Analysis

New study shrinks the gap between observed and modelled global temperatures

  • 31 Jul 2015, 16:15
  • Roz Pidcock
The heart of the NASA Center for Climate Simulation (NCCS) is the “Discover” supercomputer.

Supercomputer | NASA Goddard

It's well known in climate science that global surface temperatures over the past decade have been lower than climate models expected them to be.

Some parts of the media have jumped on this to suggest climate models  overestimate the amount of warming we can expect in future.

Now, a   new paper says the discrepancy between modelled and observed temperatures isn't as large as previously thought.

Taking into account the different ways they estimate global temperature shrinks the difference between them by more than a third, according to the study in Geophysical Research Letters.

Model mismatch

While heat-trapping greenhouse gases in the atmosphere have continued to rise, recent measurements of surface temperatures suggest the world is warming a little more slowly than models projected.

The black line in the top graph below shows how the observed temperature from  HadCRUT4 is currently tracking the lower end of the range expected by climate models used in the last Intergovernmental Panel on Climate Change report (red line and purple shading).

We'll come back to the bottom graph in a minute.

Forcings -graph

Top: Comparison of 84 model simulations of the IPCC's highest emissions scenario (RCP8.5) against HadCRUT4 observations (black), using air temperatures (red line and shading) or "blended" temperatures (blue line and shading). Coloured lines are the multi-model averages, shading is the 5-95% uncertainty range of the model simulations. Bottom: Results adjusted to include updated aerosol forcings from Schmidt et al. [2014]. Anomalies are relative to 1961-1990. Source: Ed Hawkins,  Climate Lab Book

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Drought stunts tree growth for four years, study says

  • 30 Jul 2015, 19:00
  • Robert McSweeney
Stressed trees in US

Stressed trees in US | L Anderegg

 

Trees could take up to four years to return to normal growth rates in the aftermath of a severe drought, a new study finds. 

With the frequency and severity of droughts likely to increase with climate change, we might not be able to rely on forests to absorb as much of our carbon emissions, the researchers say.

Drought stress

Forests hold almost half of the carbon found on the Earth's surface, storing it in their woody trunks and branches.  Studies show that forests are sensitive to droughts, causing tress stress and limiting how much they can grow and store carbon.

During the European heatwave in 2003, for example, tree and plant growth  fell by 30%. That meant the land surface in Europe actually produced more carbon dioxide than it absorbed that year.

The new study, published in  Science, suggests that it takes longer for trees to recover after a severe drought than previously thought.

Tree rings

Using data from the International Tree Ring Data Bank, researchers analysed tree growth at over 1,300 sites across the northern hemisphere countries. The sites are predominantly in North America and Europe, and oak and pine trees make up the majority of the species the researchers considered.

Tree rings provide a handy estimate of how quickly a tree has grown. As a tree grows, it puts on extra layers of wood around its trunk, creating a new ring each year. The quicker a tree grows, the bigger the gap between tree rings from one year to the next. 

800px -tree _rings

Tree rings. Creative Commons 2.5: Arnoldius

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Updated: The climate change papers most featured in the media

  • 29 Jul 2015, 15:45
  • Robert McSweeney
Front covers of the most influential climate papers

Climate papers | Carbon Brief

In our recent series on the top climate change papers, we brought you which ones scientists think are the  most influential and which are the most cited by other researchers.

With the help of Altmetric, we also looked into which research articles have made the biggest splash in the news and on social media. But, as a few eagle-eyed readers pointed out to us, it seems there were some papers that were overlooked.

Altmetric has now expanded their search to make sure no paper is missed. So here's our revised take on which papers have made the biggest impact in the wider world.

Media mentions

Altmetric tracks when academic papers are mentioned in online news articles and on social media platforms, such Twitter and Facebook. It collates these mentions and gives each paper a  score for how much attention it received. Featuring in a major national newspaper will contribute a bigger score to a paper than being in a niche publication. A paper with no mentions will score zero, for example, while an article with a score of  over 20 has received significant attention from journalists or perhaps caused a stir online.

To match our analysis of the most cited climate change papers, Altmetric ran a keyword search for papers mentioning "climate change" or "global warming". However, the original Altmetric search capped the number of papers it returned to 10,000, which meant some high-scoring papers were missed off.

Altmetric's founder, Euan Adie, explains to Carbon Brief:

"What I didn't realize when pulling this data the first time round was that the search engine I used to find articles with the two terms we were interested in only returned the 'most relevant' results. Instead of 17,000 results we got back 10,000, and amongst the missing articles were many that, to be consistent, should have been in the top 100. This means the original data was incomplete and the ranking was out; the updated data fixes this."

Altmetric have now extended this cap to 20,000 papers, and intend to remove the cap completely in the near future. You can try out the tool yourself with the Altmetric Explorer.

From the new set of search results, we filtered out all the entries that were news, editorials and books, leaving just research articles to analyse, which we then trimmed to a top 100.

Unfortunately, this did mean cutting out the highest-scoring climate change article of any kind, which was a spoof  News & Views piece in Nature on the reemergence of dragons due to warmer temperatures, published on 1st April this year.  

Finally, one point to note is that Altmetric only started tracking papers in July 2011, so this analysis only covers papers published over the past four years.

So what research have we all been reading and tweeting about?

Top paper

The top-ranked article is "High-Resolution Global Maps of 21st-Century Forest Cover Change" by lead author Prof Matthew Hansen at the University of Maryland in the US, which was published in November 2013.

The paper describes how the researchers used satellite data to map global forest change between 2000 and 2012. They found that forest losses of around 2.3m square kilometers (sq km) outweighed gains of 0.8m sq km. With the help of Google Earth, the team created an  interactive mapping tool to show changes in forests down to a resolution of just 30 metres.

Hansen and his colleagues found forest clearance was largest in the tropics, with increases in deforestation in Indonesia, Malaysia, Paraguay, Bolivia, Zambia and Angola offsetting a reduction in Brazil.

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Iconic British birds and wildlife at risk from climate change

  • 23 Jul 2015, 12:05
  • Roz Pidcock
Wood warbler

Wood warbler | Shutterstock

Scientists have found that 27% of England's plants and animal species will be put at risk as temperatures climb, including some of the nation's best known birds.

new report from Natural England finds that the cuckoo, peregrine, short-eared owl and barnacle goose all face very high risk of decline with 2C of warming.

The nationwide study of more than 3,000 species has attracted a fair bit of media coverage today. The  BBC focuses on the risk posed to British birds, especially the curlew.  The Express says species in the north of the country will fare better than their southern counterparts.

Grahame Madge from the Royal Society for the Protection of Birds (RSPB) tells Carbon Brief:

"This study confirms our fears that birds are vulnerable to climate change."

But not all species will suffer, as today's  Times points out. Garden favourites, such as the house sparrow, skylark, song thrush, blackbird and starling, will be reasonably unaffected. Meanwhile, wasps, bees and ants look set to flourish as temperatures rise, the research notes.

Climate 'envelope'

Plants and animals have a range of conditions in which they can live comfortably. For some, that range is small, making them vulnerable to slight changes in their environment. Others are less sensitive, being better able to tolerate a wider range of conditions.

Short Eared Owl

Short-eared owl | gbrazzil/flickr

Since there is no one-size-fits-all rule, scientists need to examine how climate change is likely to affect individual species across the UK, and then combine them to get an overall picture.

Natural England, the government's adviser for the natural environment in England, looked at how populations of 3,048 plant and animal species are distributed at the moment, and how each one's 'envelope' of habitable conditions is likely to change in future.

The scientists used the UKCP09 projections, which expect average temperature in the UK to rise by 2-7C by the end of the century. The bottom of that range is achievable only with stringent mitigation, while the top is what scientists expect if if fossil fuel emissions stay very high.

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London ‘imports’ climate change risks, warns capital's Economy Committee

  • 23 Jul 2015, 07:30
  • Robert McSweeney
City of London

City of London | Shutterstock

Updated at 14:55 with a response from a spokesman for the Mayor of London.

Financial services and other businesses in London are increasingly vulnerable to climate change through their investments and supply chains that stretch across the globe, a new report from the London Assembly warns.

More than half of companies do not have an adaptation strategy to cope with climate change, says the report, led by Baroness Jenny Jones, Green Party member of the London Assembly. The report says this leaves London's businesses "ill-prepared, and employees insufficiently skilled, to respond to the risks as they arise", it says.

Among its recommendations, the report urges Mayor Boris Johnson to "commit to the principle of a transition away from investment in certain fossil fuels, namely coal".

Climate risks

Sitting on an estuary with  £200bn of property in the Thames floodplain, London already has its fair share of climate-related risks, such as tidal flooding, heatwaves and intense rainfall events. The graphic below shows some of the impacts that businesses in the the nation's capital will need to cope with as global temperatures rise.

But a new report warns that the global reach of London's economy means it's also vulnerable to climate change impacts on the other side of the world.

London Risks

Climate risks facing London's businesses. Source: London Assembly Economy Committee (2015). Based on data from: Carbon Disclosure Project Cities 2013 report: Greater London Authority, 2013.

The report is produced by the  Economy Committee of the London Assembly -  a body of seven London Assembly members that "scrutinises the work of the mayor and investigates matters of importance to Greater London".

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Cool Arctic summer brought brief recovery in sea ice loss in 2013, study suggests

  • 20 Jul 2015, 16:20
  • Robert McSweeney
Open passage in pack ice

Open passage in ice | Shutterstock

A colder-than-expected Arctic summer led to a brief let up in the decline of sea ice, a new study says. State-of-the-art satellite data shows that after a 14% decrease in sea ice volume between 2010 and 2012, summer sea ice recovered to pre-2010 levels in 2013.

The study shows how natural fluctuations in Arctic weather will cause many ups and downs, scientists tell Carbon Brief. But the long-term patterns is a decline in sea ice through the century.

Ice thickness

Scientists have used satellites to monitor polar sea ice since the 1970s. It's how we know that the summer of 2012 saw a new record low in sea ice extent of 3.41m square kilometers - 44% below the 1981-2010 average. Compare the dotted orange line with the thick grey one in the graph below.

Arctic -sea -ice -extent -figure 21_600x 480Arctic sea ice extent for 2010 to September 2014. The 1979 to 2000 average is in dark gray. The grey area around this average line shows the two standard deviation range of the data. Source: NSIDC

But the area covered by sea ice is only part of the story. To understand how the volume of sea ice is changing, you also need to know its thickness.

The new study, published today in Nature Geoscience, is the first to use satellite data to derive sea ice thickness and volume results for the entire northern hemisphere, says lead author  Rachel Tilling from University College London.

And the results suggest that Arctic sea ice volume rebounded to similar levels seen before the record low in 2012.

Chilly summer

Tilling and her colleagues used 88m individual measurements, from October 2010 to November 2014, taken by the European Space Agency  CryoSat-2 satellite. The data show that between the summers of 2010 and 2012, sea ice volume declined by 14% - that's 1,279 cubic kilometers of ice melting into the sea.

But after this dramatic drop, the Arctic experienced a much cooler summer in 2013 - one more typical of a summer in the 1990s, Tilling says.

The chillier conditions cut the summer melt season short and allowed thick ice to hold steady on the northern coast of Greenland. The satellite data shows that by the end of the summer in 2013, the sea ice volume had grown 41% bigger than its diminished state in 2012. Sea ice then decreased again by 6% (of the 2013 volume) by the summer of 2014.

You can see this in the graphs below. The upper graph shows the CryoSat data as red stars against the long-term trend in sea ice volume from  computer models (red line). You can see the decline towards the record sea ice low in 2012 and the subsequent increase in 2013.

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NOAA State of the Climate report: Which seven records were broken in 2014?

  • 16 Jul 2015, 16:15
  • Robert McSweeney
Global surface temperature diagram from NOAA

Surface temperature | NOAA

From greenhouse gas levels to ocean heat content, 2014 was a record-breaking year for the Earth system in many different ways. That's the finding of the latest  State of the Climate report from the US National Oceanic and Atmospheric Administration's (NOAA) published today.

Now in its 25th year, the report provides a checkup of global climate using data collected from land, sea, ice and space. We take a look at seven of the records that tumbled last year.

Greenhouse gases

All the major greenhouse gases in the atmosphere, including carbon dioxide, methane and nitrous oxide, hit record high average concentrations last year.

After briefly passing 400ppm in May 2013, carbon dioxide levels at Mauna Loa in Hawaii stayed above this mark for the whole of April, May and June in 2014, the report says. Globally, 1.9ppm of carbon dioxide was added to the atmosphere in 2014, taking the average for the year to 397.2ppm.

State Of Climate 2014_Fig1Global average carbon dioxide concentrations since 1980, with photo of Mauna Loa Observatory in background. Adapted from Figure 2.36 in  State of the Climate in 2014

Concentrations of methane in the Earth's atmosphere reached 1822.9 parts per billion (ppb) in 2014. This increase of 9.2ppb from 2013 is larger than in recent years, the report says. The average levels of nitrous oxide in 2014 was 326.9ppb, an increase of 1.0ppb from 2013. This is faster than the average year-on-year increase over the decade (0.75ppb per year).

Hottest year

As was widely covered in the media, 2014 saw the highest annual average global surface temperature since records began, the report says:

"The year 2014 was forecast to be a warm year, and it was by all accounts a very warm year, in fact record warm according to four independent observational datasets."

Three of the  four datasets put 2014 as the hottest year, while the  UK Met Office put it joint top with 2010. The four estimates put 2014 at 0.27-0.29C above the 1981-2010 average.

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Global risk of wildfires on the rise as the climate warms, study says

  • 14 Jul 2015, 16:00
  • Robert McSweeney

Bushfire | Shutterstock

An average of 3.5m square kilometres of land go up in smoke each year as a result of wildfires. Annual carbon dioxide released in these infernos can exceed half the emissions from humans burning fossil fuels.

A new study finds that the number of days wildfires are likely to burn each year is increasing as global temperatures rise.

Researchers estimate that between 1979 and 2013, the wildfire season has lengthened by an average of 19% for more than a quarter of the Earth's vegetated surface.

Weather and wildfires

From the 600 fires that claimed more than 50 lives in Russia in 2010, to the series of major bushfires in Australia in 2013 that caused $9.4bn of damage, wildfires affect much of the world's surface.

Wildfires play an important role in flammable ecosystems, such as forests, grasslands, savannas, and shrublands. They can be managed to disperse plants, clear forests and promote grazing, or suppressed to protect human lives and property.

Most wildfires are triggered by humans - as much as 90% in the US, for example - while natural causes include lightning and lava. But the weather is the biggest driver of how much area that wildfires actually burn. Temperature, humidity, rainfall and wind speed all play a role in providing the right conditions for a fire.

A new study, published in Nature Communications, finds that changes in these different weather variables are conspiring to increase the risks of wildfires.

Fire season length

Researchers analysed three global weather datasets to develop a metric for "fire weather season length" - the number of days per month where conditions create a high fire danger. They then worked out how the season length had changed between 1979 and 2013 for vegetated areas across the world. You can see the results in the graphs below.

Jolly Et Al 2015 Fig 2c

Graphs show a) Global average wildfire season length (expressed as a standardised anomaly), and b) Total global average area experiencing 'long' wildfire seasons (as a % of global vegetated area) - both from 1979 to 2013. Source: Jolly et al. (2015)

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A Carbon Brief guide to the Our Common Future conference in Paris - Final day

  • 10 Jul 2015, 08:45
  • Roz Pidcock

In the biggest gathering of scientists ahead of COP21 in December, thousands of climatologists, social scientists, economists and policy experts have descended on the UNESCO headquarters in Paris today to kick off the Our Common Future under Climate Change conference.

There's an almost unfathomably large amount of research being presented here in the next four days. So here's Carbon Brief's selection of talks, posters and events caught our eye.

Carbon Brief will also be holding our final media workshop today. Come along and talk to us about how the media covers climate change, learn more about what journalists look for in a story and tell us about your own media experiences.

Come along to room VIII-Bis in the basement of the UNESCO building at 1:30pm today, sign up on the sheet outside our room or email info@carbonbrief.org to join in.

Friday 10 July

9am Joseph Stiglitz - Bridging the carbon gap in the context of the financial crisis

This morning promises an action packed plenary with Joseph Stiglitz, Nobel Laureate economist and professor at Columbia University, kicking off proceedings with a talk about the economics of climate negotiations and what we should and shouldn't expect at the Paris COP in December. (UNESCO Main plenary room 1)

10-11am Panel Discussion

No shortage of big names this morning, with a second session in the main plenary featuring a discussion between Laurence Tubiana, founder of the Institute for Sustainable Development and International Relations (IDDRI), Rachel Kyte, group vice-president of the World Bank, Hans Joachim Schellnhuber from the Potsdam Institute for Climate Impacts Research (PIK) and Rush Holt, CEO of the American Association for the Advancement of Science. (UNESCO Main plenary room 1)

12:50pm David Victor - The emergence of new structures for global governance

With the failure of top-down bargaining strategies, can bottom-up methods such as "building blocks" and "climate clubs" break the diplomatic deadlock? David Victor discusses. (UNESCO - Fontenoy Room IV)

4-6pm Closing plenary

To bring this week's proceeding to a close, Chris Field, chair of the conference's scientific committee, will summarise what's been achieved this week and what's next for climate science. The French foreign minister Laurent Fabius and Segoline Royale, the French minister for Sustainable Development, Environment and Energy, follow up with their take on what the next few month holds for climate science and policy. (UNESCO Main plenary room 1).

 

Thursday 9 July

9am Fatih Birol - Strengthening climate ambition in the energy sector

Fatih Birol, chief economist at the International Energy Agency, kicks off this morning's plenary with a summary of what the energy sector needs from COP21, including a concrete long term emissions goal, setting the conditions for a peak in emissions, and the possibility to review countries' pledges every five years. Ottmar Edenhoffer and Saleemul Huq follow with keynote talks on the global state of play in mitigation and adaptation. (UNESCO - Main plenary hall)

11:30am Billy Pizer - Socioeconomics and instruments for transforming the energy sector

Carbon markets are expanding across the world, but the separate trading systems are in sharp contrast to how carbon market "architecture" was envisioned 15 years, says Pizer. Come along to hear more about how and whether they can better link together. This is part of a wider socioeconomics session from 11:30-1pm, encompassing a special focus on policy tools for mitigation in China, India and Brazil. (UNESCO - Fontenoy room XI)

4:30pm Li Shuo - Challenges and opportunities for renewable energy development in China

A look at the rapid growth in renewable energy deployment in China, the country's ambitious targets for wind and solar energy generation and the challenges it faces in better integrating renewable energy into the grid and further reforming its aging power market. This is part of a larger session from 4:30-6pm on China's climate policies. (UNESCO - Fontenoy room XI)

5:30pm Pete Smith - The limits to negative emissions

A session on the environmental and economic implications of different carbon-negative technologies. This includes direct CO2 removal from the atmosphere, which is expensive, but has little environmental impact, and bioenergy with carbon capture and storage (BECCS), which is cheaper, but potentially uses a lot of land. The talk is the first in a larger session on negative emissions for climate change stabilisation from 5:30-7pm today. (UPMC Jussieu - Amphi 34)

6:50pm Steve Smith - Climate legislation in the UK

The UK has traditionally been seen as a progressive nation in terms of climate action, in part due to its target to reduce emissions to at least 80% below 1990 levels by 2050 as part of the Climate Change Act. This talk summarises the Act, the role of the Committee on Climate Change, set up to monitor progress towards this goal, and the key costs and technologies needed to achieve it. (Jussieu - Amphi Durand)

Conference -icebreakerDay 1 at the conference. Credit: Our Common Future under Climate Change. More photos from the conference can be found on Flickr.

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Analysis: The climate change papers most featured in the media

  • 09 Jul 2015, 16:00
  • Robert McSweeney
Front covers of the most influential climate papers

Climate papers | Carbon Brief

In this week's series on the top climate change papers, we've seen which ones scientists think are the  most influential and which are the most cited by other researchers.

But what neither of these measures captures is what impact new papers have in the wider world. So with the help of Altmetric, Carbon Brief looks into which research articles have made the biggest splash in the news and on social media.

Media mentions

Altmetric tracks when academic papers are mentioned in online news articles and on social media platforms, such Twitter and Facebook. It collates these mentions and gives each paper a  score for how much attention it received. Featuring in a major national newspaper will contribute a bigger score to a paper than being in a niche publication. A paper with no mentions will score zero, for example, while an article with a score of  over 20 has received significant attention from journalists or perhaps caused a stir online.

To match our analysis of the most cited climate change papers, Altmetric ran a keyword search for papers mentioning "climate change" or "global warming". You can do the same thing with the Altmetric Explorer.

We also experimented with using the word "climate" as the search term, but using such a common word raises a problem. Altmetric have told us that their searches produce a maximum of 10,000 papers, as the word "climate" appears in so many, the "best" matches that Altmetric finds aren't necessarily the papers with the highest scores. So rather than risk losing some of these high scorers, we went with "climate change" or "global warming" as our search terms.

From the resulting list, we filtered out all the entries that were news, editorials and books, leaving just research articles to analyse, which we then cut down to a top 100. One point to note is that Altmetric only started tracking papers in July 2011, so this analysis only covers papers published over the last four years.

So what research have we all been reading and tweeting about?

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