Analysis: Which climate papers were most prominent in the media in 2020?January 13.

Last year was to be different. The five-year anniversary of the Paris AgreementWas marked out by manyAs the year for climate action. 2020 actually followed a year when climate change was occurring. propelled onto newspaper front pagesGreta Thunberg, school strike and Extinction Rebellion.

As with many aspects in 2020, the Covid-19 pandemic quickly took center stage. 

Normal life was thrown into chaos, and news headlines and social media conversations were dominated with lockdowns and vaccines. 

There was still time to report on climate change. Throughout the year, thousands of peer-reviewed climate papers were published and vied for media attention.  

These studies were featured in news articles and blogs around the globe. These studies were also shared via social media platforms like Twitter, Facebook, and LinkedIn.

Tracking all these “mentions” was Altmetric, which scores papers and ranks them according to how much attention they get. (For more information on how Altmetric scoring works, see an earlier article.

Carbon Brief has compiled its annual list, using Altmetric data from 2020, of the 25 most discussed papers on climate change. These papers were published in the previous year. The infographic below shows which papers made it to the Top 10, while the chart at its end shows which journals are most often in the Top 25.

Covid Year: Top spot

Last year was a remarkable year for scientific journal papers and social media attention. 

This annual review has been completed six times since Carbon Brief began it. 2018 was the first year where a paper – on any topic – hit an Altmetric score of more than 10,000. In 2019Altmetric found two papers which met this milestone. 

2020 was the year with 60. All but a few were related to Covid-19.

(For Carbon Brief’s previous Altmetric articles? see the links for 2019? 2018? 2017, 2016 2015.

It’s not surprising that the top climate paper for 2020 was also about Covid-19. It was the Nature Climate Change paper, “Temporary reduction in daily global CO2 emissions during the Covid-19 forced confinement”, by Prof Corinne Le QuéréA Royal Society research professor of climate science at The University of East AngliaYou and your colleagues.

According to the study, the amount of CO2 released daily by human activity fell by as much 17% during the coronavirus crisis. It also predicted that CO2 emissions for 2019 would fall by 7.5%, compared to 2019. It was a forecast that would be surprisingly accurate. very closeTo get an estimate at year’s end.

Additionally, covering the studyCarbon Brief hosted a similar event. webinar on the impact of the Covid pandemic on CO2 emissions, with Le Quéré as one of the panellists.

The paper received an overall Altmetric score 6174. It was mentioned in 715 online news stories by 398 outlets, in 109 posts from 63 blogs, and in more than 4,000 tweets – the most of any climate paper published last year for these categories.

The study was extensively covered by the media, including extensive news coverage. Washington Post? Financial Times? Reuters? New Scientist? Guardian? BBC News? Independent? MailOnline Sky News.

Altmetric has also ranked this top climate paper at the 140th highest rank of all papers. This is another example of 2020 being a remarkable year. In comparison, the top-ranked climate newspaper in 2019 was the seventh highest overall. 

(Update: Altmetric has published its new version. Top 100 papers for 2020. It ranks the Le Quéré et al. paper in 12th place. The higher ranking is because Altmetric changed their methodology this year – rather than taking the 100 highest-scoring papers, they have selected the five top-scoring papers across 20 categories to give them a Top 100.)

Second place

The next highest scoring climate paper of 2020 was a short “News & Views” piece called “Record-setting ocean warmth continued in 2019”, published in Advances in Atmospheric Sciences, with a score of 3,954.

The paper presents new ocean heat content data, which revealed that “the world’s oceans in 2019 were the warmest in recorded human history”. 

However, because the paper is an invited commentary rather than a traditional research paper, it isn’t included in Carbon Brief’s leaderboard. 

(Commentaries are often commissioned by journal editor rather than part of an open submissions process. They are not regularly peer-reviewed. Carbon Brief does include review articles and perspective articles in its leaderboard. However, these tend to follow a more conventional editorial process that varies from journal to journal. The guidelines provide more information on the different types and types of journal articles. Nature Science as examples.)

Instead, taking second spot with an Altmetric score of 3,696 is “Future of the human climate niche”, published in the Proceedings of the National Academy of Sciences (PNAS). Its lead author is Dr Chi XuAn ecologist at Nanjing UniversityChina

The study shows that, for thousands of years, “humans have concentrated in a surprisingly narrow subset of Earth’s available climates, characterised by mean annual temperatures around 13C”. It warns that between one and three billion people could be left outside this “environmental niche” in the next 50 years, depending on the rate of warming and population growth.

229 online news stories were published about the paper from 175 outlets around the globe, including the New York Times? USA Today? CNN? Guardian? BBC News? Independent? Sun? Times of India? South China Morning Post Der Spiegel. It was also mentioned in posts on 29 blogs, and tweeted more than 3000 times.

A piece for the Conversation? University College London’s Prof Mark Maslin described the study as a “brilliant thought experiment”, but highlighted some reservations, including a focus on a “worst case scenario” of climate change and not taking into account of the “dynamic and adaptable nature of human technology and society”.

Third place

Taking the final place on the rostrum is “Global increase in major tropical cyclone exceedance probability over the past four decades”, with an Altmetric score of 3,669. 

The study finds that major tropical cyclones – category 3 or higher – have become 15% more likely at a global level between 1979 and 2017.

The study found that the North Atlantic has experienced the greatest increase in cyclone severity, with the likelihood of a major storm occurring there increasing by 49% every decade.

In May, the lead author Dr James Kossin, a climate scientist from the National Oceanic and Atmospheric Administration(NOAA) Center for Weather and Climate, told Carbon Brief:

“Our analysis finds that the global increasing trend in tropical cyclone intensity has now risen to a point where it is very unlikely to be random, even after addressing known issues with the historical data.”

The study was featured online in 739 news articles from 405 outlets including the New York Times? Washington Post? New Scientist? CNN USA Today. It was covered by 50 posts from 37 blogs and was tweeted 549 times – the smallest total of any paper in this Top 10.

(There is also a second study about tropical cyclones in Top 25. In the 25th and final place is the Nature paper “Slower decay of landfalling hurricanes in a warming world”, which finds that landfalling hurricanes are now taking longer to weaken as they move inland than they were 50 years ago.)

Top 5

In fourth place is “Sandy coastlines under threat of erosion”, published back in March in Nature Climate Change, with a score of 3,065. The study was led in part by Dr Michalis I VousdoukasA coastal oceanography researcher at European Commission Joint Research Centre.

The research, which uses satellite data, suggests that erosion driven by rising sea levels could cause “the near extinction of almost half of the world’s sandy beaches by the end of the century”. 

This stark finding received widespread media and social-media attention. There were 358 news stories from 317 outlets, 23 posts on 19 blogs, and more than 600 tweets. The following outlets reported on the study: Guardian? i newspaper? Conversation? Sun? Associated Press? CNN? Sydney Morning Herald MailOnline.

In October, Nature Climate Change published a “matters arising” response to the paper, in which another group of researchers argue that the study’s headline finding is “incorrect and potentially damaging”. 

They note that “sandy beaches are highly variable in form and setting, and it is widely accepted that there is no single response to sea level rise”. Shorelines will retreat as sea levels rise, but beaches “will survive”, they say, adding that “the biggest threat to the continued existence of beaches is coastal defence structures that limit their ability to migrate.”

However, in a reply, the original study authors say these statements “lack the evidence needed to substantiate them”. They warn that “there is the risk that coastal communities and managers are lulled into a false sense of security”.

Taking fifth spot is the Nature paper “Rebuilding marine life”, which accumulated an Altmetric score of 2,848. The review study “document[s] the recovery of marine populations, habitats and ecosystems following past conservation interventions”.

It concludes that “recovery rates across studies suggest that substantial recovery of the abundance, structure and function of marine life could be achieved by 2050, if major pressures – including climate change – are mitigated”.

The paper was published in 208 news articles from 188 outlets, 18 blogs, more than 2000 tweets, and appeared in 18 blogs. The finding that the world’s oceans could be restored within 30 years generated headlines in the Guardian? Press Association? BBC News? i newspaper MailOnlineThis was the subject of an editorial in Times. 

The Top 10

Just missing out on the Top 5 is “Dynamic ice loss from the Greenland Ice Sheet driven by sustained glacier retreat”, which is the first-ever article published in Nature’s new online journal Communications Earth & Environment. 

The research finds that retreating glaciers resulted in a “step-change” in Greenland ice sheet melt in the early 2000s and a “switch to a new dynamic state of sustained mass loss that would persist even under a decline in surface melt”.

(For more on the state of the Greenland ice sheet – and discussion of this study – see Carbon Brief’s guest post from September.)

The study received a score of 2,784. It was covered in 274 news stories, 48 posts from 37 blogs, and over 1,500 tweets. The study was covered by several outlets, including Reuters? CNN? Inside Climate News? AxiosThe Daily Express? Forbes MailOnline.

(There is also another paper on Greenland in the Top 25, with “Return to rapid ice loss in Greenland and record loss in 2019 detected by the GRACE-FO satellites” in 16th place. The study, also published in Communications Earth & Environment, finds that 2019 saw the ice sheet hit a record annual loss of 532bn tonnes.)

In seventh place, with a score of 2,543, is the Nature paper “Temperate rainforests near the South Pole during peak Cretaceous warmth“. This study presents evidence that the parts of West Antarctica was covered with temperate rainforests during the mid-Cretaceous period – one of the warmest intervals of the past 140m years. 

Landing in eighth place is another polar paper – “Fasting season length sets temporal limits for global polar bear persistence”. Published in Nature Climate Change with a score 2,528, the research warns of “. Arctic sea ice declineIt is possible to see polar bearsSpending more time on land increases the time they must fast, putting their survival chances and ability to reproduce at risk. 

In ninth position is the 2020 report of the Lancet Countdown on health and climate change, focusing on “responding to converging crises”, which has an Altmetric score of 2,468.

The latest annual report is part of a global project that involves 35 academic institutions as well as UN agencies from around the globe. began in 2015. The 2020 report “tracks the relationship between health and climate change across five key domains and over 40 indicators”. Its executive summary warns of the following:

“The changing climate has already produced considerable shifts in the underlying social and environmental determinants of health at the global level. Indicators in all domains…are worsening. Concerning, and often accelerating, trends were seen for each of the human symptoms of climate change monitored, with the 2020 indicators presenting the most worrying outlook reported since The Lancet Countdown was first established.”

Taking the final spot in the Top 10 is “The emergence of heat and humidity too severe for human tolerance” in Science Advances, with a score of 2,400. The study looks specifically at “wet-bulb” temperatures of more than 35C, which is considered to be the upper limit for the human body to “efficiently shed heat”. 

Analysing weather station data from around the world, the researchers find that some coastal subtropical locations have already reported wet-bulb temperatures of 35C and “that extreme humid heat overall has more than doubled in frequency since 1979”.

The Top 25 also includes the following:

Just missing out on the Top 10 is the Science paper “Climate change contributes to widespread declines among bumble bees across continents”, with a score of 2,379. The study shows that extreme heat is a contributing factor to the decline of bumblebees in North America as well as Europe. 

As lead author Peter SoroyeAccording to the Press AssociationWhen the paper was published 

“We found that populations were disappearing in areas where the temperatures had gotten hotter. If declines continue at this pace, many of these species could vanish forever within a few decades.”

In 12th, with a score of 2,224, is “Climate change is increasing the likelihood of extreme autumn wildfire conditions across California“. The study, published in Environmental Research Letters, finds that autumn days in California with “extreme fire weather” conditions have more than doubled since the early 1980s.

The timing of the paper’s publication in late August – during the state’s devastating wildfires – likely contributed to its widespread media coverage. The paper featured in 300 news articles – the fourth highest number in the Top 25.

Looking a little further down the leaderboard, in 18th place is the Nature paper “Asynchronous carbon sink saturation in African and Amazonian tropical forests”, with a score of 1,992.

Study with a co-author Prof Simon LewisProfessor of global science and policy at University College LondonThe University of Leeds, wrote a Carbon BriefWhen the research was published, guest posts were made about it. 

The findings, he explained, suggest that “the ability of intact tropical forests to remove CO2 from the atmosphere reached its peak in the 1990s and has since been in decline”.

In 19th is “Current and future global climate impacts resulting from Covid-19”, published in Nature Climate Change, with a score of 1,927. 

The study found that a temporary decrease in global emissions will not prevent warming of 0.01C. However, the world could avoid 0.3C of further warming by 2050 if governments invest in a strong “green recovery” from the coronavirus pandemic, the researchers say.

The paper was published in August by the lead author. Prof Piers Forster – founding director of the Priestley International Centre for ClimateThe University of Leeds – told Carbon Brief that the moment was “make or break” for global climate targets:

“Before we had coronavirus we weren’t on track, we absolutely weren’t…If we don’t do it today I think we won’t ever be able to, unfortunately.”

And, finally, towards the bottom of the Top 25 are a couple of papers on climate “tipping points” – thresholds where a small change could push a system into a completely new state. (For more information on tipping points, please see Carbon Brief’s in-depth explainer.)

In 21st place is “Regime shifts occur disproportionately faster in larger ecosystems“, published in Nature Communications, with a score of 1,893.

The modelling study shows that large systems tends to shift slower than smaller systems, but disproportionately faster. The study concludes with:

“The findings imply that shifts in Earth ecosystems occur over ‘human’ timescales of years and decades, meaning the collapse of large vulnerable ecosystems, such as the Amazon rainforest and Caribbean coral reefs, may take only a few decades once triggered.”

And in 24th place, with a score of 1,831, is the Nature paper “The hysteresis of the Antarctic Ice Sheet”. According to global warming levels, the study determines the thresholds of Antarctica’s ice losses. 

For example, the researchers find that the ice sheet’s “temperature sensitivity is 1.3 metres of sea-level equivalent per degree of warming up to 2C above pre-industrial levels”, which almost doubles to “2.4C per degree of warming between 2 and 6C”. 

These thresholds display “hysteresis behaviour”, the study says, which means that the ice sheet won’t necessarily regain the lost ice if global temperatures are reversed to present-day levels. 

All the final scores of the Top 25 climate papers for 2020 can be found here this spreadsheet.

Top journals

The journal with six papers is the most prominent among the Top 25 papers here. Nature also took first? or joint first? spot in Carbon Brief’s Top 25 in 2019, 2018, 2017 2015.

Next is Nature Climate Change, which has five papers. Then follows three journals with two papers each – PNAS, Communications Earth & Environment, and Science – and then nine journals with one paper in the Top 25.

The chart shows the frequency with which each journal appears among the Top 25 climate papers 2020. Carbon Brief created this chart. Highcharts.