Analysis

Satellites reveal rapid acceleration of Antarctic glacier ice loss

  • 21 May 2015, 19:00
  • Robert McSweeney
Antarctic research vessel

Antarctic research vessel | J.L. Bamber

Thinning of glaciers in one of the most vulnerable parts of Antarctica has accelerated at a "remarkable rate" since 2009, a new study finds.

Stable through the 2000s, the glaciers began losing large quantities of ice within just a year or two, the lead author tells Carbon Brief.

The study shows the surprising speed with which Antarctica's glaciers can react to rising ocean temperatures, and without warning, he says.

Remarkable acceleration

Glaciers are huge rivers of ice that ooze their way over land, powered by gravity and their own sheer weight. They accumulate ice from snowfall and lose it through melting.

In the new study, published today in  Science, researchers analysed changes to glaciers on the Southern Antarctic Peninsula in the last decade and a half.

For most of the 2000s, satellite data shows the glaciers lost about as much ice as they gained, meaning they stayed roughly stable. But around 2009 there was "a remarkable rate of acceleration" in ice loss, the study says.

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Limiting global warming to 1.5C is still possible, say scientists

  • 21 May 2015, 14:30
  • Simon Evans
Aerial of Forestry Plantations

Forestry plantation | Shutterstock

It's still technically possible to limit global warming to below 1.5C this century, according to new research published in Nature Climate Change.

Only a small window of opportunity remains open, the study says - and it is closing rapidly. Global carbon pricing or its equivalent should have been implemented already and must certainly be in place by 2020. The world would then need to become carbon neutral by mid-century.

The new study pitches into a live and vociferous debate over whether the world should be aiming to limit warming to 1.5C or 2C, and whether either target remains achievable. Carbon Brief puts the new study's findings in context.

Limiting warming to 1.5C

So far, the globally agreed target for avoiding dangerous climate change is to limit warming to  no more than 2C above pre-industrial levels. But more than half of the world's nations represented under the UN's Framework Convention on Climate Change (UNFCCC) are in favour of a tougher 1.5C target. These include the least developed and most vulnerable countries, such as the small island states that are already losing farmland to rising sea levels.

UNFCCC review process is underway to try to decide if a 1.5C goal would be more appropriate. Its initial findings include that the impacts of even 1.5C of warming would be "significant" and that a 1.5C limit would be "preferable" to 2C. However, it warns that the science on the impacts of 1.5C compared to 2C is "less robust" and that until new results become available, any decision on strengthening the current 2C goal may need to wait.

Today's new research aims directly into this relative scientific void. It says: "So far, only a few studies have reported scenarios consistent with a 1.5C limit… Here we fill this gap".

To find out if 1.5C remains possible it uses two " integrated assessment models" that represent the world's energy system and economy under different assumptions about the future of global policy, development and growth.

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Mountain shape a key factor in species surviving climate change

  • 20 May 2015, 08:30
  • Robert McSweeney

Himalayas | Shutterstock

One way animals and plants can cope with climate change is to relocate. Research shows some species are already shifting to higher ground or towards the poles in search of cooler climes.

But for creatures already living in mountains, the solution is not so simple. A new study of 182 high-altitude regions across the world shows how mountain shape is critical in determining whether a species will find refuge from rising temperatures further uphill.

This means the odds of survival are better for some species than others, say the authors.

Habitat range

The typical image of a mountain is a pyramid shape - a broad base that tapers to a peak. In theory, as species move upwards the habitat available to them shrinks, the paper explains.

But the study, published in Nature Climate Change, finds that over two-thirds of mountains don't follow this rule. In fact, mountains fall into one of four shapes: diamond, pyramid, inverse pyramid and hourglass, as the diagram below shows.   

Elsen & Tingley (2015) Fig1

 

Examples of four common mountain types. Colours indicate elevation, from low (blue and green) to mountaintops (yellow and orange) Source: Elsen & Tingley (2015)

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Antarctic Larsen-C ice shelf at risk of collapse, study warns

  • 13 May 2015, 00:01
  • Robert McSweeney

Larsen-C ice shelf | J. Schmaltz

In the past 20 years, warming temperatures have caused two ice shelves in Antarctica to collapse into the ocean. New research points to a third shelf, more than twice the size of Wales, which has thinned so much that it could now also face collapse.

The loss of the shelf would allow glaciers to flow more quickly into the ocean, pushing sea levels beyond current projections for this century, the researchers say.

Ice shelves

An ice shelf forms when a glacier on land reaches the coast and flows into the ocean. If the ocean is cold enough, the ice doesn't melt. Instead, it forms a permanently floating sheet of ice.

Ice Shelf Warming _labels

Ice shelf schematic. Source: British Antarctic Survey.

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Ice sheet melt is driving acceleration in sea level rise, study suggests

  • 11 May 2015, 16:05
  • Robert McSweeney

Melting glaciers | Shutterstock

Global sea levels are rising faster than previously thought, according to new research.

After researchers adjusted satellite sea level data to account for the slight rise and fall of Earth's land masses, they found sea level rise has accelerated in recent years.

The cause is likely to be increasing loss of ice from the Greenland and West Antarctic ice sheets, the researchers say.

Satellite data

Scientists first began using satellites to monitor global sea levels with the launch of the Topex/Poseidon mission in 1992. After two satellites from this mission, it was replaced by the Jason satellite missions in the early 2000s.

The data collected from satellites is verified against measurements taken directly from tide gauges on the sea surface. Tide gauges measure the height of the sea with reference to a fixed point, which is usually on land. As you can see from the red dots in the map below, most measurements are taken along coastlines.

Watson Et Al (2015) Fig1

Map showing tide gauges used in the study (red dots) to adjust satellite data. Black and blue dots show guages that the researchers ruled out for quality control reasons. Source: Watson et al. (2015).

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Climate change made England's record hot year in 2014 at least 13-times more likely

  • 01 May 2015, 10:30
  • Robert McSweeney

Evening sunset | Shutterstock

Last year was England's hottest year since records began over three and a half centuries ago, the Met Office revealed in January. Now a new study shows that this record-breaking year was at least 13-times more likely because of human-caused climate change.

And as our influence on the climate becomes more evident in the future, we can expect the chances of record hot years to increase further, the lead author tells Carbon Brief.

Hottest year

Stretching back over three and a half centuries, the Central England Temperature (CET) record is the longest instrumental record in the world. It provides daily and monthly temperatures averaged over a roughly-triangular area between London, Bristol and Lancashire.

With an average temperature of 10.93C, 2014 topped the list as England's hottest year, just edging ahead of the 10.87C recorded in 2006. Since the difference between the two numbers is smaller than the error associated with these types of measurements, scientists can't be absolutely sure that 2014 was the warmest year - but it's the most likely to be.

Cet -record -2014

40 highest-ranked years from warmest to coldest of the Central England Temperature record. Colours show the time period of each year, and height of the bar shows the uncertainty in the measurement. Source: Dr Ed Hawkins of Reading University.  Source: Dr Ed Hawkins of Reading University.

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Climate change threatens one in six species with extinction, study finds

  • 30 Apr 2015, 19:00
  • Robert McSweeney

American Pika | Shutterstock

The risk of Earth's species becoming extinct will accelerate as global temperatures rise, new research shows.

After reviewing more than one hundred scientific papers, the study finds as many as 16% of plant and animal species on land and in the oceans would be under threat with four degrees of warming.

Climate change could even overtake habitat loss and degradation as the main cause of extinctions, the lead author tells Carbon Brief.

Extinction risk

The rate at which plants and animals are becoming extinct is now a thousand times higher than before humans inhabited the Earth.

Habitat loss is the principal cause of extinctions, as forests are cleared and urban areas expand. But a new study, published in Science, suggests that climate change could soon become a key threat to species around the world.

A warmer world could have many different impacts on plants and animals, not least by pushing temperatures beyond species' physical tolerance. Shifting seasons can affect breeding patterns, and hot days may mean animals have less energy to search for food.

Changes to rainfall patterns may affect availability of water and freshwater habitats. These changes could conspire to influence how much food a species can access, and what predators and diseases it is exposed to.

The combination of habitat loss and climate change is likely to intensify their individual impacts on different species, Prof Joshua Lawler, who wasn't involved in the study but who is an author of the latest Intergovernmental Panel on Climate Change (IPCC) report, tells Carbon Brief:

"[H]abitat loss and fragmentation will make it harder for species to move to suitable climates, and climate change will drive human migrations and shifts in the distribution of cultivated lands which will, in turn, reduce habitat for species."

In the new study, Prof Mark Urban from the University of Connecticut aggregates the results of 131 studies on extinction risk to give a global picture of the risks posed by climate change.

Exponential rise

The current target for international climate policy is to limit global temperature rise to 2C above pre-industrial temperatures. Even with this level of warming, we can expect to lose around 5% of species, the study finds.

But as you can see in the graph below, the predicted extinction percentage increases as global temperatures rise beyond the 2C limit.

Urban (2015) Fig2

Predicted extinction rates from climate change rise with global temperature. Blue bubbles show individual studies, and their size shows how many species the study assessed. Source: Urban (  2015).

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UK must reform climate policies to become global leader, say economists

  • 30 Apr 2015, 17:20
  • Sophie Yeo

Alexander Chaikin | Shutterstock

A steep reduction in UK emissions over the last two decades disguises a number of ineffective government policies, argues a new report from the London School of Economics.

In a briefing on the key environmental policy issues ahead of the 7 May general election, three academics from LSE's Centre for Economic Performance look at the policies that aim to reduce the UK's emissions and examines their successes and failures.

The headline figures suggest an impressive record on tackling climate change in the UK, say authors Ralf MartinJonathan Colmer and  Antoine Dechezleprêtre.

By 2012, the UK's emissions had fallen by 25% on 1990 levels, meaning that it met its international target under the Kyoto Protocol, as well as its legally binding domestic target.

This makes the UK a leader in cutting greenhouse gas emissions among major economies, with countries such as the US and Japan still emitting more than they were in 1990.

Screen Shot 2015-04-30 At 11.50.09

Greenhouse gas emissions trends for selected countries. Source: UNFCCC and Global Carbon Budget 2014/LSE CEP report

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Hydrofluorocarbon emissions up 54% with air conditioning on the rise

  • 27 Apr 2015, 20:00
  • Robert McSweeney

Air conditioning units | Shutterstock

As spring temperatures in the UK inched above 20C in recent weeks, air conditioners in offices across the country will have rumbled into life after a silent winter.

But while these machines cool our buildings and cars, they could be having an increasing warming effect on the planet, a new study says.

Air conditioners and fridges contain potent greenhouse gases known as hydrofluorocarbons (HFCs). The new research shows global emissions of HFCs have risen by more than half between 2007 and 2012.

And as temperatures and incomes rise during this century, air conditioning use is set to grow rapidly in warm countries around the world, a second study finds.

Potent greenhouse gases

In 1987, countries around the world signed the Montreal Protocol, an agreement to phase out use of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs).

Scientists had found the gases were depleting the ozone layer, the atmospheric shield that filters the Sun's harmful ultraviolet radiation from reaching the Earth's surface.

CFCs and HCFCs were used as refrigerants in air conditioning units and fridges, propellants in aerosol sprays, and fire suppressants in extinguishers.

Scientists invented HFCs to take their place. HFCs don't damage the ozone layer, but as with their predecessors, they are potent greenhouse gases - as much as several thousand times stronger at absorbing heat than carbon dioxide.

Now a new study, published in Proceedings of the National Academy of Sciences, finds their emissions have risen rapidly in just five years.

Dramatic rise

Researchers estimated the abundance of the five most common HFCs from two global datasets: the Advanced Global Atmospheric Gases Experiment (AGAGE) and Japan's National Institute Environmental Studies (NIES ).

The data showed a dramatic rise in HFC emissions from 303 to 463 million tonnes of carbon dioxide equivalent between 2007 and 2012. This equates to an increase of 33 million tonnes per year, similar to the annual fossil fuel carbon emissions of New Zealand, the researchers say.

You can see this increase as the blue line in the graph below. The researchers also divided the results between developed countries (Annex I, green line) and developing countries (Non-Annex I, red line).

Lunt Et Al 2015 Fig2

Combined emissions of five HFCs from 2007 to 2012 for the world (blue line), developed countries only (green) and developing countries only (red line). Dotted and dashed black lines show emissions reported to the UNFCCC (for developed countries only). Grey, orange and purple lines show estimates from other studies. Source: Lunt et al. (2015)

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World's plants and soils to switch from carbon sink to source by 2100, study shows

  • 24 Apr 2015, 15:40
  • Robert McSweeney

Autumn forest | Shutterstock

Every year, trees and plants across the world absorb a vast amount of carbon dioxide from the atmosphere.

But a new study suggests this massive carbon sink could instead become a source of carbon dioxide by the end of the century.

This means we might not be able to rely on plants soaking up our emissions for much longer, the lead author tells Carbon Brief.

Extra carbon dioxide

Through photosynthesis, plants convert carbon dioxide, water and sunlight into the fuel they need to grow, locking up carbon in their branches, stems and leaves in the process.

Research suggests that as human-caused carbon dioxide emissions accumulate in the atmosphere, plants will grow more quickly because the rate of photosynthesis speeds up. This is called 'carbon dioxide fertilisation'.

This argument is sometimes used in parts of the media to suggest that additional carbon dioxide is beneficial for the Earth as extra food for plants.

But research published this week in Nature Geoscience suggests that plants won't have enough nutrients to make full use of the extra carbon dioxide in the atmosphere.  So any benefits will be limited, say the authors.

Nutrient needs

Plants need the right mix of nutrients to grow. Two of the most important nutrients are nitrogen and phosphorus. But there isn't an endless supply in soils for plants to use, lead author Dr Will Wieder, from the National Centre for Atmospheric Research in Colorado, tells Carbon Brief:

"Many ecosystems appear to be co-limited, meaning that both nitrogen and phosphorus are important for plant growth. There are places where one element or the other may be slightly more limiting, but at the end of the day plants need both to build roots, leaves and wood. This is why many fertilizers used in gardens and farms come with both nitrogen and phosphorus."

While nitrogen is abundant in the air we breathe, most plants can only take it up from the soil. Nitrogen gets into the soil by being 'fixed' from the air by microbes and certain plants, such as soy, Wieder says. Phosphorus primarily originates from rocks, and reaches the soil when they are worn down by the weather.

Nutrients can come from a little further afield as well, Weider adds:

"Both nitrogen and phosphorus can be moved around and transported through the atmosphere as dust or air pollution. The subsequent deposition of nitrogen and phosphorus also can contribute new nutrients to an ecosystem."

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