Analysis

New NASA videos show stark ice loss from Earth's ice sheets

  • 27 Aug 2015, 15:15
  • Roz Pidcock
Supra glacial Lakes over the Ice Sheet in Greenland. Aerial Shot.

Greenland ice sheet | Shutterstock

The US space agency, NASA, yesterday released brand new images showing the pace of ice loss from Earth's two vast ice sheets, Greenland and Antarctica.

The amount of ice lost from the frozen expanses at the very north and south of the planet is accelerating, say the scientists, and together have helped raise global sea level by more than 7cm since 1992.

Greenland

The Greenland ice sheet covers approximately 1.7m square kilometres (660,000 square miles), an area almost as big as Alaska. At its thickest point, the ice sitting on top of the land is more than 3km deep.

Since 2004, Greenland has been losing an average of 303bn tonnes of ice every year, according to  NASA data, with the rate of loss accelerating by 31bn tonnes per year every year.

In the animation below, red shows areas that have lost ice, blue shows areas that have gained ice.

Change in the mass of the Greenland Ice Sheet between January 2004 and June 2014, as measured by the GRACE satellite. Source: NASA Goddard's Scientific Visualization Studio.

The stunning video images above come from the Gravity Recovery and Climate Experiment (GRACE ) twin-satellite. The satellites orbit the poles, measuring changes to the Earth's land and water masses and work out differences in the planet's gravitational field every 30 days. 

Some of the ice lost from Greenland is as result of the huge glaciers melting. But most of it is down to warming air overhead directly melting the surface of the ice sheet. A NASA  press release accompanying yesterday's data explains:

"Greenland's summer melt season now lasts 70 days longer than it did in the early 1970s. Every summer, warmer air temperatures cause melt over about half of the surface of the ice sheet - although recently, 2012 saw an extreme event where 97% of the ice sheet experienced melt at its top layer."

Greenland officially reaches the end of the summer melt season next week, when scientists will be able to say how 2015 has compared with previous years in terms of the speed of ice loss.

Changing ocean currents and temperatures are also melting the Greenland ice sheet from the bottom up, scientists say. A new three-year NASA project called Oceans Melting Greenland (OMG ) aims to get a better handle on how the rate of ice loss compares to surface melting.

Antarctica

Covering nearly 14m square kilometres (5.4m square miles), Antarctica is more than eight times the area of Greenland. The continent is also losing ice, though less quickly than its northern counterpart. Antarctica has lost, on average, 118bn tonnes of ice per year since 2004, compared to Greenland's 303bn tonnes.

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Celebrating soils: Why are they so important for our climate?

  • 26 Aug 2015, 16:25
  • Professor Pete Smith
Water erosion through corn field

Water erosion | Shutterstock

A guest post from Prof Pete Smith, Professor of Soils & Global Change at the University of Aberdeen and Coordinating Lead Author of the  Agriculture, Forestry and Other Land Use (AFOLU) chapter from Working Group III of the IPCC's Fifth Assessment Report.

From the 800th anniversary of the  Magna Carta to the 60th birthday of the  Birds Eye Fish Finger, there are plenty of reasons to mark 2015 as an important year. But you could be forgiven for being unaware that 2015 is also the UN International Year of Soils.

By putting soils centre stage, the UN Food and Agricultural Organisation (FAO) aims to raise awareness of how important soils are for producing food and fuel, and keeping ecosystems healthy. But soils have also been thrust to the forefront of international science because of climate change.

Globally, the top metre of soils contains about  three times as much carbon as in our entire atmosphere. Losing carbon from the soil into the atmosphere can add to climate warming. But if soils can be managed in a way that means they store more carbon, they can help to reduce the amount of carbon in the atmosphere, and thereby help limit climate change.

Climate impacts on soils

Changes in the climate can affect how much carbon soils store, but understanding the effects is not straightforward. Rising temperatures and changing rainfall patterns can have both positive and negative implications for soil carbon storage.

Plants absorb carbon dioxide through  photosynthesis, and transfer this carbon into the ground when dead roots and leaves decompose in the soil. Rising carbon dioxide levels in the atmosphere, and warmer temperatures,  could give a boost to plant growth on the one hand and  decomposition on the other. Whether carbon in the soil increases or decreases depends on the balance between the two.

But getting this boost also depends on there being enough water and  nutrients to support the extra growth. Drier soils could also limit how well dead plant matter decomposes in the soil, leaving them more at risk of being eroded by the weather.

In other words, changes in temperature and precipitation can be both beneficial and detrimental to soil carbon storage.

Peat -bog

Irish peat bog. Credit:  Shutterstock

Regional variations

The impacts of climate on soil carbon also vary depending on the type of soil and where in the world they're found.

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Scientists warn of unprecedented damage to forests across the world

  • 20 Aug 2015, 19:00
  • Robert McSweeney
Edge of the forest with dead trees

Forest edge | Shutterstock

Forests around the world are being affected by humans - both directly by deforestation and indirectly by climate change, say experts in a special issue of the journal Science.

In a series of reviews of the latest research into the health of the world's forests, scientists find they are far from being in the best shape for coping with climate change over this century. And this could affect how well trees absorb and store carbon in the future, they say.

Forest distribution

The world's forests generally fall into three categories, according to where they're found. You have the warm, humid conditions of tropical forests around the equator, the mild conditions enjoyed by temperate forests in the mid-latitudes, and the freezing cold of boreal forests in the North.

Forest -distribution

Global forest distribution. Credit: Nicolle Rager Fuller, National Science Foundation.

Today's special issue tackles each type in turn. We'll start with tropical forests, home to half of the world's species of plants and animals.

Human impacts such as logging and clearance for farmland and mining have left less than a quarter of tropical forests intact, say the authors of  one of the special issue papers. The remaining three-quarters are either fragmented or otherwise degraded.

The grey shaded areas in the map below show where forest has been cleared since the 1700s, and the red areas show recent hotspots for deforestation. But through the coming century, the threat of forest clearance will be "increasingly combined with the impacts of rapid climatic changes," the researchers say.

Disturbed -forests

Map of current and historical year-round ("evergreen") and seasonal tropical forest extent. Source: Lewis et al. (  2015)

Tropical

Climate change will have competing impacts on forests, lead author Dr Simon Lewis, from  University College London and the University of Leeds, tells Carbon Brief:

"One the one hand more carbon dioxide in the atmosphere is good for tree growth, increasing carbon stocks. On the other higher air temperatures and drought events tend to reduce tree growth, decreasing carbon stocks."

 

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10 years on from Hurricane Katrina: What have we learned?

  • 19 Aug 2015, 17:30
  • Roz Pidcock
Hurricane Katrina from the NASA GOES Satellite

Hurricane Katrina | NASA

Shortly after 10am on 29th August 2005, Hurricane Katrina tore through the city of New Orleans, a vibrant port in the US state of Louisiana. Extreme winds and heavy flooding cost more than 1,800 people their lives and caused an estimated $108bn in damages.

As images of the destruction beamed across the world, the  media began asking questions about how far the scenes were a  product of our  own actions. The  New York Times said:

'With one American city swamped by one great hurricane and then by another one only a month later … it is no surprise that debate has flared over the role of global warming."

Or as the BBC's Richard Black put it:

"Hurricanes and global warming - a link? Here's a recipe for an explosive news cocktail."

As well as kickstarting an energetic media and public  interest in extreme weather and climate change, Katrina also put pressure on the science community to provide answers.

Carbon Brief spoke to some scientists working in the field about what has and hasn't been learned in the ten years since Hurricane Katrina made its destructive mark on Louisiana.

Screenshot 2015-08-19 17.10.28

New York Times, Aug 30th  2005

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Climate change set to fuel more "monster" El Niños, scientists warn

  • 17 Aug 2015, 17:00
  • Roz Pidcock
Flooding from November 2006 flood in Washington

Severe flooding | Wikipedia

The much-anticipated El Niño gaining strength in the Pacific is shaping up to be one of the biggest on record, scientists say. With a few months still to go before it reaches peak strength, many are speculating it could rival the record-breaking El Niño in 1997/8.

Today, a new review paper in Nature Climate Change suggests we can expect more of the same in future, with rising temperatures set to almost double the frequency of extreme El Niño events.

Supersizing

Every five years or so, a change in the winds causes a shift to warmer than normal sea surface temperatures in the equatorial Pacific Ocean - known as  El Niño.

Together with its cooler counterpart, La Niña, this is known as the El Niño Southern Oscillation (ENSO) and is responsible for most of the fluctuations in global weather we see from one year to the next.

Last week, US scientists  confirmed they expect "a strong El Niño" to peak in the next few months. The event brewing in the Pacific is already "significant and strengthening", said the statement from NOAA's Climate Prediction Centre.

The  latest temperature maps, released today, confirm parts of the tropical Pacific are up to 3C warmer than the long term average (dark red in the map below).

Average -sst -anomaliesSea surface temperature anomalies in the Tropical Pacific over the last four weeks. Source: Climate Prediction Center/NCEP,  NOAA

A separate comment piece in the same journal explains how scientists have been left scratching their heads over why El Niño has reemerged with such vigour after a false start last year.

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UK butterflies could suffer ‘widespread extinction’ by 2050, study warns

  • 10 Aug 2015, 16:00
  • Robert McSweeney
Speckled wood butterfly

Speckled wood butterfly | Jim Asher

Frequent droughts and habitat loss could push drought-sensitive butterflies in the UK to local extinction by the middle of the century, new research suggests.

Even in a very optimistic scenario, where habitat is improved, the likelihood of these butterflies surviving climate change drops to zero by 2100, if emissions stay very high.

The "alarming" results highlight the need to limit climate change by capping emissions, the lead author tells Carbon Brief.

Very hungry caterpillars

In the summer of 1995, the UK experienced an exceptionally dry summer, the most arid since records began in 1776. Among the impacts of the hot, dry season, the population of several species of butterfly collapsed, says Dr Tom Oliver, a researcher at the UK's Centre for Ecology and Hydrology.

Heatwaves and droughts affect adult butterflies, says Oliver, but caterpillars are even more sensitive to extreme weather, he explains to Carbon Brief:

"If their host plants dry out under prolonged severe drought then this can cause death or, at the very least, reduce the quality of their food so that they grow very slowly."

Populations of some species of butterfly took several years to recover to normal levels, says Oliver.

With droughts  likely to become more frequent as the climate warms, Oliver set about testing what effect this could have on butterfly numbers. Looking at data from the UK Butterfly Monitoring Service (UKBMS), they identified six species that tend to suffer a fall in number after dry years and suffered a major drop after the 1995 drought.

Selection Butterflies

The six species of butterfly considered in the study: a) Cabbage white, b) Small cabbage white, c) Ringlet, d) Green veined white, e) Speckled wood, and f) Large skipper. Source: Oliver et al. (2015)

The results of the study, published in Nature Climate Change, suggest that rising temperatures and fragmented habitats could mean we lose entire species of butterfly by the middle of the century.

Recovery time

With global temperature as it is today, we wouldn't expect another drought as severe as 1995 for more than 200 years. But climate change will drastically cut this return time in the future, the researchers say.

Even if global temperature rise is held at 2C above pre-industrial levels - that's  1.15C above the warming we've already seen to date - we could still expect to see a drought as serious as 1995 every six years. On the other hand, if emissions stay very high, a severe drought could be expected almost every year.

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Rising costs of flood defences could put world's major deltas at risk

  • 06 Aug 2015, 19:00
  • Robert McSweeney
The 2011 Mississippi flood. Credt: Mary/Flickr

Mississippi flood, 2011 | Mary/Flickr

Rising seas, sinking land and increasingly expensive flood defences could see the risk of flooding in deltas such as the Mississippi and Rhine rise eight-fold, a new study finds.

Researchers assessed the current and future flood risk in 48 deltas around the world and found that those in developed countries could face the biggest increase in risks if they can't maintain their investments in flood defences.

The Delta blues

Deltas form where rivers flow into the sea and deposit the sediment they're carrying. Some of the largest cities in the world are built on river deltas, from Cairo and Chittagong to Shanghai and San Francisco.

This sediment compacts naturally over time. So to keep the land surface from subsiding, the delta needs a regular top up, says Dr Zachary Tessler, a researcher at the City University of New York. He explains to Carbon Brief:

"In natural, or un-managed, deltas the land subsidence results in more river and coastal floods, which in turn distribute more sediment, rebuilding and maintaining the land surface elevation."

But human development can get in the way of this natural process, Tessler says:

"Human activities affect the integrity of deltas by reducing the amount of sediment in freshwater from the upstream river, and also reducing how effectively this sediment is deposited on the delta."

Building dams and reservoirs upstream of the delta holds back sediment, while using dikes and levees to control water levels can stop sediment from spreading onto the delta, Tessler says.Without adding new sediment, the land surface subsides, leaving deltas more at risk from flooding - both from the river that feeds it and the rising seas it flows into.

For cities built on river deltas, many have flood defences to protect them, but these need regular improvement and investment to keep a city protected.

Developed countries can typically afford to do this, but what if they couldn't? Tessler's study, published today in Science, asks that very question.

Risk and exposure

The researchers assessed the risk of flooding at 48 major coastal deltas across the world, home to around 340m people between them.

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Geoengineering is ‘no substitute’ for cutting emissions, new studies show

  • 04 Aug 2015, 16:30
  • Robert McSweeney
A carbon capture coal plant

A carbon capture coal plant | Flickr

Attempts to limit climate change by removing carbon dioxide directly from the atmosphere would not prevent the irreversible damage to the oceans, according to a new study.

While a second study finds that brightening clouds to reflect more of the Sun's radiation could help boost crop yields in parts of China and Africa.

Speaking to Carbon Brief, authors from both studies highlight the importance of reducing carbon emissions now, rather than trying to engineer the climate later.

Geoengineering

Geoengineering is the deliberate large-scale intervention into the Earth's climate system to try and limit human-caused climate change, and it can be divided into  two main methods.

Removing carbon dioxide from the atmosphere, often described as Carbon Dioxide Removal (CDR), is one approach. The other is reflecting some sunlight away from the Earth before it can be trapped by greenhouse gases, commonly known as Solar Radiation Management (SRM).

The two new studies explore the implications of each of these methods, and the results are decidedly mixed.

Ocean acidification

We start with the oceans. About a quarter of the carbon dioxide emitted by human activity is taken up by the world's oceans. There it reacts with water to form carbonic acid, reducing the pH level and making the oceans less alkaline.

This process is known as ocean acidification, and it can have serious implications for marine life, says Sabine Mathesius from the Helmholtz Centre for Ocean Research in Kiel in Germany. She explains to Carbon Brief:

"The resulting increase in the ocean's acidity disturbs important biological processes, like the build-up of calcium carbonate shells. If ocean acidification continues at the current rate, many species at the bottom of the food chain, as well as corals, could face extinction. In consequence, species that depend on them, including fish and ultimately humans, would be affected too."

Mathesius is the lead author of a study, published in Nature Climate Change, which investigates whether CDR could help stave off ocean acidification. Her results suggest that continuing to emit carbon dioxide in the hope of being able to remove it from the atmosphere later could consign our oceans to changes that are irreversible on human timescales.

Carbon dioxide removal

The study focuses on two scenarios, or representative concentration pathways, for how we deal with rising carbon emissions.

RCP8.5 is the highest of the emissions scenarios used by the Intergovernmental Panel on Climate Change (IPCC), and is described in this paper as "business-as-usual". While RCP2.6 is the lowest IPCC scenario, where emissions are curbed to keep global average temperature rise to within 2C above pre-industrial levels.

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Emissions cuts using biofuels could worsen water stress in US, study suggests

  • 03 Aug 2015, 20:00
  • Robert McSweeney
Switchgrass

Switchgrass | Shutterstock

Using biofuels as a way to cut greenhouse gas emissions could put US water resources under increasing pressure, a new study suggests. Researchers find that a heavy reliance on bioenergy could mean a 42% increase in water consumption across the US by 2100.

The results show that policies to mitigate climate change need to be carefully planned to avoid knock-on effects on natural resources, the researchers say.

Water deficits

The new study, published in Proceedings of the National Academy of Sciences, analysed "water deficits" across the US. Deficits occur when demand for water outstrips the supplies available in local or neighbouring rivers and reservoirs.

The map below shows that much of the US is already in deficit for water. The orange and red areas in the main map below show the counties in US that are already worst affected by water stress.

Deficit Over Demand MapAverage total annual water deficit as a fraction of demand in 2005. Source: Hejazi et al (2015)

Using computer models, the researchers simulated how these deficits might change with different approaches for tackling global carbon emissions to limit the impacts of climate change.

The results show that measures to cut carbon emissions could mean water deficits are more severe by the end of the century.

Bioenergy

The study compared the impact on water stress of two scenarios, or representative concentration pathways, for how we deal with rising carbon emissions.  RCP4.5 describes a world where the concentration of carbon dioxide in the atmosphere is stabilised at around 650 parts per million (ppm) by 2100.

In contrast, RCP8.5 is a future where emissions are not curbed and carbon dioxide concentrations rise to around 1,370ppm by 2100. The paper refers to RCP8.5 as a "business-as-usual" scenario.

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Two degree climate target not possible without 'negative emissions', scientists warn

  • 03 Aug 2015, 17:05
  • Roz Pidcock
Kemper County energy facility from the air.

Kemper Project | Wikipedia

All of our options for keeping warming below 2C above pre-industrial temperatures now involve capturing carbon dioxide and storing it underground - a technology that doesn't yet exist on a large scale, according to new research.

The study, published today in Nature Communications, argues that 'negative emissions' alone, in the absence of conventional mitigation, are unlikely to achieve the 2C goal.

And in all but the most optimistic cases, staying below 2C requires capturing and storing carbon in amounts that exceed the capabilities of current technology, say the researchers.

Ahead of a major international climate summit in Paris, the study makes an interesting contribution to the debate about the role of negative emissions in meeting the 2C target.

Budgets

In December, global leaders will gather in Paris to agree a deal for capping global temperature rise at 2C above pre-industrial levels - the internationally agreed target.

For any given temperature target, there is a finite amount of carbon that can be burned before the chances of staying below that target become minimal. This is known as a  carbon budget.

In its latest report, the Intergovernmental Panel on Climate Change (IPCC) said that to have a reasonable chance of staying below 2C, total emissions from all human activity must not exceed 1,000bn tonnes of carbon (or gigatonnes of carbon, GtC).

The world is currently not on course to meet this target and there are two options for how to get ourselves back on track, says today's paper.

The first is to produce fewer emissions, which means burning fewer fossil fuels. This is what's commonly referred to as conventional mitigation.

The other is to capture fossil fuel emissions before they enter the atmosphere, or to suck them directly out of the air - a technique known as carbon dioxide removal. A third possibility sometimes proposed is to artificially engineering parts of the climate system, such as the oceans, to take up more carbon.

Collectively, the new paper calls these "negative emissions" technologies.

(Note that this is not shorthand for what the IPCC refers to as "net negative emissions". In its latest report, the IPCC  said: "Net negative emissions can be achieved when more GHGs are sequestered than are released into the atmosphere (e.g., by using bio-energy in combination with carbon dioxide capture and storage).

Carbon Sequestration

Laboratory studies help progress the field of carbon storage, by characterising the chemical signatures that result when certain types of rocks are exposed to carbon dioxide. Credit: Idaho National Laboratory | Flickr

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