This week's short reads.

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Spraying rice with sunscreen particles during heatwaves boosts growth

Zinc nanoparticles, a common sunscreen ingredient, can make plants more resilient to climate change – in a surprising way

By James Dinneen

4 November 2024

Spraying rice with sunscreen particles during heatwaves boosts growth

Zinc nanoparticles, a common sunscreen ingredient, can make plants more resilient to climate change – in a surprising way

By James Dinneen

4 November 2024

 

Sunrise over rice terraces in Bali, Indonesia

Aliaksandr Mazurkevich / Alamy

 

A common sunscreen ingredient, zinc nanoparticles, may help protect rice from heat-related stress, an increasingly common problem under climate change.

Zinc is known to play an important role in plant metabolism. A salt form of the mineral is often added to soil or sprayed on leaves as a fertiliser, but this isn’t very efficient. Another approach is to deliver the zinc as particles smaller than 100 nanometres, which can fit through microscopic pores in leaves and accumulate in a plant.

Researchers have explored such nanoparticles as a way to deliver more nutrients to plants, helping maintain crop yields while reducing environmental damage from using too much fertiliser. Now Xiangang Hu at Nankai University in China and his colleagues have tested how zinc oxide nanoparticles affect crop performance under heatwave conditions.

 

They grew flowering rice plants in a greenhouse under normal conditions and under a simulated heatwave where temperatures broke 37°C (98.6°F) for six days in a row. Some plants were sprayed with nanoparticles and others weren’t treated at all.

When harvested, the average grain yield of the plants treated with zinc nanoparticles was 22.1 per cent greater than the plants that hadn’t been sprayed, and this rice also had higher levels of nutrients. The zinc was also beneficial without heatwave conditions – in fact, in these cases, the difference in yield between treated and untreated plants was even greater.

 

Based on detailed measurements of nutrients in the leaves, the researchers concluded that zinc boosted yields by enhancing enzymes involved in photosynthesis, as well as antioxidants that protect the plants against harmful molecules known as reactive oxygen species.

“Nanoscale micronutrients have tremendous potential to increase the climate resilience of crops by a number of unique mechanisms related to reactive oxygen species,” says Jason White at the Connecticut Agricultural Experiment Station.

The researchers also found that rice treated with zinc nanoparticles maintained more diversity among the microbes living on the leaves – called the phyllosphere – which may have contributed to the improved growth.

Tests of zinc oxide nanoparticles on plants like pumpkin and alfalfa have also shown yield increases. But Hu says more research is needed to verify this could benefit other crops, such as wheat.

 

Journal reference

Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.2414822121

 

 

Any delay in reaching net zero will influence climate for centuries

Reaching net-zero emissions is essential for halting climate change - but even after we achieve this goal, parts of the planet will continue to warm. Delaying net zero will worsen these effects

By Madeleine Cuff

11 November 2024

Ice collapsing into the water at Perito Moreno Glacier in Los Glaciares National Park, Argentina

R.M. Nunes/Alamy

 

Even a few years’ delay in reaching net-zero emissions will have repercussions for hundreds or even thousands of years, leading to warmer oceans, more extensive ice loss in Antarctica and higher temperatures around the world.

Nations around the world have collectively promised to prevent more than 2°C of global warming, a goal that can only be achieved by reaching net-zero emissions – effectively ending almost all human-caused greenhouse gas emissions – before the end of the century. But once that hugely challenging goal is achieved, the planet will keep warming.

 

“Even if we do reach net-zero emissions – and that has to be a goal – we still have lots of aspects of the climate that are going to evolve for a very long time,” says Andrew King at the University of Melbourne.

Climate modellers are using a new generation of models that capture the way carbon is absorbed and released by land and the ocean to simulate how Earth’s systems might respond to a stable net-zero emissions world.

Most of these experiments simulate a net-zero world for around 100 years, but King and his colleagues have gone further, simulating 1000 years of net-zero emissions.

 

The team modelled scenarios in which emissions continue to rise rapidly before reaching net zero at five-year intervals from 2030 to 2060. This resulted in seven simulations of net zero under different levels of warming. They found that although warming over land stabilises once net zero is achieved, the deep ocean continues to warm for centuries to come, as heat from surface waters descends, pushing up global mean temperatures.

“The unfortunate thing is that we have changed the climate, and in some aspects it is going to keep going further and further away from its pre-industrial state for quite a long time, even under net zero,” says King.

Certain parts of the world will experience more ongoing change than others. In the northern hemisphere, most land regions reach peak warming within a few centuries of net-zero emissions being reached.

 

By contrast, the Southern Ocean continues to warm for 800 to 900 years. This leads to a long-term decline in Antarctic sea ice over the centuries, and more warming in Australia than elsewhere.

The later we achieve net zero, the larger these changes will be, suggest the simulations. Delaying net zero by just five years results in a warmer ocean, lower levels of sea ice and higher average temperatures around the world. For example, if net-zero emissions are reached in 2060, under a high-emissions scenario, the city of Melbourne will warm by a further 1°C after that point.

“If we equivocate or delay in reaching net zero, it will take a long time for that delay to be washed out,” says King. “The faster we get to net zero, the better.”

While some aspects of the climate system will keep changing after net zero, others appear to return to a pre-industrial “normal” in the simulations. In some areas, such as the Mediterranean, rainfall patterns return quickly to 19th-century levels. The El Niño and La Niña weather patterns, which have seen their heating and cooling effects strengthened by climate change, will also damp down again once we reach net zero.

Much more research is needed into these kinds of regional change under net zero, says King, who cautions that the results are based on just one Earth system model. Plus, the findings may not factor in every relevant climate “tipping point” that could trigger sudden, irreversible changes to regional climate systems at a certain level of warming.

 

Nevertheless, Paulo Ceppi at Imperial College London says the results may enhance our understanding of how net-zero emissions will change regional climates. “I am sure there are some aspects here that would be robust across models,” he says.

An important thing to keep in mind is that the simulations aren’t direct predictions of a net-zero emissions future. For one, the model simulated emissions being cut from high levels down to zero overnight, rather than a more realistic tapering down over decades. “It’s completely unrealistic to go to net zero overnight,” says Ceppi.

Meanwhile, the simulations assume the world stays at net-zero emissions. Climate campaigners hope that once humanity achieves net zero, there will be an effort to remove even more carbon dioxide from the atmosphere to start reversing some climate impacts.

 

Journal reference

Earth System Dynamics DOI: 10.5194/esd-15-1353-2024

 

 

2024 is set to be the first year that breaches the 1.5°C warming limit

This year’s average global temperature is almost certain to exceed 1.5°C above pre-industrial times – a milestone that should spur urgent action, say climate scientists

By Madeleine Cuff

6 November 2024

Firefighters work to control a blaze in California in July

ABACA/Shutterstock

 

2024 is now almost certain to become the first year on record when average temperatures exceed 1.5°C above pre-industrial levels, breaching the threshold set by the Paris Agreement.

“At this point, barring an asteroid impact or a massive volcanic eruption… I think it’s safe to say this will be the first year above 1.5 degrees,” says Zeke Hausfather at US non-profit Berkeley Earth.

 

Last year, the average surface temperature across the globe was 1.45°C above the 1850-1900 average, which is used as the pre-industrial baseline, with a margin of error of 0.12°C, according to the World Meteorological Organization. It uses an average of five major datasets to arrive at this figure.

For the first eight months of 2024, the average temperature surpassed that for the same month in 2023, says the US National Oceanic and Atmospheric Administration. The average for this period was 1.54°C above pre-industrial levels, according to data from the Met Office, the UK’s weather service.

Although the average for September was cooler than at the same time last year, there is little doubt that 2024 as a whole will exceed the global target for the first time. “It would take quite a notable and unusual cooling event to bring the annual average below 1.5°C,” says Colin Morice at the Met Office.

 

Temperature datasets collected by various agencies and institutions around the world vary slightly, mainly due to differences in how ocean temperatures have been collected and analysed over the decades.

But the five main datasets are set to indicate 2024 temperatures settled around 1.5°C above pre-industrial times, with several just above this mark, says Hausfather. “While not all of the datasets are going to be above 1.5°C this year, it is going to be the first year where the average… is above 1.5°C,” he says.

The primary driver of rising global temperatures is human-caused climate change, says Carlo Buontempo at Copernicus, the European Union body that monitors climate. “This is not coming out of the blue,” he says. “The main driver for this warming is increasing greenhouse gas in the atmosphere.” A recent, strong El Niño pattern – the Pacific Ocean phenomenon that generally brings higher global temperatures – is another significant factor.

But the scale and persistence of the heat has shocked many experts, who expected temperatures to subside once El Niño ended in May 2024. Instead, the record-breaking heat continued well into the second half of the year, puzzling scientists.

Competing explanations abound. The sun reached a so-called solar maximum in 2024, slightly increasing the solar radiation hitting Earth. Meanwhile, changes to shipping pollution rules in 2020 have reduced air pollution over the world’s oceans, potentially magnifying heat absorption from the sun as certain pollutants are known to have a cooling effect.

But research into the impacts of these factors is still inconclusive, says Piers Forster at the University of Leeds, UK. “We do not completely understand why this extra spike in surface temperatures has continued,” he says.

He warns it may be that the rate of climate change has accelerated. “If you just look at historical temperature changes, they do not increase in a monotonic way – they seem to go in fits and starts,” he says.

The world has already experienced a 12-month period above 1.5°C of warming, with temperatures between July 2023 and June 2024 1.64°C above pre-industrial levels, according to Copernicus.

 

Nevertheless, the passing of the 1.5°C threshold in one calendar year is a totemic moment for the climate community. The limit has become a guiding light for it, after being included as a “stretch goal” in the 2015 Paris Agreement.

Yet years of failure to cut global emissions have made a breach almost inevitable, despite research since 2015 showing warming beyond 1.5°C would be far more dangerous than first thought.

However, a single year above 1.5°C of warming will not count as a breach of the Paris Agreement – which is judged on a 30-year average. On that basis, most climate models expect the 1.5°C threshold to be exceeded at some point in the early 2030s, unless the world makes immediate, dramatic cuts to emissions.

Nevertheless, Hausfather hopes 2024 will underscore how fast the world is changing due to human activities. “Hopefully it will serve as a wake-up call for policymakers, and then history will look back on it as the year when the world changed and started finally taking this problem as seriously as it deserves,” he says.

Forster echoes this sentiment, arguing it should spur leaders into taking action to cut real world emissions and adapting societies to prepare for future climate change. “I want to try as much as possible to connect this passing of 1.5°C with what we have to do to protect our society from the impacts of climate change,” he says.