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
The US is expected to resume its attempt to sink measures for a greener global shipping sector at closed-door talks between governments at the International Maritime Organization (IMO) in early September.
The US and oil-producing allies like Saudi Arabia want to weaken a proposed plan for cleaner fuels that aims to reduce planet-heating emissions from the industry, which relies heavily on dirty bunker fuels. Shipping currently represents 3% of global emissions.
Those that want a softer system are likely to back a Liberian proposal which expert analysis suggests would see emissions fall by only half at most by 2050, far short of the sector’s agreed climate goals.
After several years of debate, governments provisionally agreed in April 2025 on the “Net Zero Framework” (NZF), a series of emissions reduction targets for shipowners, backed up with financial rewards for meeting the targets and fees for missing them.
But in October 2025, after a high-profile intervention from US President Donald Trump and threats of sanctions and visa restrictions, the US convinced a majority of voting nations to postpone the adoption of the NZF for a year.
Ralph Regenvanu, climate minister for the Pacific nation of Vanuatu, called the delay “unacceptable” given the urgency of accelerating climate change.
After a round of low-profile talks in May, the first of three further sets of talks on how to clean up shipping will begin at the IMO’s riverside headquarters in London on Tuesday, culminating in a final public session in November.
Em Fenton, who follows the talks as senior director of climate diplomacy at Opportunity Green, an NGO focused on aviation and shipping, said governments should not be sidetracked by alternative proposals to the NZF, calling them “a distraction from a hard-fought multilateral compromise”.
“If countries want to deliver a just and fair maritime transition, there is really only one choice: back the NZF and stand together in solidarity against those who would tear it apart,” Fenton added.
Five proposals on the table
Governments will discuss five different proposals submitted in advance of next week’s meeting. The most ambitious of these is from the Pacific island nation of Tuvalu, which has proposed a levy on the entirety of a ship’s emissions rather than just those above a certain level, as the NZF envisions.
That had been the original demand of Pacific nations before the NZF was provisionally adopted in April 2025. At the time, Tuvalu’s transport minister Simon Kofe described the NZF as disappointing and not ambitious enough.
For this reason, six Pacific countries abstained in the vote on the NZF. While they supported the original plan for its adoption in October 2025, they have used the delay to push again for more ambition.
John Kautoke, advisor to a group of Pacific nations called 6PAC+, told Climate Home News that the NZF “cannot diminish its already inadequate ambition. If anything, the NZF must increase in ambition if we are going to renegotiate its parameters.”
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Analysis by the Institute of Marine Engineering, Science and Technology (IMarEST) suggests that, of the five proposals, only Tuvalu’s would meet the 2030 and 2040 emissions reduction targets for global shipping that were agreed by governments in 2023. Those were for cuts of 20% between 2008 and 2030, 70% by 2040 and then reaching net zero “by or around, i.e. close to 2050”.
Despite this, the UK, Australia, Canada and South Africa have formally proposed that governments adopt the NZF, which won support in a 63-13 vote among governments at the April 2025 talks. Trump’s US walked out halfway through.
According to IMarEst’s analysis, while the NZF proposal will not be enough to meet the industry’s targets, it will reduce emissions more cheaply than the Pacific proposal.
A proposal by Brazil – which fought hard for the NZF last October – suggests tweaking the framework to make meeting targets easier in the short term and harder in the long term.
While this compromise will make it more appealing to the owners of polluting ships and countries that support them, IMarEst estimates it would lead to higher cumulative emissions than either the NZF or Pacific proposals.
The NZF stipulates that fees for high-polluting shipowners should be be put into a Net Zero Fund and used to promote clean shipping fuels and a fairer transition. The Brazilian proposal would delay raising and spending these funds by two years, from 2029 to 2031.
Liberia’s proposal weakens emissions cuts
The US and Saudi Arabia are likely to swing behind a new proposal from Liberia, whose government makes millions of dollars a year selling the right for shipowners to register their vessels in the small West African nation via a US-based company.
This proposal would weaken the emissions reduction targets. IMarEst says it would cut the industry’s emissions at most by a half by 2050, falling far short of the target agreed in 2023 for international shipping to reach net zero “close to 2050”.
It would also replace the NZF’s fees for missing targets with a carbon trading system. As a result, there would be no Net Zero Fund and therefore less money available to incentivise green fuels and make the transition more equitable for poorer nations.
Pacific advisor Kautoke said that, as well as preventing shipping from reaching zero emissions by 2050, Liberia’s proposal would mean the Pacific “will not receive any support to deal with the disproportionately negative impacts created by the cost of the transition”.
“We get a double blow if we adopt the Liberian proposal,” he warned. “We get all the cost of a transition without any support, and we have an industry that continues to burn fossil fuels to an unforeseen point.”
Japanese proposal favours shipowners
Japan has submitted a late proposal to amend the NZF so that shipowners have more control over how the fees they would pay for emitting above a set threshold are spent.
University College London professor Tristan Smith has argued that this change means there will be no central mechanism to incentivise investments in clean fuels. He wrote on LinkedIn that under the system put forward by Japan, shipowners would be able to select which green projects their fees would go to. They could choose their own or those of a sister company or other shipowners, rather than funding broader just transition projects that would benefit marine workers or developing countries hit by rising shipping costs.
Despite its flaws, Smith added that Japan’s proposal “could still get taken seriously by some, given how appealing it may seem to shipowners who have consistently demanded control of revenues, and given how the US and other member states have pushed back against the IMO Net Zero Fund and [greenhouse gas] pricing.”
Tacit or explicit approval?
Next week, governments are expected to make statements saying which proposals – or which aspects of proposals – they prefer. Another set of talks will be held from November 23-27 before a potentially final round from November 30-December 4.
A new framework to tackle shipping emissions could be adopted at those talks if two-thirds of countries that are present and signed up to a regulation called Marpol Annex VI – endorsed by just over 100 states – vote in favour of it, as they did in April 2025.
The US and its allies are also trying to change the rules to make the next stage more difficult. Decisions that have been adopted at IMO meetings usually take effect automatically unless a certain number of countries object within a certain time period decided by governments, a system known as tacit approval.
But the US wants that to require explicit approval instead, so that any new emissions standard would not come into force unless enough governments – representing a certain percentage of the world’s shipping fleet – actively indicate support for it.
Critics say this change would give a small number of countries with large shipping registries the power to block implementation. Liberia has the world’s biggest shipping registry, run by an American company, followed by Panama and the Republic of the Marshall Islands.
Liberia and Panama have supported the US at the talks on the Net Zero Framework. The Marshall Islands has long been one of the most vocal supporters of climate action in shipping but, with its officials and shipping registry income vulnerable to US retaliation, did not sign on to the recent Pacific proposal vowing to strengthen the NZF if it is re-opened.
Brazilian negotiator Adriana de Medeiros Gabinio warned in April that the NZF’s opponents are trying to change the rules by which it comes into force as a “safety net to block” it.
The post Battle over cleaning up shipping set to resume at London talks appeared first on Climate Home News.
Battle over cleaning up shipping set to resume at London talks
SYDNEY, Wednesday 26 August 2026 — New 2026 Sustainability Reports released by supermarket giants Coles and Woolworths this week demonstrate the retailers are failing on their commitments to end deforestation in their supply chains.
Adele Chasson, Nature Policy Lead at Greenpeace Australia Pacific said:
“These so-called sustainability reports are revealing. Despite their public commitments in 2024 and 2025, neither Coles nor Woolworths have taken deforestation-linked beef off their shelves. Meanwhile, bulldozers continue to tear up forests and bushland, pushing wildlife closer to extinction and causing mass toxic runoff to flow into the Great Barrier Reef. Millions of native animals like koalas are losing their homes to beef pastures each year, while the big supermarkets put off action.
“Australians would be shocked to know that beef on the shelves of our biggest supermarkets could be pushing threatened species to the brink of extinction. Collectively Coles and Woolworths have made more than $2 billion in profits in the last year, profiting from the destruction of wildlife and precious Australian nature. Coles and Woolworths owe it to shoppers to deliver on their promises and end deforestation in their supply chains now.
“As big beef buyers, Coles and Woolworths have an essential role to play in keeping Australia’s unique forests standing. They can help stop the Great Barrier Reef from being poisoned by runoff and protect iconic forest wildlife by taking deforestation off their shelves. It’s time these big companies put their money where their mouths are and follow through on their promise of sourcing and supplying deforestation-free beef.”
New Zealand’s parliament has adopted a controversial new law blocking a whole avenue of climate litigation and shutting down its most advanced corporate lawsuit, which has been blamed by the government for shaking business confidence and investment.
The Climate Change Response (Tort Liability) Amendment Bill, expected to take effect in the coming days after it is formally signed by the Governor-General, prevents all current and future civil claims for climate loss or harm under tort law.
Justice minister Paul Goldsmith said last week that the aim was to give businesses “certainty around their climate change obligations”, noting it would not alter the government’s responsibilities under the Climate Change Response Act 2002 nor business obligations under the Emissions Trading Scheme.
“Our response to climate change is best managed by the Government at a national level and not through piece-meal litigation in the courts,” he added in a statement.
Such litigation, he said, “risks developing a new regime that contradicts the framework Parliament has already enacted” to tackle climate change.
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Goldsmith singled out a key domestic climate lawsuit brought by Northland iwi leader and activist Mike Smith against six big companies: dairy firms Fonterra and Dairy Holdings, energy firms Genesis Energy and Z Energy, New Zealand Steel and coal mining firm BT Mining. A seventh original defendant, Channel Infrastructure, was dropped after it permanently decommissioned its Marsden Point oil refinery.
Smith argued that these companies had caused him harm under public nuisance and negligence law, as well as a third breach of a duty to cease contributing to climate change that has yet to be tested domestically. He did not seek financial compensation, instead asking for the companies to immediately stop emitting or contributing to net greenhouse gas emissions.
In one of the most advanced corporate climate accountability lawsuits in the world, a trial had been scheduled for April 2027 after the Supreme Court unanimously allowed the case to continue.
Corporate lobbying in the shadows
Smith described the passing of the bill as “deeply concerning”, particularly as it coincided with the Supreme Court hearing another of his climate lawsuits. In that case, Smith v Attorney-General, he argues that the government’s response to climate change and its impacts on Māori communities in particular breaches rights to life and culture.
“That timing raises profound questions about the separation of powers and the rule of law,” said Smith. “Whatever one’s view of the merits of these cases, it is deeply troubling when parliament intervenes to remove a legal pathway while the courts are actively considering fundamental questions about climate responsibility, rights and the crown’s obligations.”
The bill – which says that no person (including the government) can be found liable in tort for emissions-related climate change effects – followed major lobbying efforts by the companies defending themselves in Smith’s lawsuit. They outlined a proposed legal amendment in a briefing note to the government in 2024.
The centre-right government has been fiercely criticised over its lack of transparency in relation to this lobbying activity. The national ombudsman recently found that the Prime Minister’s Office effectively withheld information requested by the Environmental Law Initiative about meetings, discussions and conversations regarding Smith’s case.
Green groups fail to stop bill
The bill sparked huge concern among environmental campaigners in New Zealand and elsewhere. Greenpeace Aotearoa called it a “shocking abuse of executive power” and the vast majority of submissions to a parliamentary inquiry said it should be rejected.
But in the end, it was adopted with little resistance, moving relatively smoothly through parliament, passing its third reading by 67 votes to 53. Sam Bookman, climate law lecturer at Melbourne Law School, told Climate Home News he was not surprised by this, given that the coalition government has a secure majority.
A complaint has been made to the UN special rapporteur on climate change and human rights by Smith, the National Iwi Chairs Forum Pou Tikanga and youth coalition Climate Clinic Aotearoa over what they see as the government’s heavy-handed approach. Smith is also challenging the new law in yet another lawsuit.
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Bookman thinks it “very unlikely” that such a challenge will succeed, noting that New Zealand’s constitution is firmly anchored in parliamentary sovereignty.
But the expert in climate law does not see the bill as the end of legal action in the country, noting that New Zealand has a “sophisticated climate litigation landscape with a growing number of specialist and experienced lawyers and NGOs”.
The country is also approaching its next general election in November, and some opposition parties have pledged to restore access to the courts if elected.
Amanda Larsson, global project lead on agriculture for Greenpeace International, said: “This law deserves to be tested, and I strongly encourage the international climate litigation community to unite and help defend New Zealanders’ fundamental right to hold polluters accountable before this becomes a global blueprint.”
Copycat legislation on the rise
New Zealand’s move is part of a small but growing legislative effort to shut down climate litigation around the world.
In the US, Republican politicians introduced legislation in the House and Senate in April that would shield fossil fuel firms from climate liability lawsuits. Similar laws have already been passed at state level in Tennessee, Utah, Iowa and Louisiana.
The German state of Bavaria has put forward a similar proposal to the Federal Council, aiming to block private climate claims as well as the recognition and enforcement of foreign judgments imposing such liability. There are also proposals to limit available remedies and actions in the Netherlands and Belgium.
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Bookman said he expects more efforts to counter climate damages litigation and advised plaintiffs to think about how to respond, including drawing on broader support in opposing them.
“Even though it’s very hard for plaintiffs to win these types of cases, companies are very eager to avoid the expense, embarrassment and political accountability that come even with unsuccessful lawsuits,” he said.
The post New Zealand moves to protect business with law curtailing climate litigation appeared first on Climate Home News.
New Zealand moves to protect business with law curtailing climate litigation
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