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
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
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
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.
"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
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
The density of an urban centre also affects
its carbon storage potential. Closely-packed areas such as downtown
In a similar vein, Amy Townsend-Small of the
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
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
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
There was further worrying news about the
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
As Terry Wilson of
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