As poorer countries like China, India and Brazil develop at an increasingly rapid rate, greenhouse gas emissions were found to be rising faster than ever in 2006, mirrored in the March discovery that carbon dioxide is accumulating faster than ever in the atmosphere. China’s reliance on burning coal may be fuelling an economic boom, but the pollution is suffocating its people.

The accumulation of CO₂ in the atmosphere has sparked fears that nature’s ability to absorb some of our emissions is waning. And on top of this, scientists have realised that plants have been belching or hiccupping out methane without anybody noticing. The upper estimates suggest that plants could be emitting up to 30% of global methane, a potent greenhouse gas, potentially knocking existing climate models out of kilter.

We are seeing the effects of climate change all around us. Whales are moving north as oceans warm and nearly three-quarters of a million square kilometres of perennial Arctic sea ice has melted in one year.

In February, researchers revealed that the rate of loss of the Greenland ice sheet has doubled over a decade – in fact, every 40 hours or so, a cubic kilometre of water is lost as icebergs crash into the Atlantic. Some fear the melting of Greenland’s glaciers is heading for a point of no return within a century, causing a catastrophic sea level rise.

Post-Kyoto

Hurricanes were not as severe in 2006 as the year before, but experts have been left wondering if warming is boosting them; studying ancient sediments may provide the answers.

In spite of what scientists call overwhelming evidence, the governments of rich nations stand accused of failing to respond to the threat of climate change, and there are still climate change deniers in the US.

In November, delegates at the UN climate conference in Nairobi, Kenya, failed to set a deadline for reaching agreement on new targets for reducing greenhouse gas emissions after the Kyoto Protocol ends in 2012. Trading carbon credits with Africa and burying greenhouse gases could provide some solutions to reaching existing Kyoto targets.

Day after tomorrow

In October, the former chief economist at the World Bank, Nicholas Stern, warned that the economic affects of climate change could be dire, causing a huge global recession later this century. But ultimately the world’s poor will be those who suffer the ravages of global warming most acutely.

However, as one small ray of hope, experts now deem it unlikely that the North Atlantic current which warms Europe will switch off, plunging us into a new ice age as it did in the far-fetched climate disaster movie The Day After Tomorrow.

Overfishing has also made headlines during 2006. As fishermen continue to plunder cod for our plates and the EU does little to put a brake on fishing activity, a detailed new model in November predicted that commercial fish stocks could collapse in their entirety by 2050, meaning no more seafood.

��è����Ƶs warned in February, that we are eating our way through an entire food chain. One fish at least – Thailand’s giant Mekong catfish – has been granted a royal reprieve aimed at protecting it from further exploitation.

Red alert

Fish are not the only species suffering from precipitous declines, however. In May, this year’s Red List warned that two out of every five species now face extinction.

Prawn farms, palm-oil plantations and highways have hacked away at 40% of Asia’s tiger habitat in the last 10 years – leading China to suggest farming the creatures to supply the international trade in tiger parts, and lift pressure on wild populations.

Similarly, managed hunting of lions in Africa has been put forward as a method of conserving them. In rare good conservation news, one marine biologist suggested in February that we may have massively overestimated the decline of the green turtle.

In September, web tool Google Earth highlighted environmental damage such as rampant forest destruction, retreating glaciers and explosive urban growth. Himalayan forests are quietly vanishing and the Amazon rainforest continues to be devoured at a remarkable rate. However, forest growth in many countries, such as the US, Russia and China, continues to be encouraging.

The finding suggests that an infectious agent, such as a virus, may be involved in some brain cancers, say the researchers, who compared over 13,000 incidences of the disease.

The study also found there was a two- to fourfold increase in brain tumour rates among children younger than 15 who had three or more younger siblings compared to children of the same age who had no siblings. But there was no association between the number of older siblings and brain tumours.

“We know very little about why people develop brain tumours,” says epidemiologist Andrea Altieri, who led the study at the German Cancer Research Centre in Heidelberg. The only previously established risk factors for brain tumours are large doses of radiation, a family history of brain cancer and rare genetic disorders, he says, but these together only explain about 5% of cases.

Indirect marker

Other studies have shown a link between the number of siblings and cancers such as lymphomas and leukaemia. Sibling number is thought to be a so-called “indirect marker” of infection in childhood, says Altieri. “The number of siblings a person has indicates the level of exposure they had to infection at an early age, since children come in close contact with each other and thereby share exposures to many infectious agents.”

To test this link with brain tumours, Altieri and colleagues turned to one of the world’s largest detailed databases on cancer sufferers, located in Sweden. This allowed them to look at the family history of 13,613 people who developed brain tumours.

Factoring out other possible cancer-linked factors, such as parental age, they found that people with four or more siblings were twice as likely to have developed brain cancers.

The study is one of the biggest clues so far for a link between some brain cancers and an infective agent, Altieri claims. Aside from genetics, family history and radiation, large numbers of younger siblings is now the next biggest risk factor in the development of brain tumours, he says.

According to the researchers, the finding that brain tumour rates were higher among those with younger siblings and not older siblings, suggests that infections in late childhood play the most important role in causing the disease.

Latent virus

That infectious agent could be a type of polyoma virus. A small study in 2002 found a common polyoma virus, known as JCV, in the majority of 20 samples taken from brain tumours. Polyoma viruses are found in 90% of children but are not clearly associated with any clinical illness in healthy people, says Altieri.

However, the virus remains latent in the body throughout life and can be reactivated under certain circumstances. Some evidence from laboratory studies suggest that these viruses have cancer-forming properties, Altieri, says: “However, in humans they have never proven to be carcinogenic.”

This is the strongest evidence yet for a link between large numbers of siblings and nervous system cancers, says oncologist Greta Bunin of the Children’s Hospital of Philadelphia in the US. However, the finding does not rule out the possibility that the pathogen is something other than a virus, she says.

More studies such as this, using detailed cancer databases, would help to uncover the largely mysterious causes of brain tumours, Bunin adds.

Journal reference: Neurology (vol 67, p 1979)

Globally, the disease killed nearly 3.5 million people of working age in 2005.

The first case of AIDS was diagnosed 25 years ago, UN chief Kofi Annan reminded reporters on Thursday. Since that case, a further 25 million people have been killed by the disease – and today 40 million remain infected with HIV, many with little hope for the future.

“Accountability – the theme of this World AIDS Day – requires every president and prime minister, every parliamentarian and politician, to decide and declare that ‘AIDS stops with me,'” said Annan, who is soon to step down as UN secretary general. “And it requires every one of us to help bring AIDS out of the shadows, and spread the message that silence is death.”

Former US president Bill Clinton and his charitable foundation also took the opportunity of World AIDS Day to announce a deal made with Indian drug companies to provide cheaper antiretroviral drugs aimed at children.

Two Indian pharmaceutical companies will supply drugs at almost half price to treat children in 62 developing nations across the world. Right now, about 2.3 million children are infected with HIV.

Instant expert

For more details, background and all the latest news on new treatments and the spread of HIV, see our comprehensive HIV and AIDS special report and Instant Expert.

Currently, 11,000 people contract the virus every day – find more on the state of affairs during 2006, and predictions from the World Health Organization for 2030. Also see the history of AIDS, in our timeline.

Find out more about new vaccine efforts, targeted radiation therapy, genetically altered HIV , yoghurt microbes and other ideas to treat or prevent infection from the virus.

Forensic science has become a hot subject due to US television shows such as CSI: Crime Scene Investigation and Law and Order. Forensics university courses have proliferated as students flock to this glamorous and exciting scientific discipline.

The reality may be more mundane, but forensic scientists do invaluable work linking evidence from crime scenes – such as fingerprints, injuries, weapons, DNA, computer data, drugs and counterfeit goods – to criminals themselves. Forensic scientists also help solve crimes by reconstructing faces from skulls, and sometimes animating or virtually ageing them, or studying corpses to pinpoint the cause and time of death.

Criminals almost always leave evidence at crime scenes, or unwittingly collected it. Our ability to detect this evidence is continually improving, and many court cases rely it. It is presented to juries and judges by expert witnesses and helps solve crimes from fraud and forgery to assault, rape, murder and terrorism. Forensics can even help uncover secret nuclear weapons programs, smuggled plutonium and thwart trafficking of drugs and endangered species.

Gruesome analysis

Dead bodies yield many clues. Forensic pathologists and anthropologists study them for injuries indicating violence and cause of death. Toxicology can indicate the presence of alcohol, drugs and poisons – arsenic in Napoleon’s hair, for example. Dental records are often used to identify unknown bodies – such as 75% of Thailand’s victims of the 2004 Asian tsunami and Saddam Hussein’s sons killed in Iraq in 2003.

A body’s state of decomposition, can indicate the time of death. This is easy to estimate within 12 to 24 hours of death, but later than that, investigators must use indirect evidence: such as chemical signatures or insect colonisers like blowfly maggots and flesh-eating beetles. The accuracy of dating with maggots has recently been called into question, however. In the absence of these clues – in burnt remains for example – radioisotopes can reveal time of death.

Researchers continue to study the decomposition of pig and human corpses to better understand what happens after we die. For a detailed description of the process of decomposition, see The way of all flesh.

Vital clues

Injuries can hint at crimes in the living, the dead – and even the long dead; such as 5000-year-old Ötzi the ice man, discovered in the Alps in 1991. Analysis of stab wounds, for example, can tell whether the blow was meant to be fatal, and if the wound is the product of murder or suicide.

Bite marks are present in 8 out of 10 sexual assaults and many homicides in the US. Forensic odontologists attempt to match these to suspects’ teeth. Bite marks left on chewed objects, such as food or pencils, can even link people to crimes. However, critics argue that there are no universally consistent methods for comparing bite marks. Now, a new animated method to create 3D reconstructions of marks is helping to make this less subjective and more accurate.

Blood is often found at crime scenes, and measuring splatter from gunshot wounds can give vital clues about what happened. Forensic scientists can also check for semen stains – a trick Japanese wives can use to reveal cheating husbands.

Crime scene investigators also have other tools at their disposal, such as a UV ray guns and pocket-sized labs that can detect traces of drugs and other substances. An X-ray fluorescence scanner, developed for use in space by NASA, could help detect when a suspect has fired a gun, and there is even a washing machine that filters out forensic evidence from soil.

Forensic botanists use pollen, leaves and other fragments of plant material to link suspects to crime scenes. Other forensic experts are sometimes called on to examine handwriting or match styles of written language. Criminal profilers, try to get inside the minds of serial killers and other criminals. The FBI has even used patterns of wear on jeans to incriminate suspects.

Computers, emails and digital media are routinely scanned for the faint digital fingerprints that are left even after incriminating data has been deleted or destroyed.

Fingering suspects

Matching fingerprints is one of the best-known methods of linking suspects to crimes. Devised in the 1800s, the technique made its UK court debut in 1902. Fingerprints consist of oil, sweat and skin cells, which leave behind an impression of the unique patterns of whorls and ridges each finger possesses. Even “invisible” or smudged sweaty prints can prove useful, and chemical composition of fingerprints can reveal suspects habits too, such as whether they are a smoker, or which aftershave they wear.

Fingerprints are commonly left at crime scenes. Explosive devices are even dusted for them by bomb disposal robots, before they are destroyed. But the method of matching fingerprints has scarcely been subjected to the objective scrutiny needed to determine how often bogus matches are likely to happen – though the first test of this was published in 2005. This is partly because the technique is so long-established, but some experts argue that fingerprints could be mismatched a shocking 20% of the time.

Ballistic fingerprinting aims to link the scratches and dents in bullet casings with the guns that fired them. Chemical matching of bullets had been used for a number of decades, but it was shown to be fatally flawed in 2002. The FBI were asked to downplay its use in court, and in 2005 the method was suspended.

Forensic scientists also search for firearms resides on suspects that suggest they have fired a gun – however, this technique may have led to false convictions in the past. Explosives residues can be detected in the same way, but were used to falsely imprison the UK’s “Birmingham six“, bringing that aspect of forensic chemistry into question.

DNA revolution

DNA fingerprinting, or profiling, is now superseding traditional fingerprint matching as a more rigorous method. First developed in 1985 to diagnose genetic illness, it is now commonly used in criminal investigations. The first UK arrest following a DNA match came in 1995; since then, the England and Wales National DNA Database – the largest in the world – has matched more than 600,000 people to crimes.

DNA – from as little as a single cell – is extracted from blood, semen, tissue, hair or saliva. It is analysed in the lab to derive a characteristic fingerprint, or pattern of repetition, for certain strips of non-coding repetitive DNA. This is then compared to DNA profiles held in a database, and when two samples match, they likely came from the same person or sometimes a close relative. One day these databases may hold profiles for the entire population, raising privacy issues and stirring controversy.

For a detailed explanation of DNA profiling, see DNA profiling moves to the scene of the crime.

Even if your DNA profile has never been recorded, a new method that links Y-chromosomes to men’s surnames could give police some clues. Now, new faster methods of analysis may speed up profiling in the lab, and one day even allow police to create DNA profiles on-site at crime scenes. Police can now date DNA samples to pinpoint the time of crimes.

DNA evidence often implicates rapists. And now the degradation of sperm in used condoms can pinpoint the time of rape too. Other techniques allow the detection of rape days after an attack.

Until recently, samples containing the DNA from several people, have defied analysis – a problem because contamination is common. But now, a new supersensitive method of computer analysis can tease some of these apart. This was introduced to some police forces in the UK in 2006 and may help solve thousands of unsolved crimes.

DNA profiling has famously been used to identify the victims of: Bosnian war crimes, Hurricane Katrina, the 2004 Asian tsunami, the 2001 terrorist attacks on New York and mass murder under Saddam Hussein in Iraq. DNA profiling has also been used to track rhino and tiger poaching and link marijuana to its source.

However, though DNA could prove innocence in many cases, it is still not used as evidence in many countries, partly because of expense.

Questionable science

Despite the incredible value of forensics, criticism has been levied that it is not always sufficiently scientifically rigorous – even though it is often taken as infallible proof in court. Expert witnesses can be selective in what they present, and jurors also have trouble understanding complex information, statistics and the probability of errors in forensic analysis.

Questions have also been raised over the degree of error in matching fingerprints, bullet casings, bite marks and even DNA profiles – examples exist of bone marrow donors, and relatives of criminals, being implicated for crimes they did not commit.

These criticisms may however, help hone forensic science, and a future might possibly come when we can create entire physical profiles and photofits of suspects from their DNA alone and computers will solve murder cases all by themselves. Cyber detectives will routinely link up crimes – some already allow us to detect counterfeit computer chips, fake art and the source of digital photos. Even electronic judges could be on hand in coming decades to swiftly and methodically dole out justice.

The first evidence in Europe of a species decline from a disease linked to climate change has been shown, researchers say.

A new 26-year-long study of midwife toads (Alytes obstetricans) in Spain, shows that rising temperatures are tightly linked to the impact of a deadly fungal disease.

Earlier this year, researchers found a similar correlation between the timing of frog extinctions from the same disease on South American mountains and increased temperatures in the region (see Global warming boosts fungal epidemic in frogs).

The chytrid fungus Batrachochytrium dendrobatidis is a fatal pathogen of amphibians that interferes with their ability to control water loss. It is credited with wiping out frogs and their kin in vast numbers in Australia and South America. The disease has killed 74 of Central and South America’s 110 harlequin frog species since the 1980s, for example.

Invading Europe

Within the last decade, it has been gaining a foothold in Europe too. As a result of the fungus, the midwife toad is now virtually extinct on mountains in Spain’s Penalara Natural Park, where it once thrived.

Jaime Bosch at the National Museum of Natural Science in Madrid, Spain, and colleagues compared records for toad die-offs in Penalara with meteorological data for the mountains between 1976 and 2002. They found a strong correlation with rising temperatures and increased impact of the fungus.

“This [infection] is the clearest and best example of climate change being linked to an infectious disease,” says Matthew Fisher, a team member at Imperial College London, UK.

Warm and dry

Amphibians are cold-blooded, making them much more susceptible to environmental changes in temperature, says Fisher. Temperature fluctuations render them less well-equipped to defend themselves against disease, he believes. In addition, recent mild winters may be allowing the fungus to survive from year to year, when previously it would not have.

“Warmer and drier environments might induce physiological stress in amphibians that would make these animals more susceptible to fungal infection or exacerbate the negative effects of infection,” agrees herpetologist James Hanken at Harvard University in Cambridge, Massachusetts, US.

“The researchers demonstrate a striking association between a climate variable and recorded epidemics of the chytrid fungus,” he adds.

Parks and preserves

“Declines of amphibian populations, especially those occurring in seemingly undisturbed areas since the 1970s, have been perplexing and alarming,” says ecologist Alan Pounds at Monteverde Cloud Forest Preserve in Costa Rica.

“[These declines] show that setting aside parks and preserves alone is not enough to assure species survival,” Pounds adds. His research group discovered the link between climate and frog extinctions in South America.

Bosch and Fisher now plan to carry out a much wider survey of the impact of the disease in amphibians across Europe.

Though experts are unsure why the fungal pandemic has spreading so rapidly from region to region, there is evidence that the international trade in frogs for food, pets and research is driving it (see Frogs legs are their undoing). Between 1998 and 2002, the US alone is thought to have imported 14.7 million wild amphibians.

Journal reference: Proceedings of the Royal Society B (DOI: 10.1098/rspb.2006.3713)

Males of promiscuous species that wait until they are last in line to mate may gain a sexual advantage by “parasitizing” the sperm of other males, according to new research.

In the majority of insects, and many other species, research has shown that males that are the second or last sexual partner of a female, are likely to father a higher proportion of her offspring.

Species where a “second mate advantage” has been proved, include seed beetles, yellow dung flies, drosophila, parasitic wasps and butterflies – as well as primates and ground squirrels in mammals.

This advantage can be partially explained by forms of “sperm competition”, whereby second mates produce larger volumes of sperm, or where the sperm of second mates incapacitates the sperm of earlier lovers inside the female.

Many animals also have cunning methods of removing their predecessors’ sperm – some dragonflies, for example, have barbs on their penises that dig out the sperm of rivals.

Hostile place

Now, evolutionary biologists David Hosken and David Hodgson at the University of Exeter, UK, have discovered a further explanation. The pair scoured the literature for evidence that the ejaculate of first mates may unintentionally streamline the pathway to fertilisation of sperm of second mates.

The female reproductive tract is a hostile place for sperm in most species, says Hosken. It has an acidic pH and a sperm-unfriendly complement of immune cells.

Testament to this is the fact that many species produce such prodigious quantities of sperm cells, and that very few of these make it to the fertilisation site. Mammals, for example, produce hundreds of millions of sperm in each ejaculate, but less than 0.001% make it to the female’s egg.

Environmentally friendly

Seminal fluid has a range of properties that help to mitigate the inhospitable nature of the vagina. The researchers argue that the seminal fluid expended by first mates, helps to improve the environment, but many sperm are lost in the process.

The sperm-friendly environment that results, however, means that second mates need expend less energy-draining seminal fluid and produce more sperm. This helps them pip earlier rivals to the post, or rather, the egg.

“It’s a kind of parasitism of males on males,” says Hosken. Several insect studies show that increasing the time between first and second mating decreases the advantage the second male gains, helping to back up the idea.

Now Hosken intends to experimentally test the idea in crickets, which attach sperm in packets to the outside of females. Attachment times can therefore be manipulated, he says.

Journal Reference: Journal of Theoretical Biology (DOI 10.1016/j.jtbi.2006.06.024)