China’s energy sector carbon dioxide (CO2) emissions increased 5.2% in 2023, meaning a record fall of 4-6% is needed by 2025 to meet the government’s “carbon intensity” target.
The new analysis for Carbon Brief, based on official figures and commercial data, shows rapid electricity demand growth and weak rains boosted demand for coal power in 2023, while the rebound from zero-Covid boosted demand for oil.
Other key findings from the analysis include:
- China’s CO2 emissions have now increased by 12% between 2020 and 2023, after a highly energy- and carbon-intensive response to the Covid-19 pandemic.
- This means CO2 emissions would need to fall by 4-6% by 2025, in order to meet the target of cutting China’s carbon intensity – its CO2 emissions per unit of economic output – by 18% during the 14th five-year plan period.
- China is also at risk of missing all of its other key climate targets for 2025, including pledges to “strictly limit” coal demand growth and “strictly control” new coal power capacity, as well as targets for energy intensity, the share of low-carbon energy in overall demand and the share of renewables in energy demand growth.
- Government pressure to hit the targets, most of which are in China’s updated international climate pledge under the Paris Agreement, makes it more likely that China’s CO2 emissions will peak before 2025 – far earlier than its target of peaking “before 2030”.
The deadline for peaking CO2 emissions has led officials and industries to pursue rapid emissions growth and carbon-intensive projects, while a window to do so remains open.
The government recently recognised and responded to the gap to meeting its targets, by calling for stronger controls on such projects, as well as faster renewables deployment.
Most of China’s climate targets can be met if the acceleration of clean energy deployment during 2023 is maintained – and if energy demand growth returns to pre-Covid levels.
- China’s CO2 emissions continued to increase in 2023
- China is off track to all of its 2025 climate targets
- Official energy data is over-reporting coal consumption growth
- Government response
- The clean energy boom can allow most targets to be met
- About the data
China’s CO2 emissions continued to increase in 2023
According to preliminary official data, China’s total energy consumption increased by 5.7% in 2023, the first time since at least 2005 that energy demand has grown faster than GDP.
With coal consumption growing by 4.4%, our analysis shows CO2 emissions increasing by 5.2% – at the same rate as GDP – highlighting energy-intensive recent growth patterns.
China’s economic growth during and after the Covid-19 pandemic has been highly energy- and carbon-intensive. CO2 emissions grew at an average of 3.8% per year in 2021-23, up from 0.9% a year in 2016-20, while GDP growth slowed from an average of 5.7% to 5.4%.
Another year of rapidly rising emissions in 2023 leaves China way off track against its target of cutting carbon intensity by 18% during the 14th five-year plan (2021-25).
As a result, CO2 emissions would now need to fall by 4-6% by 2025 to hit the goal. This is illustrated in the figure below, showing historical emissions (black line) and the reductions needed by 2025 to hit the carbon intensity target, depending on the rate of GDP growth.
Even if China’s GDP growth is high and averages 6% per year in 2024-25, the intensity target requires CO2 emissions to fall by 4%.
The main drivers of the emissions increase in 2023 were coal-fired power and oil consumption, which increased by 6% and 8%, respectively.
A major reason for the growth in power generation from coal was that hydropower operating rates reached the lowest level in more than two decades due to a series of droughts. These operating rates are likely to recover towards average levels in 2024.
The increase in oil consumption represents a rebound from the slow demand growth during zero-Covid and an outright drop in 2022. Gas consumption rebounded as prices came down from 2022 highs, while still remaining elevated.
The clean energy manufacturing boom also has a role in driving emissions, due to energy-intensive processes involved in the production of solar PV and batteries, in particular.
Approximately one percentage-point of CO2 emission growth can be attributed to these sectors, based on output data and emission intensities estimated for solar PV, electric vehicles and batteries.
This means that, without the clean technology manufacturing boom, China’s CO2 emissions would have grown by around 4.2%, instead of the 5.2% estimated in our analysis.
Nevertheless, the increase in manufacturing will result in a significant reduction in emissions in net terms, once the products are in use. About half of this reduction will be realised outside of China, as the products are exported.
China is off track to all of its 2025 climate targets
China’s climate pledge under the Paris Agreement (nationally determined contribution, NDC) was updated in 2021, following commitments made by President Xi Jinping earlier that year and incorporating targets set under the 14th five-year plan.
The updated NDC makes commitments to strictly limit coal consumption growth; strictly control new coal power; reduce energy and carbon intensity by 2025; and increase the share of non-fossil energy sources to 25% by 2030.
In addition, the country’s five-year plans set targets of increasing the share of non-fossil energy sources to 20% by 2025 and deriving more than 50% of the increase in energy use from 2020 to 2025 overall from renewable sources.
All of these targets are severely off track after 2023.
The table below lists the various climate- and energy-related targets, the progress seen from 2020-23 and what would be needed during 2024-25 to achieve each of the goals. (See below for further details on each indicator and what is needed by 2025.)
China’s 2025 climate commitments and targets in the energy sector
| Indicator | Target | Progress in 2020-23 | Change needed in 2024-25 |
| Carbon intensity | -18% | -4.6% (-1.5%/year) | -7%/year; reduce emissions in absolute terms |
| Energy intensity | -13.5% | -2% (-0.6%/year) | -6%/year; reduce energy use in absolute terms |
| Coal consumption growth | “strictly limit” | Annual growth increased eightfold from 0.5% in 2016-20 to 3.8% | Negative growth to limit increase to the same rate as previous five-year period |
| New coal power projects | “strictly control” | Permits increased fourfold, from 25GW per year in 2016-20 to 110GW per year | Restrict new permits and review permits already granted |
| Non-fossil share of energy overall | Increase by 4.1 percentage points | Increased by 1.8 percentage points (0.6 points per year) | Rate of increase has to double to 1.2 points per year |
| Share of energy consumption growth met by renewables | Above 50% | 30%, down from 42% in 2016-20 | Renewable energy growth needs to double and energy consumption growth needs to slow to pre-Covid rate; total consumption of fossil fuels needs to fall.Renewable energy growth needs to double and energy consumption growth needs to slow to pre-Covid rate; total consumption of fossil fuels needs to fall. |
The centrepiece of China’s 2020 and 2025 climate commitments has been reducing carbon intensity, or CO2 emissions from energy use per unit of GDP.
The country’s carbon intensity reportedly fell 48% from 2005 to 2020. China committed to an 18% fall from 2020 to 2025 – and to reducing carbon intensity by more than 65% from 2005 levels by 2030, which requires a further reduction of at least 17% from 2025 to 2030.
However, as of the end of 2023, China’s carbon intensity has only fallen 5% in the 14th five-year plan period, lagging far behind the target of 18% from 2020 to 2025. If this target is to be met, CO2 emissions will have to come down in absolute terms from 2023 to 2025.
The figure below shows how China overachieved against its carbon intensity target for 2015-2020 but is veering increasingly off track against the goal for 2020-2025.
China’s energy intensity increased by 0.5% in 2023, the first annual rise since at least 2005. From 2020 to 2023, energy intensity only fell 2%.
The figure below shows that China narrowly missed its energy intensity target during the 13th five-year plan period, spanning 2016 to 2020, as progress halted in 2020. The country is now far off track for its 14th five-year plan target.
Indeed, to meet the target of a 13.5% reduction over 2020-25 – given the lack of progress as of the end of 2023 – energy consumption would have to fall in absolute terms over the next two years, while the rate of GDP growth is maintained or accelerated. This makes the goal all but unachievable.
The share of China’s energy demand met by non-fossil sources has increased by 1.8 percentage points from 2020 to 2023, against a target of 4.1 points by 2025.
This is shown in the figure below, illustrating the targeted 15% share for non-fossil energy by 2020 and 20% by 2025, as well as progress to date.
Meeting the 2025 target would mean that the rate of increase needs to double for the next two years. Moreover, if energy demand growth continues at the exceptionally high rate of 2020 to 2023, then energy production from non-fossil sources would need to grow at 11.3% per year to meet the target, up from 8.5% in the past three years.
Alternatively, the growth of renewables and nuclear could be maintained – but energy consumption growth would have to slow down to its pre-Covid average.
Only 30% of energy consumption growth has been met by renewable energy in 2020 to 2023, against a target of more than 50% during 2020-25.
This is illustrated in the figure below, showing contributions to annual energy demand growth from fossil fuels (grey bars), nuclear (blue) and renewables (red).
The 50% target is now highly unlikely to be met without a slowdown in energy consumption growth. Without a slowdown, renewables would have to grow by 20% per year to meet the target, up from 8.9% in the past three years.
Both growth in coal consumption and new coal power projects accelerated sharply in 2021-23, despite Xi’s pledges to “strictly control” them.
This is illustrated in the figure below, with annual coal consumption growth on the left and the amount of new coal capacity added each year on the right.
Indeed, the average growth rate of coal consumption increased 8-fold from 0.5% per year in 2016-20 to 3.8% per year in 2021-23.
Similarly, new coal power approvals increased fourfold in 2022-23, compared with the five years before the “strictly control” pledge, based on analysis of Global Energy Monitor data.
Since the beginning of 2022, a total of 218 gigawatts (GW) of new coal power plants have been permitted. By the end of 2023, some 89GW of this capacity had already started construction, while 128GW had yet to break ground.
Furthermore, the government’s official policy has shifted to strongly encouraging new coal power. An assessment of the projects permitted in 2022-23 shows that requirements, set for approving new coal power plants in August 2021, have not been enforced.
Statements from developers and government officials – see below – confirm that the 14th five-year plan period until 2025 is being seen as a “window of opportunity” for new coal power plants, rather than a period when new projects are strictly controlled.
This is causing a rush to secure permits for new projects. China Shenhua called the period until 2025 “an opportune time for thermal power construction”. The provincial state-owned enterprise supervisor boasts of Inner Mongolia Energy Group “achieving a flying start” to 2023 and “seizing the policy window” for coal power projects.
The Zhejiang province energy regulator emphasised the importance of seizing the time window for thermal power construction during the 14th five-year period.
Power China called for joint efforts with local government officials to exploit the coal power development window effectively, citing a plan known as “three times 80GW”. This refers to a proposal promoted by the thermal power construction industry to permit and commission 80GW of coal power plants each year, from 2022 to 2024.
The meaning of the pledges to “strictly control” growth in coal consumption and new coal power projects lacks a precise definition. However, a sharp acceleration of coal consumption growth and coal power plant approvals, along with active government promotion of new projects, is hard to reconcile with the pledge to exert strict control.
By this logic, meeting the pledge on coal consumption growth would require, at the very least, reducing coal use from 2023 to 2025 to bring the growth rate during the 2021 to 2025 period closer to the rate during the preceding five-year period.
Similarly, meeting the commitment to control new coal power projects would require enforcing existing policy to limit new schemes, restricting new permits and reviewing permits already granted, to limit the acceleration compared with the preceding five-year period.
Official energy data is over-reporting coal consumption growth
In 2022, government policies seeking to increase coal mine output and push down coal prices led to a sharp deterioration in the quality and calorific value of coal produced.
This fall in quality meant that the weight of coal being consumed increased by far more than the amount of energy supplied or CO2 emitted from that coal.
China’s official statistics failed to capture the change and consequently over-reported the growth in coal consumption and under-reported the improvement in CO2 intensity in 2022. This 2022 data could be expected to be revised once more complete energy statistics are released later.
Unlike in 2022, the officially-reported coal consumption growth rate for 2023 is more closely aligned with growth in coal power generation and output in key heavy industry sectors. The data indicates that coal use grew 4.4% in 2023, while power generation from coal rose 6%.
However, the conclusion that CO2 emissions need to fall from 2023 to 2025 to meet the carbon intensity target holds, even if a correction to 2022 data is made.
Calculating with current official data, CO2 emissions need to fall by 3.8-6.5% in the next two years, depending on the growth rate of GDP.
Based on my previous estimate that the growth in CO2 emissions in 2022 was inflated by 2.3 percentage points, a correction for 2022 would put the required reduction at 1.6-4.3%.
Government response
Energy intensity and carbon intensity reduction are among the 20 “main indicators” specified in China’s overarching five-year plan for 2021-25.
The mid-term evaluation of progress, published by China’s top economic planner the national development and reform commission (NDRC) in December 2023, identified these indicators as two of the four that were off track, along with a key air quality target.
(Air pollution concentrations also rose in 2023 due to increased industrial and transportation emissions, along with unfavourable weather conditions.)
In late 2023, the NDRC reprimanded the provinces of Hubei, Shaanxi, Gansu, Qinghai, Zhejiang, Anhui, Guangdong and Chongqing for lagging behind on the targets to control energy intensity and total energy consumption.
Zhou Dadi, a member of the national climate change expert advisory committee, pointed to the weak growth in service industries as the reason for the lack of progress on the intensity targets.
Service sectors have relatively low energy demand and carbon emissions relative to economic output, so the decline in their share of economic activity tends to increase the energy and carbon intensity of the economy.
The NDRC’s evaluation report also identified measures to achieve the targets, including improving policies to control energy use and carbon emissions, curbing the initiation of projects with high energy consumption and high emissions, strictly limiting total coal consumption, promoting a shift to cleaner industry and transportation, promoting energy conservation and, importantly, accelerating the deployment of renewable energy.
The clean energy boom can allow most targets to be met
While China fell severely behind on its 2025 climate targets for the energy sector, the past two years saw a veritable boom in clean energy installations – particularly solar power.
This boom puts most of the targets still in reach, especially if energy demand growth returns to the pre-Covid rates.
My earlier analysis showed that China’s CO2 emissions could fall this year and then stabilise, if additions of low-carbon power generation continue at 2023 rates and electricity demand returns to trend.
Under this projection, CO2 emissions fall by approximately 1.5% from 2023 to 2025. Therefore, achieving the 4-6% reduction in CO2 emissions needed to meet the CO2 intensity target from 2023 to 2025 would require further acceleration in clean energy deployment, or a sharp slowdown in energy demand growth.
The increase in the share of non-fossil energy should be possible to achieve given the sharp increase in solar and wind installations in 2023. To start with, slow progress was partially caused by the record-low hydropower operating rates in 2023, linked to record droughts.
Even if energy demand continued to grow at the 2020-23 rate, continued low-carbon energy additions at the 2023 level should suffice to raise the share of non-fossil energy to 21%, comfortably ahead of the target.
The target of renewable energy contributing half of the growth in total energy demand is significantly more challenging.
If energy consumption growth rate slows down to its pre-Covid average and clean energy capacity additions continue at the 2023 rate, enabling the growth rate of renewable energy production to almost double to 16%, then the target would likely be reached.
This would also mean a reduction in the total consumption of fossil fuels and a reduction in energy sector CO2 emissions. This scenario would arguably also meet the commitment to “strictly limit the growth in coal consumption”.
Meeting the pledge to “strictly control” new coal power projects would mean thoroughly assessing the justification for permits granted in the past two years and restricting the issuance of new permits.
The large amount of electricity storage being deployed – especially pumped hydro, but increasingly also grid-connected batteries – reduces the need for thermal power plants.
For a significant restriction of new coal power to be possible while ensuring electricity supply security, progress would also be needed on power system reforms that increase flexibility and make more efficient use of existing capacity.
China’s clean energy boom has been happening much faster than official targets for wind and solar installations would require, driven by enthusiasm from local governments, state-owned enterprises and investors.
However, due to the rapid increase in energy consumption, meeting China’s headline climate targets now requires that the momentum of clean energy installations is maintained.
About the data
Total energy consumption and energy mix were taken from national bureau of statistics annual data. Improvements in energy intensity and carbon intensity were compiled from the bureau’s annual statistical communiques and changes in carbon emissions were calculated based on reported GDP growth and carbon intensity improvement.
Growth in total energy consumption and changes in the energy mix were taken from preliminary information released by the national bureau of statistics. Growth in CO2 emissions in 2023 was calculated using Intergovernmental Panel on Climate Change default emission factors based on changes in the consumption of coal, oil and gas.
The post Analysis: Record drop in China’s CO2 emissions needed to meet 2025 target appeared first on Carbon Brief.
Analysis: Record drop in China’s CO2 emissions needed to meet 2025 target
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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