Jennifer Marohasy

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2000 Years of North Icelandic Sea Surface Temperatures

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A new paper has been published by Sicre et al in Earth and Planetary Science Letters entitled: ‘Decadal variability of sea surface temperatures off North Iceland over the last 2000 years.’

The Abstract states:
Ocean variability at decadal time-scales remains poorly described partly because of the scarcity of high temporal resolution marine records. Here, we present a reconstruction of Sea Surface Temperatures (SSTs) over the past two millennia at unprecedented temporal resolution (2 to 5 years), from a marine core located off North Iceland. Alkenone paleothermometry was used to infer SST variability, and tephrochronology to build the age model. Spectral analyses of the SST signal indicate intermittent 20–25 year oscillations, with periods of strong and weak power, that are likely reflecting the ocean response to wind forcing, presumably the North Atlantic Oscillation (NAO). Warmer SSTs and paleo-magnetic proxy data, between 1000 and 1350 year A.D., overlapping the Medieval Warm Period (MWP), suggest enhanced heat transport across the Denmark Strait by the North Icelandic Irminger Current (NIIC). This is in contrast with the subsequent period, which includes the Little Ice Age (LIA), showing continuous cooling towards the 20th century. Reduced NIIC flow through the Denmark Strait likely resulting from higher freshwater and sea ice export from the Arctic would account for the observed colder conditions.

Keywords: Decadal variability; Sea surface temperature; North Atlantic; Alkenones; Medieval Warm Period; Little Ice Age; Iceland

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The authors state in the Discussion:

“A remarkable feature of the North Icelandic SST record is the abrupt increase of around 1–1.5 °C occurring within a decade around 980 A.D., maybe imputable to the onset of the MWP. This sustained warm period, lasting for several centuries, ends by a sharp cooling around 1350 A.D., following a brief cold episode around 1250 A.D. The same pronounced centennial-scale warming, though not exactly synchronous, has been documented by the distant records from the Sargasso Sea (Keigwin, 1996), the Eastern sub-tropical Atlantic (deMenocal et al., 2000) and estuarine sediments of Chesapeake bay (Cronin et al., 2005), confirming its widespread occurrence in the North Atlantic region.”

Hat tip to CO2Science.org

How ‘Green’ is the Hybrid Car?

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On 10th June we learned that Australia’s first locally manufactured hybrid car will roll off Toyota’s production line in less than two years, in a deal Victorian Premier John Brumby has heralded as a ‘coup’.

Prime Minister Kevin Rudd and Toyota’s president Katsuaki Watanabe made the announcement today in Japan.

ABC News: Brumby lauds $35m Toyota hybrid ‘coup’

I don’t have any axe to grind over Hybrid cars, I’d just like to know the truth about how ‘green’ they really are. In the US and UK there has been some controversy over the ‘dust to dust’ or ‘life cycle’ CO2 emissions, costs and energy useage of the Toyota Prius. Toyota supposedly produced their own report, which to the best of my knowledge has never been made public. A CNW Marketing report claimed that the dust to dust cost per mile for a Toyota Prius was $3.249, compared to $3.027 for Hummer H2. There is more in a balanced article from the UK Telegraph from 2007 entitled: Who are you kidding?

This news has reached Australia:

As more Australians scramble to buy hybrid petrol/electric cars, Britain’s biggest-selling auto magazine has taken a swipe at them, saying hybrids are no better for emissions than an efficient diesel or petrol-driven car.

The magazine Auto Express says none of the hybrids’ advertised emissions figures were borne out in their test drives.

ABC News: Hybrid cars ‘not so green’

Meanwhile, Toyota are promising a ‘plug-in’ hybrid for 2010.

Thanks to Luke for alerting me to Australia embracing the hybrid car, while I was on holiday in Spain – I’m still catching up!

Jason – 2 Ocean Research Satellite Due for Launch

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Teams of climate change researchers around the world will be anxiously counting down the launch of the Jason-2 satellite from California, scheduled for 20 June 2008. Successful lift-off will mean a whole new era in detecting the expansion of our oceans and sea level rise, both major indicators of climate change.

CSIRO: ‘Countdown to Satellite Launch and new era of ocean research’

The Only Way is UP: Reality Trumps Emissions Projections

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There is a new paper (in press) in the journal Climatic Change by Peter Sheenan of the Centre for Strategic Economic Studies, Victoria University, Melbourne, Australia entitled: ‘The new global growth path: implications for climate change analysis and policy’

The Abstract states:

In recent years the world has moved to a new path of rapid global growth, largely driven by the developing countries, which is energy intensive and heavily reliant on the use of coal—global coal use will rise by nearly 60% over the decade to 2010. It is likely that, without changes to the policies in place in 2006, global CO2 emissions from fuel combustion would nearly double their 2000 level by 2020 and would continue to rise beyond 2030. Neither the SRES marker scenarios nor the reference cases assembled in recent studies using integrated assessment models capture this abrupt shift to rapid growth based on fossil fuels, centred in key Asian countries. While policy changes must and will occur, the realism of the reference case is critical for analysis and policy formulation. Using such a reference path will have significant effects on impact and damage estimates, on the analysis of achievable stabilisation paths and on estimates of the costs of achieving stabilisation at a given GHG concentration level. Use of a realistic reference path is also essential for the international negotiations, arising out of the COP13 meeting in Bali, to achieve widely desired stabilisation goals: both the level of emission reductions to be achieved, and the preferred distribution of those reductions over countries and regions, will be heavily influenced by the reference case assumed.

Meanwhile, China has clearly overtaken the United States as the world’s leading emitter of carbon dioxide, a new study has found, its emissions increasing 8 percent in 2007. The Chinese increase accounted for two-thirds of the growth in the year’s global greenhouse gas emissions.

As UK Aussie Rolf Harris would say, “Can you tell what it is yet?”

Hat tip to Prometheus.

New Paper has Implications for Tree Ring Data

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A new paper has been published in the journal Nature entitled: ‘Subtropical to boreal convergence of tree-leaf temperatures’ by Brent R. Helliker & Suzanna L. Richter, which has implications for climate reconstructions using tree ring data.

The Abstract states:

The oxygen isotope ratio (18O) of cellulose is thought to provide a record of ambient temperature and relative humidity during periods of carbon assimilation. Here we introduce a method to resolve tree-canopy leaf temperature with the use of 18O of cellulose in 39 tree species. We show a remarkably constant leaf temperature of 21.4 2.2 °C across 50° of latitude, from subtropical to boreal biomes. This means that when carbon assimilation is maximal, the physiological and morphological properties of tree branches serve to raise leaf temperature above air temperature to a much greater extent in more northern latitudes. A main assumption underlying the use of 18O to reconstruct climate history is that the temperature and relative humidity of an actively photosynthesizing leaf are the same as those of the surrounding air. Our data are contrary to that assumption and show that plant physiological ecology must be considered when reconstructing climate through isotope analysis. Furthermore, our results may explain why climate has only a modest effect on leaf economic traits in general.

There is a summary of the paper in Nature News here.

The authors state in the text of the article:

“Our analysis shows that reconstructing ambient humidity by using tree-ring d18O becomes increasingly dubious as MAT [mean annual temperature] decreases. Caution is therefore advised when interpreting treering d18O data from high latitudes for both contemporary samples and samples of relictual wood from high-latitude forests of the past.”

and:

“The discovery of relatively invariant leaf temperatures has two important ramifications that transcend stable-isotope studies. First, elevated canopy temperature and depressed leaf relative humidity should have a large effect on real and modelled water loss from boreal ecosystems. Second, if the architectural controls of branches on leaf temperature are as widespread as our data suggest, then direct climatic selection on the evolution of leaf traits would be relaxed, whereas the selective force of climate on other plant organs (for example stems and roots) would remain. Our results therefore offer a possible explanation for the unexpected finding that climate is a minor correlate with global leaf economic traits.”

Roger Pileke Sr’s take on this is:

This study has major implications with respect to the use of tree ring data to reconstruct long term air temperature trends, as the authors indicate in their text.

This study also illustrates the dynamic response of vegetation to their environment so as to maximize the ability to grow and compete within their ecological environment. This biological effect must be incorporated within climate models that seek to accurately simulate the response of the climate to human and natural effects, including the increase of the atmospheric concentration of CO2.

Potentially Even Bigger Feral Cats to be Imported into Australia

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Feral cats, along with wild dogs and foxes, are thought to have a devastating impact on populations of small native animals in parts of the Australian bush. But the future may be even bleaker with a larger and more ferocious breed of cat, known as the Savannah, expected to be introduced into Australia in the next five years.

According to the Sydney Morning Herald:

“More than 30 savannahs – which cost $5000 for a pet and $10,000 for a breeding animal – are expected to come to Australia in the next five years, with up to 16 now in US quarantine.

“Hybrids of wild animals and domestic animals are a stupid American trend to breed more and more exotic pets,” said Professor Peacock, who works at the University of Canberra.

“This loophole will effectively lead to fitting a nuclear warhead to our already devastating feral cat population. Haven’t our native animals got enough to contend with?”

“Mr Parker dismissed suggestions that the animals could threaten native wildlife, saying they would not be allowed to roam. The company demands that customers sign a contract stipulating specific housing arrangements.

Read more here.