Friday, August 15, 2025

 

International “State of the Climate” report confirms record-high greenhouse gases, global temperatures, global sea level, and ocean heat in 2024




American Meteorological Society
Selected Significant Climate Anomalies and Events: 2024 

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Geographical distribution of selected notable climate anomalies and events in 2024. (Fig. 1.1 in The State of the Climate in 2024.)

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Credit: "The State of the Climate in 2024" (c) American Meteorological Society, 2025





According to the 35th annual State of the Climate report, greenhouse gas concentrations, the global temperature across land and oceans, global sea level, and ocean heat content all reached record highs in 2024, and glaciers lost the most ice of any year on record.

The international review of the world’s climate, published by the Bulletin of the American Meteorological Society (BAMS), is based this year on contributions from 589 scientists in 58 countries. For decades, the State of the Climate has provided the most comprehensive annual update on Earth’s climate⁠ — illuminating not only key indicators like global CO2 but also notable weather events, regional phenomena, and other data collected by environmental monitoring stations and instruments located on land, water, and ice, as well as in space.

“The State of the Climate report is an annual scientific landmark,” says American Meteorological Society President David J. Stensrud. “It is a truly global effort, in which hundreds of researchers from universities, government agencies, and more come together to provide a careful, rigorously peer-reviewed report on our planet’s climate. High-quality observations and findings from all over the world are incorporated, underscoring the vital importance of observations to monitor, and climate science to understand, our environment. The results affirm the reality of our changing climate, with 2024 global temperatures reaching record highs."  

Notable findings from the international report include:

  • Earth’s greenhouse gas concentrations were the highest on record. Carbon dioxide (CO2), methane, and nitrous oxide ⁠— Earth’s major atmospheric greenhouse gases⁠ — once again reached record-high concentrations in 2024. The globally averaged CO2 level reached 422.8±0.1 parts per million, a 52% increase from the pre-industrial level of ~278 ppm. Annual growth in global mean CO2 has increased from 0.6±0.1 ppm yr−1 in the early 1960s to an average of 2.4 ppm yr−1 during 2011–20. The growth from 2023 to 2024 was 3.4 ppm, equal with 2015/16 as the highest in the record since the 1960s.

  • Record temperatures were notable across the globe. A new annual global surface temperature record was set for the second year in a row, with records dating back as far as the mid-1800s. A range of scientific analyses indicate that the annual global surface temperature was 1.13 to 1.30 degrees F (0.63 to 0.72 degrees C) above the 1991–2020 average. A strong El Niño that began in mid-2023 and ended in boreal spring 2024 contributed to the record warmth. The last time two consecutive years reached a new global surface temperature record was in 2015 and 2016, when a strong El Niño developed during the latter half of 2015 and dissipated by May 2016. All six major global temperature datasets used for analysis in the report agree that the last 10 years (2015–24) were the 10 warmest on record. 

  • The water cycle continued to intensify. Higher global temperatures impacted the water cycle. Water evaporation from land in the Northern Hemisphere reached one of the highest annual values on record. The global atmosphere contained the largest amount of water vapor on record, with over one-fifth of the globe recording their highest values in 2024. This far exceeded 2023, where only one-tenth of the globe experienced record-high values of total column water vapor. Precipitation was globally high; 2024 was the third-wettest year since records began in 1983. Extreme rainfall, as characterized by the annual maximum daily rainfall over land, was the wettest on record. In April, Dubai in the United Arab Emirates recorded 9.8 in (250 mm) of rain in 24 hours — nearly three times its annual average.

  • El Niño conditions contributed to record-high sea surface temperatures. Strong El Niño conditions in the equatorial Pacific Ocean that emerged by the end of 2023 continued into early 2024, with neutral conditions returning in boreal spring. Daily globally averaged sea surface temperatures were at record-high levels from the beginning of 2024 until late June. The mean annual global sea surface temperature in 2024 was a record high, surpassing the previous record of 2023 by 0.11 of a degree F (0.06 of a degree C). Approximately 91% of the ocean surface experienced at least one marine heatwave in 2023, which is defined as sea surface temperatures in the warmest 10% of all recorded data in a particular location for at least five days. Only 26% of the ocean surface experienced at least one marine cold spell. The ocean experienced a record-high global average of 100 marine heatwave days and a new record low of nine marine cold spell days.

  • Ocean heat and global sea level were the highest on record. Over the past half-century, the oceans have stored more than 90% of the excess energy trapped in Earth’s system by greenhouse gases and other factors. The global ocean heat content, measured from the ocean’s surface to a depth of 2000 m (approximately 6561 ft), continued to increase, and reached new record highs in 2024. Global mean sea level was a record high for the 13th consecutive year, reaching about 4.0 in (105.8 mm) above the average for 1993 when satellite altimetry measurements began. Warming oceans have contributed an average of 1.5±0.3 mm to the rise per year since 2005, while melt from ice sheets and glaciers have contributed an average of 2.1±0.4 mm during that same period.

  • The Arctic saw near-record warmth. The Arctic had its second-warmest year in the 125-year record, with autumn (October to December) having been record warm. During the summer, an intense August heatwave brought all-time record-high temperatures to parts of the northwest North American Arctic, and record-high August monthly mean temperatures at Svalbard Airport reached more than 52°F (11°C). In September, temperatures above 86°F (30°C) were observed in Norway, marking the latest time of the year in the observational record that such high temperatures have occurred there. During the 2023/24 snow season, there were large differences in how long snow remained on the ground, from the shortest to date in the twenty-first century over parts of Canada to at or near the longest in this century in parts of the Nordic and Asian Arctic. The Arctic maximum sea ice extent in 2024 was the second smallest in the 46-year satellite record, while the minimum sea ice extent was the sixth smallest. 

  • Antarctica saw continued low sea ice. Following record lows in 2023, net sea ice extent was larger than last year but continued to be well below average during much of 2024. The Antarctic daily minimum and maximum sea ice extents for the year were each the second lowest on record behind 2023, marking a continuation of low and record-low sea ice extent since 2016.

  • Glaciers around the world continued to melt. For the second consecutive year, all 58 global reference glaciers across five continents lost mass in 2024, resulting in the greatest average ice loss in the 55-year record. In South America, Venezuela became the first Andes country to register the loss of all glaciers. In Colombia, the Conejeras Glacier was declared extinct, joining the list of glaciers that have disappeared in recent years. 

  • Tropical cyclone activity was below average, but storms still set records around the globe. A total of 82 named tropical cyclones were observed during the Northern and Southern Hemispheres’ storm seasons, below the 1991–2020 average of 87 and equal to the number recorded in 2023. Many storms made landfall and some caused major damage. Hurricane Helene brought destruction from Florida to the southern Appalachian Mountains. The storm caused devastating record flooding that contributed to over 200 deaths, the most in the United States since Hurricane Katrina in 2005. Hurricane Milton impacted Florida’s Gulf Coast just 12 days after Helene affected the region, marking the shortest time between major (Category 3 or higher) hurricane landfalls in Florida. In the northwest Pacific basin, Super Typhoon Yagi became one of the most destructive storms to affect China and Vietnam in recent years, causing more than 800 fatalities.

The State of the Climate report is a peer-reviewed series published annually as a special supplement to the Bulletin of the American Meteorological Society. The American Meteorological Society makes the full report openly available online

About the American Meteorological Society

The American Meteorological Society (www.ametsoc.org) advances the atmospheric and related sciences, technologies, applications, and services for the benefit of society. Founded in 1919, AMS has a membership of around 12,000 professionals, students, and weather enthusiasts. AMS publishes 12 scientific journals in the atmospheric and related oceanic and hydrologic sciences; sponsors more than 12 conferences annually; and offers numerous programs and services to the weather, water, and climate community

 

How the Atlantic Ocean circulation has changed over the past 12,000 years



Earth scientists from Heidelberg University and the University of Bern reconstruct Holocene circulation patterns




Heidelberg University




Using geochemical analyses of marine sediments, researchers have been able to quantitatively reconstruct the Atlantic Meridional Overturning Circulation over the past 12,000 years. An international research team, led by scientists from Heidelberg University and the University of Bern (Switzerland), is the first to calculate the large-scale circulation patterns of the Holocene. Their reconstruction shows that, while the AMOC experienced natural fluctuations over millennia, it remained stable for long periods of time.

The Atlantic Meridional Overturning Circulation (AMOC) is part of a global deep-ocean water system that redistributes heat and freshwater from the southern to the northern hemisphere, significantly impacting the weather, oceans, and climate. This makes it one of the key components of the Earth’s climate system. It includes the Gulf Stream system, a key driver of Europe’s climate. As part of the oceanic “conveyor belt”, it transports large amounts of heat from tropical regions to higher latitudes, playing a crucial role in balancing temperatures between the northern and southern hemispheres. According to Lukas Gerber, a doctoral researcher at the Institute of Earth Sciences at Heidelberg University, changes in the strength of this circulation can have far-reaching impacts on weather patterns, marine ecosystems, and long-term global climate trends. While the variability of the AMOC during the last Ice Age is well documented, its behavior during the Holocene – the comparatively mild period of Earth’s history that began some 12,000 years ago and continues to this day – is attracting increasing interest from researchers.

The reconstruction of the Atlantic circulation was based on geochemical measurements of the radioactive elements thorium and protactinium taken from sediments on the floor of the North Atlantic. The ratio of these rare radioisotopes records the circulation strength over the past 12,000 years and provides insights into the environmental conditions that have prevailed since the end of the last Ice Age. Using the data they had gathered, the scientists ran a numerical Earth system model to simulate the AMOC under various climate scenarios. This enabled them to calculate deepwater circulation patterns in the North Atlantic for the current geological epoch, the Holocene.

The team’s reconstruction shows that, after a period of recovery towards the end of the last Ice Age, the AMOC experienced another marked weakening between 9,200 and 8,000 years before present. “This phase coincides with meltwater pulses in the North Atlantic, during which large volumes of meltwater were released in a short period of time, most likely due to the collapse of the North American ice sheet,” explains Lukas Gerber. Around 6,500 years ago, the AMOC began to stabilize and eventually reached its present-day strength, according to the researchers. This is approximately 18 Sverdrups, with one Sverdrup corresponding to a volumetric flow rate of one billion liters per second.

“Our findings demonstrate that the AMOC remained stable throughout much of the Holocene,” emphasizes project leader Dr Jörg Lippold, who studies ocean dynamics with his team at the Institute of Earth Sciences at Heidelberg University. However, projections for the future clearly indicate that human-driven climate change could weaken the Atlantic circulation to levels never before seen in the present warm period of the Holocene. Dr Lippold points to current climate models that forecast a slowdown of five to eight Sverdrups, depending on the actual extent of global warming by the year 2100. In his view, such a change could have severe and unprecedented consequences for the stability of temperatures and for global precipitation patterns.

In addition to the scientists from Heidelberg and Bern, the project involved researchers from MARUM – Center for Marine Environmental Sciences at the University of Bremen, Friedrich-Alexander-Universität Erlangen-Nürnberg, and the University of São Paulo (Brazil). The work was funded by the German Research Foundation, the European Union, and Brazilian research funding. The results were published in the journal Nature Communications.

 

As the world churns — a history of ecosystem engineering in the oceans




Yale University





New Haven, Conn. — The murky world at the bottom of the oceans is now a little clearer, thanks to a new study that tracks the evolution of marine sediment layers across hundreds of millions of years.

It is a story of world-building on a grand, yet granular, scale, accomplished by a succession of marine animals that burrowed and tunneled their way through heat and cold, species expansions and mass die-offs. Scientists call the process bioturbation — the excavation and mixing of sediments and soils by burrowing animals, particularly for shelter and sustenance.

“Bioturbation is one of the most important forms of ecosystem engineering today, both in the oceans and on land,” said Lidya Tarhan, assistant professor of Earth and planetary sciences in Yale’s Faculty of Arts and Sciences, and lead author of the study published in the journal Science Advances.

“In the oceans, bioturbation plays a critical role in shaping the habitability and ecology of the seafloor, as well as in regulating nutrient cycling in overlying ocean waters,” Tarhan said. “However, how bioturbation has varied through Earth's past, and the evolutionary timing of when bioturbators became the enormously impactful 'engineers' they are today, has long been poorly understood.”

In addition to their own data — which includes observations from geologic field work in the U.S., Canada, Spain, and Australia and sediment drill cores collected from the modern oceans — Tarhan and her collaborators surveyed more than 1,000 previous scientific studies. They looked specifically for information about how intensively seafloor sediments were churned, as well as six types of fossilized burrows that have typically been among the deepest burrows in the seafloor. Ultimately, they amassed a database covering 540 million years of Earth’s history — nearly the full evolutionary history of animal life.

The team gleaned several new insights from their research.

First, they found that the two main types of bioturbation — burrowing and sediment mixing by the animals — developed separately. Deep burrowing began early in the evolution of animals; sediment mixing took hundreds of millions of years to develop.

“Burrowing animals such as worms, and later, clams and crustaceans were abundant and widespread, at least in the shallow oceans,” said Tarhan, who is also an assistant curator at the Yale Peabody Museum. “It took longer for them to venture to the deep oceans. But sediment mixing lagged behind. We hypothesize that ocean oxygen stress, particularly in intervals of warm, ‘greenhouse’ climates, may have been a major driver.”

Ocean oxygen levels were likely very low when seafloor animal communities were first establishing themselves, she said. Under warmer water temperatures, animals’ metabolic rates increase and so does their need for oxygen. That likely meant that sediment mixing, which requires a great expenditure of energy, took a backseat to less-intensive burrowing.

The researchers also were able to begin documenting how bioturbation has been affected by major environmental changes and mass extinction events throughout history. For example, during the End-Permian mass extinction 252 million years ago, when potentially more than 90% of animal species were wiped out, bioturbation ceased for a time. Then small, horizontal burrows slowly began to reappear.

Further research will explore what role this greatly reduced bioturbation had on the reestablishment of nutrients in the ocean and the eventual regrowth of ecosystems.

“Without a clear picture of how bioturbators responded to environmental stressors and how quickly they were able to rebound following extinctions, our understanding of the mechanics of the ecological cascades that drive extinction and dictate recovery is decidedly murky,” Tarhan said. “This certainly compounds the challenges we face in attempting to predict the ecological impacts of our current extinction crisis.”

Kate Pippenger, a graduate student in Tarhan’s lab at Yale, is co-author of the study. Additional co-authors are Alison Cribb of the University of Southampton, Michelle Zill and David Bottjer of the University of Southern California, William Phelps of Riverside Community College, Mary Droser of the University of California-Riverside, and Matthew Clapham of the University of California-Santa Cruz.

The research was funded by Yale and a National Science Foundation graduate research fellowship.

 

Sliteye shark discovered in remote Indian Ocean -- First-ever sighting in Chagos Archipelago






Swansea University
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A photo of a sliteye shark circling a bait box.

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Credit: Charlotte Oulton.





The sliteye shark has been recorded for the first time on the Great Chagos Bank, the world’s largest coral atoll structure—marking a major advance in understanding the geographic range of this near-threatened species.

The recent sightings in deepwater seagrass meadows underscore the ecological importance of the Chagos Archipelago and its Marine Protected Area, revealing previously undiscovered biodiversity in its reefs and seagrass beds.

Named for its distinctive, slit-like eyes—thought to enhance vision in low-light conditions—the sliteye shark (Loxodon macrorhinus) is well adapted to deeper, dimly lit environments as well as clear, shallow water, and has now been found in the Chagos Archipelago for the first time.

The sightings occurred in previously unstudied seagrass on the southern rim of the Great Chagos Bank. The sharks were captured just 11 km apart, at depths of 23-29 metres, using Baited Remote Underwater Video (BRUV) systems—underwater survey systems that attract and record marine life without human disturbance.

These observations offer new insights into deepwater seagrass habitats first discovered by the team in 2016.

Given the species’ wide distribution, researchers believe it’s unlikely that it is rare in Chagos. 

Charlotte Oulton, study lead and Master’s by Research student in the Marine and Conservation Ecology Lab at Swansea University, said: “Discovering the sliteye shark in the Chagos Archipelago was incredibly exciting. Not only is it a new record for the region, but it also highlights how much we still have to learn about deepwater seagrass ecosystems and their role in supporting marine biodiversity, particularly in remote regions of the Indian Ocean.”

Dr Nicole Esteban, Associate Professor in Marine Ecology at Swansea University, added: “Satellite tracking of green turtles led us to discover extensive seagrass meadows on the Great Chagos Bank at depths of 25–30 metres—far deeper than expected. We have now recorded a wide diversity of marine life using this seagrass habitat for shelter and food, including over 110 fish species, and as we now know, the sliteye shark.”

With sliteye shark populations projected to decline by up to 29% in the next 15 years due to fishing pressures, this discovery raises important questions about species abundance, habitat use, and conservation priorities. It also reinforces the urgent need to explore and protect deepwater habitats.

These latest findings, based on surveys conducted in late 2024, are part of a collaborative project between Swansea University and international partners, funded by the Bertarelli Foundation through the Bertarelli Foundation’s Indian Ocean Marine Science Programme.

The research aims to:

  • Map current seagrass coverage
  • Model habitat suitability to predict the likely extent of seagrass growth
  • Assess the ecological importance of deepwater seagrass ecosystems across the Archipelago.

Full findings are expected to be published in 2026.

 

Past Arctic climate secrets to be revealed during i2B “Into The Blue” Arctic Ocean Expedition 2025





UiT The Arctic University of Norway

RV Kronprins Haakon 

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RV Kronprins Haakon sailing through Arctic sea ice

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Credit: Dimitri Kalenitchenko/UiT





What’s Happening

From 16th August to 19th September 2025, the Norwegian research vessel R/V Kronprins Haakon will be sailing into the Arctic Ocean for an expedition organised and funded through the prestigious European Research Council Synergy Grant i2B – Into The Blue. The i2B Arctic Ocean Expedition team consisting of 25 scientists will collect new geological archives that will shed light on Arctic climate during past ‘warmer-than-present-day’ conditions (interglacial periods). These archives are crucial to understand the impact of a “blue” (free of seasonal sea-ice) Arctic Ocean during key interglacial periods, ca. 130,000 and 400,000 years ago. Follow the i2B Arctic Ocean Expedition: https://arcg.is/0favaf0

What are the global impacts of an ice-free Arctic? How will the Arctic develop with increasing climate warming? What does an ice-free Arctic mean for our environment and our society? These are the key questions that the i2B project will address over the coming years, using cutting-edge research, geological records, and numerical models. i2B brings together researchers from UiT The Arctic University of Norway, AWI - The Alfred Wegener Institute – Helmholtz Centre for Polar and Marine Research in Bremerhaven (Germany), NORCE Climate and Environment in Bergen (Norway), and UiB University of Bergen (Norway).

 

Why It Matters

  • The impact of global warming on the Arctic has long preoccupied researchers, because the concrete impacts on the region and our entire planet have so far been unclear.
  • Summer ice melt starts earlier and lasts longer each year, with future projections showing sea-ice-free summers before 2050.
  • These trends raise broader climate challenges in the Arctic such as marine heatwaves, Atlantification of the Arctic Ocean, ecosystem shifts, altered weather patterns, ice-albedo feedbacks, methane release, and this on top of new geopolitical dynamics in an ice-free Arctic.

 

What the i2B Arctic Ocean Expedition Will Do

  • Collect high-resolution sediment cores at multiple sites to reconstruct temperature, sea ice conditions, oceanography and the ecosystem during warm past interglacial periods, ca. 130,000 and 400,000 years ago
  • Compare these data with modern observations to test how the Arctic transitioned to a “blue ocean” state in warmer climates.
  • Examine whether the past serves as a window into our future – are we at the brink of a new tipping point?

 

Expedition Team

  • Expedition leaders/co-chief scientists: Jochen Knies and Stijn De Schepper 
  • 25 scientists from nine different countries

 

 

Links & Further Reading


Long geological archives will be collected from the Arctic Ocean seafloor. 

Credit

Jochen Knies



Co-chief scientist Dr Jochen Knies, Researcher and Adjunct Professor at the Department of Geosciences at UiT The Arctic University of Norway.

Credit

Clea Fabian / NGU


 

60 percent of the world’s land area is in a precarious state




Potsdam Institute for Climate Impact Research (PIK)





A new study maps the planetary boundary of “functional biosphere integrity” in spatial detail and over centuries. It finds that 60 percent of global land areas are now already outside the locally defined safe zone, and 38 percent are even in the high-risk zone. The study was led by the Potsdam Institute for Climate Impact Research (PIK) together with BOKU University in Vienna and published in the renowned journal One Earth.

Functional biosphere integrity refers to the plant world’s ability to co-regulate the state of the Earth system. This requires that the plant world is able to acquire enough energy through photosynthesis to maintain the material flows of carbon, water and nitrogen that support the ecosystems and their many networked processes, despite today’s massive human interference. Together with biodiversity loss and climate change, functional integrity forms the core of the Planetary Boundaries analytical framework for a safe operating space for humanity.

“There is an enormous need for civilisation to utilise the biosphere – for food, raw materials and, in future, also for climate protection,” says Fabian Stenzel, lead author of the study and member of the PIK research group Terrestrial Safe Operating Space. “After all, human demand for biomass continues to grow – and on top of that, the cultivation of fast-growing grasses or trees for producing bioenergy with carbon capture and storage is considered by many to be an important supporting strategy for stabilising climate. It is therefore becoming even more important to quantify the strain we’re already putting on the biosphere – in a regionally differentiated manner and over time – to identify overloads. Our research is paving the way for this.”

Two indicators to measure the strain and the risk

The study builds on the latest update of the Planetary Boundaries framework published in 2023. “The framework now squarely puts energy flows from photosynthesis in the world’s vegetation at the centre of those processes that co-regulate planetary stability”, explains Wolfgang Lucht, head of PIK’s Earth System Analysis department and coordinator of the study. “These energy flows drive all of life – but humans are now diverting a sizeable fraction of them to their own purposes, disturbing nature’s dynamic processes.” 

The stress this causes in the Earth system can be measured by the proportion of natural biomass productivity that humanity channels into its own uses – through harvested crops, residues and timber – but also the reduction in photosynthetic activity caused by land cultivation and sealing. The study added to this measure a second powerful indicator of biosphere integrity: An indicator of risk of ecosystem destabilisation records complex structural changes in vegetation and in the biosphere’s water, carbon and nitrogen balances. 

Europe, Asia and North America particularly affected

Based on the global biosphere model LPJmL, which simulates water, carbon and nitrogen flows on a daily basis at a resolution of half a degree of longitude/latitude, the study provides a detailed inventory for each individual year since the 1600, based on changes in climate and human land use. The research team not only computed, mapped and compared the two indicators for functional integrity of the biosphere, but also evaluated them by conducting a mathematical comparison with other measures from the literature for which “critical thresholds” are known. This resulted in each area being assigned a status based on local tolerance limits of ecosystem change: Safe Operating Space, Zone of Increasing Risk or High Risk Zone. 

The model calculation shows that worrying developments began as early as 1600 in the mid- latitudes. By 1900, the proportion of global land area where ecosystem changes went beyond the locally defined safe zone, or were even in the high-risk zone, was 37 and 14 percent respectively, compared to the 60 and 38 percent we see today. Industrialisation was beginning to take its toll; land use affected the state of the Earth system much earlier than climate warming. At present, this biosphere boundary has been transgressed on almost all land surface – primarily in Europe, Asia and North America – that underwent strong land cover conversion, mainly due to agriculture.

PIK Director Rockström: Impetus for international climate policy

“This first world map showing the overshoot of the boundary for functional integrity of the biosphere, depicting both human appropriation of biomass and ecological disruption, is a breakthrough from a scientific perspective, offering a better overall understanding of planetary boundaries,” says Johan Rockström, PIK Director and one of the co-authors of the study. “It also provides an important impetus for the further development of international climate policy. This is because it points to the link between biomass and natural carbon sinks, and how they can contribute to mitigating climate change. Governments must treat it as a single overarching issue: comprehensive biosphere protection together with strong climate action.”