What Is: El Niño, La Niña, and a Climate in Flux

Image Credit: Scientific Frontline / NOAA

The Planet's Most Powerful Climate Cycle

In 1997, a climatic event of unprecedented scale began to unfold in the tropical Pacific Ocean. Dubbed the "El Niño of the century," it triggered a cascade of extreme weather that reshaped global patterns for over a year. It unleashed devastating floods and droughts, sparked massive forest fires, decimated marine ecosystems, and crippled national economies. By the time it subsided in 1998, the event was estimated to have caused more than 22,000 deaths and inflicted over $36 billion in damages worldwide. Nearly two decades later, the powerful 2015-16 El Niño, supercharged by a background of long-term global warming, helped propel 2016 to become the hottest year on record and directly impacted the lives and livelihoods of over 60 million people.

These catastrophic events are not random acts of nature but manifestations of the planet's most powerful and influential climate cycle: the El Niño-Southern Oscillation (ENSO). This naturally occurring phenomenon is a periodic, irregular fluctuation of sea surface temperatures and atmospheric pressure across the vast expanse of the equatorial Pacific Ocean. At its heart are two opposing phases: El Niño ("The Little Boy" in Spanish), a significant warming of the ocean surface, and La Niña ("The Little Girl"), a countervailing cooling. Together with a neutral "in-between" state, they form a planetary-scale pendulum that swings irregularly every two to seven years, dictating patterns of drought and flood, storm and calm, across the globe.

Climate change may increase the spread of neurotoxin in the oceans

The researchers’ findings raise concerns about how climate change may affect the levels of methylmercury in fish and shellfish.
Photo Credit: Johnér Bildbyrå AB

Climate-driven oxygen loss in the Black Sea thousands of years ago triggered the expansion of microorganisms capable of producing the potent neurotoxin methylmercury. That is shown in a new study published in Nature Water, led by Eric Capo at Umeå University, which suggests that similar processes could occur in today’s warming oceans.

Methylmercury is a highly toxic compound that accumulates in fish and seafood, posing severe health risks to humans. It is formed when certain microbes convert inorganic mercury under low-oxygen conditions.

Today, climate change is causing such oxygen-depleted areas to expand in coastal marine environments, including parts of the Baltic Sea. Warmer and more stagnant waters mix less efficiently, and increased algal blooms contribute to oxygen loss in deeper layers, creating ideal conditions for these microbes.

Air Pollution Can Contribute to Obesity and Diabetes

The most significant sources of fine air pollutants include exhaust fumes from cars, industrial plants and heating systems, as well as emissions from construction sites and forest fires.
Photo Credit: Uvi D

Long-term exposure to fine air pollution can impair metabolic health by disrupting the normal function of brown fat in mice. A study co-led by the University of Zurich shows that this occurs through complex changes in gene regulation driven by epigenetic mechanisms. The results demonstrate how environmental pollutants contribute to the development of insulin resistance and metabolic diseases.

There is growing evidence that air pollution is not just harmful to our lungs and heart, but also plays a significant role in the development of metabolic disorders like insulin resistance and type 2 diabetes. A new study co-led by Francesco Paneni, professor at the Center for Translational and Experimental Cardiology of the University of Zurich (UZH) and the University Hospital Zurich (USZ), and Sanjay Rajagopalan, professor at the Case Western Reserve University, Cleveland, now sheds light on the topic.

Green Energy and Innovation Can Increase Greenhouse Gas Emissions

The introduction of renewable energy sources in developing Asian countries may lead to a short-term increase in greenhouse gas emissions.
Photo Credit: Nicholas Doherty

Scientists at Ural Federal University have found that the introduction of renewable energy sources (RES) and technological innovations in developing Asian countries can lead to a short-term increase in greenhouse gas emissions. The reason is the effect of rebound and insufficient effectiveness of regulatory systems. This calls into question the effectiveness of current measures to achieve the goals of the Paris Agreement, the researchers believe. They wrote on this topic in an article in the journal Energy Economics.

"In Asia, more efficient coal-fired power plants or cheaper solar energy can lower electricity prices, leading to increased energy consumption by industry and households in general. Although innovations reduce CO₂ emissions in the short term, they actually increase emissions in the medium and long term, as efficiency gains drive growth in industrial activity and energy demand. This is a classic rebound effect: efficiency stimulates economies of scale, negating the initial environmental benefits," explained Kazi Sohag, co-author of the paper and head of the UrFU Laboratory of Economic Policy and Natural Resources.

SwRI produces, evaluates sustainable aviation fuel made from e-fuel

A multidisciplinary team at Southwest Research Institute (SwRI) produced, characterized and tested standard jet fuel along with two sustainable aviation fuels (SAF), including one developed at SwRI, through an internally funded project. A custom jet engine test stand was used to gather emissions and particulate data.
Photo Credit: Southwest Research Institute

Southwest Research Institute produced a batch of blended sustainable aviation fuel (SAF) through a refinery process that started with electrofuels or e-fuels made from carbon dioxide and green hydrogen. Using internal research funding, a multidisciplinary team produced and characterized the SAF, along with two other commercially available fuels, before collecting emissions and particulate data to support the aviation industry’s emissions goals.

“Aviation is difficult to decarbonize due to the fuel density and power required for flight,” said Francesco Di Sabatino, a group leader in SwRI’s Mechanical Engineering Division. “With this project we’re gathering important data for conventional fuel and two different SAFs.”

Conventional jet fuel is made from petroleum that burns inside a jet engine. Fueling jets with SAF could help reduce carbon emissions. Worldwide air travel accounts for 2% of all carbon emissions, and 12% of all carbon emissions from transportation. The team tackled three focus areas — production, characterization and testing.

Heatwaves at Sea May Force the Ocean to Release More CO2

Marine heatwaves are disrupting the ocean’s ability to store carbon
Image Credit: Scientific Frontline / AI generated

Heatwaves not only occur on land – they also occur in the oceans, causing ocean temperatures to stay warmer than normal for longer periods. Marine heatwaves can cover huge areas of the sea and have major effects on marine life, from plankton to reefs and whales.

Now, a new study shows that marine heatwaves may also affect how carbon is stored in the ocean.

The ocean is one of Earths biggest carbon sinks. It soaks up vast amounts of CO2 from the atmosphere, and in the surface water, algae and other photosynthetic microorganisms capture it and convert it to organic carbon. When these organisms die and sink to the bottom, the carbon sinks with them. In the deep ocean, the removed carbon can be locked away for hundreds, even thousands of years.

Engineers Develop Solid Lubricant to Replace Toxic Materials in Farming

Photo Credit: Courtesy of North Carolina State University

Researchers have developed a new class of nontoxic, biodegradable solid lubricants that can be used to facilitate seed dispersal using modern farming equipment, with the goal of replacing existing lubricants that pose human and environmental toxicity concerns. The researchers have also developed an analytical model that can be used to evaluate candidate materials for future lubricant technologies.

Modern farming makes use of various machines to accurately and efficiently plant seeds in the ground. However, it can be difficult to prevent the seeds from jamming in these machines. To keep the seeds flowing smoothly, farmers use solid lubricants that prevent the seeds from clumping up or sticking together. Unfortunately, commercially available lubricants make use of talc or microplastics, and can pose threats to farmers, farmland and pollinators.

“Lubricants are essential to modern farming, but existing approaches are contributing to toxicity in our farmlands that affect farmer health, soil health and pollinators that are essential to our food supply,” says Dhanush Udayashankara Jamadgni, co-lead author of a paper on the work and a Ph.D. student at North Carolina State University. “We’ve developed a new class of safe solid lubricants that are effective and nontoxic.”

Lake Tahoe Algae Experiment Suggests Seasonal Shifts Ahead

UC Davis researchers conduct periphyton research at Lake Tahoe.
Photo Credit: Brandon Berry, UC Davis Tahoe Environmental Research Center

As the climate warms and nutrient inputs shift, algal communities in cool, clear mountain lakes like Lake Tahoe will likely experience seasonal changes, according to a study from the University of California, Davis. 

Periphyton, that fuzzy layer of attached algae covering the rocks as you step into the water, is a healthy and critical part of a lake’s food web. Periphyton blooms, however, signal changes that can degrade both water quality and a shoreline’s natural beauty.

Climate change is projected to increase global water temperatures by 1.8 to 7 degrees Fahrenheit by 2100. It’s also expected to increase nutrients to lake waters through increased runoff from higher intensity storms and more precipitation falling as rain rather than snow.

“A majority of lakes globally are warming as a result of climate change,” said lead author Nick Framsted, a master’s student in the UC Davis Environmental Science and Policy department and Tahoe Environmental Research Center when the study was conducted. “With their clear, cold waters, mountain lakes are exceptionally sensitive to changes in temperature and nutrients.”

Clam shells sound warning of Atlantic ‘tipping point’

Ocean quahog shells.
Photo Credit Paul Butler

A study of clam shells suggests Atlantic Ocean currents may be approaching a “tipping point”.

Scientists studied records of quahog clams (which can live for over 500 years) and dog cockles – because shell layers provide an annual record of ocean conditions.

They studied these natural archives to understand long-term patterns in Atlantic Ocean currents such as the Atlantic Meridional Overturning Circulation (AMOC) and the subpolar gyre (SPG).

Recent studies have debated possible AMOC and SPG tipping points – transitions that would transform climate patterns. For example, AMOC collapse would have far-reaching global effects, from harsher winters in north-west Europe to shifts in global rainfall patterns, while a weakening of the SPG would be less catastrophic but still bring substantial impacts, including more frequent extreme weather in the North Atlantic region.

What Is: Microplastics

Microplastic
Credit: Scientific Frontline

The Invisible Tide of Plastic

The modern era has been defined, in part, by the versatility and ubiquity of plastic. Yet, this celebrated 20th-century material has given rise to a paradoxical form of pollution—one so pervasive and minute that its scale was largely unrecognized until recently. Microplastics, the synthetic dust of our industrial age, represent a global environmental challenge of unprecedented complexity. These tiny particles, born from the fragmentation of larger debris and the intentional design of microscopic products, have infiltrated every corner of the planet. Scientific expeditions have confirmed their presence from the summit of Mount Everest to the abyssal depths of the Mariana Trench. More alarmingly, this invisible tide has crossed the final frontier, entering the human body itself, with researchers detecting microplastic particles in human blood, lung tissue, and even the placenta.

The ubiquity of microplastics signals a fundamental disruption of planetary systems. They are not merely inert debris but active agents in the environment, interacting with ecosystems and organisms in complex and often detrimental ways. Their journey spans the globe, carried by ocean currents, river systems, and atmospheric winds, connecting the most remote wilderness to the most densely populated urban centers in a shared system of contamination. This report provides a definitive, evidence-based synthesis of the current scientific understanding of microplastics. It aims to dissect the full scope of this issue, beginning with a fundamental definition of the pollutant and a detailed accounting of its myriad sources. It will then trace the environmental fate and transport of these particles through aquatic, terrestrial, and atmospheric systems. Finally, the report will conduct an exhaustive analysis of their multifaceted impacts on ecological integrity and human health, concluding with a critical evaluation of the policies, technologies, and strategies required to mitigate this pervasive threat.

Study first to show if nesting heat affects sea turtle hatchling ‘IQ’

A loggerhead hatchling goes through the Y-maze to test its learning abilities.
Photo Credit: Sarah Milton, Florida Atlantic University

As sand temperatures continue to rise, concerns about the future of sea turtles are growing. Hotter nests not only skew sex ratios – producing more females – but also reduce hatchling survival, slow growth, and increase the likelihood of physical deformities. Yet one important and often overlooked question remains: does this heat also affect cognitive ability – how well hatchlings can learn, adapt and respond to the rapidly changing world they face from the moment they emerge?

A new study by researchers at Florida Atlantic University’s Charles E. Schmidt College of Science offers a surprising glimmer of hope. They are the first to test whether incubation temperature affects cognitive ability in loggerhead (Caretta caretta) hatchlings – how well they can learn, adapt and problem-solve. While animal cognition has been widely studied in birds and mammals, much is yet to be discovered in reptiles.

Using a Y-maze and a visual discrimination task, the researchers trained hatchlings incubated at two female-producing temperatures (88 F and a hotter 91 F) and then tested their ability to “reverse train” when the task rules changed. Eggs were collected during the summers of 2019 and 2020 from nesting beaches in Palm Beach County.

Microbial DNA sequencing reveals nutrient pollution and climate change reinforce lake eutrophication

Lake 227 of the Experimental Lakes Area.
Photo Credit: Rebecca Garner

The algal blooms increasingly seen in Canadian lakes have been linked to both nutrient pollution from agricultural runoff and climate change. However, a new Concordia-led study using DNA sequencing of lakebed microbes reveals that these two drivers amplify each other in ways that profoundly affect the health of lake ecosystems.

Using records and samples from the International Institute for Sustainable Development Experimental Lakes Area (ELA), a group of 58 lakes in northwestern Ontario designated freshwater research facilities, the researchers paired environmental monitoring data dating back more than five decades with paleogenetic reconstructions from lakebed microbes dating back more than a century.

By sequencing DNA found in lake sediments, the researchers got insight into past algal communities’ composition and compare them to communities today. This provided critical insight into how those communities changed over decades.

“The sediment DNA archives gave us a chronology of these lakes’ history,” says lead author Rebecca Garner, PhD 2023, and currently a postdoctoral fellow at the University of California, Berkeley. “This is the first study to show that we can reconstruct the community dynamics of that ecosystem and dramatically expands the diversity of microorganisms that we were able to study.”

The study was published in the journal Environmental Microbiology.

Climate change is supercharging Europe’s biggest hail

Climate experts from Newcastle University, the Met Office and the University of Bristol used European-wide km-scale simulations to model future changes to hail with global warming. Published in the journal Nature Communications, the findings show that, under a high-emissions scenario (RCP8.5), severe hail is likely to become less common, except potentially for very large hail.

Severe hail has a diameter of 2 cm, while a diameter of 5 cm or more is considered very large. Bigger hailstones cause more damage than smaller ones, and even a small increase in their size could outweigh any benefits from having fewer hailstorms overall.  

The researchers attribute this decrease to more than one factor. Hail forms higher in the atmosphere as it warms, where storm updrafts could be weaker, and this gives hail more time to melt before reaching the ground. Another factor is the weakening large scale circulation, affecting the vertical profile of winds and leading to environments not beneficial for thunderstorm organization.

Importantly, the authors found that future warm seasons feature a warmer thunderstorm type similar to hail-producing storms found in the tropics, where the largest hailstones can still reach the surface. The findings suggest that, in the future, these storms will become most frequent over southern Europe, leading to regional increases in severe hail frequency.

Grassland Butterflies – Important Indicators of the State of Nature

Small Copper (Lycaena phlaeas), a species for which the index shows a positive trend.
Photo Credit: Werner Messerschmid

With the Grassland Butterfly Index for Germany, UFZ scientists are providing important input for the implementation of the EU Nature Restoration Regulation.

One of the goals of the EU Nature Restoration Regulation, which came into force in 2024, is to halt species loss and preserve important ecosystem services provided by agricultural landscapes. Scientists at the Helmholtz Centre for Environmental Research (UFZ), in collaboration with the Senckenberg German Entomological Institute (SDEI), have now calculated the Grassland Butterfly Index for Germany – an indicator of the state of biodiversity proposed in the EU regulation. The results, published in the journal Nature Conservation, show a negative trend, especially in recent years. For their calculations, the researchers were able to draw on 4 million observation data collected at the UFZ over the last 20 years as part of the ‘Butterfly Monitoring Germany’ program.

Wildfire Smoke May Lead to Thousands More U.S Deaths

Mammoth Mountain in California’s Sierra Nevada Range on September 8, 2025. The photo reveals significant haze and smog, much of that the result of continual wildfires in the state.
Photo Credit: Marshall Burke.

A study led by Stony Brook University faculty and published in Nature projects that smoke exposure from wildfires in the coming decades toward 2050 could result in tens of thousands of excess deaths in the United States.

This projection, by a national team of investigators led by Stony Brook’s Minghao Qiu, is based on research that assesses wildfire activity in an increasingly dry and warming climate.

Wildfires have significantly increased in recent years, often in the western U.S. but also in other regions. Warmer, drier conditions are increasing the scope, damage, and exposures to people from wildfires. The study details the use of historical data from wildfires and smoke pollution, along with statistical models and machine learning tools to estimate deaths caused by exposure to smoke particulates in climate change scenarios.

Deaths from wildfire smoke result from inhaling a complex mix of chemicals. Wildfires can expose large numbers of people to these toxic pollutants for days or weeks at a time, contributing to deaths up to three years after the initial exposure, according to the study.

Rivers in the Sky, Arctic Warming, and What this Means for the Greenland Ice Sheet

Photo Credit: Beau Mori

 “Atmospheric rivers” are large-scale extreme weather systems that are making headlines more frequently. When viewed in satellite images, they appear just as described – like rivers in the sky. Though they are often reported in places like California, these weather systems have the potential to bring high heat and dump disastrous amounts of precipitation on areas throughout the mid and high latitudes.

A team of researchers, including UConn Department of Earth Sciences associate professor Clay Tabor and Ph.D. student Joseph Schnaubelt, looked at how atmospheric rivers impacted the Greenland Ice Sheet in the past to get a better understanding of how these weather systems may enhance melting in the Arctic as the climate continues to warm. Their results are published in AGU Advances.

An important question that paleoclimate scientists like Schnaubelt and Tabor are trying to answer is how the Arctic will respond to climate change, and for this they focused deep into the past on a time called the Last Interglacial, between 130,000 and 115,000 years ago.

“Earth goes through glacial cycles, and the Last Interglacial was the last time the Arctic was warmer than present day,” says Schnaubelt. “We know that that’s the direction we’re headed toward, and we wanted to see how atmospheric rivers impacted the Greenland Ice Sheet.”

Greener rocket fuels on the horizon

SpaceX Falcon Heavy Launch
Photo Credit: SpaceX

Studying safer, cheaper rocket and missile fuels that could reduce health and environmental risks is the focus of a new $800,000 grant awarded to the University of Hawaiʻi at Mānoa Department of Chemistry by the U.S. Air Force Office of Scientific Research. The project will be led by principal investigator Professor Rui Sun with co-principal investigator Professor Ralf I. Kaiser.

The grant falls under a broader push toward green chemistry—designing chemical products and processes that reduce or eliminate hazardous substances. Current propellants can be expensive and toxic, creating risks during manufacture, storage and transport. The research seeks to help lower costs for space exploration while reducing risks to workers and communities.

Researchers Uncover a Major Shift in U.S. Landscape: ‘Wild’ Disturbances Are Overtaking Human-directed Changes

Disturbances like hurricanes and fires reshape the landscape and play vital roles in Earth’s systems, therefore, understanding what drives these kinds of disturbances is important for projecting what changes may be ahead.
Photo Credit: Malachi Brooks

If it feels like headlines reporting 100 or 1,000-year floods and mega fires seem more frequent these days, it’s not your imagination.

A project led by researchers from UConn’s Global Environmental Remote Sensing (GERS) Lab has yielded surprising insights into land disturbances and disasters in the United States since the late 1980s, including a shift in what drives those disturbances, and how they are increasing with frightening intensity and frequency. Their findings are published in Nature Geoscience.

The research is the result of a decade-long project to perform a CONterminous United States (CONUS)-wide disturbance agent classification and mapping project, explains GERS Director and Associate Professor in the Department of Natural Resources and the Environment in the College of Agriculture, Health and Natural Resources (CAHNR) Zhe Zhu. The ambitious project involved the careful analysis of Landsat satellite data spanning more than 40 years.

Disturbances like hurricanes and fires reshape the landscape and play vital roles in Earth’s systems; therefore, understanding what drives these kinds of disturbances is important for projecting what changes may be ahead.

Methane production may increase as Arctic lakes warm

 

Fältarbete vid sjöar nära Abisko naturvetenskapliga station.
Photo Credit: Sofia Kjellman

A warmer and wetter climate makes lakes more productive – which in turn leads to more methane being released from sediments. A new study involving Umeå University shows that Arctic lakes may contribute even more to the greenhouse effect in the future.

Methane is more than 25 times stronger as a greenhouse gas than carbon dioxide. Arctic lakes account for a significant share of global methane emissions, but until now, knowledge about the processes in northern lakes has been limited. An international team of researchers from Norway, Sweden and Spain has now shown that methane production varies greatly between lakes and is closely linked to their characteristics.

The researchers investigated ten lakes on Svalbard and in the subarctic region of Scandinavia, three of them via the Abisko Scientific Research Station. They found that most methane production occurs in the top ten centimeters of lake sediments, where there is abundant organic matter and favorable conditions for microbes.

Coral reefs set to stop growing as climate warms

Dead reef crest on Mexico's Caribbean coast.
Photo Credit Chris Perry

Most coral reefs will soon stop growing and may begin to erode – and almost all will do so if global warming hits 2°C, according to a new study in the western Atlantic.

An international team, led by scientists from the University of Exeter, assessed 400 reef sites around Florida, Mexico and Bonaire.

The study, published in the journal Nature, projects that more than 70% of the region’s reefs will stop growing by 2040 – and over 99% will do so by 2100 if warming reaches 2°C or more above pre-industrial levels.

Climate change – along with other issues such as coral disease and deteriorating water quality – reduces overall reef growth by killing corals and impacting colony growth rates.

To understand how changing reef ecology is impacting reef growth potential – in other words, how the balance of living organisms translates into vertical “accretion” (reef-building) – the team analysed fossil reefs from across the tropical western Atlantic region to improve understanding of how reef growth rates vary depending on the types of coral present.