Sunday, 31 December 2017

Climate Change - The link with mass extinctions

What is the worst-case scenario for climate change?

The geological record shows that when the atmosphere suddenly changes, there are big effects on living things.

Five major mass extinction events are recorded in the rock record of the last 600 million years.
The biggest extinction was at the end of the Permianaround 252 million years ago.
It is called the End-Permian mass extinction.


Only about 8% of species survived to live on in the Triassic Period.

Researchers have found evidence of a compound called fly ash, one of the products of coal combustion, in rocks laid down just before this extinction event. 

A large amount of coal had been burned over a period of tens of thousands of years.



The coal was burned by volcanic eruptions that happened in Siberia, which produced a large area of volcanic rocks called the Siberian Traps.

The burning actually happened underground, with the carbon dioxide and ash mixing with magma.



This produced vast amounts of CO2 which warmed the Earth and changed the chemistry of the oceans.

Saturday, 30 December 2017

Climate Change - The Medieval Warm Period and the Little Ice Age

Why can’t recent climate change just be an effect of 'natural causes'?

There have been climate changes in the past 2000 years.


People talk about times called the Medieval Warm Period and the Little Ice Age.


Careful research has shown that the current temperature is warmer than the Medieval Warm Period - temperatures between 1000 and 1100 AD were probably similar to parts of the 20th century, but 21st century temperatures are already warmer.


How does the Medieval Warm Period compare to current ...

The Medieval Warm Period may not even have been a global event - glaciers on Baffin Island were no smaller during that time.

A particularly cool period is often called the Little Ice Age.

However, the name "Little Ice Age" is now regarded by some scientistsas misleading.


The best estimate of the drop in temperature is, at most, 0.5°C, compared to the temperature decreases in "real" ice ages of about 8°C. 


Also, the "Little Ice Age" only lasted for 500 years at most, compared to the 20,000 years of the last ice age.


The start of that period is associated with the major volcanic eruption in 1257 of the Samalas volcano, next to Mount Rinjani on the island of Lombok, Indonesia.


Fig. 2.


This eruption was followed by famines in many places.

In 1258, a monk in England reported: "The north wind prevailed for several months… scarcely a small rare flower or shooting germ appeared, whence the hope of harvest was uncertain... Innumerable multitudes of poor people died, and their bodies were found lying all about swollen from want… 


The lowest temperatures in the "Little Ice Age", between about 1570 and 1730, were during a period of almost continuous smaller-scale volcanic activity.


The Industrial Revolution, when coal burning began on a large scale, started the recent rise in temperatures, reversing the longer-term very slow cooling trend.

Friday, 29 December 2017

Climate Change - What does 'climate' actually mean?

Some people confuse 'climate' with 'weather' - but 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.

Thursday, 28 December 2017

Climate Change - Charting the rising levels of carbon dioxide

Carbon dioxide levels in the atmosphere are rising.


The small up-and-down pattern is caused by changes during each year - in the summer in the northern hemisphere, there is more photosynthesis which causes CO2 levels to fall.

The Keeling Curve is named after the scientist who first produced accurate measurements of carbon dioxide in the air - Charles David Keeling.  


Charles David Keeling in the lab.

Keeling's collection of data began in 1958.

Concentration is measured in parts per million (ppm)

Ice core data shows humans have never breathed air containing so much CO2.


Since Keeling began recording, CO2 has risen from 318 ppm to 400 ppm... a rise of around 25%. 

The fastest rise of CO2 in the air seen in the ice core record (800,000 years) is 20 ppm in 1000 years.

There is evidence that CO2 has never risen so fast since the extinction of the dinosaurs.

The CO2 level in the atmosphere is now rising at around 20 ppm per decade.

Carbon reacts with oxygen when fossil fuels are burned.


Each carbon atom joins with two oxygen atoms to make a carbon dioxide molecule

Measurements show that this is reducing the oxygen in the air as time passes.
Several scientific organisations measure the gases in the air.

One major set of measurements are from a laboratory in Hawaii.

This is all evidence that extra carbon dioxide in the air comes from burning fossil fuels. 

We are time-warping vast amounts of ancient carbon (which we are combining with current oxygen) into the modern atmosphere.

In 2010 about 9 Gigatonnes of Carbon (GtC) were emitted from burning fossil fuels, as 33 Gigatonnes of CO2 gas.

How much is 33 Gigatonnes? 
33 billion tonnes or 33,000,000,000,000,000 grams.
9 Gigatonnes of carbon weighs about the same as 132 billion people. 

Wednesday, 27 December 2017

Climate Change - The Long-Term Effects


According to the Royal Society.......

If human emissions of CO2 stopped altogether...


.... it would take thousands of years for atmospheric CO2 to return to ‘pre-industrial’ levels.

"The climatic impacts of releasing fossil fuel CO2 to the atmosphere will last longer than Stonehenge," says University of Chicago oceanographer David Archer.

"Longer than time capsules, longer than nuclear waste, far longer than the age of human civilization so far."

Why is that?

It takes a long time for deep oceans to bury the carbon dioxide in ocean sediments. 


abyssal sea floor life

Lifee on the abyssal sea floor (depths ranging from 4000-6000 m) near the Hudson Canyon off the coast of New Jersey. Photo taken using the Deep Submersible Research Vessel (DSRV) Alvin'scamera system. Image courtesy of Deep East 2001, NOAA/OER.

Surface temperatures would stay high for at least a thousand years.


Humans would face a warmer planet due to past and current emissions.


Ice would still be melting from places like Antarctica and Greenland.



So sea level would continue to rise for many centuries, even after temperature stopped increasing.

new study published in Nature Climate Change looks at the next 10,000 years.
The researchers found that the catastrophic impact of another three centuries of carbon pollution will persist for thousands of years after the carbon dioxide releases cease.

The current warming of the Earth can't be reversed on a human timescale. 


But if fossil fuels are not phased out soon, the situation will be far worse.



Research that investigated what would happen if all the fossil fuels are burned has come to some worrying conclusions:
“Burning all fossil fuels” would warm land areas on average about 20°C (36°F) and warm the poles a stunning 30°C (54°F). 
This “would make most of the planet uninhabitable by humans, thus calling into question strategies that emphasize adaptation to climate change.” 
Calculated warming over land areas averages approximately 20°C. 
Such temperatures would eliminate grain production in almost all agricultural regions in the world.

Tuesday, 26 December 2017

Climate Change - Arctic sea ice

The Arctic includes an ocean covered by sea ice.
The area of Arctic sea ice is largest in March each year, and at its lowest each September.



The NSIDC also publish this graph, which is normally updated every day.

More graphs and other data are also available from the Arctic Data Archive System, operated by the Japanese Arctic Environmental Observation Center.

The total volume of Arctic sea ice has declined dramatically over time.


New research shows the decline in Arctic sea ice area since 1850:

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



Monday, 25 December 2017

Climate Change - Mammoths (and methane) from the permafrost

The permafrost of places like Siberia is not so permanently frozen any more.

As it slowly melts, wonderful things are emerging, some frozen for tens of thousands of years.

Baby mammoths are sometimes found in an extraordinary state of preservation.



"As the Earth warms, scientists worry that some of the carbon in permafrost could escape to the atmosphere as carbon dioxide or methane. 

Increasing the amount of these gases in the atmosphere could make Earth's climate warm up even more."

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



There are many effects of global warming, including melting permafrost, discussed in this useful document: 



The results of melting permafrost could be disastrous and irreversible.

Sunday, 24 December 2017

Climate Change - Measuring the Greenhouse Effect

Scientists have observed an increase in carbon dioxide’s greenhouse effect at the Earth’s surface.  



The graphs show carbon dioxide’s increasing greenhouse effect at two locations. 

The first graph shows COradiative forcing measurements obtained in Oklahoma

The second graph shows similar upward trends in Alaska. (Credit: Berkeley Lab)
The researchers link this to rising CO2 levels from fossil fuel emissions.

Radiative forcing measures how the planet’s energy balance is altered by atmospheric changes. 

Positive radiative forcing occurs when the Earth absorbs more energy from solar radiation than it emits as heat radiation back to space.

“We see, for the first time in the field, the amplification of the greenhouse effect because there’s more COin the atmosphere to absorb what the Earth emits in response to incoming solar radiation,” says Daniel Feldman.



Dr Feldman is a scientist in Berkeley Lab’s Earth Sciences Division and is lead author of the paper.

Saturday, 23 December 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.
 

Friday, 22 December 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.

Thursday, 21 December 2017

Winter solstice

Summer in the south, winter in the north.

Seasons are caused by the tilt in the Earth's axis.

Winter Solstice is the time of the longest night and shortest day.
























Many ancient monuments are lined up with the solstice, which suggests it was an important moment of the year for many cultures.

One is Maeshowe on Orkney.



Others include Stonehenge and Newgrange.


Winter solstice sunset at Stonehenge in the mid-1980s. Image via Wikimedia Commons.

Archaeologists have found evidence that prehistoric people brought animals to Stonehenge from as far as north-east Scotland, to take part in midwinter feasts and ceremonies.

One of the key researchers who has made a special study of Stonehenge in recent years is Professor Mike Parker Pearson.


He has written a number of academic papers and books on these recent discoveries.

Wednesday, 20 December 2017

Climate Change - The concept of sensitivity

"Climate sensitivity" is the term used for the amount of global warming to be expected if we double the amount of CO2 in the air.

For thousands of years CO2 concentration was around 260 ppm to around 280 ppm - since the Industrial Revolution it has risen to over 400 ppm.




The graph of CO2 concentration as recorded since the 1950s is known as the Keeling Curve, named after Professor Charles David Keeling, who began the regular measurements of this value.



If we get to around 560 ppm CO2 (around twice the pre-industrial level) we might well get to more than a 3 C degree rise, as that's a plausible value of climate sensitivity as reported by research from the geological record.


Climate sensitivity is well-researched from the geological record in this paper:
a warming of 2.2–4.8 K per doubling of atmospheric CO2
Even the lower value would have serious consequences, and the probability that the value is high is much greater. 

Tuesday, 19 December 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 ........"

Monday, 18 December 2017

Climate Change - Comparing the Polar Regions

Earth's polar regions 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.