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.