Analysis

Why the IPCC synthesis report is necessary but not sufficient to secure a response to climate change

  • 31 Oct 2014, 13:45
  • Simon Evans

Factory chimneys | Shutterstock

On Sunday 2nd November, the Intergovernmental Panel on Climate Change (IPCC) will publish its latest synthesis report, distilling the latest knowledge on what UN chief Ban Ki-Moon has  called the greatest threat ever faced by humanity.

The synthesis report will wrap up the IPCC's fifth assessment (AR5) of climate change. It draws together information from the IPCC's reports on the science of climate change, climate impacts and the  ways climate risks can be addressed.

It takes a mammoth collective effort on the part of scientists, economists and policymakers to produce these IPCC reports. Is it worth it?

We've collected a range of views on the need for, and wider significance of, the IPCC's work. These suggest it remains a necessary but not sufficient part of the job of addressing climate change.

The synthesis report is necessary

Does the world need an IPCC, asks former IPCC chair and former scientific adviser to the UK government Bob Watson. "My answer would be absolutely yes," he says. "I think it's critically important the IPCC does routinely report back on what we know."

The synthesis report collects together scientific opinion on the technical and socio-economic aspects of the causes of climate change, the risks it poses and the options for adaptation and mitigation. It is unique in taking such a wide ranging and considered view of climate.

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Nitrous oxide emissions could double by 2050, study finds

  • 28 Oct 2014, 17:42
  • Robert McSweeney

Emissions of nitrous oxide could double by the middle of the century if left unchecked, a new study finds. And nitrous oxide is the third biggest contributor to manmade climate warming. So should we be worried?

Laughing gas

Most people know nitrous oxide as 'laughing gas', used as a mild anaesthetic by doctors and dentists. But it is also a powerful greenhouse gas.

Nitrous oxide is the third-largest contributor to the manmade greenhouse effect, after carbon dioxide and methane.

A new study, published in the journal Environmental Research Letters, brings together all the projections for future nitrous oxide emissions from different researchers. The results show that on average emissions will increase 83 per cent by 2050, if we carry on with business as usual.

The study also looks at how emissions might be curbed between now and the middle of the century. If 'moderate' attempts are made, the study finds, nitrous oxides would still increase by around 26 per cent. But emissions could reduce by as much as 22 per cent if we really get our act together.

All the projections were made using a starting point of 2005. This means the researchers are able to see how actual nitrous oxide emissions in recent years compare to the different scenarios. And the bad news is that we're currently on the business-as-usual path, the researchers say.

Human activities

Bacteria release nitrous oxide naturally by breaking down nitrogen in the soil and oceans. Total emissions from natural sources are currently around twice those of emissions from human activities.

But while natural emissions have not changed significantly since the industrial revolution, manmade emissions have. This increase has caused nitrous oxide concentrations in the atmosphere to rise steadily since the the mid-19th century, as shown below.

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New study strengthens link between Arctic sea-ice loss and extreme winters

  • 26 Oct 2014, 19:11
  • Robert McSweeney

Winter scene in Russia | Shutterstock

Declining Arctic sea-ice has made severe winters across central Asia twice as likely, new research shows. The paper is the latest in a series linking very cold winters in the northern hemisphere to rapidly increasing temperatures in the Arctic.

But the long-term picture suggests these cold winters might only be a temporary feature before further warming takes hold.

Arctic amplification

Temperatures in the Arctic are increasing almost twice as fast as the global average. This is known as Arctic amplification. As Arctic sea-ice shrinks, energy from the sun that would have been reflected away by sea-ice is instead absorbed by the ocean.

Arctic amplification has been linked with very cold winters in mid-latitude regions of the northern hemisphere. The UK, the US and Canada have all experienced extreme winters in recent years. Just last year, for example, the UK had its second-coldest March since records began, prompting the Met Office to call a rapid response meeting of experts to get to grips with whether melting Arctic sea-ice could be affecting British weather.

The new study, published in Nature Geoscience, suggests the likelihood of severe winters in central Asia has doubled over the past decade. This vast region includes southern Russia, Mongolia, Kazakhstan, and northern China. And it's the Arctic that's driving the changes once again, the authors say.

Pronounced change

The study finds that almost all of the very cold winters in central Asia during the past decade have coincided with particularly warm conditions in the Arctic.

The paper points to sea ice loss in the Barents Sea and the Kara Sea as the cause. These sit to the north of Scandinavia and Russia and to the south of the Arctic Ocean, as shown in the map below.

 

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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.

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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.

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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)

 

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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

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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".

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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]

 

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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.

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