Tuesday, 31 January 2017

Climate Change - Floods more likely, and more damaging

Heavy rainstorms caused devastating flooding across a 12-county region of West Virginia in late June 2016.

Events like this are almost certainly made more frequent, and more intense, by global warming. 


A map from the National Weather Service shows the intensity of the rains that brought floods to the region.
Climate scientists from around the USA said that the overwhelming scientific evidence shows that the warming of the planet’s atmosphere is increasing the occurrence of, and the seriousness of, heavy rains.

Warmer air holds more water, leading to stronger and more frequent heavy precipitation events. 

This is confirmed by research done by a team of scientists of the Potsdam Institute for Climate Impact Research.


They find the worldwide increase to be consistent with rising global temperatures, caused by greenhouse-gas emissions from burning fossil fuels. 

Monday, 30 January 2017

Climate Change - How Ice Ages come & go, & why things are different now



Some people wonder if the current climate change has "natural causes".

They talk about the changes during the 'Ice Age', thinking the current events must be natural as well.

Scientists say that is not the case.

The current situation is different.

The things that caused the changes in the Ice Age are not exactly the same this time.

The graph below shows that carbon dioxide in the air has increased and decreased over hundreds of  thousands of years.

The recent increase in carbon dioxide is much bigger and faster than the natural changes.



The low readings match with times called 'glacial stages'.

During glacial stages, ice covered large areas of the Earth.


The most recent glacial stage occurred between 115,000 and 11,500 years ago. 


Glacial stages begin when those cycles cause cooling.

Glacial stages end when those cycles cause warming.

These cycles change how much solar energy reaches the Earth.

This warming changes the amount of carbon dioxide that can dissolve in the oceans.

So in that early phase, the temperature rises first, before the CO2 level rises.

(This is why some people say "CO2 lags behind temperature rise" ... which is only true in this special situation).


Then as the Earth warms, more carbon dioxide leaves the oceans.

The extra carbon dioxide gas in the air then boosts the warming effect.

At present, Milankovitch Cycles are trying to cool the Earth.

So the current warming is not part of natural processes.



Law Dome is a site in Antarctica where scientists have drilled into the ice.

Global temperatures are responding to the recent big increase in carbon dioxide.


The extra carbon dioxide has come mainly from burning fossil fuels.

The rise in carbon dioxide now means the cycle of glacial and interglacial stages may have been broken.

A research paper has looked at that issue:

"...the end of the current interglacial would occur within the next 1500 years, if atmospheric CO2 concentrations did not exceed 240±5ppmv."

So carbon dioxide would need to drop a long way below the current level for this interglacial to end.

Sunday, 29 January 2017

Climate Change - Rising sea level linked to warmer seas, and melting ice

Sea level is rising, and there are several reasons connected to global warming.


An international team of researchers has produced this graph of ocean levels, for a period of time going back to around 500 BC. 

Extra water enters the sea when ice melts from Antarctica, Greenland and other glaciers and ice caps.

Recent research suggests that the glaciers of Alaska alone now contribute 75 gigatonnes per year.

Seawater also expands as it gets warmer, just like the liquid in a thermometer expanding as temperatures rise.  This is called 'thermal expansion.'



Investigating sea level rise involves scientists using many different methods, including satellites which map the surface of the sea.

It is also important to look carefully at older records from tidal gauges all over the world.

Global sea level rise from the 20th century to the last two decades has speeded up even more than scientists previously thought, according to a new Harvard study.

NASA have reported a global sea rise of 6 cm in the last 2 decades. 

For an idea of how sea level rise might affect you: SEA LEVEL MAPS

Saturday, 28 January 2017

Climate Change - Early steps in Climate Science


1800-1870 

Level of carbon dioxide gas (CO2) in the atmosphere, as later measured in ancient ice, was about 290 ppm (parts per million).



Global temperature for 1850-1870 was about 13.6°C.

1824
Jean-Baptiste Joseph Fourier calculated that the Earth would be far colder if it lacked an atmosphere. 



1856

Eunice Foote describes filling glass jars with water vapour, carbon dioxide and air, and comparing how much they heated up in the sun.
“The highest effect of the sun’s rays I have found to be in carbonic acid gas,” 
 “The receiver containing the gas became itself much heated – very sensibly more so than the other – and on being removed, it was many times as long in cooling.”
1859
John Tyndall discovered that some gases block infra-red radiation. 



He suggested that changes in the concentration of the gases could bring climate change.





1930s 
Milutin Milankovitch proposed orbital changes as the cause of ice ages. 

1938 
Guy Callendar showed that global warming was underway, reviving interest in the question. 


1950s 
By accident, Russell Coope discovered that some past climate change events happened in just a few decades.



This came from his research into beetle fossils in 'Ice Age' layers.

1958 
Telescope studies showed a greenhouse effect raises temperature of the atmosphere of Venus far above the boiling point of water. 



1960 

Charles David Keeling accurately measured CO2 in the Earth's atmosphere.

He was not expecting to detect an annual rise.

The CO2 level was 315 parts per million (ppm)and global temperature (five-year average) was 13.9°C.

Keeling's measurements have been continued.

Current chart and data for atmospheric CO2

At the end of 2015 the level was over 400 ppm.

Global temperature in 2015 was 14.80°C.

Friday, 27 January 2017

Climate Change - Heading for 2 degrees rise in global temperatures

The highly respected Berkeley Earth project has reported that 2016 was the warmest year in the modern record.

This chart shows the annual average global temperatures up to 2015, from NASA's Goddard Institute for Space Studies (GISS)
One thing to note ….. every La Nina ‘year’ since 1998 was warmer than every El Nino ‘year’ before 1995.  

It's useful to look at average global temperatures by comparing decades.
This chart comes from the World Meteorological Organisation.

The high figures in the 1930s and 1940s were produced partly because there were strong El Ninos over a period from about 1939 to 1942.

Since the mid 20th century global temperatures have risen, decade by decade.

New research published June 2015 confirms this trend:

Over a longer term, it's obvious that the current situation is unusual.

A temperature rise of 2 degrees C above pre-industrial temperature has been agreed as a threshold beyond which climate change risks become unacceptably high.

However, there are major objections even to the "two-degree limit".
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 C —a potentially disastrous change.

The current rise in temperature has reversed all the natural trends.

Thursday, 26 January 2017

Climate Change - Repeat photography of melting glaciers

Glaciers are melting quickly in many places.



Grinnel Glacier- at the top, 1940, compared with the lower image from 2006. Repeat photography reveals this process.
melting of McCarty Glacier in Alaska


Embedded image permalink

Mount Lyell is in Yosemite National Park, California.

New research shows that glacier retreat is a global phenomenon and is "without precedent".

In 2014Exit Glacier in Alaska melted and retreated 57 metres toward the Harding ice field, which itself has lost 10 per cent of its mass since 1950.


Wednesday, 25 January 2017

Climate Change - The last 1,000 years of global temperatures

Average global temperature is now higher than it has been for a long time.


Graph by Klaus Bitterman.

Green dots show the 30-year average of the PAGES 2k reconstruction. 

The red curve shows the global mean temperature, based on HadCRUT4 data from 1850 onwards. 

In blue is the original "hockey stick" from paper by Mann, Bradley and Hughes (1999) with its uncertainty range (light blue). 

The green dots are calculated using data from many places around the world, using information from a range of temperature proxies, such as documents, ice, lakes, pollen, tree rings, corals, seabeds and speleothems.
78 researchers from 24 countries, together with many other colleagues, worked for seven years in the "PAGES 2k" Project on this climate reconstruction. 

Their study is based on 511 climate archives from around the world.

PAGES is the Past Global Changes programme launched in 1991. 

Tuesday, 24 January 2017

Climate Change - Evidence from Ice Cores

Ice cores are cylinders of ice, drilled from an ice sheet or a glacier. 


They are usually 10 centimetres in diameter, and can be taken from deep in the ice.

Ice cores provide trapped samples of ancient air.


"Air bubbles trapped in ice are like little time capsules that record the past atmospheric composition. 

"So we measure loads of different gases, and essentially we can measure greenhouse gases such as carbon dioxide and methane."

Most ice core records come from Antarctica and Greenland.


Law Dome is a location in Antarctica.

The evidence in Law Dome ice cores shows that since the 18th century, when the Industrial Revolution began, the level of carbon dioxide has risen.

Now it has reached around 400 ppm, a rise of 85 ppm in just 56 years.  

The longest ice cores are from 3km deep in ice. 

The oldest ice core records extend 123,000 years in Greenland, and now to 1 million years in Antarctica. 


The graph shows how carbon dioxide has increased and decreased over hundreds of  thousands of years.

During glacial stages, ice covered large areas of the Earth.

The most recent glacial stage occurred between about 120,000 and 11,500 years ago. 



Since then, the Earth has been in an interglacial period called the Holocene.

During glacial stages, CO2 levels were around 200 parts per million (ppm).

During the warmer interglacial periods, they hovered around 280 ppm. 

In 2013, CO2 levels passed 400 ppm for the first time in recorded history. 

A new study using evidence from a highly detailed ice core from West Antarctica shows a link between abrupt temperature changes on Greenland and Antarctica during the last ice age.

Monday, 23 January 2017

Climate Change - The Iceman

In places which are not as frozen as they were, amazing discoveries have been made.


In 1991 two hikers in the Alps found a body.

They were shocked, and reported the find.

It was even more extraordinary when the investigation found that the body was thousands of years old.



The clothing, weapons and other items found with the body give a glimpse into life when metal was first being used.



Tests later confirmed the iceman dates back to 3,300 BC.

He probably died from a blow to the back of the head. 


His body was so well-preserved that scientists were able to determine that his last meal was red deer, herb bread, wheat bran, roots and fruit.


He lived at a time, over 5,000 years ago, when the Earth was starting to cool.



So when he died high in the mountains, his body became covered with snow.

Modern warming (shown by the red part of the graph) made it possible to find him.

Sunday, 22 January 2017

Climate Change - The Greenhouse Effect

What do scientists mean by the "Greenhouse Effect"?

When the Sun's energy arrives at the Earth, it travels through the air.

Some is reflected back to space, but some hits the Earth and warms it.

The warm Earth gives off infrared radiation with various wavelengths.  


Some of those waves can pass back out of the air to space, but some are absorbed by certain gases in the air.


If there are more of those gases, less heat escapes into space.



Concentrated 'greenhouse gases' on Venus have caused the surface temperature to rise to 735 Kelvin (462 degrees C; around 900 degrees F)



Carbon dioxide levels in the atmosphere have risen quickly since people began burning large quantities of fossil fuels.

There was carbon dioxide in the air before that, at around 270 parts per million.

Without any carbon dioxide, the Earth would be very cold.

The temperature would be around -18 degrees C.

There have been times when most of the carbon dioxide was trapped in rocks.

The Earth cooled into a state called 'Snowball Earth'




These ancient events are unlikely to be repeated - they occurred when the Sun was producing less energy.

Saturday, 21 January 2017

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, 20 January 2017

Climate Change - Iceland

Iceland lies on the Mid-Atlantic Ridge, which is why it has volcanic activity.





Iceland also has ice caps and glaciers.

Iceland is one of the fastest-warming places on the planet – as much as four times the Northern Hemisphere average. 
The glaciers that cover more than 10 percent of the island are losing an average of 11 billion tons of ice a year. 
              Iceland glacial meltwater - photo Tom Harding
The water melting from Iceland's glaciers would fill 50 of the world's largest trucks every minute.
Parts of Iceland are rising as the ice caps melt, reducing the weight on the Earth's crust.

The thinning of the ice caps reduces the pressure on the rocks.
Geologists know lower pressure from above makes volcanoes erupt more easily.
Lower pressure allows volcanic gases to expand, and mantle rocks melt more easily at lower pressure as well.


So more magma can rise into the volcanic systems.
As that happens, Iceland's volcanoes may get more active.

Thursday, 19 January 2017

Climate Change - 2016 - Warmest year in modern record

2016 was the warmest year in NOAA's 137-year series. 

This is the third consecutive year a new global annual temperature record has been set. 


All 16 years of the 21st century are included in the seventeen warmest years in the modern record (1998 is currently the eighth warmest.) 

The five warmest years have all occurred since 2010.

It is increasingly likely the Earth is now warmer than at any time since the Eemian Interglacial, over 115,000 years ago.

The Eemian was warmer than the Holocene because of higher insolation.
Insolation refers to the amount of solar energy received per unit time at any one location, and it was higher due to astronomical cycles.

Wednesday, 18 January 2017

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.