Climate science

Warming tropical oceans could see ‘widespread and intense’ species loss, study warns

  • 31 Aug 2015, 16:00
  • Robert McSweeney

The tropics could see a huge drop in biodiversity as marine life heads for cooler waters, a new study suggests.

Rising sea temperatures could push fish, molluscs and crustaceans towards higher latitudes, the researchers find. But species that can't move fast enough are likely to face local extinction if emissions remain very high, the lead author tells Carbon Brief.

Sea surface temperature

There are around  230,000 known species swimming, floating and crawling around the world's oceans. A key factor in where they are located is the temperature of the water.

The map below shows the distribution of marine species around the world. You can see from the areas shaded yellow or red that there tends to be a larger number of species in warmer, tropical waters than in cooler waters towards the poles.

Total -richness -2006Current distribution of marine species in the world's oceans (as of 2006). Orange and red areas show areas where number of species is high, while blue areas show areas where biodiversity is low. Graph on right-hand side shows number of species by latitude - where the further to the right the line is, the more species found. Source: García Molinos, et al. (2015).

But warming oceans may see marine life venturing away from their current habitats. A study from earlier this year, for example, found that warming waters in the Arctic could allow more species to bridge the chilly divide between the Atlantic and Pacific oceans and mix more easily.

The new study, published in Nature Climate Change, looks at how rising sea surface temperatures could affect how species are spread across the world's oceans.

Researchers modelled the impact of future temperature change on around 13,000 marine species - over 12 times more than any other study.

Habitat range

The researchers first estimated what temperatures each species can tolerate - based on how cold and hot their existing habitats get and how far their existing ranges stretch.

The researchers then modelled how their habitat ranges could change as the oceans get warmer. Of the four pathways of future climate change developed for the Intergovernmental Panel on Climate Change (IPCC ), the study uses two: a moderate scenario where global emissions level off around the middle of the century ( RCP4.5) and the scenario with the highest emissions of the four ( RCP8.5). Global emissions are currently  tracking just above this scenario.

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

  • 27 Aug 2015, 15:15
  • Roz Pidcock

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

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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