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    When will global warming actually hit the landmark 1.5 ºC limit?

    Temperatures soared in India in April: heatwaves becomes more likely as the planet heats up. Credit: Sudipta Das/NurPhoto via Getty

    There’s a 66% chance that the annual global average temperature will hit 1.5 ºC above pre-industrial temperatures at some time in the next five years, according to a World Meteorological Organization report released on 17 May. Reaching 1.5 ºC of warming in a single year will be a landmark moment for the planet, which in 2022 was about 1.15 ºC warmer than in pre-industrial times. But it’s not quite the milestone most people mean when they talk about 1.5 ºC of warming — for that, we probably have about a decade to go.The famous 1.5 ºC figure, widely quoted as the desired ‘maximum’ for planetary warming, stems from the 2015 United Nations Paris agreement on climate change. This treaty declared the goal of keeping the global average temperature well below 2 ºC above pre-industrial levels, with a preferred limit of 1.5 ºC.The Paris agreement, however, refers to a sustained planetary average of 1.5 ºC warming — not just the average for a single year, which alone could be anomalously hotter or cooler than the longer-term average. The Paris agreement didn’t specify exactly what was meant by 1.5 ºC of warming, but the most recent report of the first working group of the Intergovernmental Panel on Climate Change (IPCC), published in 2021, clarifies that it means the midpoint of the first 20-year period when the average global surface air temperature is 1.5 ºC warmer than the 1850–1900 average.In 2018, an IPCC special report on 1.5 ºC of warming estimated that the world would probably hit the 1.5 ºC threshold at some stage between 2030 and 2052. By 2021, using a different methodology, that had been pinned down to the early 2030s. “The time frame is getting closer and closer,” says geographer William Solecki at City University of New York, an author on the IPCC special report.A massive, two-year ‘global stocktake’ of progress on the Paris agreement’s goals is winding up now, and will be presented at the next UN Framework Convention on Climate Change meeting (COP28), which will start on 30 November. So far, the stocktake has found that things aren’t going well. For a 50% chance of limiting warming to 1.5 ºC, a stocktake meeting report notes, global greenhouse-gas emissions need to peak before 2025; this hasn’t happened yet, and national emissions commitments aren’t sufficient to keep the planet within the target.The lower the betterThe 1.5 ºC number was chosen in an attempt to limit the severity of the impacts of warming, taking into account factors such as food security and extreme weather events. However, IPCC experts stressed that 1.5 ºC shouldn’t be seen as a “guardrail” below which everything would be fine, and noted that whatever temperature the world’s warming peaks at, the lower it is, the better. “Obviously there’s a continuum,” says Solecki. “The higher the temperature, the worse the outcome.”The 2018 IPCC report on 1.5 ºC of warming notes that effects of reaching this threshold could include: extreme hot days in mid-latitudes that are 3 ºC warmer than in pre-industrial times; sea-level rise of up to three-quarters of a metre by 2100; the loss of more than half of the viable habitat for 8% of plants and 4% of vertebrates; and a decrease in annual global fisheries catches of 1.5 million tonnes.The report also notes that because global warming is uneven, more than one-fifth of the world’s population currently live in regions that have already exceeded 1.5 ºC of warming in at least one season.More important than when Earth will hit 1.5 ºC of warming is what amount of warming the planet will peak at, and when that will happen. “With every tenth of a degree above 2 ºC, you’re looking at more-sustained, more-systemic impacts,” says Solecki.Those numbers won’t be apparent for decades. According to the IPCC’s 2021 projections of global temperature under different emissions scenarios, peak temperature could be anything from 1.6 ºC in around 2050 (if the globe hits net zero emissions by then), dropping to 1.4 ºC by 2100; to, with emissions still climbing, 4.4 ºC at 2100, with the peak still to come.The next few years could bring an anomalously high blip in annual temperatures compared with the longer-term average thanks to an expected El Niño event — a natural climate pattern that brings warmer temperatures to the eastern Pacific Ocean and that tends to warm the planet as a whole. In April, Carbon Brief, a website that reports on climate matters, estimated that 2023 was shaping up to be one of the six hottest years on record, most likely the fourth hottest. And in April, the global ocean spiked at the hottest temperature since records began. More

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    Found in the trash: these floating snails hang out in the ocean’s garbage patch

    Credit: Denis Riek, The Global Ocean Surface Ecosystem Alliance (GO-SEA) Field Guide (CC-BY 4.0)

    This amazing picture shows the violet sea snail Janthina sp., which builds rafts by trapping air bubbles and encasing them in mucus. Scientists discovered that oceanic gyres concentrate the floating snails in the North Pacific ‘garbage patch’, more famous for accumulating discarded plastic. By bringing them together, the currents could help these and other floating creatures to feed and reproduce. More

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    I was deathly afraid of the sea — now I work to protect it

    I grew up deathly afraid of the ocean. But that changed in 2016, when I began mapping South Africa’s kelp forests for my biology master’s degree. I used satellite imagery to find the kelp; then I assessed the potential environmental threats that the forests face, such as unsustainable offshore mining, pollution and even shadows from coastal development.As I began this survey across the 1,300-kilometre kelp-rich stretch of South Africa’s coastline, I wanted to see the kelp that was below the ocean’s surface. I vividly recall floating on my stomach looking down at this golden, waving forest. I was amazed by the biodiversity that exists underneath this big, blue blanket, including invertebrates, fish and mammals.In this image, taken near where I first encountered kelp forests off the coast of Windmill beach, south of Cape Town, I am looking for the different types of animal, including limpets, sea urchins and octopuses, that live in these forests. In my advocacy work, I use films and social media to educate the public about how, for example, over half of the atmosphere’s oxygen comes from kelp forests.So far, we have mapped only coastal kelp because it is visible to satellites during low tide. We hope to use remotely operated vehicles to map the underwater extent of it.South Africa’s natural kelp forests are among the few that are still expanding. Others around the world are endangered because of over-harvesting or coastal development. In response to increased demand for kelp, for use in products such as toothpaste and possibly as a biodegradable alternative to plastic, my team is building sustainable kelp farms. The government supports a non-lethal harvesting approach in which we collect only the tops of the stalks, allowing the plant to regrow as it continues to provide habitat.Perhaps the kelp forests’ biggest threat is the lack of awareness or appreciation of how many species call them home. It’s a spiritual place. More

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    The ocean is hotter than ever: what happens next?

    Warm oceans can bleach and kill corals.Credit: Juergen Freund/NPL

    The global ocean hit a new record temperature of 21.1 ºC in early April, 0.1 ºC higher than the last record in March 2016. Although striking, the figure (see ‘How the ocean is warming’) is in line with the ocean warming anticipated from climate change. What is remarkable is its occurrence ahead of — rather than during — the El Niño climate event that is expected to bring warmer, wetter weather to the eastern Pacific region later this year.That means warmer-than-average ocean temperatures are likely to persist or even intensify, bringing with them more-extreme weather and marine heatwaves, which spell problems for marine life from corals to whales.“We are probably looking at a string of record highs over the next year or so,” says Josh Willis, an oceanographer at NASA’s Jet Propulsion Laboratory in Pasadena, California. “This coming year is gonna be a wild ride if the El Niño really takes off.”

    Source:; NOAA Optimum Interpolation SST (OISST)

    The El Niño Southern Oscillation (ENSO) is a natural, cyclical climate pattern. During the El Niño phase, winds over the Pacific are weakened or reversed, allowing warm waters to slosh eastwards in the Pacific. El Niño tends to coincide with warmer years both in the ocean and on land. The previous record of 21.0 ºC, for example, occurred during a very strong El Niño event.ENSO is currently in a neutral phase, coming out of a rare extended three-year period of La Niña (the opposite phase to El Niño). But El Niño is expected to kick in this year: according to the World Meteorological Organization, there is a 60% chance of it developing between May and July, and an up to 80% chance of it happening by October.Return of ‘the Blob’Andrew Leising, an oceanographer at the Southwest Fisheries Science Center of the US National Oceanographic and Atmospheric Administration (NOAA) in La Jolla, California, expects to see unusually warm waters in the Pacific off the west coast of the United States during the summer and autumn. If the El Niño develops as expected, he adds, “this could create a situation like 2014 to 2015, when we got smacked by the Blob heatwave”, a particularly big and damaging marine heatwave.Marine heatwaves can be devastating for wildlife, and fisheries. Large heatwaves on the US Pacific coast tend to compress the habitable zone for many species into a narrow strip along the coast, Leising says. That can bring whales closer to shore as they chase food, which can increase ship strikes and entanglements in fishing gear. When warm waters butt up against the shore, he adds, they can host harmful algal blooms that close crab and mussel fisheries. But at the moment, Leising says, there is some unusually strong upwelling of cold water occurring along the US west coast, which could protect against some warming this year.In the lead-up to April’s record ocean temperature, some regions in the Southern Hemisphere experienced marine heatwaves, starting in February, says Huang — among them, waters off Peru’s coast and in the Southern Ocean.Unusually warm waters bring particular stress for corals. Almost all coral regions are currently experiencing remarkably high temperatures, says Matthew England, a physical oceanographer at the University of New South Wales in Sydney, Australia. “What we’re seeing now for coral reefs is they’re getting pushed to extreme temps, and they don’t get to regrow because it doesn’t come back to cooler temperatures.”The last record-breaking ocean temperature year of 2016 coincided with an unusual global bleaching event for corals, only the third ever known to have happened. Bleached corals — which have expelled the algae that give them their colour — have poorer health, and many die.“It’s fairly likely that we can expect another global bleaching event this year,” says Christian Voolstra, who studies corals at the University of Konstanz in Germany. Even if an El Niño doesn’t settle in this year, he adds, it will come soon enough. “It’s bad news no matter what.”Heating planetWarm waters are also physically less capable of holding dissolved oxygen, adding to the stress for marine life. “With ocean warming and deoxygenation, the available habitats for many species are decreasing,” says William Cheung, a marine biologist at the University of British Columbia in Vancouver.And high ocean temperatures can trigger extreme weather. The unusually warm waters off Peru this year have helped to feed intense rainfall and Tropical Cyclone Yaku — the first such storm to hit the area in decades.The ocean temperature spike — recorded by NOAA and likely the highest in more than 100,000 years — coincides with other warming trends. For example, in the southern hemisphere, the sea ice extent hit a new all-time low in February 2023. The ocean absorbs about 90% of the extra heat in the climate system resulting from global warming. But because it takes more energy to heat water than air, the surface water temperature is rising more slowly than the surface air temperature is.“This wouldn’t have happened without climate change,” tweeted Jens Terhaar, an ocean biogeochemical modeller at the Woods Hole Oceanographic Institution in Massachusetts, in response to the news of the new temperature record. “We are in a new climate state, extremes are the new normal.” More

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    Ecology: correct the digital data divide

    Autonomous sensing devices and machine-learning algorithms are being used increasingly to track ecological health and dynamics over large scales with fine resolution. However, nature management and conservation are being compromised by inequitable access to these transformative technologies.
    Competing Interests
    The authors declare no competing interests. More

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    Tree diversity enhances soil carbon and nitrogen sequestration in natural forests

    26 April 2023

    Biodiversity experiments show that a high diversity of plants increases the accumulation of soil carbon and nitrogen, but whether such conclusions hold in natural ecosystems is debated. An analysis of Canada’s National Forest Inventory provides strong evidence that the build-up of soil carbon and nitrogen on a decadal timescale increased with improved tree diversity in natural forest ecosystems. More

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    Full closure of high seas would triple the benefits

    The new United Nations High Seas Treaty (see Nature; 2023) provides a path to generating conservation, economic and social-equity gains at global and national scales from a single policy change: close the high seas to fishing. The treaty requires only three-quarters of member countries to vote to establish a marine protected area, making all of these goals politically feasible.
    Competing Interests
    The author declares no competing interests. More

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    I explore my people’s sacred space to protect biodiversity

    As a deep-sea researcher at South Africa’s Department of Environmental Affairs, I lead marine research that helps the country to reach its ocean-sustainability goals, especially the establishment of marine-protected areas (MPAs). MPAs are like national parks, but in the ocean.To establish MPAs, we need to know what lives in them. I spend about half my time on the ocean, sampling species. Otherwise, I’m analysing data, planning expeditions and advising the minister on issues such as granting marine oil and gas permits.In this picture, I’m standing on the observer platform of our research vessel, the RV Algoa. As expedition chief scientist, I am responsible for the scientific crew.One area of continuing MPA research is Cape Canyon, off Western Cape. It’s a massive undersea system, up to 3 kilometres deep. We survey marine life there as a guide for where to establish MPAs.Our recent study (Z. Filander et al. Front. Mar. Sci. 9, 1025113; 2022) documented seabed-dwelling animals in Cape Canyon, including marine sponges, deep-water corals, a rare sea urchin (Dermechinus horridus) and an ancient sea star (Brisinga sp.). The canyon head of Cape Canyon has since been made into an MPA.My tribe, the amaBhaca of the Nguni people, has a strong tie with the ocean that began with our most-ancient ancestors. We go to the beach every New Year, but just to stand at the water’s edge. The ocean is a sacred space: we don’t interact with it.Some in my community viewed my work as disrespectful because I had not remained on the shore. I explained my research and why I do it to my community members — who are now excited by my work.As a Black and Indigenous female researcher who advises the government, I strive to ensure that marginalized communities’ perspectives are accurately represented. I address past injustices using ocean sciences as a vehicle for change. More