China’s carbon dioxide (CO2) emissions stayed at, or just below, last year’s levels in the third quarter of 2024, after a fall in the second quarter.
The new analysis for Carbon Brief, based on official figures and commercial data, leaves open the possibility that China’s emissions could fall this year.
However, recent record-high temperatures caused emissions to go up in September and new government stimulus measures mean there is now greater uncertainty over the country’s emissions trajectory.
Heatwaves through much of August and September caused a major increase in electricity demand for air conditioning, which, combined with weak hydropower output, meant a 2% increase in coal-fired power generation and a 13% rise for gas-fired power in the third quarter, despite wind and solar growth continuing to break records.
The increase in emissions in the power sector was offset by falling emissions from steel, cement and oil use, plus stagnating gas demand outside the power sector, meaning China’s CO2 output in the third quarter was flat or slightly declined, relative to a year earlier.
Other key findings from the analysis include:
- Solar generation rose 44% in the third quarter of the year and wind by 24%, with both continuing to see record-breaking additions of new capacity.
- Hydro generation was up 11% compared with last year’s drought-affected figures, but remained short of expected output. Nuclear power was up 4%.
- Oil demand fell by around 2%, due to falling construction activity, the rise of electric vehicles (EVs) and natural gas (LNG) trucks, as well as weak consumer spending.
- Emissions from steel fell by 3% and cement by 12% in the third quarter, as both sectors continued to see the effect of falling construction activity.
- The coal-to-chemicals industry received renewed political backing and coal consumption in the sector has risen by nearly a fifth in the year to date.
Emissions would need to fall by at least 2% in the last three months of the year, for China’s annual total to drop from 2023 levels. This outcome is supported by the ongoing slowdown in industrial power demand growth and the end of the air-conditioning season.
However, new economic stimulus plans announced in late September with no apparent emphasis on emissions, add uncertainty to this outlook.
In any case, China will remain off track against its 2025 “carbon intensity” target, which requires emissions cuts of at least 2% in 2024 and 2025, after rapid rises in 2020-23.
Looking further ahead, policymakers recently provided new indications of the country’s plans for peaking and reducing emissions, signalling a gradual and cautious approach which falls short of what would be needed to align with the goals of the Paris Agreement.
But, if the country’s rapid clean energy growth is sustained, it has the potential to deliver emission reductions more swiftly.
Clean-energy expansion met all power-demand growth over summer
Defying predictions of slowing growth, China’s electricity demand increased by 7.2% year-on-year in the third quarter of 2024, up from an already rapid 6.9% in the second quarter.
The make-up of growth changed, however. Some 60% of the increase in demand came from the residential and services sectors, with household demand up by a blistering 15%.
Industrial power-demand growth continued to slow down, increasing by 4.6% in July–September, down from 5.9% in the second quarter.
At the same time, solar power generation increased by 44% year-on-year and wind power generation by 24%. Hydropower grew 11%, despite falling short of average utilisation, and nuclear power generation growth was muted at 4% due to few new reactors being commissioned.
The rapid rise of electricity demand outpaced these increases from low-carbon sources, with the gap between demand and rising clean supply being met by a 2% increase in coal-fired power generation and a 13% rise for gas-fired power, as shown in the figure below.
This caused a 3% increase in CO2 emissions from the sector in the third quarter of the year.
However, looking at the whole summer period, whether taken as May-September or June-August, clean-energy expansion covered all of electricity demand growth.
This year, August and September were hotter than last year, resulting in rapid growth in power demand for air conditioning. Last year, in contrast, June and July were hotter.
Thermal power generation from coal and gas fell overall during the summer period, despite the rapid increase in residential power demand, with a 7% drop in June, 5% drop in July, a 4% increase in August and a 9% increase in September. Growth rates during individual months are heavily affected by which months the worst heatwaves fall on.
In terms of newly built generating capacity, solar continued to break last year’s records, with 163 gigawatts (GW) added in the first nine months of 2024. This is equal to the combined total capacity in Germany, Spain, Italy and France, the four EU countries with the most solar capacity. China’s solar capacity additions in the third quarter were up 22% year-on-year, as shown in the figure below.
The growth in China’s solar power output this year alone is likely to equal the total power generation of Australia or Vietnam in 2023, based on growth rates during the first nine months of the year.
Wind power additions accelerated as well, with 38GW added in the year to September, up 10% year-on-year and exceeding the total wind power capacity in the UK of 30GW.
China’s State Council approved 11 new nuclear reactors for construction in one go in August. The total power generating capacity of the approved projects is about 13GW. With 10 reactors approved in both 2022 and 2023 – and now 11 in 2024 – the next batch of nuclear power capacity is getting off the ground and adding to China’s clean-energy growth.
Hydropower capacity only increased 2% year-on-year, implying that most of the 11% third-quarter increase in generation was due to a recovery in capacity utilisation.
In response to severe droughts, utilisation had fallen to its lowest level in more than a decade in 2022, and recovered only partially in 2023, so this year’s recovery was expected and is closer to expected average hydropower generation.
China’s approvals of new coal power plant projects plummeted by 80% in the first half of 2024. Just 9GW of new capacity was approved, down from 52GW in the first half of last year. However, according to the Polaris Network, an energy sector news and data provider, eight large coal power projects were approved in the third quarter, likely representing an uptick in the rate of approvals compared with the first half of the year.
Construction and oil demand slowdown continued to pull down total emissions
While power sector emissions saw a small amount of growth in the third quarter of 2024, the ongoing contraction in construction volumes pulled down total emissions.
As a result, CO2 emissions stayed flat in the third quarter of 2024, at or just below the levels seen in the same period a year earlier, as shown in the figure below.
Digging deeper into the construction-led decline in emissions outside the power sector, steel output fell 9% and cement 12%, as real estate investment contracted 10% in the third quarter, maintaining the same rate as in the first half-year.
This translated into an 11% (24m tonnes of CO2, MtCO2) reduction in CO2 emissions from cement compared with the same period in 2023, shown in the figure below.
Steel emissions only fell by 3% (13MtCO2), despite the 9% fall in steel production. The reason is that the brunt of the drop in demand was borne by electric arc steelmakers rather than the coal-based steel plants with a much higher emission intensity.
The sector lacks the incentive to prioritise electric arc furnaces, which use recycled scrap and have much lower emissions. In theory, this could be encouraged by the inclusion of steel in China’s emissions trading system.
However, if the sector is treated in the same way as power, with separate benchmarks for coal-based and electric steelmaking, it will not create incentives to switch to electricity.
As one step towards structural change in the sector, the industry ministry issued a policy suspending all permitting of new steelmaking capacity, turning a de-facto stop to new permits – observed since the beginning of the year – into a formal moratorium. Until last year, the sector had been investing heavily in new coal-based steel capacity.
The other major area where emissions fell is oil consumption, which saw a 2% (13MtCO2) reduction in oil-related CO2 emissions in the third quarter of the year, also shown in the figure above. This is based on numbers from the National Bureau of Statistics.
The reduction in oil demand and related CO2 emissions may have been even steeper. The supply of oil products, measured as refinery throughput net of imports and exports, fell much more sharply. Based on this measure, CO2 from burning oil fell 10% (63MtCO2) in the third quarter, meaning that China’s CO2 emissions overall would have fallen by 2%.
The much more modest drop reported by the statistics agency could reflect the tendency of China’s statistical reporting to smooth downturns and upticks.
Another possible explanation is that refineries had previously been producing more than was being consumed, and have now had to cut output to reduce inventories.
Regardless of the magnitude of the drop, it is possible to identify the drivers of falling oil consumption. The fall in construction volumes is a major factor, as a significant share of diesel is used at construction sites and for transporting building materials.
The increase in the share of EVs is eating into petrol demand. Demand was also driven down by household spending, which remained weak until picking up in October in response to expectations of government stimulus.
The increasing share of trucks running on LNG also contributed to the fall in diesel demand. LNG truck sales accounted for about 20% of total truck sales in the nine months to March 2024, but weak overall gas demand growth indicates that this had a limited impact.
Gas consumption growth slowed down to 3% in the third quarter, from 10% in the first half of the year. Growth took place entirely in the power sector, with demand from other sectors stagnating, likely due to weak industrial demand.
After an increase in emissions in January-February, falling emissions in March-August and an increase in September, emissions would need to fall by at least 2% in the last three months of the year, for China’s annual total to drop from 2023 levels.
There is a good chance this will happen, due to an ongoing slowdown in industrial power demand growth and the end of the air conditioning season. But, even then, China would remain off track against its 2025 carbon intensity target, which requires emissions to fall by at least 2% in both 2024 and 2025, after rapid increases from 2020 to 2023.
The fundamental reason why emissions have not fallen faster – and may not have fallen at all in the third quarter – is that energy consumption growth this year continues to be much faster than historical trends.
Total energy consumption – including, but not limited to electricity consumption – grew 5.0% in the third quarter, faster than GDP, which gained 4.6%.
Until the Covid-19 pandemic, China’s energy demand growth had been much slower than GDP growth, implying falling energy intensity of the economy.
The post-Covid economic policy focused on manufacturing appears to have reversed this trend.
Coal-to-chemicals industry received new political backing
One additional wildcard in the outlook for China’s CO2 emissions is the coal-to-chemicals industry. The sector turns domestic coal into replacements for imported oil and gas, albeit with a far higher carbon footprint.
A recent policy from the National Development and Reform Commission, China’s powerful planning agency, called for ”accelerating” the development of the coal-to-chemical industry, including “speeding up the construction of strategic bases for coal-to-oil and coal-to-gas production”.
The past weeks after the issuance of the new policy have seen construction starts of a major coal-to-oil project in Shanxi, a coal-to-chemicals park in Sha’anxi and approval of a similar project in Xinjiang.
The coal-to-chemicals industry is expected to use more than 7% of all coal consumed in China in 2024, according to China Futures Research, a consultancy.
Coal consumption by the chemicals industry increased 18% in the first eight months of 2024, after a 9% increase in 2023, based on data from Wind Financial Terminal. This increase in coal consumption for coal-to-chemicals contributed two thirds of the 0.9% increase in total fossil CO2 emissions during the January to August period.
Coal consumption growth in the sector slowed down to 5% in July-August, however, and output of chemical products continued to slow in September. This smaller contribution to growth in CO2 emissions is shown in the graph above (“chemical industry”).
The recent rise in oil and gas prices, together with efforts to increase China’s domestic coal production and drive down domestic coal prices, have provided a major boost to the coal chemicals sector, which has a high sensitivity to both oil and coal prices.
Coal-to-chemicals is the sector where China’s policy priorities of energy security and emission reductions are most directly at odds.
Economic stimulus adds uncertainty to emissions outlook
After economic data indicated continuing slowdown and shortfall against GDP growth targets over the summer, expectations of a stimulus package built up.
The government responded in late September with a set of announcements, pledging various stimulus measures. The measures were focused on financial markets, but also included a commitment to “stabilise” the housing market.
The size of the stimulus package is not very large by China’s standards, and further details have disappointed those who hoped for a more radical policy turnaround. Yet, the package is clearly thought-through and coordinated, offering insights into how China’s top policymakers are planning to address the economic headwinds.
Direct income transfers of government money to households, which have been a hot topic for the past couple of years, are now going to be tried out.
Efforts to boost household spending, instead of the energy-intensive manufacturing and construction that has been the focus of previous rounds of government stimulus, would enable China to grow in a much less energy- and carbon-intensive way.
However, the sums allocated to income transfers are very small in relation to the size of the whole package. Much more money will be spent on subsidies to car and white-goods purchases. This will free up household cash for other types of spending, but it also directs household spending in the most energy-intensive direction.
Most of the stimulus is directed through the traditional routes of local government borrowing and bank lending, which tend to go into industrial and infrastructure projects.
There is no explicit climate-related emphasis to this stimulus. Quite a bit of it is likely to flow to clean energy-related investments, simply because those have been so dominant in China’s investment flows recently, but there is no further push in that direction.
Policymakers do not see an ‘early’ peak
While the rapid clean-energy growth points to the possibility of China’s emissions peaking imminently, policymakers are still setting an expectation that emissions will increase until the end of the decade and plateau or fall very gradually thereafter.
In August, China’s National Energy Administration played down the possibility of the country’s emissions having already peaked, in response to a question from a reporter referencing analyses suggesting this was possible.
The NEA department head who responded to the question emphasised that the timeline for peaking the country’s emissions – “before 2030” – has already been set by the top leadership, implying that the NEA has no mandate to change it.
The Central Committee of the Communist Party – one of the country’s highest leadership groups – reaffirmed that the aim is to “establish a falling trend” in emissions by 2035.
An earlier State Council plan said that China would focus on controlling total CO2 emissions, rather than emissions intensity, after the emission peak has been reached, and indicated that this would not happen in the 2026-30 period.
A very gradual approach to peaking emissions and reducing them after the peak, leaving more substantial emission reductions to later decades, is permissible under China’s current commitments under the Paris Agreement.
However, such a pathway would see the country use up 90% of the global emission budget for 1.5C. In scenarios that limit warming to 1.5C, China’s emissions are cut to at least 30% below 2023 levels by 2035. And recent International Energy Agency (IEA) analysis found that emerging markets such as China would need to cut emissions to 35-65% below 2022 levels by 2035, to align with the global pledges made at COP28 or national net-zero targets.
In contrast with the cautious approach telegraphed by Chinese policymakers, maintaining the rate of clean energy additions and electrification achieved in recent years could deliver a 30% reduction in CO2 emissions from fossil fuels by 2035, relative to 2023 levels.
Similarly, the IEA’s latest World Energy Outlook found clean-energy growth would help cut China’s CO2 emissions to 24% below 2023 levels by 2035, based on current policy settings. This reduction would increase to 45% by 2035 if China met its announced ambitions and targets, the IEA said.
China’s upcoming nationally determined contribution (NDC), due to be submitted to the UN under the Paris Agreement by February 2025, is expected to provide more clarity on which emissions pathway the policymakers are pursuing.
About the data
Data for the analysis was compiled from the National Bureau of Statistics of China, National Energy Administration of China, China Electricity Council and China Customs official data releases, and from WIND Information, an industry data provider.
Wind and solar output, and thermal power breakdown by fuel, was calculated by multiplying power generating capacity at the end of each month by monthly utilisation, using data reported by China Electricity Council through Wind Financial Terminal.
Total generation from thermal power and generation from hydropower and nuclear power was taken from National Bureau of Statistics monthly releases.
Monthly utilisation data was not available for biomass, so the annual average of 52% for 2023 was applied. Power sector coal consumption was estimated based on power generation from coal and the average heat rate of coal-fired power plants during each month, to avoid the issue with official coal consumption numbers affecting recent data.
When data was available from multiple sources, different sources were cross-referenced and official sources used when possible, adjusting total consumption to match the consumption growth and changes in the energy mix reported by the National Bureau of Statistics for the first quarter, the first half and the first three quarters of the year. The effect of the adjustments is less than 1% for total emissions, with unadjusted numbers showing a 1% reduction in emissions in the third quarter.
CO2 emissions estimates are based on National Bureau of Statistics default calorific values of fuels and emissions factors from China’s latest national greenhouse gas emissions inventory, for the year 2018. Cement CO2 emissions factor is based on annual estimates up to 2023.
For oil consumption, apparent consumption is calculated from refinery throughput, with net exports of oil products subtracted.
The post Analysis: No growth for China’s emissions in Q3 2024 despite coal-power rebound appeared first on Carbon Brief.
Analysis: No growth for China’s emissions in Q3 2024 despite coal-power rebound
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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