Saturday, 31 March 2018

Climate Change - Is the Sun causing Global Warming? Or about to cause Global Cooling?

It is often claimed that the Sun is causing global climate change.

The Sun is the source of the heat on the Earth, but it has not suddenly become more active recently.

The Sun may be going into a phase of lower activity - but that will not reverse global warming.

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, so the Earth warms.

In the graph below, from the Stanford Solar Center, carbon dioxide data comes from the Law Dome ice core in Antarctica, and from the observatory on Mauna Loa in Hawaii.


There is no doubt why the Earth is warming.

A new study says that even if the Sun's activity did drop off for a while, it wouldn't have much impact on rising global temperatures. 

It could mean a higher chance of some chilly winters in Europe and the US, but the researchers say:

The idea that global temperature over the last few centuries is connected to solar activity has been disproved by astronomers.

There is now too much carbon dioxide in the air for there to be a repeat of the 'Little Ice Age'.


In fact, it is very likely that human activity has finally broken the cycle of glacial and interglacial stages.

Friday, 30 March 2018

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. 

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. 

Thursday, 29 March 2018

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



Some people claim 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.

Wednesday, 28 March 2018

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

Tuesday, 27 March 2018

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.



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

Global temperature in 2015 was 14.80°C.

Monday, 26 March 2018

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. 

Sunday, 25 March 2018

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.

Saturday, 24 March 2018

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.

Embedded image permalink

Mount Lyell is in Yosemite National Park, California.

New research shows that glacier retreat is a global phenomenon and is being caused by climate change:
....in many places, the centennial-scale retreat of the local glaciers does indeed constitute categorical evidence of climate change.
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.


Friday, 23 March 2018

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.

Thursday, 22 March 2018

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) - this is not going to happen on Earth.


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.

Wednesday, 21 March 2018

Climate Change - 2017 global temperature report

According to the US National Oceanic and Atmospheric Administration, 2017 was the warmest year in the modern record without an El Niño present in the tropical Pacific Ocean.


The 2017 average global temperature across land and ocean surface areas was:

..... 0.84°C above the 20th century average of 13.9°C, behind the record year 2016 (+0.94°C) and 2015 (+0.90°C, the second warmest year on record). 

2015 and 2016 were both influenced by a strong El Niño episode. 



The chart above comes from State of Climate in 2017, a report from the World Meteorological Organisation.

Tuesday, 20 March 2018

Spring Equinox in the Northern Hemisphere

Every place on earth experiences 12 hours of daylight twice a year, on the Spring and Autumn Equinox.



The Sun is at its lowest path in the sky on the Winter Solstice

After that day, the Sun follows a higher and higher path through the sky each day, until it is in the sky for exactly 12 hours. 

On the Spring Equinox, the Sun rises almost exactly in the east, travels through the sky for 12 hours, and sets almost exactly in the west. 



The March equinox marks the moment the Sun appears to cross the celestial equator – the imaginary line in the sky above the Earth’s equator – from south to north. 

After the March equinox, northern days continue to lengthen until the June solstice.

Monday, 19 March 2018

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.

Daniel Rothman, Professor of geophysics in the MIT Department of Earth, Atmospheric and Planetary Sciences and co-director of MIT’s Lorenz Center, has identified “thresholds of catastrophe” in the carbon cycle that, if exceeded, would lead to an unstable environment, and ultimately, mass extinction.

Sunday, 18 March 2018

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.

Saturday, 17 March 2018

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 was set. 


All 17 years of the 21st century are included in the 18 warmest years in the modern record (1998 completes the top 18.) 

Preliminary analysis puts 2017 as the warmest non-El Nino year.

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.

Friday, 16 March 2018

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.


For more on research into the climate of the Pliocene, and what it can tell us about the likely effects of 400 ppm CO2, "Science News" has a very good article.