Jennifer Marohasy

a forum for the discussion of issues concerning the natural environment

Archives for April 30, 2008

Antarctic Snowfall and Temperature Trends in Global Climate Models

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”We compare new observationally-based data sets of Antarctic near-surface air temperature and snowfall accumulation with 20th century simulations from global climate models (GCMs) that support the Intergovernmental Panel on Climate Change Fourth Assessment Report. Annual Antarctic snowfall accumulation trends in the GCMs agree with observations during 1960–1999, and the sensitivity of snowfall accumulation to near-surface air temperature fluctuations is approximately the same as observed, about 5% K−1. Thus if Antarctic temperatures rise as projected, snowfall increases may partially offset ice sheet mass loss by mitigating an additional 1 mm y−1of global sea level rise by 2100. However, 20th century (1880–1999) annual Antarctic near-surface air temperature trends in the GCMs are about 2.5-to-5 times larger-than-observed, possibly due to the radiative impact of unrealistic increases in water vapor. Resolving the relative contributions of dynamic and radiative forcing on Antarctic temperature variability in GCMs will lead to more robust 21st century projections.”

The above is the abstract from:

Monaghan, A. J., D. H. Bromwich, and D. P. Schneider (2008), Twentieth century Antarctic air temperature and snowfall simulations by IPCC climate models, Geophys. Res. Lett., 35, L07502, doi:10.1029/2007GL032630.

Roger Pielke Sr comments:

“This paper provides further evidence that the multi-decadal global climate models are significantly overstating the water vapor input into the atmosphere, and thus are not providing quantitatively realistic estimates of how the climate system responds to the increase in atmospheric well mixed greenhouse gases in terms of the water vapor feedback. This water vapor feedback is required in order to achieve the amount of warming from radiative forcing projected in the 2007 IPCC report.”

Changing Habitat – A Note from Gavin

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A former resident of Canberra complained today on talkback radio about how the city had become “tatty” during her brief absence. Apparently her family now lives somewhere up the north coast and have green lawns. The difference I reckoned was that the ACT region has missed out again in late autumn with our miserable share of La Nina.

Out on the western fringe of suburbia a few local residents have been watching two strange visitors for a week or so. Opposite my place is another dead tree, a large Eucalyptus nicholii that was planted as a street tree back in the early 1970’s. A few bird droppings on parked cars was the first clue. My neighbor pointed up to some high branches and eventually I recognized the shapes, a pair (?) of tawny frogmouths perched motionless in the higher branches.

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This messy old tree would normally have been condemned as a neighborhood hazard and removed on schedule with many others, however overnight it became “habitat” for what I believe after glimpsing another big wary gray bird on the outer limb late yesterday, two young owls left day by day by their parents.

Despite prying eyes, noisy cars, trucks and machinery underneath these beautifully camouflaged individuals remained seemingly motionless for days. Unfortunately I think a gang of currawongs has finally driven them off.

Note the clear blue sky in my latest photo.

Gavin

Earth’s CO2 Balance

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Using evidence from an Antarctic ice core, Zebee and Caldiera calculated that over a period of 610,000 years the long-term change in atmospheric CO2 concentration was just 22 parts per million volume (ppmv), although there were larger fluctuations associated with the transitions between glacial and interglacial conditions.

By comparison, two centuries of human industry have raised levels by about 100 ppmv.

BBC News website: Nature’s carbon balance confirmed

Nature Geoscience: Close mass balance of long-term carbon fluxes from ice-core CO2 and ocean chemistry records

Richard E. Zeebe & Ken Caldeira

Natural Gas to Replace Oil in Australia?

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The recent prediction by the head of Caltex Australia that the price of oil may very well double the already record highs for crude, have only heightened concerns about the security of Australia’s future fuel supplies. The Federal Government, for instance, has launched a national energy security assessment.

As oil production in Australian fields declines, the Government has also sought and won approval under the United Nations Convention on the law of the sea, to expand its search for oil offshore by an area equivalent to five times the size of France.

But Federal Resources Minister Martin Ferguson agrees that unless there is soon a “eureka oil strike”, Australia must find a new fuel alternative with sufficient reserves to power a vast and vital national car and transport fleet.

But there are those who say there’s an obvious solution to the fuel crisis right under our collective nose, a solution that could cut fuel bills by up to 60 per cent: natural gas.

ABC – The 7.30 Report: Natural gas: the future of fuel?

Mercedes is offering the new Sprinter transporter with natural-gas drive, with operating costs 30 per cent lower than comparable diesel-engined versions.

Drive.com.au: Mercedes van with natural-gas drive