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January 20, 2012 10:05 pm
This winter is turning out mild over the mid-latitudes of Europe and north America but we should not feel complacent. The severe cold experienced in 2009/10 and 2010/11 could turn out to be a feature of northern hemisphere winters over the next few years, according to research by US climatologists.
Their study, published in the journal Environmental Research Letters, explains the apparent contradiction between recent harsh winters, global warming and the loss of Arctic sea ice.
The past two decades have seen strong warming during the summer and early autumn over the Arctic, which has caused unprecedented melting of sea ice. The result is more moisture in the atmosphere, which, in turn, results in increased precipitation over the northern Eurasian continent – where it is still cold enough in the autumn to fall as snow rather than rain.
The researchers, who come from Atmospheric & Environmental Research and the universities of Massachusetts and Alaska, say data analysis confirms that average October snow cover over Eurasia – and particularly Siberia – has grown since 1988.
The effect of increased autumn snow cover is to intensify the seasonal cooling of the Eurasian continent and strengthen the area of high pressure that forms over Siberia in the winter. As a result the Arctic Oscillation, the atmospheric pressure pattern in the mid-to-high latitudes, is more likely to be in the “negative phase” that feeds cold polar air across the eastern half of the US and northern Europe.
“In my mind there is no doubt that the globe is getting warmer,” says Judah Cohen, lead author of the paper. “However, I do think that the increasing trend in snow cover has led to regional cooling… and I see no reason why this won’t continue into the near future.”
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But if climate change proceeds further, to a stage where the increased autumnal precipitation over Siberia falls as rain rather than snow, the winter cooling effect will disappear.
The authors say conventional climate models have failed to pick up on the winter cooling observed recently because they do not account well for the variability of snow cover – which could greatly improve the accuracy of seasonal forecasts.
“Without correctly simulating the coupling of winter climate patterns and the variability of snowfall, the models currently used by government centres miss an important influence on winter and will therefore continue to be deficient in predicting winter weather,” says Cohen.
Want a long life? It’s all in the telomeres
Telomeres, the protective stretches of DNA that cap the ends of the genetic chromosomes in all living creatures, play an important role in ageing. As an individual grows older, the telomeres gradually erode away, but scientists do not know how strongly this erosion influences longevity.
Now Glasgow University researchers have carried out the first study in which telomere length has been measured in individuals repeatedly over their lifetime.
They worked with zebra finches, taking samples of blood cells from a group of birds whose lifespan varied from just 210 days to almost nine years. The study was published in the Proceedings of the National Academy of Sciences.
The best predictor of longevity was telomere length at 25 days. “While there was a lot of variation among individuals in telomere length, those birds that lived longest had the longest telomeres at every measurement point,” says Britt Heidinger of Glasgow.
Variation in telomere length is partly inherited but also varies in response to factors such as exposure to stress.
“Our study shows the great importance of processes acting early in life,” says Pat Monaghan, the research leader. “We now need to know more about how early life conditions can influence the pattern of telomere loss, and the relative importance of inherited and environmental factors.”
Duncan Baird of Cardiff University medical school says: “[This study] provides a nice demonstration of how telomere length at a specific developmental stage can predict longevity. However translating this information into the long-lived and heterogeneous human population will be more challenging.”
Tiny frog leaps into the record books
A tiny frog, recently discovered in New Guinea, has taken the title of the world’s smallest known vertebrate. Paedophryne amauensis, named after Amau village where a US zoological expedition found it, has an adult body size ranging from just 7mm to 8mm. The previous smallest vertebrate was an Indonesian fish, Paedocypris progenetica, with an adult size of 8mm to 10mm.
“It was particularly difficult to locate Paedophryne amauensis due to its diminutive size and the males’ high pitched insect-like mating call,” says the expedition leader Chris Austin of Louisiana State University. “But it’s a great find. New Guinea is a hotspot of biodiversity, and everything new we discover there adds another layer to our overall understanding of how biodiversity is generated and maintained.”
The new discovery, described in the journal PLoS One, is the smallest of a group of tiny frog species that live among the damp leaf litter of New Guinea’s rainforests.
“The ecosystems these extremely small frogs occupy are very similar,” says Austin. “We now believe that these creatures aren’t just biological oddities, but instead represent a previously undocumented ecological guild – they occupy a habitat niche that no other vertebrate does.”
Excluding amphibians and fish, the smallest vertebrates are geckos, one of which has a mature body size of just 16mm. At the other extreme is the blue whale, which reaches an average of 25m in adulthood.
What dentists learn from their mummies
Dental schools have long had a problem giving students hands-on experience before they are allowed to practise on live patients. The solution, according to Dundee University, is to use bodies donated for medical purposes, which are preserved using a new technique that is much more lifelike than traditional embalming.
Dundee is the first UK dental school to adopt the Thiel method, developed at the University of Graz in Austria, which retains lifelike flexibility and colouring in human tissues – unlike conventional formalin embalming.
“It is extremely difficult to give dental students an opportunity to practise in a way that gives them a realistic experience,” says Christine Hanson, lecturer in oral surgery. “Using simulators or mannequins, or even animal heads, does not offer the same experience.”
Sue Black, director of Dundee’s Centre for Anatomy and Human Identification, led the introduction of Thiel embalming to the university. “As well as this very exciting opportunity for the dentists, we have been working with colleagues in the university’s Institute for Academic Anaesthesia who have found particular benefits in using the bodies to examine the effects of anaesthetics administered with the aid of ultrasound imaging,” she says.
Dundee has launched a fundraising campaign to build a new morgue to support the Thiel method. The Million for a Morgue campaign aims to raise £1m from donors.
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