December 2008 Archives

At last year's AGU Fall Meeting, environmentalresearchweb spoke to David Crisp of NASA to find out more about the Orbiting Carbon Observatory (see http://environmentalresearchweb.org/cws/article/research/32196). Since then, progress has been good and the satellite is due for launch sometime after January 30th 2009 from an air force base near Los Angeles.

Speaking at a press briefing, Crisp's colleague Scott Denning detailed how the observatory will help us find out more about Earth's carbon sinks. Currently these vary in the amount of carbon they absorb from year to year and nobody knows why. "Some years almost all the fossil carbon enters the atmosphere, some years almost none," he said. "On average it's about half."

This variability adds to the uncertainty of our climate future, especially as we don't know how land and ocean uptake will change in the long-term. Denning says that by the end of the century it's estimated that the ocean could be absorbing between 3 billion and 9 billion tonnes of carbon a year. The land, meanwhile, could be taking up as much as 11 billion tonnes or even acting as a source of 6 billion tonnes a year if there are large amounts of forest and ecosystem dieback. So depending on how this plays out, the same levels of human emissions of carbon could lead to atmospheric levels of carbon dioxide that differ by up to 300 parts per million.

What's more, with the introduction of systems such as the European Carbon Exchange, carbon sinks are becoming a commodity. On November 11th of this year, the price of carbon on the exchange was $102 per tonne. Earth's carbon sinks currently absorb around 4 billion tonnes of carbon a year: to buy that amount of carbon removal on the exchange (assuming it were available, which it isn't) would cost $408 billion. As Denning put it, "that's a lot of money even by bailout standards".

This year's AGU Fall Meeting session on geoengineering had twice as many submissions as last year - proof that the field is attracting increasing serious attention. But it's still a highly controversial area. Not only are there ethical issues involved in committing future generations to maintaining the technology and the fact that it may negatively affect some regions of the globe, but also little is known about which approach is best, how effectively it will work or how much it will cost.

One potential method - introducing sulphate aerosols into the atmosphere to reflect sunlight away from Earth - has already been tested to some degree by nature as a result of volcanic eruptions. Alan Robock of Rutgers University, US, outlined his estimates of the costs of injecting 1 Teragram of sulphur (in the form of hydrogen sulphide) into the lower stratosphere. Robock says hundreds of US KC-135 Stratotankers for refuelling jets are about to become obsolete and could be diverted for geoengineering use. That would cost around $70 million a year, which compares relatively favourably with the $30 billion a year he estimates for using balloons or naval rifles to inject the sulphur, or the $800 billion it could take to develop a space elevator. "Using airplanes would not be costly, especially if we use existing military ones," concluded Robock, "but there are still many reasons not to."

David Mitchell of the Desert Research Institute, on the other hand, is looking at modifying cirrus clouds to prevent them trapping so much of the longwave radiation from the surface of the Earth. Seeding the clouds with a compound such as silver iodide leads to the production of larger ice crystals that fall out of the cloud quicker. Ultimately the system could result in less cirrus cloud coverage and lower atmospheric humidity levels, enabling more longwave radiation to escape into space. Mitchell says we could introduce the seeds into the upper troposphere either at mid-latitudes and the poles, where the greenhouse effect is largest, or over the whole globe. One means to do this could be for the airline industry to dope fuel with the seeding compound or introduce it separately into jet engine exhaust fumes.

 Mitchell sees the technique as potentially buying time for a transition to green technologies and stresses that it wouldn't solve ocean acidification. But it does have the advantage over sulphur injection techniques that it wouldn't cause acid rain or ozone depletion.

"We have a much sharper knowledge of global climate sensitivity than is usually stated and the Faustian bargain we have cut for ourselves is nastier than we have recognized," said Jim Hansen of NASA to a packed lecture theatre on day three of the AGU Fall Meeting.

Hansen believes that governments don't yet recognize the urgency of climate change. "There are a lot of governments who say they understand the problems, but a lot of it is greenwash," he said. "The Venus Syndrome [in which Earth undergoes runaway warming and the oceans boil off] is the greatest threat to humanity's existence. Earth is Goldilock's choice of the planets - not too hot, not too cold, it's just right."

In the past there have been several periods where temperatures have dropped so low that the planet entered a "Snowball Earth" state, with ice covering the entire surface of the globe. But that slows the process of weathering by rocks and enables carbon dioxide levels to build up in the atmosphere, eventually leading to warming.

According to Hansen, there is no escape from the Venus Syndrome, which could occur for a forcing of 10-20 Watts per square metre. For comparison, the net forcing today is between 0 and 3 Watts per square metre. Although in the past carbon dioxide levels have reached 4000 parts per million (ppm) without a runaway warming effect, solar irradiance was lower. And today humans are increasing carbon dioxide levels at 2 ppm per year, 10,000 times faster than natural rates, which does not allow time for feedback effects to kick in.

"If we burn all the coal, we might kick in a runaway greenhouse effect, and if we burn all the tar shale and tar sands we definitely will," said Hansen, who reckons we could decide to leave coal in the ground or use it only with carbon dioxide capture and storage. "We're going to have to figure out how to power ourselves without it anyhow so why not do it sooner rather than later?"

Hansen is a strong advocate of a carbon tax, the profits of which go to the public to encourage them to buy into new technologies. "Caps aren't going to work," he said. "I think we will solve the problem but that does require a carbon price that is significant and rising." He also believes that the US should have continued R&D on fourth-generation nuclear power, which enables the burning of nuclear waste to leave substances with a radioactive half-life of a few tens of years rather than tens of thousands of years.

It's not just tropical rainforests that store carbon - cities do too, in features such as soil, vegetation, people, landfill and wood in buildings, furniture and books. In fact, human settlements store 18 Pg of carbon, equivalent to the amount locked up in US croplands. So says Galina Churkina of the Leibniz Centre for Agricultural Landscape Research in Germany, who reckons that the cities of the future could use massive amounts of interior wood panelling to act as a carbon store.

The density of an urban centre also affects its carbon storage potential. Closely-packed areas such as downtown San Francisco are efficient as they release fewer carbon emissions per head and store more carbon per unit area in their tall buildings. But suburban areas store more carbon overall, in lawns and vegetation, although they're likely to have higher emissions from transport for commuting and shopping.

In a similar vein, Amy Townsend-Small of the University of California, Irvine has been measuring the greenhouse gas emissions from four parks in Orange County, California. If the grass photosynthesizes during the day faster than it respires overnight, on balance it will remove carbon from the atmosphere. And you can increase the chances of this by adding water and fertilizer. But there is a downside - too much fertilization and overwatering can induce the plant to give off nitrous oxide, a greenhouse gas 300 times more powerful than carbon dioxide.

Of the four parks Townsend-Small and co-workers examined, the older sites had stored the most carbon because of carbon accumulation. But the oldest park was a net source of greenhouse gases because of its nitrous oxide release. The newer parks, in contrast, were net greenhouse gas sinks, although the calculations didn't include carbon emissions from fuel used in park maintenance and from transporting water. Townsend-Small says the research could lead to recommendations for park-managers to use less fertilizer.

While you might assume that a peak and subsequent decline in oil production would be good news for the climate, there's so much coal left that the effect is likely to be limited. "The amount of oil is not very important in determining future carbon dioxide emissions," said Ken Caldeira of the Carnegie Institute. "Coal is the big bear on the block."

That said, the way that we replace oil is still significant. "Will the end of oil usher in a century of coal or a century of low carbon technologies?," pondered Caldeira. "The need for liquid fuels could drive coal liquefaction."

The upper atmosphere is expanding and contracting in cycles with periods of 5, 7 and 9 days, according to Jeff Thayer of the University of Colorado, Geoff Crowley of ASTRA, and Marty Mlynczak of NASA, who spoke about their work at a press briefing at the AGU Fall Meeting. The researchers believe the density changes are caused by the rotation of solar coronal holes - dark fixed features on the solar surface that project strong solar winds - as the sun goes round. The resulting changes in solar wind stream speed reaching Earth lead to geomagnetic storms and auroras, which act as a heat source.

This newly discovered "breathing mode" could affect satellite movements, the avoidance of collisions with space debris, the electron density in the ionosphere, radio communications, GPS systems, atmospheric composition, vertical wind circulation, and even weather at the Earth's surface. According to Crowley, there are two potential connections to weather - changes in the ionosphere could cause thunderstorms, and auroral particles could create nitric oxide that's then transported to the lower atmosphere where it could affect ozone distribution at high latitudes. "We wouldn't expect a 9 day cycle of weather," he said, "but somebody should look at that".

There was further worrying news about the Arctic at the AGU Meeting this morning. Igor Semiletov of the University of Alaska Fairbanks detailed results from a 12,000 nautical mile long survey of the entire Eurasian Arctic continental shelf for International Polar Year. Worryingly, the International Siberian Shelf Study (ISSS-08)  found that methane is emerging from the East Siberian Arctic Shelf, as evidenced by bubble clouds of methane in the sea and methane bubbles trapped in sea ice in the winter. It looks like the sub-sea permafrost is failing due to warmer ocean temperatures and allowing methane to escape; because the Siberian Sea is very shallow the methane isn't oxidized as it travels to the surface. "We didn't know that the huge carbon pool there is extremely vulnerable," said Semiletov. Some have predicted that a 6 ppm increase in atmospheric methane concentrations could induce abrupt climate change - Semiletov says that would require the release of only 1-2% of the methane stored under the East Siberian Arctic Shelf.

It's fair to say that climate change is an issue that's in the public eye but the same's not true for its close relation, ocean acidification. In one of the first pieces of public outreach work for the topic, researcher Elizabeth Kolbert wrote an article for the New Yorker in 2006 entitled "The Darkening Sea". Retired history teacher Sven Huseby read the piece and was horrified - since then he's created a documentary, together with Niijii Films, that it's hoped could be the "Inconvenient Truth" for ocean acidification.

Each year weather-related phenomena such as hurricanes, tornadoes, forest fires, flooding, heavy snows and drought cause damage worth billions of dollars across the US. Knowledge about how climate change will affect these and other factors is critical for local and regional planning, supporting the introduction of carbon reduction ideas such as cap-and-trade, forecasting for renewable energy sources like wind turbines, and predicting the release of methane from permafrost, according to Jack Fellows, vice-president of  the University Corporation for Atmospheric Research (UCAR).

Welcome to environmentalresearchweb's first blog entry from the American Geophysical Union Fall Meeting. It's been a hectic day as nearly 15,000 researchers gather from around the globe in a San Francisco experiencing its second day of rain after a nearly month-long dry spell.

As Terry Wilson of Ohio State University, US, explained, measurements of ice loss in Antarctica and the Arctic should become a whole lot more accurate as data starts to come in from an International Polar Year project. In turn, that should help predictions of global sea level rise.