The year 2023 saw the coronation at Westminster Abbey of a new king, the mugshot of a former US president and the rebranding of a social media platform to a single letter.

But behind the biggest stories of the year, thousands of studies detailing new research also made the headlines. And climate change and energy were among the topics that received the most attention.

Each year, Altmetric tracks how often research papers from academic journals are mentioned in online news articles as well as on blogs and social media platforms. It then gives each paper a score according to the attention it receives.

Using Altmetric data for 2023, Carbon Brief has compiled its annual list of the 25 most talked-about climate- or energy-related papers that were published the previous year.

(The list focuses on peer-reviewed research papers only – commentaries or other papers that are not formally peer-reviewed are not included.)

The infographic above shows which papers made it into the top 10, while the article includes analysis of the full list of 25, including the diversity of their authors and which journals feature most frequently.

The list covers research into the climate projections of a major oil company, the human cost of global warming and the catastrophic failure of breeding penguins – as well as the curious case of the high-scoring paper that received almost no news coverage at all.

Antarctic ice shelves

The most talked-about journal papers of 2023 are again dominated by research relating to Covid-19, continuing the pattern seen in recent years.

For example, the highest-scoring paper of any published in 2023 is a review into the effectiveness of measures to reduce the spread of respiratory viruses, such as Covid, swine flu and severe acute respiratory syndrome (Sars). 

The study’s Altmetric score of 25,730 puts it almost 10,000 points ahead of the second-placed paper, which is also about Covid.

But the top-scoring paper relating to climate is not far behind, landing fourth in the overall list with a score of 13,886.

The study, “Change in Antarctic ice shelf area from 2009 to 2019”, gains the highest score for any climate paper in any of Carbon Brief’s annual reviews by some distance – the previous highest was 7,803 in 2022.

(For Carbon Brief’s previous Altmetric articles, see the links for 2022, 2021, 2020, 2019, 2018, 2017, 2016 and 2015.)

The study, published in the Cryosphere, uses satellite observations to produce a dataset of changes in the “calving front” – that is, where icebergs break off – and area of the ice shelves that surround Antarctica between 2009 and 2019. It shows that, overall, the area of Antarctic ice shelves has grown by around 5,300 square kilometres (km2) since 2009, with 18 ice shelves retreating and 16 larger shelves growing in area.

Specifically, ice-shelf area has decreased on the Antarctic Peninsula (by 6,693km2) and in west Antarctica (by 5,563km2), and increased in east Antarctica (by 3,532km2) and on the large Ross and Ronne-Filchner ice shelves (by 14,028km2), the paper says.

The map from the study below shows the growth (blue) and retreat (red) of ice shelves around Antarctica, where the size of the circles indicates the scale of the change from 2009 to 2019.

While the high scores of climate-related papers in previous years have primarily been driven by news coverage, this paper appears in just seven news stories.

As study author Prof Anna Hogg from the University of Leeds explains to Carbon Brief: 

“Somewhat unusually, we didn’t put out a press release for the paper as we assumed the scientific community that needed the dataset would make use of it naturally.”

Instead, the paper’s high Altmetric score is principally a result of a huge number of mentions on Twitter – more than 63,000 posts from around 48,000 accounts. (Altmetric includes weightings in its scoring system, so news articles (with a weighting of eight) are deemed to have more impact than tweets (0.25).)

A closer look suggests that the paper has been widely quoted by the Twitter accounts of a number of prominent climate sceptics in an attempt to push back on concerns around climate change and the loss of Antarctic ice. These posts have then been widely retweeted by other accounts. 

To see the paper “being used as evidence to suggest that climate change isn’t happening” was a “real surprise”, says Hogg, because the paper “doesn’t make any such statement”.

Specifically, the gains the study identifies in ice-shelf area in east Antarctica do not detract from the risks of retreating ice shelves on other parts of the continent, says Hogg:

“The decrease in ice shelf area in west Antarctica is particularly important as this ice shelf area actively ‘buttresses’ the flow of ice from the ice sheet behind it, which through ice dynamic processes is one of the reasons why west Antarctica is contributing significantly to present-day sea level rise.” 

Indeed, the seventh most-talked about paper in 2023 (see below) is a Nature Climate Change study warning that accelerated melt of west Antarctica’s ice shelves is now locked in, even for the most ambitious emissions reduction scenarios. The authors provide this stark conclusion:

“These results suggest that mitigation of greenhouse gases now has limited power to prevent ocean warming that could lead to the collapse of the west Antarctic ice sheet.”

The misleading way the study has been used by some climate-sceptic social media accounts has been “incredibly challenging”, says Hogg, with the authors unable “to reply to every incorrect tweet” about their work. However, they did find “a fair number” of responses from other accounts “saying that they had read the paper and it didn’t provide evidence against climate change”. 

This perhaps shows “open access doing its job”, says Hogg, as the paper was published in an open-access journal and so is freely available for anyone to read. In another high-scoring statistic, the full paper has now been viewed more than 150,000 times on the journal’s website.

ExxonMobil

Landing in second place with an Altmetric score of 8,686 is the review paper, “Assessing ExxonMobil’s global warming projections”. Published in Science, the study analyses the global warming projections documented and modelled by scientists at the oil major ExxonMobil between 1977 and 2003. 

(There is a higher-scoring paper, “The 2023 state of the climate report: Entering uncharted territory”, in the journal BioScience, but it is a “special report” and was not formally peer reviewed.)

The results indicate that “in private and academic circles since the late 1970s and early 1980s, ExxonMobil predicted global warming correctly and skillfully”, the paper says, adding: 

“ExxonMobil’s average projected warming was 0.20C ±0.04C per decade, which is, within uncertainty, the same as that of independent academic and government projections published between 1970 and 2007.”

The findings reveal that ExxonMobil “knew as much as academic and government scientists knew” about global warming decades ago. But, the paper adds, “whereas those scientists worked to communicate what they knew, ExxonMobil worked to deny it”.

The study was covered by 823 news stories by 555 outlets, including BBC News, the Associated Press, CNN, Vice, CNBC and Inside Climate News. It was also included in 48 blog posts and more than 13,000 tweets. It is the 12th most talked-about paper on any topic in 2023.

Extreme heat

In third place is the Nature Medicine paper, “Heat-related mortality in Europe during the summer of 2022”, with a score of 7,821. The study finds that more than 60,000 deaths in the summer of 2022 – Europe’s hottest season on record – were linked to the heat. 

Across 35 countries, the highest numbers of heat-related deaths occurred in Italy (18,010 deaths), Spain (11,324) and Germany (8,173), the study says. It also finds that the “burden of heat-related mortality was higher among women”, with 56% more heat-related deaths in women than men, relative to population.

The study was picked up in 943 news stories from more than 650 outlets – the largest number of any paper in the top 25. It was picked up by outlets across Europe, including Sky News and ITV News in the UK, Agence France-Presse in France and Der Spiegel in Germany. Carbon Brief also covered the article in detail.

The widespread coverage was likely to be in part because Europe was experiencing a heatwave dubbed “Cerberus” when the paper was published in July. 

Lead author Dr Joan Ballester Claramunt from the Barcelona Institute for Global Health tells Carbon Brief that the paper also “received so much attention from the media because society is increasingly aware of the health risks of environmental factors, and particularly in a context of rapidly warming temperatures”. 

Rest of the top 10

In fourth place is, “Warning of a forthcoming collapse of the Atlantic Meridional Overturning Circulation”, which was published in Nature Communications. 

The study uses statistical techniques to detect early warning signs of a shutdown in the Atlantic Meridional Overturning Circulation (AMOC), one of the major current systems in the world’s oceans that plays a crucial role in regulating climate.

While assessments using climate model simulations typically suggest that AMOC is “unlikely” to pass a tipping point within the 21st century, the study says a collapse could occur “around mid-century under the current scenario of future emissions”.

(Another paper that also uses observation-based early warning signals to assess the stability of AMOC featured in second place in Carbon Brief’s leaderboard for 2021.)

The paper’s Altmetric score of 6,216 reflects its widespread news coverage, covering 672 stories from more than 500 outlets, including the Washington Post, Politico, El País, CNN and Der Spiegel.

The papers in fifth and ninth place both set out frameworks for assessing “safe” boundaries for the Earth to be a habitable place for humans. 

In fifth place with a score of 5,411 is the Science Advances paper, “Earth beyond six of nine planetary boundaries”. Providing the latest assessment of the boundaries that were first established in 2009, the paper warns that “Earth is now well outside of the safe operating space for humanity”. 

The ninth-placed paper, “Safe and just Earth system boundaries”, shares a number of the same authors and sets out to quantify limits for “climate, the biosphere, water and nutrient cycles and aerosols at global and subglobal scales”. When the paper was published in May, Carbon Brief reported on the mixed reaction the paper received from other scientists, including concerns that a “self-selected group of scientists” were defining the “safe space” for the planet.

In sixth place is the Science paper, “Global glacier change in the 21st century: Every increase in temperature matters”, which reveals a “strong linear relationship between global mean temperature increase and glacier mass loss”.

The study projects that glaciers outside of Antarctica and Greenland will lose between 26% and 41% of their collective mass by 2100, relative to 2015, under warming of 1.5C to 4C, respectively. Such a loss would cause 49-83% of glaciers to disappear and see 90-154mm added to global sea levels, the study says.

In seventh place is the Nature Climate Change paper, “Unavoidable future increase in West Antarctic ice-shelf melting over the 21st century”, as mentioned above. The findings, the authors say, present a “sobering outlook” for ice shelves in the Amundsen Sea. 

The paper made an appearance in the Science round of Carbon Brief’s annual quiz. 

The eighth-placed paper is, Quantifying the human cost of global warming, published in Nature Sustainability. It quantifies this cost in terms of the number of people left outside the “climate niche” in which human civilisation has flourished for centuries. 

The study shows that climate change has already put around 9% of people outside this niche, and that, by end-of-century, current policies leading to around 2.7C global warming could leave 22-39% of people outside the niche as well.

Finally, rounding out the top 10 is, “Climate extremes likely to drive land mammal extinction during next supercontinent assembly”, in Nature Geoscience. 

The study looks at the prospects for humans and other mammals on Earth based on first-ever supercomputer climate modelling of the distant future. The knock-on impacts of all Earth’s continents eventually converging to form the supercontinent “Pangea Ultima” would see huge amounts of CO2 released into the air through volcanic eruptions, it says. 

The resulting global temperatures of up to 75C would, as a headline in the i newspaper put it, “one day wipe out humanity – but not for another 250m years”.

Elsewhere in the top 25

The rest of the top 25 includes a mix of research, including a paper on the impacts of El Niño on economic growth, a study on the environmental impacts of different types of diets and analysis of the amount of global warming still “in the pipeline” by former NASA scientist Dr James Hansen.

In 14th place is the Nature paper, “Assessing the size and uncertainty of remaining carbon budgets”, which presents an updated estimate of the remaining carbon budget for limiting warming to 1.5C and 2C.

In a 2022 Carbon Brief guest post, some of the study authors present a similar analysis, concluding that the remaining carbon budget to limit warming to 1.5C could be just 260bn tonnes of CO2 (GtCO2) – the equivalent of around six years of emissions. They add:

“Cutting global CO2 emissions to zero by 2050, in line with limiting warming to 1.5C, would require them to fall by about 1.4GtCO2 every year, comparable to the drop in 2020 as a result of Covid-19 lockdowns around the world, but this time driven by a long-term, structural change of the economy.

“This highlights that the scale of the challenge is immense, no matter the precise figure of the rapidly shrinking carbon budget.”

Antarctic sea ice made headlines around the world both in 2022 and 2023, by setting two consecutive years of record low sea ice extent. In August 2023, researchers published a sobering study in Communications Earth and Environment under the title, “Record low 2022 Antarctic sea ice led to catastrophic breeding failure of emperor penguins”. 

The study finds that melting ice led to widespread “breeding failure” across Antarctic emperor penguin colonies and received widespread media attention. It has been mentioned in 537 news articles, generating headlines such as, “Thousands of penguins die in Antarctic ice breakup”, from BBC News and, “Thousands of penguin chicks killed by early sea ice breakup, study says”, in the Washington Post. 

The Guardian, New Scientist and Daily Telegraph were among the other publications that reported on the study. This surge of attention pushed the paper to 15th in the Carbon Brief ranking, with an Altmetric score of 3,551.

Meanwhile, the Lancet Countdown on health and climate change slipped down the rankings this year. After three years in the Carbon Brief’s top 10, this year’s report lands in 20th place with an Altmetric score of 3,191.

The report is an epic annual publication, which reviews vast swathes of literature and has more than 100 authors this year. This year’s report introduced some key new indicators of the links between climate change and human health. It was also the first to include projections on how the indicators might worsen in a warmer world.

The report finds that loss of labour due to heat exposure resulted in a $863bn loss of “potential income” in 2022. The agriculture sector was hit the hardest by the loss of labour, accounting for 82% of losses in least developed countries, the authors add.

Carbon Brief’s coverage of the report highlights this loss of income due to heat stress. The graph below shows effective income losses in 2022 due to heat stress in agriculture (blue) and other sectors (red), as a percentage of GDP, by continent.

One spot below the Lancet report is a Geophysical Research Letters study which warns that climate change is making air turbulence stronger and more frequent. The findings, which were picked up in more than 500 news articles, have worrying implications for aircraft passengers.

Back in 2017, study author Dr Paul Williams wrote a Carbon Brief guest post warning that “the most severe [type of turbulence] – the kind that can launch passengers out of their seats and cause serious injuries – is set to become twice or even three times as common by the latter half of the century”. And a recent Carbon Brief guest post on the fastest jet stream winds – known as “jet streaks” – also forecasts an increase in clear-air turbulence for aircraft passengers. 

And in 24th place is the Nature paper, “Glacial lake outburst floods threaten millions globally”, with an Altmetric of 2,991. The study warns that 15 million people globally are exposed to impacts of potential “glacial lake outburst floods” (GLOFs). (For more on GLOFs, see Carbon Brief’s guest post from 2020, which explains how lakes formed by melting glaciers around the world have increased in size by 50% over the past 30 years.)

Top journals

This year there is a clear winner for the journal with the most papers featuring in Carbon Brief’s top 25: Science takes top spot with five papers.

Following Science are the three journals of Nature Climate Change, Nature Communications and the Lancet, each with two papers in the top 25. 

For the rest of the top 25, the remaining 14 journals appear once each.

All the final scores for 2023 can be found in this spreadsheet.

Diversity of the top 25

The top 25 climate papers of 2023 cover a huge range of topics and scope. However, despite the variety in the climate research the papers present, analysis of their authors reveals a distinct lack of diversity.

In total, the top 25 climate papers of 2023 have more than 440 authors. Carbon Brief recorded the gender and country of affiliation for each of these authors. (The methodology used was developed by Carbon Brief for analysis presented in a special 2021 series on climate justice.)

The analysis reveals that the authors of the climate papers most featured in the media in 2023 are predominantly men from the global north.

The chart below shows the institutional affiliations of all authors in this analysis, broken down by continent – Europe, North America, Oceania, Asia, South America and Africa.

The analysis shows that nine out of every 10 authors are affiliated with institutions from the global north – defined as North America, Europe and Oceania. Meanwhile, only six authors are from Africa and South America.

Further data analysis shows that there are also inequalities within continents. The map below shows the percentage of authors from each country in the analysis, where dark blue indicates a higher percentage. Countries that are not represented by any authors in the analysis are shown in white.

The top-ranking countries on this map are the UK and the US, which together account for almost half of all authors in this analysis (25% and 18%, respectively).

More than half of all researchers from the global south are from China – which accounts for around 6% of all researchers in the analysis.

Meanwhile, only one-third of authors from the top 25 climate papers of 2022 are women. Similarly, only seven of the 25 papers have a female lead author.

The plot below shows the number of male (purple) and female (orange) authors in this analysis from each continent.

The full spreadsheet showing the results of this data analysis can be found here. For more on the biases in climate publishing, see Carbon Brief’s article on the lack of diversity in climate-science research.