Analysis

Factcheck: Will climate change lead to giant, man-eating snakes, tiny horses and shrunken goats?

  • 22 Oct 2014, 14:01
  • Robert McSweeney

The film 'Anaconda'. Time

Rising temperatures have caused mountain goats in the Alps to 'shrink' by up to 25 per cent, according to new research . The news follows on from recent stories of how climate change could bring us huge spiders, tiny horses and giant snakes.

Despite the slightly ridiculous headlines such research prompts, there is actually some science behind it all.

Behavioural change

So, first things first; rising temperatures haven't actually caused any goats to shrink per se. Rather the research, published in the journal Frontiers in Zoology, finds that young goats aren't as big as they were 30 years ago.

Scientists analysed records of the Alpine Chamois goat in the Italian Alps and found they were as much as 25 per cent smaller than goats of the same age in the 1980s.

Read more

Worst case scenarios of sea level rise, and why scientists and policymakers consider them

  • 21 Oct 2014, 17:52
  • Robert McSweeney

Thames Barrier | Shutterstock

Sea levels could rise by a maximum of 190 centimetres by the end of the century, according to a new study, which examines a worst case scenario for sea level rise.

In reality, the amount of sea level rise we get is likely to be less than that. But scientists and policymakers examine such 'worst case' scenarios to safeguard against climate risks.

Upper limit

With 10 per cent of the world's population living less than 10 metres above sea level, the threat of  coastal flooding is significant. The Intergovernmental Panel on Climate Change (IPCC) expects sea level rise to cause a ' significant increase' in sea levels extremes and the risk of coastal flooding.

The new study, published in  Environmental Research Letters, considers the assessment of 13 ice sheet experts. They conclude that the contribution from ice sheets is likely to be greater than projected by the IPCC. The paper suggests that sea levels could rise by as much as 190 cm this century.

Projections of sea level rise are typically constructed by working out the contribution to sea level rise from different  factors. The biggest contribution is from water expanding as it warms, followed by melting glaciers, then melting ice sheets on Greenland and Antarctica.

The crucial question for sea level rise this century is how much ice will be lost from the ice sheets, the authors argue. But it remains one of the largest uncertainties. In its Fifth Assessment Report (AR5), the IPCC says there isn't sufficient evidence for them to give probabilities of large-scale losses of ice sheets.

The new study uses expert judgement to consider areas of ice sheet loss that are often not included in the sea level  models that the IPCC bases its assessment on. They then combine these judgements with the methods used in AR5 to produce their upper-limit figure of 190 cm.

Read more

New study maps countries most at risk from El Niño flooding

  • 20 Oct 2014, 20:00
  • Roz Pidcock

From South America to the Sahel, scientists have for the first time mapped how flood risk rises and falls across the world each time the extreme weather phenomenon known as El Niño hits.

With an El Niño brewing in the Pacific right now, being prepared for flooding can help protect vulnerable communities and curb damages, say the researchers.

Changing rainfall

Every five years or so, a change in the winds in the  equatorial Pacific  causes a shift to warmer than normal ocean temperatures - known as El Niño, or cooler than normal - known as La Niña.

The warm and cool phases, together known as the El Niño Southern Oscillation (ENSO) affect  rainfall patterns worldwide.

While scientists have looked before at the consequences for specific countries, such as Australia, the new study is the first to take a global view, mapping flood risk right across the world.

Flood _volume (Ward Et Al)

Percentage of land experiencing changes in flood volume with return periods of 100 years, during El Niño years (top) and La Niña years (bottom). Source: Ward et al. (2014)

 

Read more

Probing the deep: An in-depth look at the oceans, climate change and the hiatus

  • 20 Oct 2014, 08:40
  • Roz Pidcock and Rosamund Pearce

Waves in ocean via Shutterstock

Oceans cover more of the planet than anything else. So it makes sense that we need to know what's happening to them to understand how humans are changing the climate. 

If you follow climate science, you'd be forgiven for being a little confused recently by different news reports suggesting the oceans are warming, slightly  cooling or doing  nothing at all.

So are the oceans hotting up or aren't they? And how does what happens beneath the waves influence what we feel up here on earth's surface? Here's our top to bottom look at the oceans and climate change.

More heat in, less heat out

Scientists have known for centuries that greenhouse gases in the atmosphere, such as carbon dioxide and methane, trap heat and warm the planet. This is known as the greenhouse effect.

Scientists use satellite measurements to monitor how much of the sun's energy enters earth's atmosphere. A different set of measurements tells them how much finds its way out again.

The difference between those numbers is increasing, which means the earth is  trapping more heat than it used to. And that means the planet  must be warming.

A hiatus in surface warming

An interesting question is why temperatures at earth's surface - that's the air above land and the very top of the ocean - don't always reflect what's happening to the planet as a whole.

Over the last 15 years or so, surface temperatures have risen  much slower than in previous decades, even though we're emitting greenhouse gases  faster than we were before.

This is what's become known as the "hiatus", "slowdown" or even "pause" in surface warming.

This raises an obvious question. If earth is  gaining heat but the surface isn't warming very much, where is the heat going instead?

Where does the heat go?

Oceanheatadjustedocean 2nologo

Read more

Climate change and the extinction of the Aldabran banded snail

  • 13 Oct 2014, 11:45
  • Professor Georgina Mace

Aldabra banded snail | Wikicommons

On September 20th 2014, The Times published  an article, "Snail 'wiped out by climate change' is alive and well."

It reported the rediscovery of the Aldabran banded snail (Rhachistia aldabrae), which was declared extinct in 2009 by the International Union for the Conservation of Nature (IUCN), after repeated searches in its known habitat found no sign of the snail for over a decade.

In 2007,  a scientific paper had pieced together the recent history of the snail population and the climate, and concluded that the snails extinction could be explained by the increasing frequency of dry years, leading to lower survival and reproduction.

But an expedition in August 2014 rediscovered the species in dense mixed scrub of a little-visited part of Aldabra.  Conservationists celebrated the rediscovery, while also noting that the species is still extremely rare and its persistence by no means assured.

The Times article developed the story in a completely different direction, using it to challenge the basis for conclusions that the Intergovernmental Panel on Climate Change (IPCC) published earlier this year on species extinctions under climate change.

The Times claims that the Aldabran banded snail was cited in another paper (which I infer to be  Cahill et al. 2013), a review of existing evidence, as "the clearest example of man-made climate change causing an extinction". It states that this was a major strand of evidence in the IPCC's conclusions on future extinction risks, which were summarised as: "A large fraction of both terrestrial and freshwater species faces increased extinction risk under projected climate change during and beyond the 21st century".

Read more

Scientists stay poised for imminent arrival of El Niño

  • 10 Oct 2014, 12:30
  • Roz Pidcock

The Pacific weather phenomenon known as El Niño looks to be firmly on its way. After a slow start, forecasters yesterday confirmed an El Niño should be making an appearance in the next month or two, though it's likely to be a weak one.

Pacific fluctuations

Every five years or so, a change in the winds causes a shift to warmer than normal ocean temperatures in the  equatorial Pacific Ocean - known as El Niño, or cooler than normal - known as La Niña, moving briefly back to normal in between.

The warm and cool phases together are known as the El Niño Southern Oscillation (ENSO), and are responsible for most of the fluctuations in global weather we see from one year to the next.

Each time a switch occurs, changes in the ocean and atmosphere above affect   global temperature and rainfall patterns worldwide.

ENSO

Sea surface temperature during El Niño (left) and La Niña (right). Red and blue show warmer and cooler temperatures than the long term average. [Credit: Steve Albers, NOAA]

 

Read more

Behind the pictures: What does climate change mean for the walrus?

  • 08 Oct 2014, 16:36
  • Robert McSweeney

Group of walrus | Shutterstock

Last week the media was awash with pictures of a ' mass haul-out' of around 35,000 walrus on the shores of Alaska. The sight of so many walrus lounging on land rather than sea-ice led many to herald it as further evidence of climate change.

We take a look at what retreating sea-ice might mean for this iconic Arctic mammal.

Haul-out

Walrus are typically found in the shallow coastal waters of the Arctic circle, migrating with the sea-ice as it expands and contracts through the seasons. Walrus typically 'haul-out' by climbing onto sea ice and using it as a platform for feeding, resting and breeding.

There are two main types of walrus, Atlantic and Pacific, named after the oceans in which they're found. It was the latter that were captured on camera in such large numbers on the Alaskan coast last week.

Read more

How air pollution caused Europe’s rivers to fill

  • 06 Oct 2014, 17:02
  • Robert McSweeney

River Wisla | Shutterstock

Air pollution from Europe resulted in a 25 per cent increase in river flows in Poland and Germany during the late 20th century, a new study finds. The researchers say their findings show how the impact of burning fossil fuels is not just limited to increasing temperatures.

Solar dimming

In the sixties and seventies, air quality across much of Europe was very poor. Coal power stations and inefficient cars belched out tiny particles, known as aerosols, into the atmosphere. These aerosols caused widespread health problems and contributed to the famous 'pea-souper' smogs in London.

This new piece of research, published in Nature Geoscience, finds that these aerosols also caused an increase in the amount of water flowing in rivers across Europe.

Some sources of aerosols are natural, such as volcanoes, plant vapours and chemicals released by tiny sea creatures. However, since the industrial revolution, humans have been emitting more and more aerosols through fossil fuel burning.

One type of aerosols, called sulphate aerosols, are emitted from cars and power stations. Once in the atmosphere, these aerosols affect the climate in two ways. They directly scatter sunlight and reflect it back out to space. They can also react with clouds in complex ways, causing the clouds to reflect more light back out to space. This process, known as 'solar dimming', reduces the amount of the sun's energy that reaches the Earth's surface.

Read more

Scientists weigh in on two degrees target for curbing global warming

  • 02 Oct 2014, 13:15
  • Roz Pidcock

Yesterday, two scientists published a  stern critique of the longstanding target to limit global warming to two degrees above pre-industrial levels.

Branding the target "wrong-headed" and "tenuous", the authors argue we should ditch the two degree target in favour of a suite of "vital signs" that would let us track the Earth's health.

The  commentary, published in the journal Nature, has  generated a  certain  amount of  interest. We asked climate scientists for their thoughts.

Setting a target

In 1992, the United Nations Framework Convention on Climate Change (UNFCCC) decided the objective of global climate policy should be to stabilise humans' influence on the climate below the level at which it can be considered "dangerous".

As temperatures rise, so do the risks of climate change. As the recent report on climate change impacts from the Intergovernmental Panel on Climate Change (IPCC) puts it:

"Increasing magnitudes of warming increase the likelihood of severe, pervasive, and irreversible impacts."

With governments worldwide recognising the need to keep rising temperatures in check, it's important to have a goal, Professor Nigel Arnell, director of the Walker Institute for Climate System Research, tells us:

"When we're trying to work out what future climate change might do and how to reduce it, you need some form of metric or indicator on order to judge how well particular policies achieve that goal."

A good indicator

Curbing temperature rise has been central tenet of climate policy for two decades. One of Victor and Kennel's main criticisms in the Nature commentary is the international community's narrow focus on temperatures at earth's surface.

Read more

How we can make good decisions about geoengineering

  • 30 Sep 2014, 15:15
  • Dr Rob Bellamy

NERC

Next month's synthesis report from the Intergovernmental Panel on Climate Change (IPCC) is due to give the organisation's verdict on geoengineering, a radical set of proposals to use large-scale technologies to tackle climate change.

There are two types of geoengineering. Carbon geoengineering seeks to remove carbon dioxide from the atmosphere, for example by capturing it from the air and storing it underground, or by adding iron to the oceans to trigger carbon-absorbing algal blooms.

Solar geoengineering is different. It seeks to reflect some sunlight away from the Earth before it can be trapped by greenhouse gases.This can be done, for example, by spraying clouds with sea salt to make them more reflective, or by stratospheric aerosol injection, where reflective particles are pumped into the atmosphere.

Geoengineering

My colleagues and I have been  examining the importance of 'opening up' discussion about geoengineering to alternative options, different perspectives and real world complexity.

'Closing down' assessment

Our earlier research has shown that the ways in which researchers frame assessments of geoengineering have important effects on the conclusions people come to.

Read more