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Hundreds of scientists in dozens of institutions are embarking on the next phase of the world’s largest coordinated climate-modelling effort.

Climate-modelling groups use supercomputers to run climate models that simulate the physics, chemistry and biology of the Earth’s atmosphere, land and oceans.

These models play a crucial role in helping scientists understand how the climate is responding as greenhouse gases build up in the atmosphere.

For four decades, the Coupled Model Intercomparison Project (CMIP) has guided the work of the climate-modelling community by providing a framework that allows for millions of results to be collected together and compared.

The resulting projections are used extensively in climate science and policy and underpin the landmark reports of the Intergovernmental Panel on Climate Change (IPCC).

Now, the seventh phase of CMIP – CMIP7 – is underway, with more than 30 climate-modelling centres expected to contribute more than five million gigabytes of data – so much that downloading it using a fast internet connection would take two and a half years.

Here, we look at what is new for CMIP7, including its model experiments, updated emissions scenarios and “assessment fast track” process.

What is CMIP?

Around the world, climate models are developed by different institutions and groups, known as modelling centres.

Each model is built differently and, therefore, produces slightly different results.

To better understand these differences, CMIP coordinates a common set of climate-model experiments.

These are simulations that use the same inputs and conditions, allowing scientists to compare the results and see where models agree or differ.

The figure below shows the countries that have either produced or published CMIP simulations.

CMIP across the globe
Countries that have contributed modelling or data infrastructure for CMIP. Credit: CMIP

During this time, scientists use new and improved models to run experiments from previous CMIP phases for consistency, as well as new experiments to investigate fresh scientific questions.

These simulations produce a trove of data, in the form of variables – such as temperature, rainfall, winds, sea ice extent and ocean currents. This information helps scientists study past, present and future climate change.

As scientific understanding and technical capabilities improve, models are refined. As a result, each CMIP phase incorporates higher spatial resolutions, larger ensembles, improved representations of key processes and more efficient model designs.

CMIP7 objectives

Each CMIP phase has an “experimental design” that outlines which climate-model experiments should be run and their technical specifications, including the time period the models should simulate.

The CMIP7 experimental design has several components.

As in CMIP6, for a modelling centre to contribute, they are asked to produce a suite of experiments that maintain continuity across past and future CMIP phases.

This suite of experiments is known as the “diagnostic, evaluation and characterisation of klima” (DECK) and is used to understand how their model “behaves” under simple, standard conditions. These experiments are designed and requested directly by CMIP’s scientific governing panel.

Alongside the DECK, CMIP also incorporates experiments developed by model intercomparison projects (MIPs) run by different research communities. For example, experiments exploring what the climate could look like under different levels of emissions or those that explore how sea ice might have changed between the last two ice-ages.

Currently, CMIP is working with 40 MIPs. These groups investigate specific scientific questions at their own pace, rather than on timelines prescribed by CMIP.

Running a large number of simulations can take modelling centres a long time. To speed up the process, CMIP7 has launched the “assessment fast track”.

This is a small subset of CMIP7 experiments, drawn from past and present community MIPs, identified through community consultation as being critical for scientific and policy assessments.

Data from the assessment fast track will be used in the reports that will together form the seventh assessment (AR7) of the IPCC.

It will also be used as an input by other groups that create climate information, including organisations involved in regional downscaling and modelling climate impacts and ice-sheet changes.

The figure below shows the different components of CMIP7. It shows how a subset of CMIP7 experiments will be delivered on an accelerated timeline, while the majority of experiments will be led by MIPs.

CMIP7 infographic
The different components of CMIP7. Credit: CMIP

CMIP7 experiments

There are three categories of experiments set to take place in CMIP7:

  • Historical experiments, which are designed to improve scientific understanding of past climates. Model runs exploring the recent historical period also allow scientists to evaluate the performance of models by checking how well they replicate real-world observations.
  • Prediction and projection experiments, which allow scientists to analyse what different climates could look like under varying levels of greenhouse gas emissions, as well as near-term (10-year) prediction experiments.
  • Process understanding experiments, which are designed to better understand specific processes and isolate cause-and-effect relationships. For example, a set of experiments might change the emissions of one greenhouse gas at a time to see how much each pollutant contributes to warming or cooling the climate.

Modelling centres typically produce and publish their data for the historical and projection experiments first.

CMIP expects the first datasets to be available by this summer, with broader publication recommended by the end of the year, in time to be assessed by IPCC AR7 authors.

Drafting of the reports of AR7 is currently underway. However, countries are yet to agree on the timeline for when they will be published. This presents a challenge for the climate-modelling community, given the difficulties of working with a moving deadline.

(For more on the ongoing standoff between countries around the timing of publication of the reports, read Carbon Brief’s explainer.)

New emissions scenarios

Scientists use emissions scenarios to simulate the future climate according to how global energy systems and land use might change over the next century.

Crucially, these scenarios – also known as “pathways” – are not forecasts or predictions of the future.

The group tasked with designing the scenarios for CMIP phases, as well as producing the “input files” for climate models, is the “scenario model intercomparison project”, or ScenarioMIP.

In a new paper, the group has set out the new set of scenarios for CMIP7:

  • High (H): Emissions grow to as high as deemed plausibly possible, consistent with a rollback of current climate policies. This scenario will result in strong warming.
  • High-to-low (HL): Emissions rise as in the high scenario at first, but are cut sharply in the second half of the century to reach net-zero by 2100.
  • Medium (M): Emissions consistent with current policies, frozen as of 2025, leading to a moderate level of warming.
  • Medium-to-low (ML): Emissions are slowly reduced, eventually reaching net-zero emissions by the end of the century.
  • Low (L): Emissions consistent with likely keeping warming below 2C and not returning to 1.5C before the end of the century.
  • Very low (VL): Emissions are cut to keep temperatures “as low as plausible”, according to the paper. This scenario limits warming to close to 1.5C by the end of the century, with limited overshoot beforehand.
  • Low-to-negative (LN): Emissions fall slightly slower than in the VL scenario, with temperatures just rising above 1.5C. Emissions then rapidly drop to negative to bring warming back down.

The figures below show the emissions (left) and the estimated global temperature changes (right) under the seven new scenarios for CMIP7, from the low-to-negative emissions scenario (turquoise) to a high-emissions scenario (brown).

The greenhouse gas emissions for each of the CMIP7 climate scenarios (left) and the associated estimated average temperature change from 1850-1900 (right) using the FaIR emulator. Source: Adapted from Van Vuuren et al. (2026)
The greenhouse gas emissions for each of the CMIP7 climate scenarios (left) and the associated estimated average temperature change from 1850-1900 (right) using the FaIR emulator. Source: Adapted from Van Vuuren et al. (2026)

As a set, the ScenarioMIP scenarios “cover plausible outcomes ranging from a high level of climate change (in the case of policy failure) to low levels of climate change resulting from stringent policies”, the paper says.

Compared to the scenarios in CMIP6, the range in future emissions they cover is now narrower, the authors say:

“On the high-end of the range, the CMIP6 high emission levels (quantified by SSP5-8.5) have become implausible, based on trends in the costs of renewables, the emergence of climate policy and recent emission trends…At the low end, many CMIP6 emission trajectories have become inconsistent with observed trends during the 2020-30 period.”

Put simply, progress on climate policies and cheaper renewable technologies means that scenarios of very high emissions have now been ruled out.

However, this progress has not been sufficient to keep society on track for the Paris Agreement’s 1.5C goal. The paper notes that, “at this point of time, some overshoot of the 1.5C seems unavoidable”.

The change to the high end of the scenarios has sparked misleading commentary in the media and on social media – even from US president Donald Trump. A Carbon Brief factcheck unpacks the debate.

Also notable in the new scenarios is the “low-to-negative” pathway, which has the explicit feature of emissions becoming “net-negative”. In other words, through carbon dioxide removal (CDR) techniques, society reaches the point at which more carbon is being taken out of the atmosphere than is being added through greenhouse gas emissions.

Reaching net-negative emissions is fundamental to “overshoot scenarios”, where global warming passes a target and then is brought back down by large-scale CDR.

Overshoot scenarios allow scientists and policymakers to investigate the impacts of a delay to emissions reductions and better understand how the world might respond to passing a warming target. This includes the question of whether some impacts of climate change, such as ice sheet melt, are reversible.

CMIP has encouraged modelling centres to run simulations using the “high” and “very low” scenarios first to ensure downstream users of the data – including groups working on regional climate projections (CORDEX), climate impacts modelling (ISIMIP) and ice-sheet modelling (ISMIP) – have enough time to produce their data for IPCC reports.

These two scenarios were selected as they sit at opposite ends of the spectrum of climate outcomes. The high scenario will demonstrate how models behave under high emissions, while the very low scenario will demonstrate how models behave when emissions are rapidly reduced.

CMIP has recommended that modelling centres then run the “medium” and “high-to-low” scenarios. The remaining scenarios should then follow and no official recommendation has been made yet on their production order.

Other new features

In addition to the assessment fast track and new scenarios, CMIP7 has a number of other new developments.

Updated data for simulations

Climate models use input datasets to define the set of external drivers – or “forcings” – that have caused the global warming observed so far. These drivers include greenhouse gases, changes to incoming solar radiation and volcanic eruptions.

CMIP recommends modelling groups use the same input datasets, as this makes it easier to compare model results.

In CMIP7, the historical forcing datasets available for modelling groups to use have been improved to better represent real-world changes and extended closer to the present day. The historical simulations will be able to simulate the past climate from 1850 through to the end of 2021, whereas CMIP6 only simulated the past climate through to 2014.

CMIP is also planning to extend these historical datasets through to 2025 and maybe further throughout the course of CMIP7.

Emissions-driven simulations

CMIP7 introduces a new focus on CO2 emissions-driven simulations, providing a more realistic representation of how the climate responds to changes in emissions.

In older generations of climate models, atmospheric levels of CO2 and other greenhouse gas concentrations have been needed as an input to the model. These levels would be produced by running scenarios of CO2 emissions through separate carbon cycle models. The resulting climate-model runs were known as “concentration-driven simulations”.

However, many of the latest generation of models are now able to run in “emissions-driven mode”. This means that they receive CO2 emissions as an input and the model itself simulates the carbon cycle and the resulting levels of CO2 in the atmosphere.

This development is important, as climate policies are typically defined in terms of emissions, rather than overall atmospheric concentrations.

This new development in modelling will enable a more realistic representation of the carbon cycle and a better understanding of how it might change under different levels of warming.

Enhanced model documentation and evaluation

All CMIP7 models will be required to supply standardised model documentation that ensures consistency across model descriptions and makes it easier for end users to understand the data.

Additionally, CMIP scientists have developed a new open-access tool that dramatically speeds up the evaluation of climate models.

This “rapid evaluation framework” allows researchers to compare model outputs with real-world observations, providing immediate insight into model performance.

The post Guest post: How CMIP7 will shape the next wave of climate science appeared first on Carbon Brief.

Guest post: How CMIP7 will shape the next wave of climate science

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Energy transition policymaking must evolve to fit an age of rupture

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Andreas Sieber is head of political strategy at 350.0g. Cat Abreu is director of the International Climate Politics Hub.

From the US abduction of Venezuela’s president at the start of this year to the Iran war which rumbles on, disruption is the new normal for global geopolitics, more often than not linked to conflict over supplies of oil and gas. 

Events so far in 2026 – driven largely by the desire of the Trump administration to grab control of fossil fuels around the world – show that the climate community’s approach to energy diplomacy will have to evolve if we are to operate effectively and push for climate action in such a volatile landscape.

Today’s climate and energy governance must be able to cope with trade wars, genocide, fascism, spiralling inequality and challenges to multilateralism. The increasingly dominant paradigms of economic competitiveness, energy security and green industrialisation can help drive the transition but they also challenge our collective mission to deliver an equitable green shift.

US-China rivalry dominates

Longer-term geopolitical trends that are seeing power move from West to East and North to South have fuelled a US–China “superpower rivalry”, which is pulling the global economy apart and reining in trade.

A key question will be how the fracture “lines” are drawn: by the US and China, or also by other countries or blocs? Many governments will try to remain “in the middle” between the two giants to capture economic gains from both sides. Yet despite the language of “strategic autonomy”, Washington and Beijing may be in a position to force choices via market access, export controls and sanctions.

    At first glance, this may not seem particularly relevant for climate and energy politics. But Huawei’s exclusion from 5G operations across the political West and India following the so-called Clean Network Campaign by the US government serves as a warning of what could happen to climate green tech.

    And the recent debate to cut out Chinese inverters from European markets follows the same pattern – US security forces perceive a risk and start encouraging their allies to drop Chinese technology.

    The new drivers: competition and security

    Despite this fracturing geopolitical and economic context, energy transition is still happening. To ensure it is effective and equitable, we need to understand what is driving it and how to adapt climate politics so that it better responds to these drivers.

    Put simply, China is supplying the world with low-cost renewables (roughly 60% of critical wind and 80% of solar components), batteries, EVs and other key elements. Other countries now also want their piece of the green tech pie and are forming industrial policies to get it.

    It is this new competitiveness-driven logic that will shape the quest for decarbonisation, which has shifted from cooperating around the cost of tackling climate change to rivalry for the benefits of climate action.

    Over 90% of new renewables projects are now cheaper than fossil alternatives. Gas-fired power is 3–4 times more expensive than solar and wind. In 2015, most decarbonisation policies were “traditional” emissions-cutting strategies like carbon pricing or net zero dates, whereas green industrial policies now underpin the majority.

    Iran war could boost fossil fuel phase-out push, says Colombian minister

    Meanwhile, security has become a central driver of energy politics. We are living through the second major fossil fuel crisis in just four years. Elevated oil and gas prices will impose up to $1 trillion in additional costs on the global economy by the end of the year if disruption continues in the Strait of Hormuz. Fossil fuel supply chains have exposed countries to conflict, coercion and brutal price shocks.

    Fossil fuel volatility destabilises whole economies – higher fuel costs drive up food prices, increase political instability, and push millions into poverty and hunger. This incentivises governments to shield themselves from global shocks, especially in countries that are net fossil fuel importers and home to roughly three-quarters of the world’s population. 

    Yet security fears can cut both ways. The same instability that makes fossil fuel dependence untenable is also sharpening concern over China’s dominance of critical clean technologies and supply chains.

    Equity, cooperation and the opportunity for change

    Developing countries benefit from the rapid uptake of renewables enabled by low-cost Chinese technologies. But significant fiscal space and public investment is needed for the electricity grids and infrastructure required to fully unleash the energy transition, as well as for green industrialisation to diversify revenue streams.

    Despite this, industrial-scale domestic production and ownership often remain out of reach for too many countries that lack the fiscal space to allow green supply chains to flourish and compete with their traditional industrial base. But more just and diversified green tech supply chains could be achieved with concomitant support.

    Can giant batteries unlock Africa’s green industrial future?

    For the first time in decades, the international order is being substantially reshaped. If within this context, decarbonisation is increasingly driven by green industrial policy, energy security and competitiveness, the climate policy community must better anticipate where these debates are moving. We must speak the same language, and enter the forums where decisions are made, including security, trade and bilateral or trilateral spaces.

    We should build on an enlightened self interest recognising that cooperation remains essential and beneficial. This includes using the UN climate process differently: less as an ever-expanding negotiation machine, and more as a space for norm-setting, political alignment and deal-making. In an age of fragmentation, effective cooperation must not only be framed as necessary but thought of as a strategically compelling source of resilience and shared advantage.

    The post Energy transition policymaking must evolve to fit an age of rupture appeared first on Climate Home News.

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    Extreme heat costing India’s poorest workers 2% of GDP, survey finds

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    Low-income Indian workers, many of them migrants from rural areas hit by climate change, are paying for worsening extreme heat through lost working days and health complications, with the cost equivalent to 2% of national GDP per year, new research shows.

    The International Institute of Environment and Development (IIED), a London-based think-tank, worked with local organisations to survey around 540 households of informal workers in three Indian cities: Ajmer, Delhi and Agra. Most had migrated from rural areas to find work in industries such as construction, brick-making, garment manufacturing and food packaging.

    The survey found them struggling through long working days with little access to shade, cooling, rest or water, as well as few toilets for women. And even when they go home, many live in makeshift shelters or airless cramped rooms with barely a single fan, bringing almost no respite.

    Outdoor workers are losing about 24 days of work a year due to heat, costing them nearly a tenth of their annual earnings, while indoor workers sacrifice roughly 15 days. On top of losing income, they are also bearing the cost of health problems like heat exhaustion, psychological stress and kidney damage brought on by repeated dehydration.

    If the survey’s findings are extrapolated to a national level, the IIED researchers estimate that the decline in productivity and effects of kidney disease combined add up to lost wages of $78 billion each year.

      Vishram Meena, 45, from Alwar in Rajasthan, has worked on construction sites in Ajmer for more than a decade, toiling for 10 to 12 hours a day carrying materials and mixing cement in the full sun.

      In May 2024, on one of the hottest days, he collapsed after feeling dizzy and suffering a nosebleed. His wife and colleagues managed to get him to hospital where he was diagnosed with heat stroke. He has since returned to the same building work because the family needs the money.

      “I went back because what else could I do? We are not machines. We are human beings. The heat is killing us slowly,” he was quoted as saying in a report on the survey’s findings.

      “Victorian-era” conditions

      Ritu Bharadwaj, IIED’s director of climate resilience, finance and loss and damage, described some of the stories from workers about their experiences of extreme heat as “genuinely horrifying”.

      Kusum, a tailor at a garment manufacturing and export unit in Kapashera, Delhi, recounted how the machines for ironing finished garments are in the same tiny room where workers are making the clothes, with steam and hot air building up through her shift.

      Fans are too far apart to move the air and nothing has changed in over a decade, she said, adding that “in summer, the unit feels like a furnace”.

      “These are Victorian-era working conditions and they’re completely unacceptable in the 21st century,” said Bharadwaj. She called for stepped-up social protection from the government to pay people for days they are unable work due to heat, as well as micro-insurance schemes with payouts triggered by temperature measurements.   

      This money would help families buy food and pay medical bills when their income dips if they fall ill or cannot work their usual hours due to soaring temperatures.

      Climate change-driven heatwaves hit Delhi’s Red Fort market traders

      The aim of the IIED study, Bharadwaj added, is to get policy-makers’ attention by showing the scale of damage extreme heat is doing to India’s GDP in an economy whose growth relies on service-led industries. “If the workers within them start falling sick, you know it’s the economic growth which is going to get impacted,” she told a webinar to present the research.

      “Whether [policymakers] care about the workers or not, at least they would care about the GDP, and therefore then invest in their care,” she explained.

      Labour code leaves out heat

      However, Bharadwaj noted that a 2026 reform to India’s labour law bringing a range of regulations together in one code does not include heat-related protections for workers and only applies to businesses above a certain size. She urged the government to introduce a temperature threshold above which all workers would be able to stop their activities.

      IIED and its partners have also carried out a similar study in Bangladesh which will be published later this month, showing that extreme heat is costing its workforce the equivalent of nearly 1.4% of GDP.

      Shakirul Islam, chairperson of the Ovibashi Karmi Unnayan Program (OKUP) in Bangladesh, said the government had introduced stricter safety policies for garment-making companies after the Rana Plaza complex collapsed in 2013. But, he said, these rules are rarely followed by manufacturers, especially at the level of smaller subcontractors.

      The workers’ welfare centres that do exist are open mainly during work hours so they are difficult to visit. Some companies also make saline water available for heat stress, which is no good for those with high blood pressure, he noted.

      For Indian women workers, a just transition means surviving climate impacts with dignity

      Archana Shukla Mukherjee, CEO of India’s Change Alliance, which also partnered with IIED on the survey, said it was time to hold both the government and businesses accountable for finding solutions to the intensifying problem of extreme heat’s effects on workers.

      She said that employee state insurance schemes should identify heat stroke as an occupational disease while companies along the whole supply chain should start putting in place heat protection measures, including for informal workers and migrants.

      If the tools and mechanisms available to help workers do not reach the most vulnerable and marginalised people, “then I think we are not doing something right,” she said.

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      Top maritime court rejects bid to halt UN deep-sea mining inquiry

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      A United Nations investigation into deep-sea mining firms will continue after the world’s top maritime court rejected their bid to suspend the inquiry triggered by a US-backed push to extract critical minerals from the ocean floor.

      In two orders issued on Saturday, the International Tribunal for the Law of the Sea (ITLOS) declined to halt an inquiry launched by the International Seabed Authority (ISA) into whether permit holders, including Tonga Offshore Mining Ltd (TOML) and Nauru Ocean Resources Inc (NORI), have breached their obligations under UN exploration contracts.

      The two companies are subsidiaries of Canadian firm The Metals Company (TMC), which earlier this year sought permits from the United States to commercially mine the deep seabed in an area already covered by its UN exploration licences, bypassing the ISA’s regulatory process.

      The inquiry was opened after TMC’s move raised questions over whether its subsidiaries had complied with their contractual obligations to the ISA, which regulates mining in international waters under the UN Convention on the Law of the Sea. TOML and NORI sued the ISA last June for allegedly targeting them “in breach of due process” and without “good faith”.

        While allowing the inquiry to proceed, the court ordered the ISA to ensure the companies receive due process. Judges said the regulator must explain the factual and legal basis of its inquiry, clarify the procedures being followed and provide TOML and NORI with a meaningful opportunity to respond.

        The companies seeks to mine an area called the Clarion-Clipperton Zone, which holds vast reserves of critical minerals like nickel, manganese and rare earths but is also home to a little-studied deep ocean ecosystem with thousands of unnamed species.

        In response to the court’s ruling, the ISA welcomed the decision, saying the inquiry “remains in effect” and would continue “with due regard to all applicable legal requirements”.

        Last week, during an annual meeting of its member governments, ISA secretary-general Leticia Carvalho said the resources in the ocean floor are “the common heritage of humankind” and upheld the agency’s role as “more important than ever”.

        TMC also welcomed the court decision in a statement and claimed that judges ruled to “protect the rights of TMC subsidiaries”.

        “Contractors like NORI and TOML, who have together spent hundreds of millions of dollars on the promise of a fair regulatory framework, should be informed of the factual and legal basis of any non-compliance inquiries, understand the procedure being applied, and receive a meaningful opportunity to respond,” said Gerard Barron, CEO of The Metals Company.

        Iridogorgia and bamboo coral pictured around the Johnston Atoll Unit of the Pacific Remote Islands Marine National Monument (Photo: NOAA Office of Ocean Exploration and Research)

        Environmental groups said the ruling allows scrutiny of the companies’ actions to continue.

        Louisa Casson, deep-sea mining campaigner with Greenpeace, said the “entire litigation has been an egregious waste of time and money”, which was part of the industry’s “textbook distraction tactic” meant to delay the consequences of the inquiry.

        “If the inquiry confirms that TMC’s subsidiaries are breaching their contracts, governments must send the strongest possible signal that complicity in unlawful deep sea mining will not be tolerated,” she said.

        While investigation is still ongoing, NORI’s contract is set to expire this week and is up for review. Governments asked the ISA to report back and make “make appropriate recommendations” by the next ISA assembly, its main decision-making body set to take place next week from July 27 to 31.

        The court ordered both the ISA and TMC to submit a report on how they complied with the ruling by August 31, and called on both to “cooperate and refrain from any action that might lead to
        aggravating the dispute”.

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        Top maritime court rejects bid to halt UN deep-sea mining inquiry

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