Hot Science: Methane Emissions, Biodiversity Declines & More

"Hot Science" is a joint effort of the Bezos Earth Fund and World Resources Institute. While we aim to highlight the most significant climate science literature compiled from leading peer reviewed journals, this is not meant to be comprehensive.

Want to get this delivered straight to your inbox? Subscribe to Hot Science here.

Rapid ice melt in west Antarctica now inevitable, research shows

Scientists determined that no matter how much carbon dioxide (CO2) emissions are reduced, there will be accelerated ice melt in west Antarctica. The regional ocean model found the rate of melting floating ice shelves in the Amundsen Sea will be three times faster this century compared with the last century. This melting will impact regions crucial for ice-sheet stability. Ultimately, this melting could lead to the collapse of the West Antarctic Ice Sheet.

Marine stores of frozen methane may be more vulnerable to warming than once assumed 

Buried within ocean sediments, gas hydrates – naturally occurring, ice-like crystals of water and methane – contain as much carbon as the world’s remaining oil and gas reservoirs. Rising temperatures can melt these hydrates, releasing this potent greenhouse gas (GHG) into the ocean and, potentially, the atmosphere. 

Until recently, scientists focused primarily on hydrates within relatively shallow waters, where temperatures are just cold enough to keep the hydrates frozen and even small levels of warming can thaw these methane crystals. Hydrates trapped hundreds of meters below the seabed in deeper waters were considered relatively safe from climate change; the potential for methane released from these reservoirs to reach the atmosphere was thought to be “negligible.” 

But a new study published in Nature Geoscience shows that not even these methane hydrates are immune to rising temperatures. Analyzing 3D seismic imagery of the seafloor, the authors discovered that hydrates in deeper waters off the coast of West Africa migrated at least 40 kilometers toward land, and then vented methane through 23 craters – likely during warmer, interglacial periods. 

These findings suggest that hydrates could release substantially more methane than anticipated as the world warms.

Climate impacts in the U.S. are 'far-reaching and worsening,' federal report finds 

The Fifth National Climate Assessment evaluated climate change impacts, risks and responses in the United States. It found that extreme climate events cost the United States government $150 billion every year and that risks from climate change are increasing with extreme weather and natural disasters. It also concluded that local communities are differentially impacted, with low-income areas and communities of color often taking on an unequal share of the burden.

We have entered “uncharted territory” as records were smashed in 2023 

The 2023 State of the Climate Report analyzed 35 indicators or “vital signs” of a changing climate (e.g., tree cover loss, GHG emissions, and sea ice extent) and found 20 of them show record extremes. At the same time, the authors report “minimal progress” in combating climate change.

World Meteorological Organization (WMO) report card in, and it’s not pretty 

The WMO’s annual Greenhouse Gas Bulletin estimates that concentrations of CO2 reached roughly 417.9 parts per million last year – a value that is 150% of pre-industrial levels. Methane and nitrous oxide levels are now 264% and 124% of atmospheric concentrations before 1750, respectively. The increase in nitrous oxide from 2021 to 2022 was greater than any increase on record. And the WMO finds that the climate system is nearing several irreversible tipping points, including Amazon rainforest dieback, the destabilization of large ice sheets, and slowing of the North Atlantic circulation.

Climate sensitivity may be higher than estimated 

A study led by Dr. James Hansen placed equilibrium climate sensitivity – the long-term global temperature change per doubling of CO2 in the atmosphere – at 4.8°C, much higher than the recent Intergovernmental Panel on Climate Change (IPCC) estimate of 3.0°C. The study arrived at the new estimate via analysis of temperatures and CO2 levels over the past 66 million years. It argues that warming is accelerating and is set to breach 1.5°C in the 2020s and 2.0°C by 2050 “under the present geopolitical approach.” The study has garnered pushback from other scientists, most prominently Dr. Michael Mann.

Amazon deforestation causes warming 100 kilometers (km) away 

A new study estimates that deforestation in the Amazon causes warming up to 100 km away from the site of forest loss. Previous studies have documented local warming from deforestation, but regional-level warming is less well understood. The new study finds that including regional effects increases estimates of warming due to deforestation by a factor of four. The analysis leveraged remotely sensed observations of forest loss and land temperature over a 20-year period and applied a machine-learning algorithm to estimate deforestation-induced warming. The study’s findings suggest that stemming deforestation in the Brazilian Amazon could reduce future warming in the region by 0.56°C.

Drought conditions expose rivers to hotter water temperatures 

Drought conditions can influence river water temperatures. Researchers used data from the United Kingdom as a case study to look at the mechanisms that control river water temperature. They identified three mechanisms that influence water temperatures: (1) energy flux dynamics, (2) reach-scale habitat conditions, and (3) water source contributions. Such drastic changes in water temperature have significant implications for ecosystems. Understanding the variables that contribute to extreme water temperatures can result in better planning and management for climate change.

Some of the ocean’s smallest organisms help the ocean sequester and store far more carbon than previously thought

Like plants, plankton take up carbon via photosynthesis and store it in their organic tissue, and when these tiny organisms die, their carbon-rich particles – known as marine snow – sink to the bottom of the ocean. These processes form the ocean’s biological pump, which the IPCC previously estimated helped store about 11 gigatonnes of carbon (GtC) each year. 

A recent study, however, finds that this may be an underestimate. Using observational data collected by oceanographic ships since the 1970s, the authors modelled organic carbon fluxes across the world’s ocean. They found that the ocean may store 15 GtC per year – about 20% higher than the IPCC’s most recent estimate. Though the ocean remains a major player in global carbon cycles, the authors caution that these absorption processes are quite slow and cannot offset rapidly rising CO2 emissions.

A new assessment of forests’ potential to sequester and store carbon underscores the importance of protecting and restoring these ecosystems 

Reflecting a joint effort among hundreds of forest ecologists, a recent paper published in Nature finds that forests outside of agricultural lands and urban areas could hold another 226 GtC, nearly 50 times the United States’ emissions in 2022. Combining satellite imagery and ground-sourced data, these authors show that relatively intact forests, in which protection and sustainable management can enhance carbon sequestration through the recovery of degraded stands, account for about 61% of this global mitigation potential. 

The remaining 39% exists in highly fragmented or otherwise deforested areas, in which restoration will be needed to enable carbon uptake and storage. This finding suggests that forest conservation not only helps avoid emissions from deforestation, but can also enhance the drawdown of carbon from the atmosphere. The authors, however, caution that large-scale tree planting of a single species will not be sufficient to realize this potential – safeguarding biodiversity will prove critical.

Deforestation declines to a five-year low in the Brazilian Amazon 

Brazil permanently lost about 9,000 square kilometers of forests between August 2022 and July 2023—down 22% from the previous year. The country’s National Institute of Space Research also estimates that, by reducing deforestation rates, Brazil avoided emitting just over 130 million tonnes of carbon dioxide equivalent MtCO2e into the atmosphere, an amount of GHGs roughly equivalent to 7.5% of the nation’s emissions in 2020.

The past two decades have seen the Gulf Stream warm twice as fast as the global ocean

Flowing north along the western side of the Atlantic Ocean, this current plays a critical role in the planet’s climate system by carrying heat and nutrients from the tropics to higher latitudes and by influencing weather patterns and storms. Assessing over 25,000 salinity and temperature profiles collected by autonomous floats and underwater gliders over the past two decades, authors of a recent Nature Climate Change paper find that the Gulf Stream is moving toward the coast at a rate of roughly 5 kilometers each decade. 

When coupled with the ocean’s uptake of heat from the atmosphere, these factors are spurring warming across the Gulf Stream, with the near-surface layer warming by an average of 1°C over the past 20 years. One of this study’s “triumphs” is that it confirms numerical simulations’ predictions for a warming world.

Himalayan glaciers react, blow cold winds down their slopes 

Himalayan glaciers are responding to climate change by cooling the air that encounters the ice’s surface. Warmer temperatures trigger a cooling response, causing cold wind to flow down the slopes of Mt. Everest. These cold winds are helping to stabilize nearby ecosystems from additional warming and deviate from traditional warming patterns resulting from climate change. However, scientists warn that this cooling is probably temporary, even as it provides a unique window of opportunity to help save global glaciers before they reach their tipping point.

This is what the Arctic's record-hot summer looked like 

A report card released by the U.S. National Oceanic and Atmospheric Administration (NOAA) finds that more frequent extreme weather and climate events are altering the Arctic. The report card finds that the Arctic continues to become less icy, wetter, and greener. In 2023, the Arctic experienced the warmest summer since 1900. It was also the 6th wettest year on record since 1950. The report card is further evidence that climate change is having extreme impacts on people and ecosystems all over the world.

Wildfires

Wildfires have erased two decades’ worth of air quality gains in the western United States 

A new study found that air quality has worsened in the western United States as a result of increased wildfire frequency and strength. Using satellite data and ground-based stations, the researchers calculated the concentration of black carbon, a fine-particle air pollutant, across the continental United States. The researchers conclude that the decrease in air quality from smoke has increased premature deaths by 670 people per year. The findings support the idea that reducing increased fire risk from climate change is critical for public health.

Wildfires also impact aquatic ecosystems 

Climate change is projected to increase the occurrence of wildfires, which has broader impacts for ecosystem function. A study led by researchers at the University of California San Diego used a gradient design experiment to determine the effect of terrestrial organic matter from fires on aquatic systems. They discovered multiple changes to aquatic ecosystems that received burned plant material. For example, they found that burned organic material increased the concentration of nitrogen, potassium, and phosphorus and decreased the amount of dissolved organic carbon and carbon dioxide. The authors concluded that wildfires have the power to alter ecosystem functions in aquatic habitats.

Biodiversity

Ongoing declines for the world's amphibians in the face of emerging threats 

Human activity is the biggest threat to biodiversity. The Global Amphibian Assessment evaluated >8,000 amphibian species for the International Union for the Conservation of Nature Red List. The assessment found that, of the drivers of decline evaluated in the study, climate change has driven 39% of status deteriorations since 2004. Amphibians are the most threatened vertebrate class, and conservation action is critical to prevent further losses.

The changing climate creates more noise in the oceans 

There are many surprising impacts of climate change. One unique effect is that climate change may be altering how sound travels in the ocean through alterations to the ocean’s thermal structure. This study used numerical modeling to evaluate the impact of climate change on sound propagation. The authors projected that “in some places, by the end of this century, the sound of ships, for example, will be five times as loud” and that “this will interfere with the behavior of many species of fish and marine mammals.” This research demonstrates the complex ways climate change alters the natural world.

Extreme weather displaces animals, too, a new study suggests 

As climate change increases, so does the frequency of extreme weather events. Researchers at the Chinese Academy of Sciences conducted a meta-analysis using 443 studies to compare the response of non-native and native animals to different types of extreme weather events. They found that terrestrial and freshwater non-native animals were adversely affected by storms and heatwaves, whereas native species negatively responded to droughts, cold spells, and heatwaves in terrestrial ecosystems and most extreme weather events in freshwater ecosystems. These results are an important contribution to our understanding of the impacts of climate change on biodiversity.

Coral reefs in peril from record-breaking ocean heat 

Coral reefs in the eastern tropical Pacific and the wider Caribbean are experiencing historically high heat stress. This Science Perspective paper used historical data from NOAA to determine that these reefs are experiencing historically high heat stress beginning up to 12 weeks earlier than usual. The authors find that this information comes at a critical opportunity for swift action on both biodiversity protection and climate change mitigation. They used historical data from NOAA to determine that these reefs are experiencing historically high heat stress beginning up to 12 weeks earlier than usual.

Public Health and People

Climate crisis a ‘substantial risk’ to fight against malaria, says WHO 

The World Health Organization (WHO) warns of increased malaria risk as a result of more extreme weather events and warmer temperatures. The World Malaria Report 2023 focused a chapter on the nexus between climate change and malaria. It found that climate change has altered the dynamics of malaria transmission, as many people do not have access to the resources necessary to prevent, detect, or treat the disease. This report demonstrates the intersection and feedback loops that connect people, disease, and climate change.

Hot weather hits productivity – even in air conditioned factories 

Extreme weather events have multifaceted implications for people. A study published in Environmental and Resource Economics analyzed the effect of outdoor heat on the productivity of >35,000 workers. The authors found that an increase of 10 degrees Celsius resulted in an 8.3% decrease in output for workers in a climate-controlled factory. This is a decrease in productivity of 0.83% for every degree Celsius increase in outdoor temperature. The researchers summarized an important implication of their work, apart from the economics, which is that “we usually think about climate change in terms of its impacts at huge scales, but it also affects individuals.”

Costs

Climate crisis costing $16 million an hour in extreme weather damage, study estimates 

This paper in Nature Communications used data collected from multiple extreme event attribution studies. The researchers then combined them with data on the socio-economic costs of extreme weather events and extrapolated missing data. They found that extreme weather events attributed to climate change cost an average of $143 billion a year. Of those costs, 63% are due to the loss of human life, which is often underestimated in similar modeling.