Science excellence

Natural aerosols cloud climate certainty


Recent NERC-supported research established that particles released into the atmosphere by natural sources such as volcanoes and plants are a major cause of uncertainty about how greenhouse gases affect the climate.

The scientists analysed a global model of these particles, known as aerosols, concluding that our uncertainty over historic aerosol levels limits our ability to confidently assess the effects of human emissions on clouds and the climate.

Their study, published in Nature, says many of the uncertainties created by aerosols are difficult to resolve; some may even be impossible. They suggest a change of emphasis in climate research towards trying to understand recent climate change in more detail.

Water vapour in the atmosphere needs aerosols to form cloud droplets. More aerosols means more droplets form and clouds get brighter, reflecting more sunlight into space and cooling the planet. This can mask some of the warming influence of greenhouse gas emissions.

To understand how the climate has responded to our emissions, we would need to know what the atmosphere was like before they were introduced. But the extent of our emissions makes this very difficult; even relatively untouched areas like Antarctica are unlikely to be representative of the pre-industrial atmosphere.

"Our poor knowledge of aerosols prior to the industrial revolution dominates the uncertainty in how aerosols have affected clouds and climate," says lead author Professor Ken Carslaw of the University of Leeds. "We can't go back and measure the atmosphere in 1750 - we need a new baseline. It might be better looking at the past few decades, where we've got an incredible amount of data, but it won't be simple because the climate is a very complex system."

'Large contribution of natural aerosols to uncertainty in indirect forcing' - Nature (2013)

Ancient water could hold clues to life on Mars

Surface of Mars

Image: ESA/DLR/FU Berlin-G.Neukum

A UK-Canadian team of scientists discovered ancient pockets of water, which have been isolated deep underground for billions of years and contain chemicals known to support life elsewhere.

This water could be some of the oldest on Earth, and may contain life - this is still being tested. The similarity between the rocks that trapped it and those on Mars even raises the possibility that comparable life-sustaining water could lie buried beneath the red planet's surface. The findings may force us to rethink which parts of the Earth can harbour life, and provide clues to how microbes evolve in isolation.

Researchers from the universities of Manchester, Lancaster, Toronto and McMaster used innovative geochemical techniques to analyse water from a mine 2·4km beneath Ontario, Canada. They showed it is rich in dissolved gases like hydrogen, methane and different isotopes of noble gases such as helium, neon, argon and xenon. Indeed, it contains similar hydrogen levels to those found near hydrothermal vents in the deep ocean, many of which teem with microscopic life.

The crystalline rocks surrounding the water are around 2·7 billion years old, but the water was assumed to be younger. Analysis of the noble gas isotopes shows the fluid is at least 1·5 billion years old. The hydrogen and methane present could provide energy for microscopic organisms that may not have been exposed to the sun for billions of years.

"We've found an interconnected fluid system in the deep Canadian crystalline basement that's billions of years old, and capable of supporting life," says co-author Professor Chris Ballentine of Manchester. "Our finding is of huge interest to researchers who want to understand how microbes evolve in isolation, and is central to the whole question of the origin of life, the sustainability of life, and life in extreme environments and on other planets," he adds.

'Deep fracture fluids isolated in the crust since the Precambrian era' - Nature (2013)

Some plankton thrive despite ocean acidification

Coccolithophore phytoplankton

Image: Alison R Taylor/PLOS

An international team studied the effect of ocean acidification on plankton in the North Sea over the past 40 years in search of clues about the effects of future changes in pH. They discovered that acidification has a more complex impact than previously suspected, and is not always obviously harmful.

As CO2 emissions dissolve in seawater they lower the ocean's pH, making them more corrosive to shells; there is widespread concern about the impact on ocean life. But a review of long-term data on ocean conditions and plankton abundance, published in PLOS ONE, shows that different species react differently.

Plankton such as foraminifera and coccolithophores seem to be surviving unexpectedly well in more acidic conditions. But numbers of pteropods and the larvae of bivalve shellfish are falling. It's uncertain whether these effects are due to changing pH levels alone, or arise from a combination of stress factors like warming, overfishing and excess nutrients in water.

"We found no statistical connection between the abundance of calcifying plankton and the changes in pH. If pH is affecting calcifying plankton in the area then its effect is being masked by other climatic effects. What we do know is that laboratory experiments have shown pH changes affect pteropods adversely," says co-author Professor Jason Hall-Spencer of Plymouth University.

Scientists had previously thought species react differently to ocean acidification simply because of variations in the mineral composition of the shells. It now appears that the damage also depends on other environmental stresses, including lack of food.

Plankton sit at the bottom of ocean food chains, supporting almost all marine life. Falling numbers could ultimately cause food shortages, particularly in countries where people eat lots of seafood and fish.

'Long-term trends in calcifying plankton and pH in the North Sea' - PLOS ONE (2013)

Animal infection may trigger diabetes

Dictionary with the word diabetes highlighted

Researchers from the universities of Newcastle and Liverpool found variations in the frequency of type 1 diabetes that suggest some cases may be triggered by an infectious disease carried by animals.

They analysed data on children diagnosed with type 1 diabetes in north-east England between 1990 and 2007 and found that cases vary in frequency over both a six-year cycle and over a shorter annual cycle, with peaks in winter.

Previous research had suggested diagnoses cluster in time, but this study revealed these temporal patterns in much greater detail. The scientists suggest the combination of short- and long-term cycles that they found adds weight to the idea that an infection carried by wild animals, such as rodents, triggers diabetes in those already genetically predisposed to the disease.

The long-term cycle is typical of animal disease patterns, but not of other environmental factors, such as weather. Meanwhile the shorter seasonal cycle may be because the infection is more easily transmitted at this time of year.

This seasonal pattern wasn't seen every year, but Dr Colin Muirhead of Newcastle University, who led the study, believes this strengthens the argument.

"Diseases don't occur at the same strength every year," he says. "Influenza shows us that you do get a seasonal peak, but it doesn't always occur at the same time or to the same extent. Type 1 diabetes shows a very similar pattern."

The next step is to identify the infections involved, so more can be done to prevent exposure and improve treatment.

NERC supported the work through the UK Joint Environment & Human Health Programme, alongside several other research funders.

'How do childhood diagnoses of type 1 diabetes cluster in time?' - PLOS ONE (2013)

Dinosaur body shape changed the way birds stand

Bone structure of Heterodontosaurus dinosaur

Research published in Nature explained for the first time how birds gained their characteristic posture. Scientists examined how dinosaurs' body shape changed over their evolutionary history and ultimately determined the way today's birds stand and move.

They scanned 17 skeletons belonging to animals ranging from dinosaurs' crocodile-like forebears to modern birds. They then digitally restored muscle and skin to model their posture and movement patterns. This was the first quantitative study to reconstruct a branch of evolution using whole-body dimensions from extinct animals.

Around 235 million years ago, dinosaurs evolved from an earlier group known as archosaurs. Most walked on all fours, but birds' first dinosaur ancestors were already bipedal. Modern birds have inherited this, but they have also developed an unusual crouched posture because their centre of mass is so far forward that their feet need to be further forward too.

Archosaurs originally resembled crocodiles, and until now scientists thought their descendants' centre of mass moved forward as they lost their heavy tails. The new study shows that the real cause was the development of large forelimbs, which added weight to dinosaurs' fronts. This meant they developed increasingly bird-like posture. The large forelimbs eventually became wings, but initially developed to grab prey and perhaps climb.

"We had set out to simply use modern, computer-aided techniques to illustrate how and when the centre of mass changed its position in dinosaurs. The timing of that change had been controversial: either gradual, or more sudden and associated with the first birds and the origin of flight," says Dr Vivian Allen, who was working at The Royal Veterinary College when he led the study.

NERC supported the work via a grant to co-author Professor John Hutchinson of the Royal Veterinary College.

'Linking the evolution of body shape and locomotor biomechanics in bird-line archosaurs' - Nature (2013)

Glacier's impact on sea level depends on shape

Aerial view of a glacier

Image: Dirk van As

An international team including NERC-funded researchers from the universities of Bristol and Durham estimated that four of Greenland's most important glaciers will add up to 3cm to sea levels if global temperatures rise 2·8°C by the end of the 22nd century.

They created computer models of the glaciers, which drain around 22% of the Greenland ice sheet into the ocean, in order to predict their future contribution to sea-level rise.

The results show that the speed of a glacier's retreat depends on its shape and the landscape it flows over, so previous estimates of future melting based only on past rates may have been excessive.

All four glaciers are retreating, but their different shapes mean they accelerate in different ways. By understanding the processes affecting individual glaciers, scientists can make better predictions of how they will react to climate change and thus of their individual contributions to sea-level rise under different scenarios.

Two of the glaciers studied, Helheim and Kangerdlugssauaq, are most sensitive to temperature rise where they meet the ocean. In contrast, the Petermann glacier's long, thin shape means it is mostly affected by ice melting underneath it.

The shapes of all four glaciers studied mean their retreat is unlikely to continue accelerating at current rates. Instead, under a mid-range climate scenario the four glaciers are predicted to contribute up to 3cm to sea-level rise by 2200 - less than previous estimates. But the scientists warn that other glaciers which have not yet shown rapid changes may start to retreat. And if temperatures increase by 4·5°C, the four glaciers could contribute around 5cm to sea-level rise.

'Future sea-level rise from Greenland's major outlet glaciers in a warming climate' - Nature (2013)

Researchers warn of Pine Island Glacier retreat

Aerial view of Pine Island Glacier

Pine Island Glacier, the largest single contributor to sea-level rise in Antarctica, has started shrinking, say scientists.

Supported by a NERC grant and the ice-2-sea project, researchers have shown that the glacier's retreat may have begun an irreversible process that could quintuple the amount of water it is adding to the ocean.

The team included scientists from the CSC-IT Center for Science in Finland, the Chinese Academy of Sciences and the universities of Exeter and Bristol. They used computer models and field observations to study how the glacier's ice flows and to simulate how this will change over the coming decades.

The models agreed that the glacier has become unstable, and will keep retreating for tens of kilometres. They suggest this recession will not stop and cannot be reversed.

"We have seen that not only is more ice flowing from the glacier into the ocean, but it's also flowing faster across the grounding line - the boundary between the grounded ice and the floating ice. We also can see this boundary is migrating further inland," said team-member Dr G Hilmar Gudmundsson from NERC's British Antarctic Survey.

The Pine Island Glacier shows the biggest changes in this area at the moment, and its instability may have implications for the whole West Antarctic Ice Sheet.

At the moment the sea is rising around 2mm a year. Pine Island Glacier retreat could contribute an additional 3·5-5mm in the next twenty years, so it would lead to a considerable increase from this area alone.

Pine Island Glacier currently contributes a quarter of the total ice loss from West Antarctica. If the entire West Antarctic Ice Sheet was to retreat, it could cause sea level to rise up to five metres.

'Retreat of Pine Island Glacier controlled by marine ice-sheet instability' - Nature Climate Change (2014)

Geologists show contribution of landslide to Japan tsunami

The remains of the town of Minamisanriku, Japan

Scientists from NERC's British Geological Survey found that the 2011 tsunami, which killed up to 20,000 people in Japan and caused the partial meltdown of the Fukushima nuclear plant, was made worse by a submarine landslide.

Geologists realised the magnitude-nine earthquake alone could not explain the height of the waves that struck the country's northern Tohoku peninsula.

The tsunami was the first for which offshore wave data was recorded by GPS buoys, showing a high-frequency component that could only be from a landslide. An international team, led by BGS's Professor Dave Tappin, used the buoy data to identify the most likely location of the landslide, then used maps of that area of the seabed to find it. They identified a landslide 40km long, 20km wide and 2km thick.

They team then used computer models to simulate the tsunami from the dual source of the earthquake and the landslide, to produce the high water levels along the north Honshu coast.

This research is the first to demonstrate the extent of the contribution that underwater landslides can make to tsunamis generated by giant quakes, and according to Tappin it raises a big problem for early-warning systems. Where the risk of landslides goes unrecognised, the likelihood of tsunamis generated by similar earthquakes could be badly underestimated.

The research was presented in December 2013 at the Fall Meeting of the American Geophysical Union.