Friday, 28 April 2017

Climate Change - The Carbon Bubble

Burning fossil fuels produces carbon dioxide.


Carbon dioxide emissions need to be limited. 

However, the potential carbon dioxide emissions contained in fossil fuel reserves are vast.



So it's not possible for all current fossil fuel reserves to be used, if the Earth's warming is to be kept below 2 °C. 

This huge excess quantity of fossil fuel is sometimes called the 'Carbon Bubble'.

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—a potentially disastrous change.

Various scientific research projects have looked at what would happen if all the fossil fuels were burned.

One project concluded:
The Antarctic Ice Sheet stores water equivalent to 58 metres in global sea-level rise.  
... burning the currently attainable fossil fuel resources is sufficient to eliminate the ice sheet. 
...........with an average contribution to sea-level rise exceeding 3 metres per century during the first millennium.

Thursday, 27 April 2017

Climate Change - Climate prediction is not weather forecasting

The chaotic nature of weather makes it unpredictable beyond a few days. 
To predict the weather you need to know exactly what is happening in the atmosphere down to the smallest scale. 
Climate is the average weather pattern of a region over many years (usually a period of 30 years).

Weather forecasts depend on knowing exactly what is going on in the atmosphere, down to the smallest scales. 

Climate forecasts look for patterns over a longer time. 
Will it be generally wetter in winter? 
Will there be more heavy downpours?
A paper published in the journal Science in August 1981 made several projections regarding future climate change.

The projections were rather accurate — and their future is now our present.

"Potential effects on climate in the 21st century include the creation of drought-prone regions in North America and central Asia as part of a shifting of climate zones, erosion of the West Antarctic ice sheet with a consequent worldwide rise in sea level, and opening of the fabled Northwest Passage.”
Their predictions have turned out to be correct.

"Drought-prone regions" are receiving less rainfall.

The West Antarctic ice sheet is melting.

Some ships are using the Northwest Passage as a polar short-cut. 

Projecting changes in climate due to changes in atmospheric composition or other factors is easier than predicting the weather.


It is impossible to predict the age at which any particular man will die, but we can say with high confidence what the average age of death for men is.

Similarly, a climate prediction might say that average summer rainfall over London is predicted to be 50% less by the 2080s.

It will not predict that it will be raining in London on the morning of 23rd August 2089.

Another way to predict the outcomes of climate change is to examine the geological record of ancient events.

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.


Global average temperatures were 2-3°C warmer than today.


Sea level rose by up to 20 metres in places.

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.

There were no humans then, and no farming.

Wednesday, 26 April 2017

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 reliable farming was not possible until the climate settled down, according to researchers:
"....the possibility of cultivation is not excluded for the late Pleistocene, however we argue that it did not become a reliable means of subsistence until the Holocene. 
 This period coincides with a decrease in the amplitude of climatic oscillations ........"

Tuesday, 25 April 2017

Climate Change - March 2017


According to the US National Oceanic and Atmospheric Administration (NOAA) the combined global average temperature over the land and ocean surfaces for March 2017 was 1.05°C above the 20th century average of 12.7°C.

This was the first time the monthly temperature departure from average surpasses 1.0°C in the absence of an El NiƱo episode in the tropical Pacific Ocean.



Monday, 24 April 2017

Climate Change - Comparing the Polar Regions

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

One reason is that energy is carried to the poles by large weather systems.


The Arctic includes an ocean covered by sea ice.

Arctic sea ice melts in Summer and then refreezes in Winter.

The area of Arctic sea ice is largest in March each year, and at its lowest each September.
It is reducing over time - the graph comes from the US National Snow and Ice Data Center.

Research suggests the remarkable decline of  Arctic sea ice over the last century is far beyond anything seen for a long time. 


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

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



Ice shelves around Antarctica are also affected by global warming.

For a useful comparison of Antarctic and Arctic sea ice follow this link……

Arctic vs Antarctic




You can explore the Earth's melting ice using NASA's Global Ice Viewer.

Sunday, 23 April 2017

Climate Change - "Weather on Steroids" in 2010

There were some very unusual weather events in 2010, which may be a warning of future effects of climate change.

Each time there are extreme weather events, people debate "Is there a link to climate change?"

It might be hard to prove in many cases.

Some recent events, however, are extraordinary.

The phrase 'weather on steroids' has been used to describe these events.


In 2010, China and Brazil had serious droughts, and in the first part of the year the Northern Hemisphere warmed fast, melting the winter snow cover very quickly.



The picture shows the dried-up River Negro in Brazil, with a bridge in the distance.  

But the biggest events were the heatwave in Russia and the flooding in Pakistan.

In PakistanGovernment officials said that from July 28 to Aug. 3, parts of Khyber Pakhtunkhwa province recorded almost 12 feet (3.6 metres) of rainfall in one week

The province normally averages slightly above 3 feet (around 1 metre) for an entire year.

        
       Pakistan Floods                                  Russian forest fire

In Russia, the heatwave went on for weeks, causing forest fires and destroying crops.

The Russian harvest was reduced in 2010, so the government stopped exports of grains.



Thanks to the Russian drought of 2010, global food prices in early 2011 were the highest since the food crisis of 1972 - 1974. 

This event has been linked to the "Arab Spring" of 2011.

The link between the floods and the heatwave was a blocked jet stream.

Saturday, 22 April 2017

Climate Change - Glaciation in Antarctica

Around 34 million years ago, at the Eocene-Oligocene Transition (EOT), the Earth was undergoing a period of global cooling. 


Antarctica changed from a green forested continent to the land of ice we know today. 

The cooling was partly caused by declining atmospheric carbon dioxide levels, but it also coincides with changes in the geography of the Southern Ocean.

This is an image of how this ancient world might have looked, created recently by Alan Kennedy of the University of Bristol -



Around 55 million years ago, CO2 levels rose during the Paleocene-Eocene Thermal Maximum (PETM).
Weathering of the newly-building Himalayas caused CO2 levels to begin to fall.
CO2 in rain makes a weak acid, which causes chemical weathering (especially of carbonate rocks like limestone, but of other rocks as well).
Rivers carry the carbon compounds down to the oceans, where various processes (such as the formation of calcareous shells by organisms) eventually deposit the material on the ocean floor.


Antarctic glaciation began when CO2 level fell to around around 750 ppmand spread more widely as the CO2 level continued to fall.

So...... what could be the future for Antarctica as global warming continues?

CO2 concentration in the atmosphere now is just over 400 ppm, but no one expects Antarctic ice sheets to melt entirely at any point soon.

If CO2 stopped rising now, ice would continue to melt from ice sheets and glaciers for a very long time.

There would still be a great deal of ice in Antarctica... the process would stabilise at a certain level of ice coverage.

Making Europe wild again
Even melting a fraction of Antarctica's ice would raise sea levels by a significant amount.
However, if CO2 levels get to over 750 ppm, eventually Antarctica could indeed be ice-free.

It would take time, as it takes a lot of energy to turn ice at zero degrees C into water at zero degrees C.... and the ice needs to warm up to zero degrees C before that.

Researchers have discovered this might take thousands of years, but would eventually happen if all the fossil fuels were to be burned.

Their analysis suggests that this would cause sea level to rise by 3 metres each century during the first thousand years.
Antarctica from space
If all of the Antarctic ice melted, sea levels around the world would rise about 58 metres.

Friday, 21 April 2017

Climate Change - Animals are moving

Animals are reacting to climate change very quickly.

Some move to higher places, others move north or south.

Dragonflies love warmer temperatures.

UK dragonflies have mainly stayed in the south of the country, until recently.


Ruddy Darter (Sympetrum sanguineum)
That is over 2km per year..... nearly 6 metres per day.

For example, the ruddy darter (Sympetrum sanguineum) and the hairy dragonfly, (Brachytron pratense), have moved into north-west England. 

This is evidence that the UK’s climate is growing warmer.

"So much has happened to dragonflies in Britain since the 1990s that there is a most compelling case for the Government to adopt them as indicators of climate change", said Steve Brooks.
Mr Stephen Brooks

Scientists from the University of York  found that, on average, living things have "moved uphill" at 12.2 metres per decade.
  They are moving away from the equator at 17.6 kilometres per decade.
“These changes are equivalent to animals and plants shifting away from the Equator at around 20 cm per hour, for every hour of the day, for every day of the year. 
This has been going on for the last 40 years and is set to continue for at least the rest of this century.”
Dr I-Ching Chen said: 


“We have for the first time shown that the amount by which the distributions of species have changed is correlated with the amount the climate has changed in that region.”

I-Ching Chen and her colleagues discovered that moths had on average moved 67 metres uphill on Mount Kinabalu in Borneo.

Comma butterfly. Photo: Butterfly Conservation & Jim Asher
The Comma butterfly has moved 220 kilometres northwards from central     England to Edinburgh, in only two decades.

Thursday, 20 April 2017

Climate Change - Where does the heat go?



As global warming continues, heat goes into all parts of the Earth's systems.

The Earth is gaining more heat than it loses, and most of that heat is going into the oceans.

More heat is going into the upper parts of the oceans.

The water in the oceans is expanding, which is one reason sea level is rising.



The deepest oceans are still cold.

Some of the heat is involved in melting ice, including Arctic sea ice.



The recent reduction in Arctic sea ice is very dramatic.

The ice sheets of Greenland and Antarctica are also melting.

Wednesday, 19 April 2017

What factors can cause climate change?

The energy that affects the climate on the Earth originates from the Sun.
The energy emitted by the Sun passes through space, until it hits the Earth’s atmosphere.
Only about 40% of the solar energy hitting the top of the atmosphere passes through to the Earth’s surface.
The rest is reflected, or absorbed by the atmosphere. 

Here are some of the many factors that can cause the Earth's climate to get hotter or colder.  

These factors are sometimes referred to as 'forcings'.

Strength of the sun

The energy output of the sun is not constant, it varies over time.
Recently it has been reducing slightly.

The next two factors are astronomical cycles.

Changes in the Earth’s orbit

The Earth’s orbit around the Sun is an ellipse, not a circle, but the ellipse changes shape.
Sometimes it is almost circular - and the Earth stays approximately the same distance from the Sun as it orbits.
At other times the ellipse is more stretched, so that the Earth moves closer and further away from the sun as it orbits.
When the Earth is closer to the sun our climate is warmer.
Circular orbit

Elliptical orbit – when the Earth is closer to the Sun, its climate is warmer

Changes in the angle of the Earth’s axis of rotation



The Earth rotates around an axis (imagine a line that joins the north and south poles) but the Earth’s axis is not upright, it leans at an angle.
This angle changes with time.
Over about 41 000 years it moves from 22.1 degrees to 24.5 degrees and back again.
When the angle increases, the summers become warmer and the winters become colder.
Quantity of greenhouse gases in the atmosphere

These include carbon dioxide, methane and water vapour.
Of these, water vapour makes the greatest contribution to the greenhouse effect because there is more of it.
However, if one of those gases increases or decreases more than the others, it will be that gas that begins to affect the global temperature.

Carbon dioxide content of the oceans

The oceans contain more carbon dioxide (CO2) than the atmosphere and they can also absorb CO2 from the atmosphere.
When the CO2 is in the oceans it does not trap heat as it does when it is in the atmosphere.
Plate tectonics

Over time, plate tectonic processes cause continents to move to different positions on the globe.
For example, Britain was near to the equator 300 million years ago, and therefore was hotter than it is today.
The movement of the plates also causes volcanoes and mountains to form and these too can contribute to a change in climate.
Mountain ranges formed by plate tectonics. Large mountain chains can influence the circulation of air around the globe, and consequently influence the climate.  Warm air might be deflected somewhere cooler by the mountains.
Volcanoes formed by plate tectonics. Volcanoes affect the climate through the gases and dust particles thrown into the atmosphere during eruptions. The effect of the volcanic gases and dust may warm or cool the Earth's surface, depending on how sunlight interacts with the volcanic material.

Ocean currents

Ocean currents
Ocean currents carry heat around the Earth.
The direction of these currents can shift so that different areas become warmer and cooler.
Oceans store a large amount of heat, so that small changes in ocean currents can have a large effect on coastal and global climate.

Vegetation coverage on the land

On a global scale, patterns of vegetation and climate are closely correlated.
Vegetation absorbs carbon dioxide and this can buffer some of the effects of global warming.

Sum of the parts

Each of the above factors contribute to changes in the Earth’s climate, however the way they interact with each other makes it more complicated.
A change in any one of these can lead to additional and enhanced changes in the others.
For example, we understand that the oceans can take carbon dioxide out of the atmosphere:
When the quantity of CO2 in the atmosphere increases, the temperature of the Earth rises.
This in turn would contribute to a warming of the oceans. 

Warm oceans are less able to absorb CO2 than cold ones, so as the temperature rises, the oceans release more CO2 into the atmosphere, which in turn causes the temperature to rise again.

More on climate feedbacks here from the UK Met Office.

Tuesday, 18 April 2017

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

Fig A2


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