"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.
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Warming beyond 1.5 degrees C (2.7 degrees F) will escalate the risk of triggering multiple tipping points
Assessing more than 200 recent studies on climate modelling, paleoclimatology, and observational analysis of the climate system, authors of a new paper published in "Science" identified nine critical tipping points globally, as well as seven regional ones. These tipping points occur when changes in parts of the climate system (defined as “tipping elements”) become self-perpetuating above warming thresholds. Once triggered, these changes will likely lead to abrupt, irreversible and increasingly disastrous impacts for people around the world.
Already, current levels of global warming (1.1 degree C or about 2 degrees F) put the world within range of reaching five tipping points, including:
- The collapse of the Greenland ice sheet and West Antarctic ice sheet
- Shutdown of the sub-polar gyre in the North Atlantic Ocean
- Widespread mortality of low-latitude coral reefs, and
- Abrupt permafrost thaw in the boreal region
Should global temperature rise climb to between 1.5 and <2 degrees C (2.7 and <3.6 degrees F), the world risks crossing a total of 10 tipping points, with six categorized as “likely” and four as “possible” at this level of warming.
By 2100, permafrost could release more greenhouse gases (GHGs) than the United States has emitted since the Industrial Revolution
Covering just 15% of the world’s soil area, the permafrost region contains at least 33% of the global soil carbon pool. Already, rising temperatures across the Arctic have led to abrupt permafrost thaw, whereby this melting causes soil erosion or subsidence that releases stored carbon into the atmosphere as methane or carbon dioxide (CO2). Continued warming will likely amplify abrupt permafrost thaw, as well as rapid, nonlinear losses in permafrost carbon, potentially triggering a dangerous feedback loop that could accelerate global temperature rise.
Relying on the latest regional models, as well as scientific studies published over the past decade, authors of a recent paper forecast cumulative CO2 and methane emissions from permafrost this century under low, medium and high warming scenarios. Under a low-warming scenario (below 2 degrees C or 3.6 degrees F), cumulative GHG emissions from permafrost through the end of this century still surpass those emitted by Russia over 100 years; under a high-warming scenario, this figure jumps to just below total GHG emissions from China over 100 years (assuming both countries’ 2019 emissions remain constant from 2000 to 2099).
Meeting Paris Agreement targets critical for avoiding extreme sea level rise
The East Antarctic Ice Sheet is considered less vulnerable to melting than the West Antarctic Ice Sheet. Still, some portions of the ice sheet have been documented as melting in recent years. A new study explores how past periods of warming impacted the East Antarctic Ice Sheet.
Based on those learnings, the authors project that beyond 2100, high-emissions scenarios could lead to up to 5 meters (16 feet) of sea level rise. However, if the Paris Agreement’s goals are met, this ice loss could largely be avoided.
Dangerous heat stress to blanket much of world
The concept of a heat index, which measures heat exposure to humans, was developed to control indoor working conditions, such as in boiler rooms. Now, the index is being used to describe outdoor conditions due to warming. Even if warming is limited to 2 degrees C (3.6 degrees F), scientists find that the heat index will increase 50-100% across most of the tropics.
In midlatitudes, the heat index would increase three- to ten-fold. By the end of the century, many in tropical regions will be exposed to dangerous heat levels “most days of each typical year.” Rare record-breaking deadly heat waves are projected to become annual occurrences.
Last eight years on track to be the warmest on record, driven by accumulated heat and rising concentrations of GHGs in the atmosphere
Published at the start of COP27, the World Meteorological Organization’s (WMO) Provisional State of the Global Climate in 2022 estimates that, in 2022, the global average temperature reached 1.15 degrees C (2.07 degrees F) above preindustrial levels. Although the cooling effect of La Niña will likely relegate 2022 to the fifth- or sixth-hottest year on record, the long-term warming trend remains strong.
The report also chronicles the increasingly dramatic signs of the climate crisis unfolding around the world, from accelerating rates of sea level rise to record-breaking glacier melt across the European Alps to continued losses of the Greenland ice sheet mass.
Emissions and Removals
Atmospheric concentrations of three major GHGs reached record-breaking highs (again) in 2021
The WMO’s annual Greenhouse Gas Bulletin estimates that concentrations of CO2 reached roughly 415.7 parts per million last year – a value that is 149% of pre-industrial levels. Methane and nitrous oxide levels are now 262% and 124% of atmospheric concentrations before 1750, respectively.
Especially concerning, the WMO finds that the increase in CO2 concentrations from 2020 to 2021 alone exceeded the average annual growth rate in CO2 levels over the last decade, and the jump in atmospheric methane concentrations during the same period represents the highest year-on-year rise since measurements began almost 40 years ago.
Nationally determined contributions (NDCs) updated since COP26 make a negligible dent in reducing GHG emissions in 2030
The United Nations Environment Programme’s (UNEP) latest Emissions Gap Report 2022 finds that, despite the Glasgow Climate Pact’s request for countries to strengthen their 2030 mitigation targets, new or updated unconditional NDCs published since November 2021 reduce projected GHG emissions in 2030 by just 0.5 gigatonnes of CO2 equivalent (GtCO2e). And if fully implemented, this most recent round of unconditional NDCs (including all those submitted ahead of and after COP26) gives the world a 66% chance of limiting warming to 2.6 degrees C (4.7 degrees F) this century.
Getting on track to limit global temperature rise to 1.5 degrees C (2.7 degrees F) will require countries to close an emissions gap of about 23 GtCO2e in 2030.
Released just a day before the Emissions Gap Report 2022, the UNFCCC secretariat’s NDC Synthesis Report reaches a similar conclusion — national commitments are still falling “pitifully short” of delivering the GHG emissions cuts needed to avoid intensifying climate impacts. More specifically, it finds that, although full implementation of countries’ latest NDCs could cause annual GHG emissions (excluding those from land-use, land-use change and forestry) to peak before 2030, these new pledges will only lower GHG emissions in 2030 by 0.3%, relative to 2019. And implementation of unconditional NDCs still put the world on track for warming of 2.5 to 2.9 degrees C (4.5 to 5.2 degrees F) by the end of this century.
Uncertainty in climate mitigation benefits of restoring “blue carbon” ecosystems
Reviewing recently published literature on carbon sequestration and long-term storage rates associated with restoring mangrove forests, seagrass meadows and tidal marshes, authors of a recent study find that restoring these vegetated coastal ecosystems delivers “uncertain and unreliable” carbon removal benefits.
More specifically, they identify seven issues that impact the reliability of carbon accounting associated with this mitigation strategy, which range from high variability in carbon burial rates to fluxes in methane and nitrous oxide to vulnerability to future climate change, such as sea level rise. In turn, the authors found that blue carbon ecosystem restoration has “questionable cost effectiveness” when considered for mitigation alone.
Still, the lead author emphasized that “every effort should be made to halt, and wherever possible reverse, the worldwide loss of coastal vegetation,” because these ecosystems “are more than carbon stores — they also provide storm protection, support biodiversity and fisheries, and improve water quality."
Warming oceans constrain the carbon sink potential of kelp forests
Macroalgae, which includes kelp and is more commonly known as seaweed, plays a critical role in global carbon cycling. These organisms absorb CO2 during photosynthesis and, through several different mechanisms, then export this carbon to the deep ocean and its sediments, where it remains effectively sequestered from the atmosphere (though scientists are still debating the magnitude of this potential carbon sink).
A recently published paper suggests that warming ocean temperatures could accelerate the decomposition of detritus for two dominant kelp species in the northern hemisphere, and this change could impact kelp’s role in carbon cycling, as slower decomposition of kelp detritus generally increases the chances that carbon stored within this dead organic matter will reach the deep ocean and its sediments.
Put simply, the authors find that kelp’s contributions to deep sea carbon stores could decrease at warmer, lower latitudes.
Industry practices for burning methane less effective than previously thought
A recent study of three major oil and gas basins across the United States shows that flaring — a widely used industry practice to dispose of unwanted natural gas — is less effective in destroying methane (by turning it into CO2, a less potent GHG) than previously assumed by both government and industry.
Analyzing airborne samples of plumes from more than 300 distinct flares, the authors calculated that, primarily due to unlit flares and inefficient combustion, flares across these three basins destroy an average of 91.1% of methane, rather than 98% that the EPA estimated in the 1980s. This finding represents a fivefold increase in emissions of this potent GHG than currently assumed.
Warming threatens trees’ ability to stay cool and sequester carbon
Leaf temperature strongly influences photosynthesis — and, therefore, trees’ uptake of carbon. As temperatures rise, they could soon cross critical thresholds, particularly in tropical forests, after which photosynthesis and the strength of this terrestrial carbon sink could decline.
Some scientists have hypothesized that leaves maintain a cooling response that can help mitigate this impact of climate change. Essentially, they can keep their daytime temperatures close to the range needed for photosynthesis and below higher air temperatures. But findings from a recent study call this theory into question.
Analyzing high-frequency thermal images of canopy leaf temperature across forests in North and Central America, the paper’s authors found that these leaves do not consistently cool below daytime air temperatures, and nearly all photosynthesis across these forest ecosystems occurs when leaf temperatures surpass air temperatures.
These findings suggest that global warming could increase canopy leaf temperatures and, in doing so, limit carbon uptake within forests, as well as cause heat damage.
Warming ocean waters will likely not trigger the release of methane stored across the seafloor into the atmosphere
Scientists have long wondered if naturally occurring methane reservoirs contained within ice-like crystals of water and gas (known as gas hydrates) could “melt” as ocean temperatures rise, thereby releasing catastrophic amounts of the GHG into the water column and, eventually, the atmosphere.
But a new study finds that, in the mid-latitude oceans, there is no evidence of methane seeping into surface waters where the water column depth is more than 430 ± 90 meters (gas hydrates only exist at depths of 550 meters in this region).
This suggests that decomposing gas hydrates represent a “negligible” source of atmospheric methane. Instead, the authors suggested that methane released into deeper waters is then degraded by marine microbes, which turn this potent GHG into CO2.
Globally, ocean warming is accelerating
A recent study on ocean heat content, a measure of ocean warming, finds that oceans have experienced substantial warming since the 1950s, with the upper 2,000 meters of water experiencing a net increase of roughly 351 zeptojoules globally from 1958 to 2019. The rate of warming has more than doubled from the 1960s to the 2010s, with the most significant increases occurring across the Atlantic and Southern oceans.
By the end of this century, the authors project that warming across the top 2,000 meters of the world’s oceans will be two to six times that of current levels, with the lower and upper bounds of this range associated with low-emissions and high-emissions scenarios respectively. This added heat already is intensifying hurricanes and marine heatwaves, as well as accelerating sea level rise and glacial melt.
In the Gulf of Maine, 900-year cooling trend reversed by dramatic ocean warming during the 20th century
Analyzing geochemical signatures of oxygen, nitrogen and other elements in shells that spanned 300 years, alongside outputs from climate model simulations, authors of a new paper found that the Gulf of Maine experienced cooling over nearly all of the past 10 centuries. But warming that began in the late 1800s — likely caused, in part, by increasing concentrations of GHGs — reversed this long-term cooling trend and accelerated warming across the Gulf of Maine during the 20th century.
As one of the authors noted, “it took about 900 years to cool by 2°C and only 100 years to warm by 2°C,” and, “unfortunately, warming in the Gulf of Maine will likely continue and worsen in the coming decades with negative impacts on the entire ecosystem."
Arctic Ocean acidification occurring faster than in any other ocean
Analyzing pH data collected from 1994 to 2020, authors of a study recently published in Science estimated that the rate of acidification in the Arctic Ocean is occurring three to four times faster than in other oceans. They attributed this rapid change to losses in sea ice.
Essentially, sea ice once acted as a barrier between the ocean and the atmosphere, impeding the transfer of CO2 from the air into the water. But as it melts, these cold ocean waters, which can hold more CO2 than warm waters, are increasingly exposed to the atmosphere and absorb CO2.
At the same time, this meltwater also weakens seawaters’ buffering capacity, limiting their ability to resist acidification. The implications of these changes in Arctic ocean chemistry for sea life, one author predicted, will be “huge.”
Ice and Permafrost
New seafloor maps reveal past pulses of rapid retreat in the Thwaites Glacier
Scientists have estimated that complete loss of West Antarctica’s Thwaites Glacier could raise global sea levels by 3 to 10 feet (0.9 to 3 meters), and a recently published paper suggests that phases of rapid retreat are likely to occur in the near future. Mapping the seafloor directly in front of the glacier in high resolution for the first time, the authors observed patterns of more than 160 parallel ridge lines in the ocean sediments, which formed as the glacier’s leading edge bobbed up and down with the tides.
The placement of these ridge lines, then, provide a geological marker of glacial retreat, allowing scientists to retrace the footprints of the Thwaites Glacier. Their analysis of these ridge lines shows that, over the course of 5.5 months, the grounding zone of Thwaites Glacier — or the point at which the ice transitions from a grounded ice sheet to a floating ice shelf — retreated at a rate of 2.1 kilometers (1.3 miles) per year, which is twice as fast as the rate documented by satellites from 2011 to 2019. Such pulses of sustained, rapid retreat, the authors found, have occurred several times at the Thwaites Glacier in the past 200 years and could happen again as the grounding zone continues to move landward.
Unavoidable sea level rise from Greenland Ice Sheet melting higher than previously thought
Melting across the Greenland Ice Sheet ranks among the largest sources of modern-day sea level rise. Analyzing the balance between the amount of snowfall that thickened this ice sheet and the amount of ice loss that occurred along its edges from 2000 to 2019, authors of a recently published study estimate that the ice sheet will lose approximately 3.3% of its total volume.
This unavoidable loss, they find, will commit the world to at least 27.4 centimeters (10.8 inches) of sea level rise — more than twice as much as scientists had previously estimated and much of which could occur by the end of the century.
Warming temperatures amplify submarine melting of the Greenland Ice Sheet
Scientists have previously shown that increasing air and ocean temperatures both cause the Greenland Ice Sheet to melt. But a new study shows how these processes interact to intensify ice loss. Essentially, the authors find that rising air temperatures increase melting, and when this meltwater reaches the ocean, it heightens seawater circulation.
This increased movement of water, in turn, transfers heat from the ocean back to the parts of the ice sheet that remain submerged underwater, spurring additional melting. Authors of the paper compared this effect to ice cubes in glass of water, noting that “ice cubes in a drink will also melt faster if you stir the drink.” This finding underscores the sensitivity of the world’s second-largest ice sheet to climate change.
Rapid warming across the Arctic will likely increase the frequency and intensity of rainfall
Historically, more snow falls across the world’s northernmost region than rain, but if unabated, climate change could reverse this trend by 2100. A recent paper finds that, under a high-emissions scenario, the frequency of rainy days could approximately double across the Arctic by the end of the century, and these rainfall events may begin more than a month earlier than they currently do, with the onset of spring rainfall projected to occur as much as three months earlier than present-day in some regions.Local warming across the Arctic will also increase the intensity of these rainfall events, as well as expand their range. This shift from snow to rain, the authors note, is “a serious cause for alarm” that could accelerate loss of sea ice cover, heighten permafrost melt and trigger widespread ecological impacts.
New evidence of a hidden, subglacial river system longer than the Thames stretching across Antarctica
Previous research in Greenland suggests that water at the base of ice shapes glaciers’ response to climate change, particularly ice flow rates and, therefore, contributions to sea level rise. But less is known about the role of this “basal water” in Antarctica. Simulating the evolution of the continent’s hydrological system in the Weddell Sea region, authors of a new paper identified large channels of water that persist under the ice year-round — a system that’s up to 460 kilometers (286 miles) long.
These extensive channels carry basal water into the ocean, where the grounded ice transitions to floating ice shelves and, in doing so, triggers additional melting in area that’s critical for ice sheet stability. As the less dense fresh water rises, deeper, warmer water is drawn up to this grounding zone.
Scientists identify an unusual suspect driving melting ice across Antarctica
At the base of Antarctica’s ice sheets, some areas remain frozen, while others have begun to thaw. But until recently, few studies have focused on the impacts of warming temperatures at the ice sheet’s base. Authors of a recent paper published in Nature Communications simulated thawing at the ice sheet base across areas within 100 kilometers (62 miles) of fast flowing ice and, in doing so, found that such warming could lead to significant ice loss across regions that are not currently considered unstable within a 100-year period. Less than 5 degrees C (9 degrees F) of warming at the ice sheet base, for example, could cause frozen patches across key regions of East Antarctica to begin thawing, thereby creating a new center of mass ice loss.
Forest fires impacting Arctic sea ice
Forest fires emit aerosols which can lead to cloud changes, impacting the amount of solar radiation being absorbed by the Earth’s surface. A new study uncovers a link between biomass burning in northern hemisphere mid-latitudes and Arctic sea ice decline between 1997 and 2014. The sea ice was found to be impacted by biomass burning emissions, even those thousands of miles away. Interestingly, in years of high fire levels, more aerosols are emitted via the smoke, thickening clouds and protecting the ice.
Glacial runoff triggering ice sheet melt
Scientists have identified a mechanism that can lead to accelerated ice melt throughout West Antarctica. As ice melts, leading to freshwater runoff, the ocean current next to ice shelves is stratified, increasing the heat transport of the water current along the coast. The warmer salt water is trapped along the underside of the ice shelves, warming them and in turn increasing melt.
Changes to the Hydrological Cycle
Severe water shortages across the Tibetan Plateau
A recent modeling study finds that by mid-century, under a mid-range warming scenario, climate change will lead to declines in water supply capacity by 119% and 79% in the Amu Darya and Indus basins, respectively. This would equate to a “total collapse of water supply” for central Asia and Afghanistan, and a near collapse in Pakistan, Kashmir and northern India by mid-century.
Desert in Central Asia expanding
Scientists have revealed that since the mid-1980s the desert of Central Asia has expanded northward by over 100 kilometers (62 miles) in mid-latitudes, leading to declines in agricultural lands and diminishing glaciers. The region is already susceptible to drought and rainfall fluctuations, given its aridity.
More intense rains in the United States
It is well established that warmer air holds more water. While there is a significant body of research on extreme precipitation events, less research has been conducted on how climate has impacted daily precipitation. Examining changes to 17 regions in the United States between 1951-1980 and 1991-2020, researchers found evidence of more intense rain in most of the U.S.
Possible megaflood in California’s future
Exploring a “plausible worst case scenario” climate modelers explored whether storms in California could become so extreme that they lead to conditions suitable for “megafloods.” In the mid-19th century, such a flood occurred, creating an inland sea nearly 300 miles (483 kilometers) in length.
The researchers found that climate change has already doubled the likelihood of an event capable of catastrophic flooding. As a result of increased precipitation and decreased snow, runoff from extreme storms is 200 to 400% greater than historical levels.
Dust due to droughts carrying pathogens
A new study finds that in a drier world, more dust can be transported around the world, carrying microbes from elsewhere. Studying the Sierra Nevada mountains in California, researchers uncovered dust from as far away as China’s Gobi Desert. While dust can be beneficial for montane ecosystems, carrying fungi and bacteria, it also can bring pathogens, negatively impacting species as well as human respiratory health.
Global lakes experiencing water loss
Studying 1.42 million lakes from 1985 to 2018, researchers found that the lakes have lost a significant amount of water — about 1500 cubic kilometers (360 cubic miles) per year — and the rate of evaporation has increased over the period. The loss of water is larger than previously thought.
Wildfire plumes getting taller, spreading smoke and aerosols farther
A new study finds that wildfire plumes, which transport smoke, are reaching new heights. And, as a result, more aerosols are being injected into the atmosphere, impacting regional air quality. Aerosols from fires have been linked to respiratory illness.
The authors note that these trends could degrade air quality at even a continental scale. In another recent study, researchers found that smoke due to recent wildfires in the U.S. has reversed decades of policy-driven health increases. Over 25 million people across the U.S. were impacted by dangerous levels of smoke in 2020 alone.
Tree cover loss due to fires in California
Over the last 37 years, California has lost almost 7% of its tree cover. While tree cover increased in the 1990s, after 2000 it has declined given larger and more frequent wildfires. Shrubs and grasses have taken over, especially in warmer and drier areas, potentially permanently wiping out the tree population. These impacts threaten California’s ecosystems and carbon sink.
Climate change has impacted wide range of diseases
“Health at the Mercy of Fossil Fuels”
This year’s Lancet Countdown report, published in October, was dedicated to the links between climate change and human health, covering health impacts from extreme weather, spread of infectious disease and pressure on food security. The report links fossil fuel dependence with human health and well-being directly.
Another recent report issued by Oxfam finds that climate change has acted as a threat multiplier to acute hunger and starvation.
Extreme Heat Impacts
Virtually all children to be impacted by frequent heatwaves by mid-century
A new report by UNICEF finds that over 2 billion children — almost every child — will experience more frequent heatwaves by mid-century. The report, entitled “The Coldest Year of the Rest of Their Lives,” provides an urgent appeal for adapting child services to a changing climate.
Almost a million deaths due to extremes in major Latin American cities in recent years
Increase heat has disproportionate impact on economic growth
Between 1992 and 2013, economic losses due to extreme heat were around $16 trillion globally. This equated to a loss of 6.7% of GDP in regions that were in the bottom income decile. In contrast, regions in the top income decile only lost 1.5% over the same period.
Species and Ecosystems
Cloudy waters making it harder for seabirds to hunt
Climate change has increased the turbidity of some parts of the water, which in turn negatively impacts underwater visibility. Recent research tested the impact of turbid waters on the ability of one diving seabird species — the Manx shearwater — to find its prey. It found that the birds dove deeper in clearer waters. The scientists conclude that climate change could make it more challenging for seabirds to find food.
Lemurs and other primates spending more time on the forest floor
As a result of climate change, habitat loss and other factors, primates in the Americas and Madagascar — which largely spend time in trees — are using the ground more. Given rising temperatures and a decline in canopy cover, they are shifting their behavior to spend more time on the ground, and shifting their diets as well as they forage on the forest floor.
Narwals changing migration timing to keep up with warming
Researchers have revealed that over the past 21 years, narwhals in the Canadian Arctic have delayed their autumnal migration, at a rate of 10 days per decade, Delayed departure could put them at risk of encounters with predators and getting trapped by ice.
Little time left to save coral reefs
Studies often look at impacts of one driver on coral reefs — for example, marine heatwaves or pollution or ocean acidification. However, when all disturbances are analyzed together, rather than independently, the average year during which conditions are unsuitable for coral reefs is 2035 (as opposed to 2050 for any one disturbance studied alone).
Fish stocks depleted with warming
Studying 226 marine ecoregions around the world, scientists have discovered that more than half have experienced reduced fish stocks due to climate change. At high degrees of warming, even if fishing levels were lowered, fish stocks would be unable to rebuild themselves, especially in West Africa, Eastern Tropical Pacific, Indo-Pacific and central and south Pacific.
Fish die off in north temperate lakes
Scientists have used historical data on mass fish die offs in Minnesota and Wisconsin to model the relationship between fish mortality events and warming of temperate lakes across North America. They find that by the end of the century, fish mortality events will increase six-fold due to warmer water temperatures and 34-fold due to air temperature increases.
Southern boreal forests to be impacted greatly by a changing climate
A new study exposing various juvenile forest types to different temperature and precipitation regimes over five years finds that southern boreal forests were impacted the most, with even modest amounts of warming (1.6 degrees C, or 2.9 degrees F). The scientists further find that neighboring temperate forests may not be able to keep pace with the loss of boreal species, compromising the ecosystem integrity even further.
On the other hand, a recent article found that a boreal conifer normally found at higher latitudes — the white spruce — has expanded its range significantly into the Arctic tundra, advancing 4 kilometers (2.5 miles) per decade. This can in turn exacerbate warming as the tundra (which reflects sunlight especially in the winter due to snow cover) is covered in darker trees, absorbing more solar radiation.
Warmer and wetter climates impacting bumblebees’ wings
Studying museum specimens of four bumblebee species across Britain, researchers found that the bumblebees had experienced stress, leading to asymmetric wings. Higher levels of wing asymmetry appeared in wetter and hotter years. Populations of bumblebees have declined recently.
Soil erosion to dramatically increase by mid-century
As rainfall becomes greater and more intense, it can impact soil erosion. A recent study suggests that the erosive power of rainfall, leading to soil erosion and in turn nutrient losses, will increase between 26 and 29% by 2050 and 27 and 34% by 2070, compared with 2010 levels.
Wheat prices to spike in a changing climate, exacerbating food insecurity
While studies show that CO2 fertilization can benefit wheat, new research finds that wheat prices are to spike with even 2 degrees C (3.6 degrees F) of warming, impacting developing countries the most. Today wheat provides 20% of calories and protein for 3.4 billion people around the world.
Heat exposure in West Africa linked to malnutrition
A new study finds that extreme heat exposure increased chronic and acute malnutrition across five West African countries. The authors project that with 2 degrees C (3.6 degrees F) of warming, the average effect of growth stunting from malnutrition would nearly double, negating gains made between 1993 and 2014.