Supervolcano caused global cooling

The supervolcano which erupted 74,000 years ago at Toba in northern Sumatra was the most devastating natural event ever witnessed by humans. Now new evidence has emerged that the blast had long term implications for global ecosystems as it led to many years of drought, caused by a dramatic and prolonged drop in global temperatures.

Beautiful but deadly, and nowhere near the size of the Toba eruption, 74,000 years ago. Image Credit: Flickr/Roberto Zingales

An international team of researchers have shown that the forests which covered India before the volcanic eruption were replaced by open scrubland, and moisture-loving plants like ferns disappeared. The results suggest the global climate became much colder and, consequently much drier, which destroyed forests that depended on warm moist conditions.

To make their discovery, the researchers analysed long vertical sections of soil and marine sediment, called cores. The Toba eruption blew so much ash and rock into the atmosphere that it forms an easily-distinguished layer in soil and sediment cores from much of southern Asia. This meant the researchers could easily identify pre- and post-eruption deposits of soil and sediment and analyse their composition.

The researchers used the ratio of different carbon isotopes found in soil layers deposited before and after the eruption to examine the effect it had on vegetation that grew in India. Different types of vegetation leave different signature ratios of carbon isotopes in the soil because they use different chemical pathways to produce food through photosynthesis. The change in carbon isotope ratio showed that the vegetation changed from lush tropical forest to open scrubland just after the eruption occurred.

They also found much less pollen from ferns, which prefer warm, wet conditions, in marine sediment from after the eruption, suggesting there were far fewer of these plants alive at the time.

The Toba eruption was the most powerful volcanic eruption on Earth in the past two million years, causing temperatures to fall and resulting in massive droughts, which lasted for almost two thousand years!  It’s easy to why scientists have suggested deliberately pumping tonnes of sulphate particles, just like those produced by volcanic eruptions such as Toba, into the upper atmosphere to reduce global temperatures in the face of anthropogenic climate change.

Paper Reference: Williams, M., et al (2009) ‘Environmental impact of the 73 ka Toba super-eruption in South Asia’. Palaeogeography, Palaeoclimatology, Palaeoecology. doi:10.1016/j.palaeo.2009.10.009

Pollutants freed from icy prisons

Sea-level rise might not be the only problem caused by melting glaciers; they may also be releasing harmful pollutants back into the environment, according to a team of German and Swiss researchers. Persistent organic pollutants from the last half of the 20^th Century were locked up in glacial ice which is now melting, spilling these dangerous chemicals into alpine lakes fed by glacial meltwater.

Aletsch Glacier, Switzerland - Beautiful but deadly? Image: Flckr/Didier Baertschiger

Levels of persistent organic pollutants in Swiss lakes increased in the 1960s and 1970s before falling as people stopped releasing them into the environment. In a glacier-fed lake studied by the researchers the levels of pollutants then increased again from 1997 to 2005, when the research began. In contrast, the levels continue to drop in low-altitude lakes that are not fed by glaciers, suggesting the pollutants are reaching the lake in glacial meltwater. Tellingly, the rate of influx of pollutants into the glacier-fed lake seems to be similar to that seen during the ‘60s and ‘70s, when the pollutants were entering the lake from the atmosphere.

To make their discovery, the researchers took sediment cores from Lake Oberaar in Switzerland, which is fed by the Oberaar Glacier, and compared these to sediment collected from low-altitude lakes, which receive no glacial meltwater. Over time, sediment settles on the bottom of the lakes in regular layers, preserving a record of pollutant levels when the sediment was laid down. Researchers can work out exactly when the sediment was created so the sediment cores – vertical slices through the layers of sediment on the lake-bed – provide an ordered record of everything settling to the bottom of the lake, including the persistent organic pollutants, going back to 1953.

Persistent organic pollutants include pesticides and other industrial chemicals that do not break down over time. They have been associated with all sorts of illnesses in humans, and have a major negative impact on wildlife. As many alpine glaciers have shrunk by around 12% since 1999, more of these pollutants have been released back into the environment – an unforeseen and worrying side effect of climate change.

Paper Reference: DOI: 10.1021/es901628x

Climate change upsets Arctic ecosystems

The effects of climate change are being felt most severely by Arctic plants and animals, according to a review by an international team of researchers. Warmer temperatures have allowed invasive species to expand their range northwards, putting pressure on vulnerable Arctic species.

Spot the Arctic fox... Image: US Fish & Wildlife service

The research cites the example of the European winter moth (Operophtera brumata); the caterpillar of which causes massive damage to the trees on which it feeds. The moth has recently moved north, destroying large areas of birch trees in Lapland as it goes. Similarly, the highly specialised Arctic fox (Alopex lagopus), with is ghostly white winter coat, has been out-competed by invading red foxes (Vulpes vulpes) taking advantage of the warmer conditions to colonise new areas.

The warming climate has had other effects on the Arctic ecosystem as it upsets the natural processes animals have become adapted to: birds that nest and breed in spring, when insects are most abundant, are also suffering. Spring is beginning several weeks earlier than it was just ten years ago so the birds are missing the peak in food supply, meaning newly-hatched chicks are going hungry.

Many Arctic species have become highly specialised to take advantage of the unique Arctic environment and any changes to the climate will affect these vulnerable species first. In particular, animals that depend on sea ice to breed or escape predators are under threat as it melts.

So what do these changes mean for us? The researchers suggest they foreshadow the changes that will affect lower latitudes. Ultimately, damaged ecosystems will not be able to provide the services we rely on them to provide, like food production, clean air and water, and control of disease and other pests. In the UK, warmer winters have allowed midges carrying bluetongue virus from the continent to become established in a few small areas. Bluetongue is a livestock disease and its introduction to the UK could have serious implications for food security and the agricultural economy.

The study stresses the rapidity with which some of these changes have occurred. It also highlights how little we still know about the ecosystems under threat.

Here today... Image: NOAA

Astronomers go to ends of Earth to find site for telescope

Research carried out by a group of Australian astronomers has identified what they claim to be the best place on Earth to build an optical telescope. Unfortunately, it’s 4000 metres above sea-level on an icy ridge in Antarctica, so accessibility could be an issue.

Antarctica - a chilly place to sit and look at the stars. Image: Wikimedia Commons/Jerzy Strzelecki

By analysing climate information the astronomers found the site, known as “ridge A”, to be ideally suited to their needs. The weather on ridge A is cold (reaching minus 70^oC in winter!), exceptionally dry and almost completely windless. As a result, the air will be clear and still, which would allow astronomers to take crystal-clear images of the heavens. In fact, the astronomers believe images taken at the site would be three times sharper than those taken from the best sites elsewhere. The only problem with ridge A is the southern aurora, which may sometimes get in the way.

Between ground-based optical telescopes and space are many miles of atmosphere, which can dim and distort the view of the stars. To counter this, the best telescope sites are found on the top of mountains in Hawaii and Chile, but recently the astronomical world has started looking to Antarctica for new telescope sites. The hunt began in 2004 when a study suggested pictures taken from a different site in Antarctica would be almost as good as those taken by NASA’s Hubble Space Telescope.

But how difficult would it be to build and operate a telescope in Antarctica? According to the Anglo-Australian Observatory, an optical telescope being planned for yet another Antarctic site will cost in the region of AUD$10million to build! Some astronomers will go to almost any length to get an unobstructed view of the stars.

Clearing the air

Summer: a time of barbeques and beaches, cricket and cloudless skies. It’s also the time of year when air pollution is at its worst, particularly in our heavily-populated cities.

Even when at levels governments deem “safe”, air pollution can still stop our lungs functioning properly. Fortunately, scientists are also finding ways to dispel the noxious clouds surrounding us, and have shown how short-term policy measures to reduce pollution can have immediate effects on air quality.

Air pollution can damage our health: one UK government report suggests air pollution can reduce our lifespan by 7-8 months! Air pollution is better now than it has been historically, but it’s still a major health problem in cities around the world.

So what’s the latest word on the state of our urban atmosphere? Well, do you want the bad news, or the good?

Struggling to breathe…

First the bad news. American Researchers have shown that even low levels of ozone can have a noticeable effect on the workings of our lungs. They exposed healthy volunteers to different levels of ozone during long periods of exercise, whilst checking their lung function at regular intervals. The results showed that lung function decreased at levels of ozone well below the exposure limits set by the US government. If ozone can cause problems for healthy people, how much more dangerous is it for those with respiratory problems such as asthma?  More research is definitely needed.

But it’s not all bad news. Two recent projects have shown how we can improve air quality in our cities and towns.

Take a deep breath…

Swiss researchers have shown how simply planting trees down the middle of urban roads can cut air pollution, but not in the way you might imagine.

Using models of streets lined by tall buildings –an “urban canyon” – the researchers have shown that well-spaced trees create eddies in air currents flowing along the streets. The eddies stop pollution settling near the ground, instead carrying it up and away from pedestrians.

Planting trees is a worthwhile aim, but not always practical. Fortunately, an American and Chinese research project has demonstrated how more direct action can also have immediate benefits.

Before the Olympic Games in Beijing, the Chinese authorities brought in tough rules to tackle the thick smog often experienced by the city. The researchers measured the air quality in Beijing before, during and after the games and showed that controls on emissions and vehicle use dramatically improved air quality. Ultimately, the research could help local authorities clear the air of heavily-polluted cities and towns.

A lot of people spend time in urban environments exposed to traffic fumes and other sources of pollution. Whilst we still don’t fully understand the effects of this air pollution on our bodies, it seems there are a few simple measures town planners can take to help us all breathe a little easier.

As near as we get to a "cloudless" British summer