Carbon Brief reviews the most closely watched climate articles in 2019

In 2019, the two climate papers with the highest Altmetric scores were critical articles. One is the World scientists' warning on the Climate crisis (World Scientists' Warning of a Climate Emergency) in the journal BioScience, with an Altmetric score of 10950. The article "makes it clear that the earth is facing a climate crisis", especially when it was signed by 11258 scientists from 153 countries and attracted media attention. The other is "Climate tipping Point-the risk of betting that the Climate tipping Point will not come" (Climate Tipping Points- Too Risky to Bet Against) in Nature magazine, with an Altmetric score of 8552. The article reached a similarly stark conclusion, warning that the evidence from the climate tipping point alone suggests that we are in a state of planetary crisis, in which the risk and urgency are very serious. The two papers ranked third and fifth with the highest Altmetric scores of all the studies published in 2019, respectively. However, since they are critical articles, they are not included in the Carbon Brief list of research papers.

In first place was the article "New elevation data triples Global vulnerability estimates to Sea-level rise and Coastal Flood" (New Elevation Data Triple Estimates of Global Vulnerability to Sea Level Rise and Coastal Flooding), published in Nature Communications, with an Altmetric score of 7136. The study, conducted by Dr. Scott Kulp and Dr. Benjamin Strauss of the U.S. Climate Center website (Climate Central), estimated the global population's risk of sea-level rise using a new digital elevation model (DEM), revising previous estimates of the vulnerability of global sea-level rise to three times that of the NASA data set. In low-emission scenarios, the study shows that 190 million people around the world currently use land below the 2100 peak. In high-emission scenarios, this number will increase to nearly 1 billion. The study was mentioned in 318 online news articles, 30 blogs and more than 21000 tweets, including BBC News, Reuters, the Guardian, the Daily Mirror, the Independent, the Daily Telegraph, CNN and the New York Times.

In second place was Global Tree Restoration potential (The Global Tree Restoration Potential), published in Science magazine, with an Altmetric score of 6354, mentioned in 582 news reports. The study, led by Dr. Jean-Francois Bastin of the Federal Institute of Technology in Zurich, showed that 4.4 billion hectares of canopy cover could exist in the current climate, with the potential to add an additional 900 million hectares of tree space and store 205 billion tons of carbon. The article points out that global tree restoration is by far the most effective solution to climate change. This striking conclusion has received a lot of attention, but it has also been criticized by other scientists. Science magazine published five technical reviews on the article, arguing that the study overestimated the mitigation potential of large-scale tree planting and questioned whether it was the "most effective" way to reduce carbon dioxide. for example, compared with energy efficiency and the deployment of non-fossil fuels.

In third place was "the Global decline of insects: a Review of its drivers" (Worldwide Decline of the Entomofauna: AReview of Its Drivers), published in Biological Conservation (Biological Conservation), with an Altmetric score of 5429. The study, conducted by Dr Francisco S á nchez-Bayo of the University of Sydney and Dr Kris Wyckhuys of the University of Queensland, shows that a significant decline in insect rates could lead to the extinction of 40 per cent of the world's insect species in the coming decades. Habitat loss caused by intensive agriculture is the main driver of insect reduction, and other causes include climate change, pollution and species invasion.

In fourth place was "Food in the Anthropocene: committee on healthy eating in a Sustainable Food system in the Lancet" (Food in the Anthropocene: the EAT-Lancet Commission on Healthy Diets from Sustainable Food Systems), published in the Lancet, with an Altmetric score of 4560. The study believes that in order to provide a healthy diet for nearly 10 billion people around the world within food production by 2050, there is an urgent need for global changes in the food system, which is both necessary and achievable.

In fifth place was the journal Nature's "committed emissions from existing energy infrastructure endangers the achievement of the 1.5C climate target" (Committed Emissions from Existing Energy Infrastructure Jeopardise 1.5C Climate Target), with an Altmetric score of 4434. The study, conducted by Dr. Dan Tong of the University of California, Irvine, found that committed emissions from the world's existing and proposed energy infrastructure alone were more than offset by a carbon budget limited by a global temperature rise of 1.5C.

In sixth place is the article "Global warming weakens the population dynamics of corals" (Global Warming Impairs Stock-Recruitment Dynamics of Corals), published in the journal Nature. The study, led by Professor Terry Hughes of James Cook University in Australia, details that the growth of new coral larvae on the Great Barrier Reef fell 89 per cent in 2018 due to large numbers of adult parent fish dying under high temperatures in 2016 and 2017. The results show that given the expected increase in the frequency of extreme weather events over the next 20 years, the extent to which the Great Barrier Reef has recovered from the collapse of the population replenishment model remains uncertain.

In seventh place is Nature's article "there is no evidence of a globally consistent warm and cold period in the pre-industrial first year" (No Evidence for Globally Coherent Warm and Cold Periods over the Preindustrial Common Era). Through global paleoclimate reconstruction, the study found strong evidence that man-made global warming is unprecedented not only in terms of absolute temperature, but also in terms of spatial consistency over the past 2000 years.

In eighth place is the Quaternary Science Review (Quaternary Science Reviews) article "the impact of the extinction of the absolute Earth system after Europeans arrived in America since 1492" (Earth System Impacts of the European Arrivaland Great Dying in the Americas after 1492). The study found that the decline in atmospheric CO2 concentrations in the 16th century was partly due to carbon absorption from abandoned farmland, which was left behind by widespread deaths of Native Americans.

Ranking ninth is the Lancet's "Global epidemic of Obesity, malnutrition and Climate change: the Lancet report" (The Global Syndemic of Obesity, Undernutrition, and Climate Change: The Lancet Commission Report), which points out that obesity, malnutrition and climate change are the three most serious threats to human health and survival and have become interrelated and interacting "global co-epidemics" (Global Syndemic). Systematic action must be taken to jointly address obesity, malnutrition and climate change.

At No. 10 is Science magazine's "how fast is the ocean warming?" "(How Fast are the Oceans Warming?), observational data show that the global ocean is heating up over the past few decades, and multiple pieces of evidence from four independent research teams suggest that the observed warming trend of ocean heat content (OHC) is stronger.

Among the 25 most concerned articles on climate change, the most are from Nature and PNAS, with 4 each. This is followed by Science and Lancet with 3 articles each, followed by Nature Climate Change and Nature Communications with 2 articles each. There is one article in each of the other seven journals.

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