Last summer, Carbon Brief delved into the canon of published climate papers to discover which were the most influential, most cited and most covered by the media.

Our analysis covered as many climate papers as the relevant databases would allow. Our article on media coverage went back as far as July 2011, for example.

Now, with 2015 only just behind us, we’ve narrowed the search to look at which of last year’s research papers have been the biggest hits in the news and on social media.

Scoring system

Our analysis uses Altmetric, which scores academic papers based on how many times they’re mentioned in online news articles and on social media platforms. You can read more about how the Altmetric scoring system works in our previous article.

We’ve used much the same approach again this time, except we have only counted academic papers published during 2015, and we have expanded the search terms to include a broader set of keywords. This is to ensure we capture relevant climate papers on topics from sea level rise to carbon emissions, and from ice shelves to forests.

Our infographic above shows which 10 climate papers most featured in the media in 2015.

On top

The highest-scoring climate paper comes from the very beginning of the 2015. Published on 8 January – and with an Altmetric score of 2,061 – is the Nature article, “The geographical distribution of fossil fuels unused when limiting global warming to two degrees” by Dr Christophe McGlade and Prof Paul Ekins at University College London.

The paper describes how keeping global temperature rise to no more than 2C above pre-industrial levels requires 80% of known coal reserves, 50% of gas reserves and 30% of oil reserves to remain unburned.

Carbon Brief produced the infographic below based on the findings as part of our coverage of the research when it was first published.

The paper scored highest for mentions on Twitter and was featured in 129 news stories from 76 outlets, including 10 in the Huffington Post, 10 in the Guardian, two in the Washington Post, and one each in the New York Times, Daily Mail and BBC News website.

The paper also placed third in our previous analysis of all published climate papers back to July 2011.

Coming in second

In runners-up place is “Climate change in the Fertile Crescent and implications of the recent Syrian drought” by lead author Dr Colin Kelley from the University of California, Santa Barbara. This paper was published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).

The research suggests that the severe drought in the region since 2006 was a catalyst for the Syrian conflict and that climate change has made such droughts in the region more than twice as likely.

The study received a lot of media attention when it was originally published in March and was frequently cited throughout the year in debates over potential climate-conflict links. Perhaps most notably, in an interview with Sky News, Prince Charles highlighted climate change as one of the contributing factors to the Syrian conflict, which was widely reported by the national media with varying degrees of accuracy.

The paper’s overall Altmetric score of 1,801 includes 145 news stories from 99 outlets – seven articles in the Guardian, five in the Huffington Post, four in the Washington Post, two in the New York Times, as well as featuring once each in the Independent, Telegraph and Daily Mail – tweets from 762 users and wall posts from 31 Facebookers.

Third place

Ranked third is the Nature article, “Mapping tree density at a global scale” by lead author Dr Thomas Crowther at Yale University. This paper contains the striking estimate that there are 3tn trees on Earth – some eight times more than previously thought. But the news isn’t as good as it sounds – deforestation means our forests are shrinking by around 10bn trees every year.

Published in September, the paper generated 89 news stories from 81 publications, tweets from 950 accounts and 30 Facebook wall posts, giving it an overall score of 1,578.

The researchers produced the animation below to describe their research.

How many trees are there in the world? Credit: Nature video.

The best of the rest

Fourth place goes to the paper that was reported by more news outlets than any other (122): “Future temperature in southwest Asia projected to exceed a threshold for human adaptability” in Nature Climate Change.

This study projected that conditions in the Middle East could become so hot and humid by the end of the century that being outside for more than six hours would be intolerable for humans.

And in fifth is the Science paper, “Possible artifacts of data biases in the recent global surface warming hiatus” which finds the much-discussed “slowdown” in warming at Earth’s surface may not exist after all. The study was picked up in 118 stories in 77 news outlets.

Elsewhere in the Top 10, seventh place goes to another Nature Climate Change article “Reaching peak emissions”, which was published during the climate summit in Paris in early December.

Using preliminary figures for 2015, researchers found that rapid growth in global carbon dioxide emissions over the last decade seem to have stalled. The break in the emissions trend is mainly down to a drop in coal use in China, the study said.

The paper generated 81 news stories in 65 publications.

Closely behind in eighth place is the Science article: “Planetary boundaries: Guiding human development on a changing planet”. The research found that human activity has pushed the Earth into critical mode. Four out of nine “planetary boundaries” have now been crossed, the researchers said, with biodiversity loss, fertiliser use, climate change and land use all now exceeding the point where the risk of sliding into a “much less hospitable” world becomes high.

The paper was reported by 43 news outlets in 55 stories, tweeted by 662 people and made it onto the Facebook walls of 93 users.

Final score

If you want a closer look at the final scores, you can take a look at our spreadsheet, which also contains the rest of the Top 25 climate papers of 2015.

These include the likes of “Volume loss from Antarctic ice shelves is accelerating” (17th) and “Accelerating extinction risk from climate change” in Science (19th), and “Long-term decline of the Amazon carbon sink” in Nature (22nd). You can read more about all three in our coverage here, here and here, respectively, when the papers were originally published.

Also nipping into the Top 25 is the paper, “Energy use, blue water footprint, and greenhouse gas emissions for current food consumption patterns and dietary recommendations in the US” in Environment Systems and Decisions (21st). It generated a number of news stories about lettuce being three times worse for the environment than bacon, which were swiftly followed by articles disputing the claim.

Overall, the Top 25 is made up of seven papers each from journals Nature and Science, followed by six in Nature Climate Change, two each in PNAS and Science Advances, and one in Environment Systems and Decisions.

Main image: Graphic by Rosamund Pearce for Carbon Brief.