Tuesday, 25 February 2020

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"

Monday, 24 February 2020

Climate Change - The Australian Heatwave of December 2019

Eucla, in south-east Western Australia, hit 49.8 degrees Celsius on December 19th, 2019.

World temperatures map shows Australia is on fire

The map shows Australia coloured dark red, indicating temperatures around 40°C. However, some spots of the country are covered with white spots, indicating the heat was inching towards 50°C.

Leading climate scientist Stefan Rahmstorf said.....
"the probability for this extreme heat occurring by chance in a world without global heating is essentially zero. "
Braidwood fire
Huge bushfires swept through many areas, destroying homes and wildlife.

It is estimated that around a billion animals died.
Another leading climate scientist, Michael Mann, said ...
"Yes -we might have still seen an Australian heat wave, but we wouldn't have seen such a RECORD early summer heatwave in the absence of human-caused planetary warming..."


Sunday, 23 February 2020

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 NiƱe 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:
2017 was the warmest non-El Nino year in the modern record.



This chart shows global temperatures month by month, coded according to El Nino and La Nina, with neutral conditions in grey.

Saturday, 22 February 2020

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.



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, and floods the delta-top.




Friday, 21 February 2020

Climate Change - Have humans caused climate change for longer than thought?

An international research project has found human activity has been causing global warming for almost two centuries, according to a report in Phys.Org
Humans have caused climate change for 180 years
Australian National University researcher Associate Professor Nerilie Abram. Credit: Stuart Hay, ANU
Lead researcher Associate Professor Nerilie Abram from The Australian National University (ANU) said that their study found that warming began during the early stages of the Industrial Revolution.

Warming is first detectable in the Arctic and tropical oceans around the 1830s, much earlier than scientists had expected.
CO2 information from ice cores shows that atmospheric CO2 levels began to rise from around 280 ppm as the 19th century began.
Atmospheric CO2 concentration over the last millennium, as reconstructed from ice core data obtained by Etheridge et al. (1998) at Law Dome, Antarctica.

Thursday, 20 February 2020

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.

Wednesday, 19 February 2020

Climate Change - The Palaeocene-Eocene Thermal Maximum

The geological record contains examples of major temperature changes, associated with changes in atmospheric CO2.


Matthew Huber at Purdue University calculated that warming slightly in excess of 10 degrees C—like that of the PETM and of pessimistic scenarios for future fossil-fuel burning—could render large portions of the planet uninhabitable for many creatures. He has said:
"There used to be subtropical forests near the poles 50 million years ago, and that doesn’t sound so bad.
"But the fossil record closer to the equator is really poor, and that may be an indication that life was extremely stressed during these warm periods.
"If over half the surface area of the planet becomes inhospitable, it will not render Earth uninhabitable, but it will be unrecognizable and existentially challenging for the majority of the people, species and communities on Earth."
Some researchers suggest the Palaeocene-Eocene Thermal Maximum, might be partly connected to an impact event that ignited forests.

During the PETM, a massive influx of carbon flooded the atmosphere and Earth warmed by 5 - 8 C degrees.

A recent research paper contains this quote:
"Given currently available records, we demonstrate that the present anthropogenic carbon release rate is unprecedented throughout the Cenozoic (past 66 million years)."
This graph compares the current situation with the PETM event around 56 million years ago:
We are doing something very extraordinary......

At current emissions rates, we’re just five generations away from creating an atmosphere the likes of which hasn’t been seen in 56 million years.

There are a number of other suggestions about how all the carbon compounds were added to the atmosphere to cause the PETM.

One is that the vulcanism along the newly-rifting Atlantic margins (producing the Atlantic Ocean basin) broke through various fossil fuel deposits such as oil and gas reservoirs.
Another is that stored methane was released from the oceans, again perhaps due to heating caused by that vulcanism.
Another is that a large shallow seaway that cut across a continent may have become cut off and then dried out; this exposed lots of peat-type material that became oxidised and hence produced lots of CO2.