Ice CORES, TREE RINGS, OCEAN SEDIMENTS, COSMOGENIC EXPOSURE DATING
Header source: https://climate.nasa.gov/news/2616/core-questions-an-introduction-to-ice-cores/.
All three major global surface temperature reconstructions:
show that the Earth has warmed since 1880[1] The year 2015 was the first time global average temperatures were 1 degree Celsius or more above the 1880-1899 average[2], and surface temperatures continue to increase. Most of the warming has occurred in the past 35 years, with 15 of the 16 warmest years on record occurring since 2001. Recall that only gases which can absorb longwave (IR), low photon energy radiation can reradiate the Earth’s energy.
How do we know this?
Ancient air bubbles trapped in ice enable us to step back in time and see what Earth's atmosphere and climate were like in the distant past[3]. They tell us that levels of carbon dioxide (CO2) in the atmosphere are higher than they have been at any time in the past 400,000 years. During the ice ages, CO2 levels were around 200 parts per million (ppm), and during the warmer interglacial periods, they hovered around 280 ppm (see fluctuations in the graph below). In 2013, CO2 levels surpassed 400 ppm for the first time in recorded history. This recent relentless rise in CO2 shows a remarkably constant relationship with fossil-fuel burning, and can be well accounted for based on the simple premise that about 60 percent of fossil-fuel emissions stay in the air.
Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks. This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly ten times faster than the average rate of ice-age-recovery warming.
Drilling in the Antarctic
Presently (2019), scientists are retrieving ice core samples in Antarctica that provide physical evidence of how CO2 levels have risen from 280 parts per million to more than 400 parts per million. Within 2 years, they expect to start digging 280 metres deep into the ice in the hope of retrieving a core of ice that will record changes going back a million years to see how the system operated in the longer term. Two parallel cores are planned to provide the best chance of success and to validate findings.[4]
Drilling is also under way in the Antarctic for molecules known as hydroxyl radicals which bond oxygen and hydrogen and act like atmospheric scrubbers destroying non-CO2 greenhouse gasses such as methane, which contribute about a third of the extra warming on the planet by trapping additional heat from the sun in the atmosphere.[5] Hydroxyl is naturally produced in the atmosphere, but is so reactive that a radical only lasts about a second before destroying a pollutant molecule and itself. It is very difficult to quantify, even in the modern atmosphere, and we presently have no idea whether this cleanser has increased or decreased since pre-industrial times.
The researchers won't be able to find the radical compound itself because hydroxyl is not successfully stored for any length of time in a container, let alone for hundreds of years in ice. Rather, the scientists are after a proxy molecule, the carbon-14 isotope of monoxide, which is radioactive and will indirectly reveal the past abundance of hydroxyl.
So delicate are the experiments that the drills can't use drill fluids that would otherwise have allowed them to go deeper to, say, 1750 when the industrial era roughly began. Also, the ice has to be treated immediately it is extracted to preserve as much as possible the purity of the cores. Upon extraction, the ice is melted and the key evidence placed in stainless steel tanks and shipped away for testing. The process is anticipated to take over a year at research facilities such as the ANSTO nuclear facility at Lucas Heights in Sydney.
Those involved in the testing expect to see a decline of hydroxyl during the post-industrial period. Similar testing is also taking place in the northern hemisphere, involving drilling into Greenland's ice sheets although those cores are likely to be much dirtier than in the Antarctic. The implications of proving a reduced ability to destroy methane, which now has a life in the atmosphere of about a decade, would be profound, depending on the scale of any decline, and the potential for hydrogen to serve as a "clean fuel" could also be placed in doubt. A recalibration of the major climate models underpinning the Paris climate agreement that almost 200 nations have signed up to may also be required. [5]
Other methods of research
Another method is “cosmogenic exposure dating”: testing chunks of rock for isotopes created by cosmic radiation[6]. This technique has been utilised on the remote and tiny island of South Georgia in the South Atlantic Ocean to determine whether the ice sheets in that area have shrunk or remained constant over a period. Seeing the amount of isotopes, like aluminium and beryllium, in the rock shows scientists how long ago the rock was covered by ice. As the ice sheet goes past the piece of bedrock under scrutiny it exposes that rock to cosmic rays[6] and starts the clock. Testing revealed that the ice sheets in that area had shrunk to a tenth of their original size since the last ice age, likely as a result of our planet’s warming climate, and showed how sensitive marine based ice sheets are to ocean warming. It was formerly thought that they were more of less the same as they are today.
[1] https://www.ncdc.noaa.gov/indicators/; http://www.cru.uea.ac.uk/cru/data/temperature; http://data.giss.nasa.gov/gistemp
[2] http://www.giss.nasa.gov/research/news/20160120/
[3] This material is from “Graphic: the relentless rise of carbon dioxide: NASA Global Climate Change. Vital signs of the planet” at https://climate.nasa.gov/climate_resources/24/ See also https://climate.nasa.gov/evidence/
[4] Julie Power, "Ancient history locked in the ice", SMH, 4 January 2019.
[5] Finbar O’Mallon, “Going to the ends of the earth for science”, Sydney Morning Herald, 20 March 2017, p 11.
[5] This is an edited summary of an article by Peter Hannam, “Deep dig for missing piece of puzzle”,which appeared in the Sun-Herald, 27 January 2019: https://www.smh.com.au/environment/climate-change/terrifying-scientists-dig-deep-for-missing-piece-of-climate-puzzle-20190125-p50tjs.html
[6] Cosmic rays are a type of radiation that comes from space. Cosmic rays aren't really "rays". They are particles (mostly protons) with very high energies. Cosmic rays come from various places, including the Sun, supernova explosions, and extremely distant sources such as radio galaxies and quasars. They were discovered by the Austrian-American physicist Victor Hess in 1912: http://www.windows2universe.org/physical_science/physics/atom_particle/cosmic_rays.html
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All three major global surface temperature reconstructions:
- the National Climatic Data Centre, now NOAA (see below),
- the Climatic Research Unit (a component of the University of east Anglia), and
- NASA’s Goddard Institute for Space Studies)
show that the Earth has warmed since 1880[1] The year 2015 was the first time global average temperatures were 1 degree Celsius or more above the 1880-1899 average[2], and surface temperatures continue to increase. Most of the warming has occurred in the past 35 years, with 15 of the 16 warmest years on record occurring since 2001. Recall that only gases which can absorb longwave (IR), low photon energy radiation can reradiate the Earth’s energy.
How do we know this?
Ancient air bubbles trapped in ice enable us to step back in time and see what Earth's atmosphere and climate were like in the distant past[3]. They tell us that levels of carbon dioxide (CO2) in the atmosphere are higher than they have been at any time in the past 400,000 years. During the ice ages, CO2 levels were around 200 parts per million (ppm), and during the warmer interglacial periods, they hovered around 280 ppm (see fluctuations in the graph below). In 2013, CO2 levels surpassed 400 ppm for the first time in recorded history. This recent relentless rise in CO2 shows a remarkably constant relationship with fossil-fuel burning, and can be well accounted for based on the simple premise that about 60 percent of fossil-fuel emissions stay in the air.
Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks. This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly ten times faster than the average rate of ice-age-recovery warming.
Drilling in the Antarctic
Presently (2019), scientists are retrieving ice core samples in Antarctica that provide physical evidence of how CO2 levels have risen from 280 parts per million to more than 400 parts per million. Within 2 years, they expect to start digging 280 metres deep into the ice in the hope of retrieving a core of ice that will record changes going back a million years to see how the system operated in the longer term. Two parallel cores are planned to provide the best chance of success and to validate findings.[4]
Drilling is also under way in the Antarctic for molecules known as hydroxyl radicals which bond oxygen and hydrogen and act like atmospheric scrubbers destroying non-CO2 greenhouse gasses such as methane, which contribute about a third of the extra warming on the planet by trapping additional heat from the sun in the atmosphere.[5] Hydroxyl is naturally produced in the atmosphere, but is so reactive that a radical only lasts about a second before destroying a pollutant molecule and itself. It is very difficult to quantify, even in the modern atmosphere, and we presently have no idea whether this cleanser has increased or decreased since pre-industrial times.
The researchers won't be able to find the radical compound itself because hydroxyl is not successfully stored for any length of time in a container, let alone for hundreds of years in ice. Rather, the scientists are after a proxy molecule, the carbon-14 isotope of monoxide, which is radioactive and will indirectly reveal the past abundance of hydroxyl.
So delicate are the experiments that the drills can't use drill fluids that would otherwise have allowed them to go deeper to, say, 1750 when the industrial era roughly began. Also, the ice has to be treated immediately it is extracted to preserve as much as possible the purity of the cores. Upon extraction, the ice is melted and the key evidence placed in stainless steel tanks and shipped away for testing. The process is anticipated to take over a year at research facilities such as the ANSTO nuclear facility at Lucas Heights in Sydney.
Those involved in the testing expect to see a decline of hydroxyl during the post-industrial period. Similar testing is also taking place in the northern hemisphere, involving drilling into Greenland's ice sheets although those cores are likely to be much dirtier than in the Antarctic. The implications of proving a reduced ability to destroy methane, which now has a life in the atmosphere of about a decade, would be profound, depending on the scale of any decline, and the potential for hydrogen to serve as a "clean fuel" could also be placed in doubt. A recalibration of the major climate models underpinning the Paris climate agreement that almost 200 nations have signed up to may also be required. [5]
Other methods of research
Another method is “cosmogenic exposure dating”: testing chunks of rock for isotopes created by cosmic radiation[6]. This technique has been utilised on the remote and tiny island of South Georgia in the South Atlantic Ocean to determine whether the ice sheets in that area have shrunk or remained constant over a period. Seeing the amount of isotopes, like aluminium and beryllium, in the rock shows scientists how long ago the rock was covered by ice. As the ice sheet goes past the piece of bedrock under scrutiny it exposes that rock to cosmic rays[6] and starts the clock. Testing revealed that the ice sheets in that area had shrunk to a tenth of their original size since the last ice age, likely as a result of our planet’s warming climate, and showed how sensitive marine based ice sheets are to ocean warming. It was formerly thought that they were more of less the same as they are today.
[1] https://www.ncdc.noaa.gov/indicators/; http://www.cru.uea.ac.uk/cru/data/temperature; http://data.giss.nasa.gov/gistemp
[2] http://www.giss.nasa.gov/research/news/20160120/
[3] This material is from “Graphic: the relentless rise of carbon dioxide: NASA Global Climate Change. Vital signs of the planet” at https://climate.nasa.gov/climate_resources/24/ See also https://climate.nasa.gov/evidence/
[4] Julie Power, "Ancient history locked in the ice", SMH, 4 January 2019.
[5] Finbar O’Mallon, “Going to the ends of the earth for science”, Sydney Morning Herald, 20 March 2017, p 11.
[5] This is an edited summary of an article by Peter Hannam, “Deep dig for missing piece of puzzle”,which appeared in the Sun-Herald, 27 January 2019: https://www.smh.com.au/environment/climate-change/terrifying-scientists-dig-deep-for-missing-piece-of-climate-puzzle-20190125-p50tjs.html
[6] Cosmic rays are a type of radiation that comes from space. Cosmic rays aren't really "rays". They are particles (mostly protons) with very high energies. Cosmic rays come from various places, including the Sun, supernova explosions, and extremely distant sources such as radio galaxies and quasars. They were discovered by the Austrian-American physicist Victor Hess in 1912: http://www.windows2universe.org/physical_science/physics/atom_particle/cosmic_rays.html
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