“Concentrations will probably hover around 401 ppm over the next month as we sit near the annual low point. Brief excursions towards lower values are still possible but it already seems safe to conclude that we won’t be seeing a monthly value below 400 ppm this year—or ever again for the indefinite future,” Ralph Keeling, director of the CO2 program at Scripps Institution of Oceanography, wrote in a blog post.
The increase in CO2 levels runs parallel to a marked increase in global temperatures.
Scientists have observed an increase in carbon dioxide’s greenhouse effect at the Earth’s surface for the first time. The researchers, led by scientists from the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), measured atmospheric carbon dioxide’s increasing capacity to absorb thermal radiation emitted from the Earth’s surface over an eleven-year period at two locations in North America. They attributed this upward trend to rising CO2levels from fossil fuel emissions.
The influence of atmospheric CO2 on the balance between incoming energy from the Sun and outgoing heat from the Earth (also called the planet’s energy balance) is well established. But this effect has not been experimentally confirmed outside the laboratory until now. The research is reported Wednesday, Feb. 25, in the advance online publication of the journal Nature.
The results agree with theoretical predictions of the greenhouse effect due to human activity. The research also provides further confirmation that the calculations used in today’s climate models are on track when it comes to representing the impact of CO2.
The scientists measured atmospheric carbon dioxide’s contribution to radiative forcing at two sites, one in Oklahoma and one on the North Slope of Alaska, from 2000 to the end of 2010. Radiative forcing is a measure of how much the planet’s energy balance is perturbed by atmospheric changes. Positive radiative forcing occurs when the Earth absorbs more energy from solar radiation than it emits as thermal radiation back to space. It can be measured at the Earth’s surface or high in the atmosphere. In this research, the scientists focused on the surface.
They found that CO2 was responsible for a significant uptick in radiative forcing at both locations, about two-tenths of a Watt per square meter per decade. They linked this trend to the 22 parts-per-million increase in atmospheric CO2 between 2000 and 2010. Much of this CO2 is from the burning of fossil fuels, according to a modeling system that tracks CO2 sources around the world.
“We see, for the first time in the field, the amplification of the greenhouse effect because there’s more CO2 in the atmosphere to absorb what the Earth emits in response to incoming solar radiation,” says Daniel Feldman, a scientist in Berkeley Lab’s Earth Sciences Division and lead author of the Nature paper.
“Numerous studies show rising atmospheric CO2 concentrations, but our study provides the critical link between those concentrations and the addition of energy to the system, or the greenhouse effect,” Feldman adds.
He conducted the research with fellow Berkeley Lab scientists Bill Collins and Margaret Torn, as well as Jonathan Gero of the University of Wisconsin-Madison, Timothy Shippert of Pacific Northwest National Laboratory, and Eli Mlawer of Atmospheric and Environmental Research.
The scientists used incredibly precise spectroscopic instruments operated by the Atmospheric Radiation Measurement (ARM) Climate Research Facility, a DOE Office of Science User Facility. These instruments, located at ARM research sites in Oklahoma and Alaska, measure thermal infrared energy that travels down through the atmosphere to the surface. They can detect the unique spectral signature of infrared energy from CO2.
Other instruments at the two locations detect the unique signatures of phenomena that can also emit infrared energy, such as clouds and water vapor. The combination of these measurements enabled the scientists to isolate the signals attributed solely to CO2.
“We measured radiation in the form of infrared energy. Then we controlled for other factors that would impact our measurements, such as a weather system moving through the area,” says Feldman.
The result is two time-series from two very different locations. Each series spans from 2000 to the end of 2010, and includes 3300 measurements from Alaska and 8300 measurements from Oklahoma obtained on a near-daily basis.
Both series showed the same trend: atmospheric CO2 emitted an increasing amount of infrared energy, to the tune of 0.2 Watts per square meter per decade. This increase is about ten percent of the trend from all sources of infrared energy such as clouds and water vapor.
Based on an analysis of data from the National Oceanic and Atmospheric Administration’s CarbonTracker system, the scientists linked this upswing in CO2-attributed radiative forcing to fossil fuel emissions and fires.
The measurements also enabled the scientists to detect, for the first time, the influence of photosynthesis on the balance of energy at the surface. They found that CO2-attributed radiative forcing dipped in the spring as flourishing photosynthetic activity pulled more of the greenhouse gas from the air.
A new material powered by sunlight could help to drastically cut carbon emissions
Emissions from coal power stations could be drastically reduced by a new, energy-efficient material that adsorbs large amounts of carbon dioxide, then releases it when exposed to sunlight.
In a study published today in Angewandte Chemie, Monash University and CSIRO scientists for the first time discovered a photosensitive metal organic framework (MOF) – a class of materials known for their exceptional capacity to store gases. This has created a powerful and cost-effective new tool to capture and store, or potentially recycle, carbon dioxide.
By utilising sunlight to release the stored carbon, the new material overcomes the problems of expense and inefficiency associated with current, energy-intensive methods of carbon capture. Current technologies use liquid capture materials that are then heated in a prolonged process to release the carbon dioxide for storage.
Associate Professor Bradley Ladewig of the Monash Department of Chemical Engineering said the MOF was an exciting development in emissions reduction technology.
“For the first time, this has opened up the opportunity to design carbon capture systems that use sunlight to trigger the release of carbon dioxide,” Associate Professor Ladewig said.
“This is a step-change in carbon capture technologies.”
A promising and novel class of materials, MOFs are clusters of metal atoms connected by organic molecules. Due to their extremely high internal surface area – that could cover an entire football field in a single gram – they can store large volumes of gas.
PhD student Richelle Lyndon and lead author of the paper said the technology, known as dynamic photo-switching was accomplished using light-sensitive azobenzene molecules.
“The MOF can release the adsorbed carbon dioxide when irradiated with light found in sunlight, just like wringing out a sponge,” Ms Lyndon said.
“The MOF we discovered had a particular affinity for carbon dioxide. However, the light responsive molecules could potentially be combined with other MOFs, making the capture and release technology appropriate for other gases.”
The researchers, led by Professor Matthew Hill of CSIRO, will now optimise the material to increase the efficiency of carbon dioxide to levels suitable for an industrial environment.
The study was supported by the Science and Industry Endowment Fund.
A family of nanoporous materials well known for their gas separation properties can sort molecules with much more sophistication than previously thought. Researchers in Australia have discovered that certain zeolites don’t act as simple molecular sieves, but rather separate molecules according to their ability to open ‘molecular trapdoors’ within the zeolite structure. Carbon dioxide molecules are particularly adept at slipping through these trapdoors, making it a promising discovery for industrial gas separation technologies such as carbon capture.
The trapdoor mechanism was discovered by Paul Webley at the University of Melbourne, Jefferson Liu at Monash University and their colleagues. The researchers were investigating new zeolite structures as part of their work for the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) when they noticed some unusual behaviour. The particular zeolite they were studying, a chabazite, wasn’t just taking up carbon dioxide in preference to larger molecules – expected behaviour for a molecular sieve – it was also taking up carbon dioxide in preference to smaller ones.
Key to this behaviour, the researchers found, was the behaviour of free metal ions in their chabazite structure. These cations balance the negative charge of the zeolite framework and sit within the oxygen-rich nanopores that act as doorways through which gases enter the structure. ‘It’s a bit like when you want to go into a bar and there’s a bouncer at the door,’ says Webley. ‘If you sweet-talk the bouncer then he’ll move aside and let you through – and that’s what the CO2 molecule is able to do.’
Carbon dioxide can slip past the cation bouncers because of its electron-rich oxygen atoms. By interacting with the cation and partly stabilising it, the cation becomes less tightly bound within the doorway, moving aside enough for the carbon dioxide molecule to slip past. The cation then snaps back into place, preventing other gases from riding on the carbon dioxide’s coat tails. Webley suspects that other, known zeolites might also work in the same way.
The material’s behaviour is promising for two key industrial gas separation processes: separating carbon dioxide from nitrogen in flue gases and removing carbon dioxide from natural gas. ‘We see a nice take-up of CO2 and almost no take-up at all of nitrogen or methane,’ says Webley. ‘Those selectivities are right in the ballpark for what we are looking for.’
Randy Snurr, who researches nanoporous materials for gas separation at Northwestern University, US, is impressed by the research. ‘It provides a new insight into what people thought they had understood for a long time, this old idea of molecular sieving,’ he says. ‘They have used a whole array of techniques to back up this picture, but then they do the very practical thing and pass gas mixtures through the material and they see this very nice selectivity.’
While the zeolite’s selectivity is high, its CO2 uptake capacity is modest, admits Webley. However, the team’s future work will include efforts to grow the zeolites in the form of membranes through which only CO2 can pass, circumventing the capacity issue.
J Shang et al, J. Am. Chem. Soc., 2012, DOI: 10.1021/ja309274y
Editors note: Original article can be found here.