Analysis

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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US emissions increase hints at limitations of Obama’s clean power plan

  • 22 Oct 2014, 17:10
  • Mat Hope

President Obama | Shutterstock

US energy sector emissions increased slightly in 2013, according to new data from the Energy Information Administration (EIA). This may seem like bad news for President Obama, who has pledged to cut the country's emissions 17 per cent by 2020.

Obama unveiled his  clean power plan earlier this year to much fanfare. The centrepiece of the plan is to reduce emissions from electricity generation by 30 per cent by 2020.

The US's rising energy sector emissions seem to  suggest the policy may not be as effective as Obama hopes.

Obama's clean power plan specifically targets emissions from power generation, which accounts for   about 32 per cent of the US's total emissions. Cutting emissions from the US's homes and businesses is a much smaller part of his wider   Climate Action Plan.

The EIA's data shows the potential limitations of focusing on cutting power generation emissions without addressing the country's broader energy consumption.

Emissions increase

US energy sector emissions increased 2.5 per cent in 2013 compared to year before, the EIA's data shows. The EIA says the main reason for the increase was colder weather.

Winter temperatures at the start of 2013 were lower than a year before, and the US also experienced a particularly mild spring last year. Temperatures fell again later in the year, when the US was  engulfed by the polar vortex.

Screen Shot 2014-10-22 at 16.15.40.png
Source: National Oceanic and Atmospheric Administration, average monthly temperatures. Graph by Carbon Brief.

Households and businesses turned up their thermostats in response to the lower temperatures, which meant burning a lot more gas and a bit more oil. The residential sector was responsible for 48 per cent of 2013's emissions increase, mostly due to heat demand, the EIA says.

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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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US military outlines plan to deal with increasing climate change threat

  • 14 Oct 2014, 15:00
  • Mat Hope

Flood trucks | US Navy

"A changing climate will have real impacts on [the US] military and the way it executes its missions", US Defense Secretary Chuck Hagel yesterday said. And the US military is planning how to deal with the threat now.

The Department of Defense's 2014 Climate Adaptation Roadmap, published yesterday, suggests climate change has the potential to exacerbate some of the world's most significant challenges, from disease to international conflict. It calls climate change a "threat multiplier" with the potential to increase the impact of numerous security concerns.

This  isn't the first time the US military has expressed its concerns about climate change. But the roadmap is one of the first documents to "really go into great detail about what the US military should be doing in response to climate change now" Francesco Femia, co-director of the Center for Climate and Security thinktank, tells Carbon Brief. The report shows that military has decided the risk from climate change "is great and it's immediate", Femia says.

New activities

The roadmap outlines a number of new ways climate change could cause the military to be called into action. Its findings are driven by two things, Femia says: developments in climate science and "what the military is seeing on the ground".

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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.

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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.

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Get ready for hotter summers and more flooding in the UK, say scientists

  • 29 Sep 2014, 16:10
  • Roz Pidcock

Weather-wise, the UK saw it all last year. The coldest spring for 50 years, a sweltering summer heat wave and the wettest winter since records began. Today, a new report examines whether climate change is upping the odds of these events occurring.

The collection of papers, published in a  bumper edition of journal Bulletin of the American Meteorological Society, looks at 16 weather events that took place last year across the world. From Colorado to Korea, the scientists examine heatwaves, droughts, heavy rain and storms.

Human fingerprints

Globally, there is  evidence for changes in some types of extreme weather, and evidence for a human fingerprint in those changes. But different types of event are affected differently.

Climate change is greatly increasing the odds of heatwaves worldwide, today's report concludes. For storms, rainfall and drought the picture is less clear, however. Big differences between regions, natural variability in the climate and limited data make detecting changes over time far more difficult.

The science of disentangling human and natural influences on our climate is known as attribution. Dr Peter Stott, head of the climate change detection and attribution team at the Met Office and an editor on the report, explained more in a recent  guest blog  for us:

"[The aim is] to compare what actually happened with what might have happened in a world without anthropogenic climate change."

Understanding how our activities are changing the risk of some types of extremes is important for making decisions about how we can prepare for the future.

Hot summers

In summer 2013, western Europe experienced an extreme heatwave. Average temperatures for the June to August period sit just below those of 2003 - the hottest summer in Europe for at least  500 years.

At the same time, the UK experienced its hottest day since 2006 with temperatures of 33.5 degrees Celsius recorded at Heathrow airport, the report notes.

UKheatwave 2014

Sun-seekers flock to Margate in July 2013. Source:   UK heatwave via Shutterstock

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