Global yields of wheat are around 10% lower now than they would have been without the influence of climate change, according to a new study.
The research, published in the Proceedings of the National Academy of Sciences, looks at data on climate change and growing conditions for wheat and other major crops around the world over the past 50 years.
It comes as heat and drought have this year been putting wheat supplies at risk in key grain-producing regions, including parts of Europe, China and Russia.
The study finds that increasingly hot and dry conditions negatively impacted yields of three of the five key crops examined.
Overall, global grain yields soared during the study period due to technological advancements, improved seeds and access to synthetic fertilisers.
But these yield setbacks have “important ramifications for prices and food security”, the study authors write.
Grain impacts
Most parts of the world have experienced “significant” yield increases in staple crops since the mid-20th century.
The new study notes that, in the past 50 years, yields increased by 69-123% for the five staple crops included in the research – wheat, maize, barley, soya beans and rice.
But crop production is increasingly threatened by climate change and extreme weather. A 2021 study projected “major shifts” in global crop productivity due to climate change within the next two decades.
Earlier this year, Carbon Brief mapped out news stories of crops being destroyed around the world by heat, drought, floods and other weather extremes in 2023-24. Maize and wheat were the crops that appeared most frequently in these reports.
Hot and dry weather is currently threatening wheat crops in parts of China, the world’s largest wheat producer, Reuters reported this month.
In the UK, wheat crops are struggling amid the “driest start to spring in England for almost 70 years”, the Times recently reported. Farm groups say some crops are already failing, the Guardian said.
As a result, global wheat supplies are “tight”, according to Bloomberg, with price rises possible depending on weather conditions in parts of Europe, China and Russia.
Food security and prices
The study uses climate datasets, modelling and national crop statistics from the UN Food and Agriculture Organization to assess crop production and climate trends in key grain-producing countries over 1974-2023, including Argentina, Brazil, Canada, China, the EU, Russia and the US.
The researchers assess climate observations and then use crop models to calculate what yields would have been with and without these climate changes.
For example, “if it has warmed 1C over 50 years and the model says that 1C leads to 5% yield loss, we’d calculate that the warming trend caused a loss of 5%”, Prof David Lobell, the lead study author and a professor at Stanford University, tells Carbon Brief.
The study looks at two reanalysis climate datasets that include information on temperature and rainfall over the past 50 years: TerraClimate (TC) and ERA5-Land. (Reanalysis data combines observations with a modern forecasting model.)
The researchers find that yields of three of the five crops are lower than they would have been without warmer temperatures and other climate impacts in the past 50 years.
Yields were lower than they otherwise would have been by 12-14% for barley, 8-12% for wheat and 4% for maize.
The impacts on soya beans were less clear as there were “significant differences” between data sources. But both datasets show a negative impact on yields, ranging from 2% to 8%.
The effects on rice yields were inconclusive, with one dataset showing a positive effect of around 1% while the other showed a negative effect of about 3%.
The chart below shows the estimated yield impacts for each crop based on the calculations from the two climate datasets.
Given soaring overall crop yields during this time, impacts of 4-13% “may seem trivial”, the researchers write. But, they say, it can have “important ramifications for prices and food security” given growing food demand, noting:
“The overall picture of the past half-century is that climate trends have led to a deterioration of growing conditions for many of the main grain-producing regions of the world.”
Water stress and heat
The study also assesses the impacts that warming and vapour pressure deficit – a key driver of plant water stress – have on crop yields.
Vapour pressure deficit is the difference between the amount of water vapour in the air and the point at which water vapour in the air becomes saturated. As air becomes warmer, it can hold more water vapour.
A high deficit can reduce plant growth and increase water stress. The models show that these effects may be the main driver of losses in grain yield, with heat having a more “indirect effect”, as higher temperatures drive water stress.
The study finds that vapour pressure deficit increased in most temperate regions in the past 50 years.
The researchers compare their data to climate modelling simulations covering the past 50 years. They find largely similar results, but notice a “significant underestimation” of vapour pressure deficit increases in temperate regions in most climate models.
Many maize-growing areas in the EU, China, Argentina and much of Africa have vapour deficit trends that “exceed even the highest trend in models”, they write.
The researchers also find that most regions experienced “rapid warming” during the study period, with the average crop-growing season now warmer than more than 80% of growing seasons 50 years ago.
The findings indicate that, in some areas, “even the coolest growing season in the present day is warmer than the warmest season that would have occurred 50 years ago”.
An exception to this is in the US and Canada, they find, with most maize and soya bean crop areas in the US experiencing lower levels of warming than other parts of the world and a “slight cooling” in wheat-growing areas of the northern Great Plains and central Canada.
(The central US has experienced a cooling trend in summer daytime temperatures since the middle of the 20th century, according to the National Oceanic and Atmospheric Administration. There are many theories behind this “warming hole”, which has continued despite climate change.)
CO2 greening
Dr Corey Lesk, a postdoctoral researcher at Dartmouth College who studies the impacts of climate on crops, says these findings are in line with other recent estimates. He tells Carbon Brief:
“There are some uncertainties and sensitivity to model specification here – but it’s somewhat likely climate change has already reduced crop yields in the global mean.”
The study’s “main limitation” is that it is “behind” on including certain advances in understanding how soil moisture impacts crops, Lesk adds:
“Moisture changes and CO2 [carbon dioxide] effects are the largest present uncertainties in past and future crop impacts of climate change. This paper is somewhat limited in advancing understanding on those aspects, but it’s illuminating to pause and take stock.”
The research looks at whether the benefits of CO2 increases during the past 50 years exceed the negative effects of higher levels of the greenhouse gas.
Rising CO2 levels can boost plant growth in some areas in a process called “CO2 fertilisation”. However, a 2019 study found that this “global greening” could be stalled by growing water stress.
Yield losses for wheat, maize and barley “likely exceeded” any benefits of CO2 increases in the past 50 years, the study finds.
The opposite is true for soya beans and rice, they find, with a net-positive impact of more than 4% on yields.
Climate science has “done a remarkable job of anticipating global impacts on the main grains and we should continue to rely on this science to guide policy decisions”, Lobell, the lead study author, says in a press release.
He adds that there may be “blind spots” on specialised crops, such as coffee, cocoa, oranges and olives, which “don’t have as much modelling” as key commodity crops, noting:
“All these have been seeing supply challenges and price increases. These matter less for food security, but may be more eye-catching for consumers who might not otherwise care about climate change.”
The post Global wheat yields would be ‘10%’ higher without climate change appeared first on Carbon Brief.
Global wheat yields would be ‘10%’ higher without climate change
As an extreme El Niño breaks marine temperature records, COP31 is set to boost the profile of the ocean’s role in solving climate change, but finance and clear conservation measures will be needed for it to move the needle, experts said.
The Turkish presidency has announced plans for an Antalya Ocean Declaration that recognises the centrality of the global ocean – the world’s largest carbon sink – in regulating the climate and minimising the now unavoidable overshoot of global temperatures above 1.5C over pre-industrial levels.
Meanwhile, as part of the formal UN negotiations, Australia has announced plans to land a cover decision in Antalya, which, according to veteran former US negotiator Sue Biniaz, would be the only section of the formal negotiations where the role of oceans could be included.
She added that an outcome at COP31 seems likely, given the initiative from both presidencies and a push from over 100 countries – including Brazil, the EU and the African Group of countries – calling for the UN negotiations to deliver a plan for implementing ocean measures.
Governments will arrive in Antalya with a “super El Niño” adding stress to marine ecosystems and expected to continue to intensify until December 2026, with parts of the Pacific averaging almost 30C (86F) – over 3C more than normal – in October, according to monthly EU sea temperature data.
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Needs for ocean conservation and funding
While elevating the ocean agenda is “critical”, it must lead to funding for ocean conservation and a clear plan for reaching the global target – set at UN biodiversity talks in 2022 – of protecting 30% of the global ocean by 2030, said Pradeep Singh, senior ocean governance expert at Oceano Azul Foundation.
The ocean is precisely where governments are farthest off track from meeting this target – informally known as the 30×30 goal. Even if countries meet all their nature conservation plans, only about 12% of the global ocean would be protected, the UN says.
“Acknowledgment of marine protected areas and the 30×30 target as climate infrastructures will certainly boost efforts and funding for science and management,” Singh told Climate Home News.
Shamini Selvaratnam, director of international climate and clean energy at Ocean Conservancy, said an ocean commitment that makes a difference in coastal communities “takes funding, local capacity and support that countries can actually access”.
An analysis by climate think tank Zero Carbon Analytics shows that investment in the blue economy – through activities like sustainable fisheries or cleaner shipping – is only at about 2% of the needs, which are estimated at $550 billion per year.
Following-through on commitments
Selvaratnam added that countries must also establish mechanisms to follow through on these measures, which currently only exists in the form of a non-binding dialogue that is not expected to produce any negotiated agreements.
She said that countries at COP31 must find ways for their ocean commitments to inform the next global stocktake, the UN’s five-yearly review of progress on climate action. Some countries – including African countries, Latin American nations, small island states and the European Union – have backed a process that culminates in the next global stocktake.
At climate negotiations, countries are not mandated to include ocean conservation measures in their climate plans. But a group of countries led by France and Brazil is pushing them to do so voluntarily through an initiative called Blue NDC Challenge. Seventeen countries have joined the initiative so far.
In its list of COP31 priorities, the EU has called for the “critical role” of oceans to be recognised, but falls short of calling for any specific actions to feature marine action more prominently in climate plans.
As part of their demands, ocean campaign groups have called for the establishment of an “Antalya Ocean Compact”, a platform where countries can coordinate efforts across different environmental treaties, including the UN climate, biodiversity and high seas negotiations.
Ultimately, Selvaratnam said a strong deal “must accelerate emissions cuts, clean energy, and a transition away from fossil fuels, including offshore oil and gas”.
Ilana Seid, chair of the AOSIS group of small island states and permanent representative of Palau to the UN, said during a press briefing last week that “meaningful progress” on emissions reduction is “the best way” to alleviate stress on the ocean.
The post ‘Blue COP31’ set to spotlight need for ocean protections amid record heat appeared first on Climate Home News.
‘Blue COP31’ set to spotlight need for ocean protections amid record heat
In the wake of its recent glacial flooding disaster, Nepal and the kingdom of Bhutan have proposed a new agenda item on mountains and climate change for the COP31 summit which opens on Monday in the Turkish city of Antalya.
In a submission addressed to the COP31 presidency and the head of the UN climate secretariat (UNFCCC), Nepal said the agenda item, entitled “1.5°C Warming in Mountains”, is an effort to strengthen the response of the international community to the climate risks facing the world’s mountain regions.
The item proposes that mountain issues should become a regular part of the formal UN climate change process, with a focus on scientific assessment of the risks associated with warming overshooting 1.5C, an annual high-level dialogue, a dedicated work programme and improved access to climate finance.
Maheshwar Dhakal, chief of the climate change management division of Nepal’s Ministry of Agriculture, Forests and Environment, told Climate Home News that Himalayan countries face similar problems such as collapsing glaciers and flooding from glacial lakes.
“We are trying to bring all Himalayan countries together under this agenda item,” he said.
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At this year’s UN General Assembly, Nepal’s Prime Minister Balendra Shah called for strong global action to ensure climate justice and proposed creating a Himalayan Climate Resilience Mechanism led by India, China and Nepal. It would share satellite data, monitor glacial slopes and lakes, strengthen early warning systems and coordinate cross-border disaster response.
Nepal has experienced significant infrastructure losses and human casualties from flooding every year since 2020. In late August, the collapse of a glacial slope on the border with Tibet caused a torrent of water and debris to course down the Bhote Koshi River, leaving more than 6,000 people dead or missing.
According to a government needs assessment, the disaster caused an estimated $2.7 billion in physical damage and economic losses, while around $4.8 billion will be required for recovery and reconstruction.
More research needed on threats
Although high mountain regions are known to be fragile ecosystems, especially as global warming accelerates glacier melt, the extent of their vulnerability is still not fully understood. When the devastating Bhote Koshi floods hit, it opened the eyes of the world to the risks.
Dhakal said the Bhote Koshi floods “have proved the impacts of climate change in the Himalayan region”, which were linked to rising temperatures by scientists with the World Weather Attribution group. “Therefore, Nepal wants scientific studies, research and political discussions on mountain climate risks to receive greater attention at international climate conferences,” he added.
Nepal has been making efforts on this front since 2009, when it held a cabinet meeting at Kalapatthar near Mount Everest. Since COP28 in Dubai, Nepal has organised high-level events and dialogues on mountain issues at COPs and is co-hosting one at COP31 with Bhutan, Pakistan, Kyrgyzstan and Tajikistan.
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Dhakal said the dialogues held so far have raised awareness, but mountain concerns must become part of the formal UN climate process to unlock climate finance and technical support that can bolster countries’ capacity to tackle climate threats.
If specific indicators and priorities are developed for mountain regions, vulnerable developing countries like Nepal would have better access to finance to help them adapt to the climate warming they have done very little to cause, he added.
More detailed data would enable them to prepare stronger project proposals for international climate funds, including the Green Climate Fund (GCF). In 2025, the GCF backed a project to protect livelihoods from climate-induced flooding in Nepal but it took seven years to get approval.
Sindhu Dhungana, an alternate board member at the GCF, said the problem is becoming more widespread and urgent for the Hindu Kush Himalaya region.
“The economies, cultures and almost everything in Himalayan countries depend on mountains,” he explained. “For us, climate change is mountain change… [it has] affected everything, including the economy and biodiversity.”
Destroyed development projects
Nepal wants the UN climate process to address mountain risks both before and after disasters. Countries need better research, technology, early warning systems and other adaptation measures to protect people and infrastructure. But even when countries take precautions, loss and damage is likely to occur and will require international support to address it.
Nepal has been provisionally allocated $21.6 million from the United Nations’ new Fund for Responding to Loss and Damage (FRLD) to help with the aftermath of the Bhote Koshi disaster, but this is just a fraction of needs and the money will come only months after it made an initial request.
Dhakal pointed to the damage caused by floods to infrastructure built with loans, such as the Melamchi Drinking Water Project, which received $312 million from the Asian Development Bank but was destroyed by a major flood in 2021, shortly after it began operating. The recent Bhote Koshi disaster wiped out a dozen hydropower facilities, as well as solar energy systems.
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Nepal wants international discussions on what should happen when climate-related disasters destroy development projects built using credit, and how the loans should be treated afterwards.
“Climatic disasters wash out… projects, but the burden of loan is still paid by Nepal,” Dhakal said.
For now, it remains unclear whether the opening session of COP31 will consider or adopt the proposed agenda item on mountains and climate change, with consultations on how to respond still underway among governments and the COP31 co-presidencies.
“If countries agree to discuss the proposal and include it in the agenda, that would be another step forward,” Dhakal said. “Further discussions in the coming years could gradually give the mountain agenda a stronger shape.”
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Nepal seeks stronger recognition of mountain issues in UN climate process