Saturday, 30 April 2016

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, 29 April 2016

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.

Thursday, 28 April 2016

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).


Schematic diagram of 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.

Wednesday, 27 April 2016

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"

Tuesday, 26 April 2016

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 Niñe 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:

Monday, 25 April 2016

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.

Sunday, 24 April 2016

Climate Change - The Warmest Winter - December 2015 to February 2016

The northern hemisphere winter , December 2015 to February 2016, was the warmest in the records. 

The average temperature, taken for northern land and ocean surfaces, was 
1.13°C above the 20th century average. 

This was the highest for December, January and February in the 1880–2016 record, passing the previous record of 2007 by 0.29°C.


December 2015–February 2016 also marks the highest 3-month departure from average for any 3-month period on record.

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

There is an obvious 'blue blob' in the North Atlantic. 

Some scientists have linked this to melt-water from Greenland.

“It is conspicuous that one specific area in the North Atlantic has been cooling in the past hundred years while the rest of the world heats up,” says Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research.

The accumulated monthly total mass balance of the Greenland ice sheet measured from satellites, relative to June 2006
The accumulated monthly total mass balance of the Greenland ice sheet measured from satellites, relative to June 2006 (dotted line). This curve ends in April 2015 at the end of the accumulation season. Source: Barletta et al. 2013.

Greenland is losing mass at about 250 bn tonnes per year.

Saturday, 23 April 2016

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 precious stone set in the silver sea,
Which serves it in the office of a wall,
Or as a moat defensive to a house,
Against the envy of less happier lands,

This blessed plot, this earth, this realm, this England

(With apologies to other parts of the British Isles)

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

Friday, 22 April 2016

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.

Thursday, 21 April 2016

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.

Wednesday, 20 April 2016

Climate Change - Global Temperatures for March 2016

The global average temperature for March 2016 was 13.92°C, according to the US National Atmospheric and Oceanic Administration.

This is the highest March average temperature in the 1880–2016 record, at 1.22°C  above the 20th century average of 12.7°C .


This marks the highest monthly temperature departure among all 1,635 months on record, beating the previous all-time record set just last month by 0.01°C. 

Overall, the nine highest monthly temperature departures in the record have all occurred in the past nine months. 

March 2016 also marks the 11thconsecutive month a monthly global temperature record has been broken, the longest such streak in NOAA's 137 years of record keeping.

Tuesday, 19 April 2016

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.

The US National Hurricane Center gives regular information about hurricanes.

Monday, 18 April 2016

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.

Sunday, 17 April 2016

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.

Saturday, 16 April 2016

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 said: "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."




Globally-averaged temperatures for the year 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.