A global treaty on plastics, which is being touted as the most important environmental treaty since the 2015 Paris Agreement, is set to be negotiated in South Korea over the next week.
At the fifth and final scheduled session of the UN’s Intergovernmental Negotiating Committee on Plastic Pollution (INC-5), member countries hope to finalise and approve the text of the “international legally binding instrument on plastic pollution”.
A successful treaty could have important implications for climate change.
The production, use and disposal of plastics is responsible for around 5% of global greenhouse gas emissions and they are typically made from fossil fuels. Plastics production is expected to be one of the leading drivers of oil demand growth over the coming years.
Measures to reduce plastics use will be a key part of the agenda, as around 90% of emissions from plastics come from production. The negotiations will see countries discuss setting targets, accountability and transparency measures.
Carbon Brief analysis shows that without any agreement to cut plastic production, emissions from plastics could consume half of the remaining carbon budget for limiting warming to 1.5C above pre-industrial levels.
One expert tells Carbon Brief that the best outcome possible for the negotiations is to ratify a global target to limit plastics production, coupled with legally binding national targets.
However, she warns that oil-producing countries are likely to veto any such proposal.
Below, Carbon Brief presents five key charts showing why the plastics treaty matters for climate change.
- Plastics currently cause triple the emissions of aviation
- Plastics will drive up oil demand over the coming decades
- Plastics could use up half the remaining carbon budget for 1.5C by 2050
- A plastics treaty could curb future plastics emissions
- Could the plastics sector become net-zero by 2050?
- Methodology
1. Plastics currently cause triple the emissions of aviation
Greenhouse gas emissions in 2023, in billion tonnes of CO2e. Source: Carbon Brief analysis of Karali et al (2024), the OECD and the UNEP Emissions Gap Report (2024).
Plastics are a versatile and durable material that have revolutionised industries from fashion to medicine. However, they also cause serious environmental problems.
The most commonly discussed downside of the widespread global use of plastic is the ecosystem damage caused by waste. Even if disposed of safely, the production and disposal of plastics produce greenhouse gas emissions that contribute to global warming.
Carbon Brief calculations suggest that plastic lifecycles generated more than 2.7bn tonnes of CO2 equivalent (GtCO2e) in 2023 – around 5% of global emissions. This is roughly three times more than the emissions produced by aviation, as shown in the graphic above.
Around 90% of emissions from plastics come from production – the process of extracting fossil fuels and converting them into plastics. The world produces around 400m tonnes of plastics every year and this number is expected to grow over the coming decades.
Most plastics are made from fossil fuels, using oil, coal or gas converted into feedstock chemicals. Extracting the fossil fuels needed from underground is directly associated with greenhouse gas emissions, for example due to leaky mines, wells and pipes that contribute to rising methane emissions.
Overall, extracting oil, gas and coal from the ground accounts for around one-fifth of plastics production emissions.
The rest of the emissions associated with plastics production come from the processes required to first convert the fossil fuels into plastics. The fossil fuels are refined to produce petrochemical feedstocks, such as ethane and naphtha.
In one of the most emissions-intensive steps of the process, these feedstocks are broken apart in a high-pressure steam cracker to produce chemicals called monomers. Finally, the monomers are joined into chains called polymers, which are used to construct plastics.
The remaining plastic emissions – which account for around 10% of the total – are emitted when materials are disposed of. One study finds that in this “end-of-life” stage, only around 9% of all plastics ever have been recycled, while 79% ended up in landfill and 12% were incinerated.
2. Plastics will drive up oil demand over the coming decades
Annual growth in oil demand, in millions of barrels. Source: IEA Oil 2024 report
The world’s consumption of oil is currently around 100m barrels per day. According to an International Energy Agency (IEA) special report, around half of the oil produced globally is currently used to fuel road transport – and this is being squeezed by the rising popularity of electric vehicles (EVs).
Along with renewables substituting for oil-fired electricity generation and increasingly efficient engines, EVs are the major driver of expectations that global oil demand could soon peak.
Petrochemicals feedstocks – chemical substances derived from fossil fuels that can then be used to make products such as plastics, rubbers and fertilisers – are widely seen as the last growth market for global oil demand. As such, the future of the $700bn plastics production industry is a key concern of the fossil-fuel industry.
Currently, only 14m barrels per day are used as a petrochemical feedstock – the majority of which is used to produce plastics. But the IEA expects this to grow further in the coming years, even as demand in other sectors falls.
The figure above shows projected annual growth in oil demand from petrochemical feedstocks (red) and other sectors, such as road transport and aviation (blue), up to 2030, according to the IEA’s Oil 2024 report.
Numbers above zero indicate an increase in oil demand compared to the previous year, while numbers below zero mean a decrease.
3. Plastics could use up half the remaining carbon budget for 1.5C by 2050
Annual lifecycle greenhouse gas emission, in billions of tonnes of CO2e. Source: Carbon Brief analysis of Karali et al (2024), OECD, Cabernard et al (2021) and the UNEP Emissions Gap Report (2024).
To have a 50% chance of limiting global warming to 1.5C above pre-industrial levels, humanity can only emit a further 200bn tonnes of CO2, according to the latest estimate from the emissions gap report from the UN Environment Programme (UNEP).
Unless there is a change in current trends, plastics production is expected to use up a significant proportion of this carbon budget.
A landmark 2024 report from the Lawrence Berkeley National Laboratory (LBNL) outlines two scenarios for plastics growth between now and 2050. Under its “conservative growth scenario”, the report says that plastics production will grow by 2.5% per year, based on projections of the Organisation for Economic Co-operation and Development (OECD).
Meanwhile, an alternative scenario is defined by a much more rapid 4% per year growth scenario, based on projections from National Academies of Sciences, Engineering and Medicine (NASEM)
Carbon Brief finds that, under the conservative growth scenario, annual “lifecycle” emissions from plastics could double by 2050, reaching 5.2GtCO2e. Under this scenario, plastics production, use and disposal would cumulatively emit 104GtCO2e between 2024 and 2050, consuming more than half of the remaining carbon budget.
Under the rapid growth scenario, cumulative emissions would be 130GtCO2e – or around 65% of the remaining carbon budget.
The rise in annual emissions from plastics, including all stages from fossil-fuel extraction to plastics disposal, are shown above. The black line indicates historical emissions, while the dark blue line shows the conservative growth scenario from the LBNL report, originally taken from the OECD.
4. A treaty could curb future plastics emissions
Annual lifecycle greenhouse gas emissions, in billions of tonnes of CO2e. Source: Carbon Brief analysis of Karali et al (2024), OECD, Cabernard et al (2021) and Rwanda/Peru 40×40 proposal from INC-4 negotiations.
At the negotiations in South Korea, countries will attempt to ratify a legally binding agreement on curbing plastics pollution.
Daniela Duran Gonzalez is a senior legal campaigner focused on the plastics treaty at the Centre for International Environmental Law (CIEL). She tells Carbon Brief that when discussing emissions from plastics at INC-5, experts usually focus on limiting production because plastics production is “challenging to decarbonise”.
At the negotiations, countries will consider a global target to limit plastics production, Duran explains. She likens this to the Paris Agreement 1.5C warming limit, arguing that “it gives us a north star, but it doesn’t provide any enforceable obligation to any country to actually achieve it”.
If it is agreed, the treaty could stipulate different ways to achieve this overall target. The first option, which Duran says is “very vague”, is for countries to all work towards the target at their own discretion, without any targets set.
Another method with more accountability would be for countries to set their own voluntary, non-legally binding and non-enforceable measures – similar to the climate pledges (“nationally determined contributions”) that countries submit under the Paris Agreement.
The most enforceable method on the table would be to set legally binding targets for each country, Duran explains. She says this could work in a similar way to the Montreal Protocol, which successfully cut global emissions of substances that deplete the ozone later.
To set targets, countries would need to agree on a baseline year to measure against, a goal and a deadline for the goal to be met.
For example, at the last set of negotiations (INC-4) earlier this year in Ottawa, Rwanda and Peru put forward a global target for a 40% reduction on 2025 levels by 2040. Under this scenario, plastics would emit 52GtCO2e by 2050.
Others have suggested a cap on plastic production at 2025 levels – a scenario that would see the production, use and disposal of plastics emit 76bn tonnes of CO2e by 2050. These scenarios are shown in light blue and blue on the graph above.
In early November, Ecuadorian ambassador Luis Vayas Valdivieso – chair of the INC – developed and submitted his non-paper three to the committee for the talks. This document set out his proposed basis for the negotiations.
Under the proposal, a single party would be able to veto any decision, similar to the process under the UN climate regime. WWF warns that this “can result in a stagnant and dead treaty, incapable of adapting to changing developments and circumstances in the future”.
Developed countries have already been accused of bowing to pressure from lobbyists seeking to avoid any caps on plastics production at the international negotiations. According to CIEL analysis, at the last set of talks, 196 fossil fuel and industry lobbyists registered, up from the 143 who registered at the previous discussions in Nairobi.
Duran tells Carbon Brief that plastics production is an “existential” issue for Gulf countries, whose economies currently rely on continued oil and gas extraction.
As a result, she says that these countries likely will not be “negotiating in good faith” at the INC-5 and “will never accept a treaty that has any mention of plastic production, because it’s their lifeline”. She argues for other countries to “overcome this idea of universal ratification” to ensure a “good” treaty.
According to expert interviews conducted by the University of Portsmouth, crucial outcomes from the negotiations include deciding on a voting mechanism as a backup if consensus cannot be reached.
(The UN climate regime must take all decisions by consensus because rules on how it makes decisions – including voting – were never agreed.)
5. Could the plastics sector become net zero by 2050?
Carbon content flows for the proposed ‘circular carbon’ net-zero plastics sector pathway in the year 2050, million tonnes of carbon (MtC). TWh = terawatt hour. Source: Based on Meys et al (2021)
INC-5 negotiations could lead to a reduction in plastics production, which could be key to limiting emissions from the industry. However, decarbonising the production, use and disposal of plastics could also help to bring down the carbon footprint of the sector.
One way to reduce emissions is to recycle plastics. Only 9% of plastics that have ever been produced have been recycled. However, the present-day number is likely higher, as recycling rates around the world are rising.
A report by the IEA says that most plastics recycling today is physical or “mechanical”. This involves grinding down plastics without changing their chemical structure, but can lead to the quality of plastics degrading over time.
Meanwhile, chemical recycling is becoming more popular, it says. This involves breaking down the plastics back into small chemical sections called monomers, which can be used to make new plastics. This method generally produces a higher-quality plastic, but it can be more energy intensive, resulting in higher emissions.
Another option is to switch from using petrochemical feedstocks, which are derived from fossil fuels, to using alternative feedstocks.
Bio-based feedstocks, such as starch, can also be used to produce plastics. These biological materials draw down carbon as they grow and also do not have the emissions associated with fossil fuel extraction.
Meanwhile, carbon capture, utilisation and storage (CCUS) can be used to draw down CO2 from chemical plants before it enters the atmosphere. The captured CO2 can be combined with hydrogen to generate synthetic feedstocks. Using renewable energy to produce the hydrogen for this process can help to keep the materials’ carbon footprint low.
The IEA report says that the “use of alternative feedstocks, including bio-based feedstock, remains a niche industry due to a considerable cost gap and competing demand with other sectors”.
A 2021 study explores four pathways through which the global plastics industry could reach net-zero by 2050. These are: a recycling pathway; a CCUS pathway; a biomass pathway; and a circular carbon pathway that combines the three approaches in an “optimal” way.
The combined pathway, shown above, is the only scenario that reaches net-zero emissions.
The chart shows the flow of carbon (in million tonnes) through the full lifecycle of plastics under a net-zero scenario in the year 2050. The width of each arrow corresponds to the amount of carbon flowing. In this scenario, around 38% of plastic feedstocks would be made from biomass, 17% from synthetic feedstocks, 44% from recycling and less than 1% from fossil fuels. This scenario would require an effective recycling rate of around 61%, with only 5% of plastics going to landfill and 34% ending up in the atmosphere through incineration.
However, the authors highlight how challenging it would be to fully decarbonise plastics, if production levels continue to rise.
Cutting emissions while production increases would require a significant uptick in the rate of plastics recycling, they note – and the feasibility of fully decarbonising plastics production will be limited by the amount of renewable energy and biomass available to the sector.
In the scenario above, the plastics sector would require 9,900 terawatt hours of renewable electricity (more than global renewable generation in 2023 or 14% of renewables generation under IEA net-zero scenario in 2050), and 19.3 exajoules of biomass (11% of “untapped” biomass potential in 2050).
Duran tells Carbon Brief that, while the INC-5 can talk about limiting production levels, it has not “entered into the discussion of decarbonising the petrochemical industry”.
She says that there are many reasons for this, including political factors and the uncertainty around measures such as CCUS. However, she also says that “decarbonisation is an issue of the United Nations Framework Convention on Climate Change (UNFCCC)”.
She explains that the UNFCCC cannot make rulings on plastics production, but can set out frameworks for the transparency and reporting of greenhouse gas emissions caused by plastic production.
Methodology
The Carbon Brief analysis on the lifecycle greenhouse emissions in this article is based on using the production-related emissions figures from the LBNL study (Karali et al., 2024), and combining this with an estimate of the end of life emissions from OECD data.
In order to make these datasets compatible, it is assumed that the percentage share of emissions from end of life, calculated from OECD data, remains constant at 10.8% and then this is applied to the production-related emissions from LBNL.
Due to differences in methodology, scope and poor availability of detailed data, generally, there are varying estimates of the climate impact from plastics. This analysis uses the values from LBNL study because it is the most recent and comprehensive evaluation of the climate impact from plastics, as confirmed by an expert that Carbon Brief spoke to.
However, the emissions measured in that study are higher than commonly cited estimates from the OECD, which suggests that production emissions in 2019 are around 28% lower than the LBNL estimate. This highlights the large uncertainty in measuring the climate impact of plastic, but the LBNL study authors also note that their higher estimate is “due to the increased level of granularity in modelling production processes, technologies and routes”. Their study also has no “by-product’ assumption”, which they say leads to an underestimation of the climate impact of plastics in other studies if they do not attribute emissions by mass across all the products of a given chemical process.
Historical data for plastics emissions is taken from a combination of LBNL, OECD and Cabernard et al (2021). Due to differences in methodology and uncertainty in the data, these different datasets do not match exactly and, therefore, have been scaled based on overlapping years to ensure that they are aligned with the values from the LBNL.
In order to model future emissions in a consistent manner, a constant emissions intensity per tonne of plastic produced from the LBNL study is used (4.9tCO2e per tonne of plastic, excluding end-of-life emissions) and applied to the production projections for each of the three scenarios presented (2.5% growth, cap at 2025 levels, 40% reduction from 2025 levels by 2040).
The baseline plastics-production projections are taken from the LBNL study, which uses OECD projections of plastics demand under a 2.5% growth scenario and assumes that annual plastics production matches annual demand. The projected end-of-life emissions from plastics are then calculated by using the assumed constant percentage share of emissions (10.8%) from end of life, as per above. For the 40% reduction scenario, it is assumed that production levels continue to reduce at the same rate between 2040 and 2050.
The post Five charts: Why a UN plastics treaty matters for climate change appeared first on Carbon Brief.
Five charts: Why a UN plastics treaty matters for climate change
N.C. Gov. Josh Stein wants state lawmakers to rethink tax breaks for data centers. The industry’s opacity makes it difficult to evaluate costs and benefits.
Tax breaks for data centers in North Carolina keep as much as $57 million each year into from state and local government coffers, state figures show, an amount that could balloon to billions of dollars if all the proposed projects are built.
The Global Environment Facility (GEF), a multilateral fund that provides climate and nature finance to developing countries, has raised $3.9 billion from donor governments in its last pledging session ahead of a key fundraising deadline at the end of May.
The amount, which is meant to cover the fund’s activities for the next four years (July 2026-June 2030), falls significantly short of the previous four-year cycle for which the GEF managed to raise $5.3bn from governments. Since then, military and other political priorities have squeezed rich nations’ budgets for climate and development aid.
The facility said in a statement that it expects more pledges ahead of the final replenishment package, which is set for approval at the next GEF Council meeting from May 31 to June 3.
Claude Gascon, interim CEO of the GEF, said that “donor countries have risen to the challenge and made bold commitments towards a more positive future for the planet”. He added that the pledges send a message that “the world is not giving up on nature even in a time of competing priorities”.
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Donors under pressure
But Brian O’Donnell, director of the environmental non-profit Campaign for Nature, said the announcement shows “an alarming trend” of donor governments cutting public finance for climate and nature.
“Wealthy nations pledged to increase international nature finance, and yet we are seeing cuts and lower contributions. Investing in nature prevents extinctions and supports livelihoods, security, health, food, clean water and climate,” he said. “Failing to safeguard nature now will result in much larger costs later.”
At COP29 in Baku, developed countries pledged to mobilise $300bn a year in public climate finance by 2035, while at UN biodiversity talks they have also pledged to raise $30bn per year by 2030. Yet several wealthy governments have announced cuts to green finance to increase defense spending, among them most recently the UK.
As for the US, despite Trump’s cuts to international climate finance, Congress approved a $150 million increase in its contribution to the GEF after what was described as the organisation’s “refocus on non-climate priorities like biodiversity, plastics and ocean ecosystems, per US Treasury guidance”.
The facility will only reveal how much each country has pledged when its assembly of 186 member countries meets in early June. The last period’s largest donors were Germany ($575 million), Japan ($451 million), and the US ($425 million).
The GEF has also gone through a change in leadership halfway through its fundraising cycle. Last December, the GEF Council asked former CEO Carlos Manuel Rodriguez to step down effective immediately and appointed Gascon as interim CEO.
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New guidelines
As part of the upcoming funding cycle, the GEF has approved a set of guidelines for spending the $3.9bn raised so far, which include allocating 35% of resources for least developed countries and small island states, as well as 20% of the money going to Indigenous people and communities.
Its programs will help countries shift five key systems – nature, food, urban, energy and health – from models that drive degradation to alternatives that protect the planet and support human well-being by integrating the value of nature into production and consumption systems.
The new priorities also include a target to allocate 25% of the GEF’s budget for mobilising private funds through blended finance. This aligns with efforts by wealthy countries to increase contributions from the private sector to international climate finance.
Niels Annen, Germany’s State Secretary for Economic Cooperation and Development, said in a statement that the country’s priorities are “very well reflected” in the GEF’s new spending guidelines, including on “innovative finance for nature and people, better cooperation with the private sector, and stable resources for the most vulnerable countries”.
Aliou Mustafa, of the GEF Indigenous Peoples Advisory Group (IPAG), also welcomed the announcement, adding that “the GEF is strengthening trust and meaningful partnerships with Indigenous Peoples and local communities” by placing them at the “centre of decision-making”.
The post GEF raises $3.9bn ahead of funding deadline, $1bn below previous budget appeared first on Climate Home News.
GEF raises $3.9bn ahead of funding deadline, $1bn below previous budget
Tropical cyclones that rapidly intensify when passing over marine heatwaves can become “supercharged”, increasing the likelihood of high economic losses, a new study finds.
Such storms also have higher rates of rainfall and higher maximum windspeeds, according to the research.
The study, published in Science Advances, looks at the economic damages caused by nearly 800 tropical cyclones that occurred around the world between 1981 and 2023.
It finds that rapidly intensifying tropical cyclones that pass near abnormally warm parts of the ocean produce nearly double – 93% – the economic damages as storms that do not, even when levels of coastal development are taken into account.
One researcher, who was not involved in the study, tells Carbon Brief that the new analysis is a “step forward in understanding how we can better refine our predictions of what might happen in the future” in an increasingly warm world.
As marine heatwaves are projected to become more frequent under future climate change, the authors say that the interactions between storms and these heatwaves “should be given greater consideration in future strategies for climate adaptation and climate preparedness”.
‘Rapid intensification’
Tropical cyclones are rapidly rotating storm systems that form over warm ocean waters, characterised by low pressure at their cores and sustained winds that can reach more than 120 kilometres per hour.
The term “tropical cyclones” encompasses hurricanes, cyclones and typhoons, which are named as such depending on which ocean basin they occur in.
When they make landfall, these storms can cause major damage. They accounted for six of the top 10 disasters between 1900 and 2024 in terms of economic loss, according to the insurance company Aon’s 2025 climate catastrophe insight report.
These economic losses are largely caused by high wind speeds, large amounts of rainfall and damaging storm surges.
Storms can become particularly dangerous through a process called “rapid intensification”.
Rapid intensification is when a storm strengthens considerably in a short period of time. It is defined as an increase in sustained wind speed of at least 30 knots (around 55 kilometres per hour) in a 24-hour period.
There are several factors that can lead to rapid intensification, including warm ocean temperatures, high humidity and low vertical “wind shear” – meaning that the wind speeds higher up in the atmosphere are very similar to the wind speeds near the surface.
Rapid intensification has become more common since the 1980s and is projected to become even more frequent in the future with continued warming. (Although there is uncertainty as to how climate change will impact the frequency of tropical cyclones, the increase in strength and intensification is more clear.)
Marine heatwaves are another type of extreme event that are becoming more frequent due to recent warming. Like their atmospheric counterparts, marine heatwaves are periods of abnormally high ocean temperatures.
Previous research has shown that these marine heatwaves can contribute to a cyclone undergoing rapid intensification. This is because the warm ocean water acts as a “fuel” for a storm, says Dr Hamed Moftakhari, an associate professor of civil engineering at the University of Alabama who was one of the authors of the new study. He explains:
“The entire strength of the tropical cyclone [depends on] how hot the [ocean] surface is. Marine heatwave means we have an abundance of hot water that is like a gas [petrol] station. As you move over that, it’s going to supercharge you.”
However, the authors say, there is no global assessment of how rapid intensification and marine heatwaves interact – or how they contribute to economic damages.
Using the International Best Track Archive for Climate Stewardship (IBTrACS) – a database of tropical cyclone paths and intensities – the researchers identify 1,600 storms that made landfall during the 1981-2023 period, out of a total of 3,464 events.
Of these 1,600 storms, they were able to match 789 individual, land-falling cyclones with economic loss data from the Emergency Events Database (EM-DAT) and other official sources.
Then, using the IBTrACS storm data and ocean-temperature data from the European Centre for Medium-Range Weather Forecasts, the researchers classify each cyclone by whether or not it underwent rapid intensification and if it passed near a recent marine heatwave event before making landfall.
The researchers find that there is a “modest” rise in the number of marine heatwave-influenced tropical cyclones globally since 1981, but with significant regional variations. In particular, they say, there are “clear” upward trends in the north Atlantic Ocean, the north Indian Ocean and the northern hemisphere basin of the eastern Pacific Ocean.
‘Storm characteristics’
The researchers find substantial differences in the characteristics of tropical cyclones that experience rapid intensification and those that do not, as well as between rapidly intensifying storms that occur with marine heatwaves and those that occur without them.
For example, tropical cyclones that do not experience rapid intensification have, on average, maximum wind speeds of around 40 knots (74km/hr), whereas storms that rapidly intensify have an average maximum wind speed of nearly 80 knots (148km/hr).
Of the rapidly intensifying storms, those that are influenced by marine heatwaves maintain higher wind speeds during the days leading up to landfall.
Although the wind speeds are very similar between the two groups once the storms make landfall, the pre-landfall difference still has an impact on a storm’s destructiveness, says Dr Soheil Radfar, a hurricane-hazard modeller at Princeton University. Radfar, who is the lead author of the new study, tells Carbon Brief:
“Hurricane damage starts days before the landfall…Four or five days before a hurricane making landfall, we expect to have high wind speeds and, because of that high wind speed, we expect to have storm surges that impact coastal communities.”
They also find that rapidly intensifying storms have higher peak rainfall than non-rapidly intensifying storms, with marine heatwave-influenced, rapidly intensifying storms exhibiting the highest average rainfall at landfall.
The charts below show the mean sustained wind speed in knots (top) and the mean rainfall in millimetres per hour (bottom) for the tropical cyclones analysed in the study in the five days leading up to and two days following a storm making landfall.
The four lines show storms that: rapidly intensified with the influence of marine heatwaves (red); those that rapidly intensified without marine heatwaves (purple); those that experienced marine heatwaves, but did not rapidly intensify (orange); and those that neither rapidly intensified nor experienced a marine heatwave (blue).
Dr Daneeja Mawren, an ocean and climate consultant at the Mauritius-based Mascarene Environmental Consulting who was not involved in the study, tells Carbon Brief that the new study “helps clarify how marine heatwaves amplify storm characteristics”, such as stronger winds and heavier rainfall. She notes that this “has not been done on a global scale before”.
However, Mawren adds that other factors not considered in the analysis can “make a huge difference” in the rapid intensification of tropical cyclones, including subsurface marine heatwaves and eddies – circular, spinning ocean currents that can trap warm water.
Dr Jonathan Lin, an atmospheric scientist at Cornell University who was also not involved in the study, tells Carbon Brief that, while the intensification found by the study “makes physical sense”, it is inherently limited by the relatively small number of storms that occur. He adds:
“There’s not that many storms, to tease out the physical mechanisms and observational data. So being able to reproduce this kind of work in a physical model would be really important.”
Economic costs
Storm intensity is not the only factor that determines how destructive a given cyclone can be – the economic damages also depend strongly on the population density and the amount of infrastructure development where a storm hits. The study explains:
“A high storm surge in a sparsely populated area may cause less economic damage than a smaller surge in a densely populated, economically important region.”
To account for the differences in development, the researchers use a type of data called “built-up volume”, from the Global Human Settlement Layer. Built-up volume is a quantity derived from satellite data and other high-resolution imagery that combines measurements of building area and average building height in a given area. This can be used as a proxy for the level of development, the authors explain.
By comparing different cyclones that impacted areas with similar built-up volumes, the researchers can analyse how rapid intensification and marine heatwaves contribute to the overall economic damages of a storm.
They find that, even when controlling for levels of coastal development, storms that pass through a marine heatwave during their rapid intensification cause 93% higher economic damages than storms that do not.
They identify 71 marine heatwave-influenced storms that cause more than $1bn (inflation-adjusted across the dataset) in damages, compared to 45 storms that cause those levels of damage without the influence of marine heatwaves.
This quantification of the cyclones’ economic impact is one of the study’s most “important contributions”, says Mawren.
The authors also note that the continued development in coastal regions may increase the likelihood of tropical cyclone damages over time.
Towards forecasting
The study notes that the increased damages caused by marine heatwave-influenced tropical cyclones, along with the projected increases in marine heatwaves, means such storms “should be given greater consideration” in planning for future climate change.
For Radfar and Moftakhari, the new study emphasises the importance of understanding the interactions between extreme events, such as tropical cyclones and marine heatwaves.
Moftakhari notes that extreme events in the future are expected to become both more intense and more complex. This becomes a problem for climate resilience because “we basically design in the future based on what we’ve observed in the past”, he says. This may lead to underestimating potential hazards, he adds.
Mawren agrees, telling Carbon Brief that, in order to “fully capture the intensification potential”, future forecasts and risk assessments must account for marine heatwaves and other ocean phenomena, such as subsurface heat.
Lin adds that the actions needed to reduce storm damages “take on the order of decades to do right”. He tells Carbon Brief:
“All these [planning] decisions have to come by understanding the future uncertainty and so this research is a step forward in understanding how we can better refine our predictions of what might happen in the future.”
The post Marine heatwaves ‘nearly double’ the economic damage caused by tropical cyclones appeared first on Carbon Brief.
Marine heatwaves ‘nearly double’ the economic damage caused by tropical cyclones
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