."  

What does the word 'climate' mean?

It normally means the average of conditions over 30 years.


Climate normally means 'an average over 3 conventional decades'.

conventional decade is, for example, 2001-2010, or 1961-1970.

So ..... 3 full, conventional decades......such as 1981 to 2010.

For example .... rainfall in Ireland.


And another example - 'Average temperature 1951-1980'

The definition of 'climate' goes back at least 100 years.

So if we are discussing climate change, that is what 'climate' means.

But in recent times, there has been a lot of variation in global temperatures.

So it can be useful to look at single conventional decades.


Chart from the World Meteorological Organisation.