Ice cores drilled in the Greenland ice sheet, recounting the history of the last great warming period more than 120,000 years ago, are giving scientists their clearest insight to a world that was warmer than today.
In a paper published today in the journal Nature, scientists have used a 2540 metre long Greenland ice core to reach back to the Eemian period 115-130 thousand years ago and reconstruct the Greenland temperature and ice sheet extent back through the last interglacial. This period is likely to be comparable in several ways to climatic conditions in the future, especially the mean global surface temperature, but without anthropogenic or human influence on the atmospheric composition.
The Eemian period is referred to as the last interglacial, when warm temperatures continued for several thousand years due mainly to the earth’s orbit allowing more energy to be received from the sun. The world today is considered to be in an interglacial period and that has lasted 11,000 years, and called the Holocene.
“The ice is an archive of past climate and analysis of the core is giving us pointers to the future when the world is likely to be warmer,” said CSIRO’s Dr Mauro Rubino, the Australian scientist working with the North Greenland Eemian ice core research project.
Dr Rubino said the Greenland ice sheet is presently losing mass more quickly than the Antarctic ice sheet. Of particular interest is the extent of the Greenland continental ice sheet at the time of the last interglacial and its contribution to global sea level.
Deciphering the ice core archive proved especially difficult for ice layers formed during the last interglacial because, being close to bedrock, the pressure and friction due to ice movement impacted and re-arranged the ice layering. These deep layers were “re-assembled” in their original formation using careful analysis, particularly of concentrations of trace gases that tie the dating to the more reliable Antarctic ice core records.
Using dating techniques and analysing the water stable isotopes, the scientists estimated the warmest Greenland surface temperatures during the interglacial period about 130,000 years ago were 8±4oC degrees warmer than the average of the past 1000 years.
At the same time, the thickness of the Greenland ice sheet decreased by 400±250 metres.
“The findings show a modest response of the Greenland ice sheet to the significant warming in the early Eemian and lead to the deduction that Antarctica must have contributed significantly to the six metre higher Eemian sea levels,” Dr Rubino said.
Additionally, ice core data at the drilling site reveal frequent melt of the ice sheet surface during the Eemian period.
“During the exceptional heat over Greenland in July 2012 melt layers formed at the site. With additional warming, surface melt might become more common in the future,” the authors said.
The paper is the culmination of several years work by organisations across more than 14 nations.
Dr Rubino said the research results provide new benchmarks for climate and ice sheet scenarios used by scientists in projecting future climate influences.
Media: Craig Macaulay. Ph: +61 3 6232 5219 E: email@example.com
Carbon dioxide emission reductions required to limit global warming to 2°C are becoming a receding goal based on new figures reported today in the latest Global Carbon Project (GCP) calculations published today in the advanced online edition of Nature Climate Change.
“A shift to a 2°C pathway requires an immediate, large, and sustained global mitigation effort,” GCP executive-director and CSIRO co-author of the paper, Dr Pep Canadell said.
Global CO2 emissions have increased by 58 per cent since 1990, rising 3 per cent in 2011, and 2.6 per cent in 2012. The most recent figure is estimated from a 3.3 per cent growth in global gross domestic product and a 0.7 per cent improvement in the carbon intensity of the economy.
Dr Canadell said the latest carbon dioxide emissions continue to track at the high end of a range of emission scenarios, expanding the gap between current trends and the course of mitigation needed to keep global warming below 2°C.
He said on-going international climate negotiations need to recognise and act upon the growing gap between the current pathway of global greenhouse emissions and the likely chance of holding the increase in global average temperature below 2°C above pre-industrial levels.
The research, led by Dr Glen Peters from CICERO, Norway, compared recent carbon dioxide emissions from fossil fuel combustion, cement production, and gas flaring with emission scenarios used to project climate change by the Intergovernmental Panel on Climate Change (IPCC).
“We need a sustained global CO2 mitigation rate of at least 3 per cent if global emissions are to peak before 2020 and follow an emission pathway that can keep the temperature increase below 2˚C,” Dr Peters said.
“Mitigation requires energy transition led by the largest emitters of China, the US, the European Union and India”.
He said that remaining below a 2°C rise above pre-industrial levels will require a commitment to technological, social and political innovations and an increasing need to rely on net negative emissions in future.
The Global Carbon Project, supported by CSIRO and the Australian Climate Change Science Program, generates annual emission summaries contributing to a process of informing policies and decisions on adaptation, mitigation, and their associated costs. The summaries are linked to long-term emission scenarios based on the degree of action taken to limit emissions.
Media: Craig Macaulay Ph: +61 3 6232 5219 Alt Ph: +61 4 1996 6465 E: Craig.Macaulay@csiro.au
The Australian Government has awarded almost $50 million to build a research facility that will help make cuts to Australia’s greenhouse gas emissions.
The National Geosequestration Laboratory (NGL), being built in Perth, will provide critical research to advance technologies to store CO2 emissions securely and safely underground.
The geological storage of CO2 is a key technology that can help reduce greenhouse gas emissions from the atmosphere by injecting the gases into deep underground rock formations.
We recently blogged about the Otway Project, which has shown that depleted gas fields can be used to store significant amounts of our CO2 emissions.
The NGL will play a crucial role in achieving a low-emission economy for Australia and reducing its carbon footprint.
Exhausted gas reservoirs could provide the solution to reducing global greenhouse gas emissions.
Researchers working on the CO2CRC Otway Project in Victoria have shown that depleted gas fields can be used to store significant amounts of our carbon dioxide emissions.
Since 2008, over 65,000 tonnes of CO2 rich gas has been injected, stored and monitored two kilometers underground in a depleted natural gas reservoir in the Otway Basin.
The project has demonstrated that the deep underground storage (‘geosequestration’ in technical terms) of CO2 is a technically and environmentally safe way to make deep cuts into Australia’s greenhouse gas emissions.
Link to CO2CRC media release: http://www.co2crc.com.au/dls/media/11/OtwayProjectPNAS_final.pdf