Analysis

Amazon rainforest is taking up a third less carbon than a decade ago

  • 18 Mar 2015, 18:05
  • Robert McSweeney

Amazon at dawn | P. van der Sleen

The amount of carbon that the Amazon rainforest is absorbing from the atmosphere and storing each year has fallen by around a third in the last decade, says a new 30-year study by almost 100 researchers.

This decline in the Amazon carbon sink amounts to one billion tonnes of carbon dioxide - equivalent to over twice the UK's annual emissions, the researchers say.

If this pattern exists in other forests around the world, deeper cuts in human-caused carbon dioxide emissions are needed to meet climate targets, the researchers say.

Three billion trees

The Amazon rainforest is the largest rainforest in the world. Spanning nine countries in South America, it's 25 times the size of the UK.

Using a process known as photosynthesis, the Amazon's three billion trees convert carbon dioxide, water and sunlight into the fuel they need to grow, locking up carbon in their trunks and branches.

As they grow, Amazon trees account for a quarter of the carbon dioxide absorbed by the land each year. Studies suggest that as human-caused carbon dioxide emissions increase, forests will absorb and store more carbon, assuming they have enough water and nutrients to grow.

But a new study, published today in Nature , suggests the Amazon has passed saturation point for how much extra carbon it can take up.

Diminishing carbon sink

A team of almost 500 people monitored trees in more than 300 sites across eight countries. Between 1983 and 2011, the researchers measured the trees in each plot, recording the number, size and density to calculate how much carbon each one stored.

The trees took up more carbon and grew more quickly during the 1990s, before levelling off since the year 2000. You can see this in the middle chart below.

Brienen Et Al (2015) Fig1

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Farming Africa’s wet savannahs would have a high climate cost, study warns

  • 17 Mar 2015, 14:10
  • Robert McSweeney

Irrigation in Zambia | Lyndon Estes

As the global population rises, some scientists have suggested that Africa's wet savannahs could be ideal for growing the extra crops needed to meet the growing demand for food and bioenergy.

But it isn't quite the solution it seems, according to new research. The idea that Africa can provide food and biofuels while keeping emissions low "does not add up", the researchers say.

The wet savannah

'Wet savannah' describes warm, tropical areas areas that are wet enough to support crops and aren't covered with dense forest. Africa is home to around half of the world's wet savannah. Much of it is found in the Guinea Savannah, which makes up around a third of sub-Saharan Africa

Searchinger Et Al (2015) Fig1

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Cyclone Pam: Untangling the complex science on tropical storms and climate change

  • 16 Mar 2015, 20:30
  • Roz Pidcock

Winds of up to 300 kilometres per hour tore through the South Pacific island nation of Vanuatu over the weekend, hitting the heavily populated capital of Port Vila on Saturday morning.

Aid agencies say Cyclone Pam could be one of the worst disasters ever to hit the region, the BBC reports. The death toll currently stands at eight and is expected to rise as rescuers reach the more remote islands.

Speaking at a disaster preparedness conference in Japan, Vanuatu's President Baldwin Lonsdale said he thought climate change was contributing to the rise in extreme weather.

With aid finally reaching the storm-stricken nation, Carbon Brief looks at how climate change is altering how often this part of the world bears the brunt of such a destructive force.

Screen Shot 2015-03-16 At 18.58.16

Wind speed in Cyclone Pam at 1900 GMT on 16th March 2015. Winds of more than 200 km per hour (red) are still being recorded as the cyclone continues its path from Vanuatu down the east coast of New Zealand. Images courtesy of Cameron Beccario via  earth.nullschool.net

Storm severity

A cyclone is a tropical storm. Tropical storms are given different names depending on which ocean they form in. They are called hurricanes in the north Atlantic and northeast Pacific, typhoons in the northwest Pacific, and cyclones in the Indian Ocean.

Vanuatu frequently experiences cyclones. The cyclone season runs from December to April when the weather in the region is hot and wet. Tropical storms  derive energy from the warmth of the ocean and convert it into wind strength.

While strong storms aren't unusual for the region, Cyclone Pam was exceptional. Prof Kevin Trenberth, expert in climate change and extreme weather at the US National Centre for Atmospheric Research, tells Carbon Brief:

"In the large area around Vanuatu the sea surface temperatures were one to two degrees Celsius above normal … So the atmosphere all around there has some 10 to 20% more moisture in it than a comparable storm in the 1970s would have had."

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La Niña boosts the odds of tornadoes and hailstorms in the US, study shows

  • 16 Mar 2015, 16:00
  • Robert McSweeney

Tornado on US plains | Shutterstock

Last week, scientists announced the arrival of a long-awaited El Niño event. It's well known that El Niño triggers extreme weather around the world. But a new study published today shows how the event's little sister, La Niña, can be destructive too.

La Niñas tend to bring more tornadoes and hailstorms to the southern US, the study finds. Knowing this will allow scientists to forecast hail and tornado frequency a season in advance for the first time, the lead author tells Carbon Brief.

El Niño and La Niña

Every five years or so, weakening trade winds cause a shift to warmer than normal ocean temperatures in the eastern equatorial Pacific Ocean. The phenomenon, known as El Niño, has a cold water counterpart, called La Niña. During La Niña, the opposite happens. The trade winds strengthen and the central and eastern Pacific Ocean become colder than normal.

Together, these warm and cold events form the El Niño-Southern Oscillation (ENSO), and cause most of the fluctuations in global weather we see from one year to the next.

The impact of ENSO events can be dramatic. La Niñas, for example, are known to bring floods to Central and South America, and hurricanes to the Atlantic Ocean.

Now a new paper, published in Nature Geoscience, suggests there could be a link with a different type of extreme weather event. The southern US is on the receiving end of more tornadoes and hailstorms during La Niña events and fewer during El Niños, the research finds.

La -nina

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Scientists link Arctic warming to intense summer heatwaves in the northern hemisphere

  • 12 Mar 2015, 18:00
  • Roz Pidcock

The Arctic is warming up, and the impacts are being felt right across the world. A new study suggests rising temperatures there could even be contributing to longer-lasting heatwaves in the northern hemisphere, like the one Russia experienced in 2010.

Published today in the journal Science, the paper is the latest in a line of research suggesting how rising temperatures in the high north could be affecting our weather patterns much further south.

But there's a lot still to understand before the links can be well and truly pinned down, scientists say.

Extreme Arctic warming

The Arctic is warming at least twice as fast as the globe as a whole. Scientists begun noticing the pattern emerge in temperature records since about the year 2000. It's known as  Arctic Amplification.

Part of the reason for it is that, as sea ice is diminishing, heat from the sun that would have been reflected back to space by snow and ice is being absorbed by the oceans instead, warming them up.

As the Arctic warms faster than the rest of the world, the temperature difference between the pole and the equator is getting smaller. Since this temperature contrast drives much of the atmospheric circulation in the northern hemisphere, the smaller it gets, the weaker the circulation becomes.

These atmospheric circulation patterns are responsible for delivering the weather systems that create warm, cold or wet conditions in the northern hemisphere. So, it follows that disrupting the circulation will, in turn, have consequences for the weather we see.

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Earth entering new era of rapid temperature change, study warns

  • 09 Mar 2015, 16:00
  • Robert McSweeney

Trees at sunset | Shutterstock

The rate of climate change we're experiencing now is faster than at any time in the last millennium, a new study shows.

Researchers compared how temperature varied over 40-year periods in the past, present and future, and concluded that the Earth is entering a new "regime" of rapid temperature change.

We're already locked into fast-paced changes in the near future because of past emissions, the researchers say.

That means we'll need to adapt to minimise the impacts of climate change, even if greenhouse gas emissions are cut substantially.

Peaks and troughs

A look back at how global temperatures have changed over the past century shows how temperature  rise of the Earth's surface has been anything but smooth.

These peaks and troughs are in part caused by natural phenomena, such as  volcanic eruptions and  El Niño, which influence the Earth's climate from year to year.

The graph below shows average global surface temperatures for every year back to the 1850s. You can see that temperature changes from decade to decade do not always happen at the same pace. This is the impact of  natural cycles in climate, which can either work to enhance or dampen the long-term warming trend over short timescales.

A new study, published in Nature Climate Change, shows how much faster temperature has increased in recent decades compared to any time over the last 1,000 years.

 

Tempdatasets 2--5_cropped

How the major global surface temperature datasets compare. Showing NASA GisTEMP (purple), JMA (orange), NOAA MLOST (green) and Met Office/CRU (blue). Credit: Rosamund Pearce, Carbon Brief

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Reflections on climate-conflict research: More confusion than knowledge

  • 06 Mar 2015, 14:25
  • Prof Halvard Buhaug

A guest post from Prof Halvard Buhaug, Research Director and Research Professor at the Peace Research Institute, Oslo (PRIO).

Does climate change constitute a threat to peace and security? Many agree that it does. The US administration's new National Security Strategy, launched last month, portrays climate change as 'an urgent and growing threat.'

And this week, a new  study appears to add scientific credibility to this concern, suggesting human-caused climate change contributed to the drought that preceded the Syrian civil war.

So does the Syrian case represent a general pattern, where climate changes and extremes are systematically increasing conflict risk? The short answer is no. But if scientists want to explore these links more closely, there are a few steps they need to take.

Cacophony of different findings

Recent  research has reported a strong effect of climate extremes on violent conflict,  yet many researchers question the robustness of such a link. Some even argue the relationship between climate and conflict is so complex that it can never fully be captured and understood.

There are legitimate reasons to be concerned about the impacts of climate change on security. However, a decade of research into the area appears to have produced more confusion than knowledge. But the  cacophony of different findings and  inadequate scientific evidence could be the result of poor data and simplistic research designs, rather than because no relationship exists.

In trying to establish links that can be observed and quantified, I see five key challenges that need to be addressed.

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The Carbon Brief Interview: Ed Davey

  • 05 Mar 2015, 06:00
  • Leo Hickman

Ed Davey, the Liberal Democrat MP for Kingston and Surbiton, has been the UK's longest-serving secretary of state for energy and climate change since taking office in February 2012. The Liberal Democrats have been in coalition with the Conservative party since the last general election in 2010.

Here, Davey discusses a wide range of issues: his vision for a zero-carbon Britain by 2050; why the Treasury's economic modelling assumptions are "rubbish"; why some Conservatives are "crazy" about fracking; why the proposed Hinkley C nuclear plant would be value for money; why the world needs to get off fossil fuels within "30-40 years"; why maximising North Sea oil doesn't contradict low-carbon objectives; what form of energy he'd invest his own money in; and why energy bills would have been higher if a Conservative had been in charge of his department since 2010 instead of a Liberal Democrat...

CB: This week, you've been setting out the "Green Magna Carta" and the Lib Dems have pledged for the UK to be zero-carbon by 2050. What does that mean exactly and how do you intend we get there? And how are we going to pay for that?

ED: The Green Magna Carta is going to be on the frontpage of the Lib Dem manifesto. It's basically five green bills and I had that idea because I wanted to make sure that we could build on the success that we've had here in energy and climate change, in our department, but also fill in the gaps in other departments, DCLG [Department for Communities and Local Government], DEFRA [Department for Environment, Food and Rural Affairs] and others, to really take forward the environment and climate change agenda, very strongly in the first half of the next Parliament, with a big legislative agenda. So, we've got the green transport bill, the zero waste bill, the green homes bill, a nature bill and a zero-carbon Britain bill. The zero-carbon Britain is about raising our ambition.


View on YouTube

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Polar bears and climate change: What does the science say?

  • 04 Mar 2015, 13:45
  • Roz Pidcock

We've all seen the pictures of polar bears stranded on sea ice. They're  all too often used as the iconic poster animals of a rapidly changing climate.

Every now and again, claims emerge in the media that polar bears' plight might not be so serious after all. Just recently, Peter Hitchens said in the  Mail on Sunday polar bears are "doing extremely well right now" and that claims otherwise are "just hot air".

Carbon Brief has dug through the literature and spoken to polar bear experts. While little is known about some remote bear populations, it's clear there's no scientific basis for such optimism. As temperatures rise, polar bears face a bleak future ahead, scientists tell us.

Claims about polar bears on the up

The crux of Hitchens' argument is that polar bear numbers are rising around the world, not falling. He quotes biologist  Dr Susan Crockford, who says:

"On almost every measure, things are looking good for polar bears ... It really is time for the doom and gloom about polar bears to stop."

                                       Screenshot 2015-03-04 14.42.14

Source: Ben Webster, The Times,  Feb 27th 2015

This stems from a report authored by Crockford and published last week by the Global Warming Policy Foundation, a climate skeptic think tank. Entitled, "  20 good reasons not to worry about polar bears", the report describes itself as a "resource for cooling the polar bear spin".

The Times quoted the report's conclusion that:

"Polar bears are not currently threatened with extinction due to declining sea ice, despite the hue and cry from activist scientists and environmental organisations."

Similarly, a Mail on Sunday  article from last September, also featuring Crockford, claimed: "The poster boys of climate change thrive in the icy Arctic: Polar bears defy concerns about their extinction."

So, what is the evidence for the claims? And do other scientists agree there's no cause for alarm?

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Leaf-eating insects may limit how much carbon forests absorb, study says

  • 03 Mar 2015, 17:20
  • Robert McSweeney

Forest tent caterpillar | Mary Jamieson

Insects could restrict how well trees absorb and store carbon in the future, according to a new study. In experiments simulating carbon dioxide levels in 2050, insects munched their way through almost double the number of leaves than under current conditions.

With fewer leaves, the trees are likely to become less effective at absorbing carbon dioxide from the air, the researchers say.

Carbon dioxide fertilisation

Trees are the biggest carbon sink on land. Through a process known as photosynthesis, trees convert carbon dioxide, water and sunlight into the fuel they need to grow, locking up carbon in their trunks and branches as living biomass.

Research suggests that when there's more carbon dioxide in the air, trees grow more quickly because the rate of photosynthesis speeds up. This is called 'carbon dioxide fertilisation'.

Scientists expect that as human-caused carbon dioxide emissions increase, forests will absorb and store more carbon, assuming they have enough water and nutrients to grow.

But the results of a three-year experiment, just published in Nature Plants, suggests that insects, such as caterpillars, may make it harder for trees to absorb this extra carbon by munching their way through the trees' leaves. With fewer leaves to absorb sunlight, the trees can't photosynthesise as much, and they absorb less carbon dioxide from the air.

'Double whammy'

The researchers set up their experiment at the Aspen FACE facility (Free-Air Carbon Dioxide Enrichment) in Wisconsin in the northern US. At the facility, birch and aspen trees are surrounded by vertical vents that release different gases to simulate future conditions.

FACE Aerial 2005 -25

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