2024年3月，中国的二氧化碳（CO2）排放量下降了3%。这标志着自2022年12月放宽防疫措施、重启经济活动以来，中国碳排放量连续14个月的增长告一段落。
Carbon Brief基于官方数字和商业数据进行的新分析显示，中国CO2排放量在2023年或已达峰。
2024年3月CO2排放量下降的驱动因素包括光电和风电的快速增长，这满足了电力需求增长的90%，以及建筑活动的减少。
石油需求增长也陷入停滞，表明疫情后的经济反弹可能已临近尾声。
如果中国能维持去年创纪录的清洁能源建设水平，该国有望在2023年实现碳达峰。
然而，整个行业和政府对清洁能源的增长前景看法不一。如果中国尚未实现碳达峰，如何弥合分歧将是决定碳达峰何时到来的关键因素。
该分析的其他关键发现包括：
- 尽管电力需求强劲增长，但光电和风电的增长推动化石燃料发电量份额从前一年的67.4%下降至2024年3月的63.6%。
- 由于中国房地产建设活动的持续萎缩，2024年3月钢铁产量下降了8%，水泥产量下降了22%。
- 电动汽车现在约占中国道路上汽车总量的十分之一，将汽油需求增长拉低了约3.5个百分点。
- 去年创纪录的太阳能新增发电装机中，约45%是规模较小的分布式光伏，导致看似出现了“数据缺失”问题。
为什么三月排放量出现下降？
根据中国国家统计局发布的初步能源消费数据，2024年第一季度中国的碳排放量总体显著增加。
今年1月和2月的碳排放量仍较2023年的低基数大幅增长，彼时中国经济仍因刚结束不久的清零防疫措施而受到抑制。
因此，与2023年同期相比，2024年第一季度的CO2排放量同比增长了3.8%，煤炭消费量增长了3%，石油消费量增长了4%，天然气消费量增长了11%。
转折点出现在今年3月份。由于该月份的煤炭消费量降低了1%，石油消费保持平稳，而水泥产量则下降了22%，导致3月CO2排放量同比下降了3%。尽管天然气消费量增长了14%，但由于其在中国能源结构中占比较小，从而影响有限。
如下图所示，自2022年12月放宽疫情限制措施后，中国的碳排放量从2023年2月开始回升。
因此，2023年1月至2月的同比比较仍然受到去年疫情导致的低基数影响，这使得3月的数据成为能够清楚地反映碳排放趋势的首个月度数据。
近年来，中国碳排放量增长的主要推动力来自电力部门（见下文）。
反之，3月碳排放趋势转为下降，主要原因也是电力部门的排放量增长的大幅放缓。由于光电和风电的强劲增长，电力部门3月的碳排放量仅同比增长了1%。
如下图所示，尽管电力部门的排放量企稳，但建筑业对钢铁和水泥的需求持续下降，这才是3月份碳排放量减少的最主要原因。
钢铁产量下降了8%，因此炼钢厂的主要燃料炼焦煤的产量也随之降低。水泥产量同比骤降了22%。
由于政府对房地产行业高杠杆的打击和对金融风险的管控，以及建筑行业过去的繁荣导致了产能过剩，房地产行业投资已连续第三年收缩，这使得上述排放趋势可能会继续维持。
尽管建筑业需求出现收缩，但中国对钢铁和其他能源密集型金属的需求并未出现预期的大幅下降。
这背后的原因是制造业的快速增长和对该行业的投资，而在设施建设和工业机械生产中都需使用金属制品。
但是，随着全球各种商品和大宗货物的市场逐渐饱和，这种制造业的增长不太可能持续下去。当局的经济政策现在强调“新质生产力”，这是推动经济增长摆脱对传统重工业的依赖的最新尝试。“新质生产力”指高端的制造和研发，这些领域的能源密集程度大多比中国的传统工业部门更低。
从2024年3月其他行业的情况来看，运输用油的需求在经历了几个月的强劲增长之后，变得与去年同期相比近乎持平。这表明疫情后的需求反弹可能正在逐渐消失。
航空燃料（+35%）和汽油（+7%）产量仍在增长，说明客运需求出现增长。但柴油产量增长停滞（+1%），原油加工量也仅增加了1%。
电动汽车的增长正显著削减石油需求量。根据过去十年的累计销售数据估计，电动汽车在道路上所有车辆中的占比从去年的7.0%增加到10.5%。这表明，电动汽车的普及使汽油需求增长降低了3.5个百分点。
天然气需求出现大幅反弹，同比增长14%。此前天然气价格高企导致需求下降。天然气消费的增长主要来自工业和家庭部门。
随着燃气电厂利用率有所恢复，电力部门的天然气消费量增长了8%，但这仅占总体增长很小的一部分。
天然气在中国能源结构中的占比曾连续增长了二十多年，在2021至2023年间有所下降，现在开始恢复增长。
近期推动碳排放量增长的一个因素仍在继续：化工行业的煤炭消费量增长了14%，延续了2022和2023年两位数的增长趋势。
尽管目前还没有足够的数据来估算4月份的CO2排放量，但当月的工业数据表明，3月排放下降的趋势仍在继续。
由于光伏发电满足了大部分的电力需求增长，火力发电量——主要来自煤电——缓慢增长了1.3%。钢铁、水泥和焦炭产量分别下降了8%、9%和7%，反映出建筑需求的持续减少。炼油量下降了3%。
国内煤炭开采量下降了3%，而进口量增加了11%，这意味着总供应量减少了5%。
天然气需求进一步强劲增长，进口量增长了15%，国内产量增加了3%。在能源密集型行业中，化工和有色金属行业的产量继续保持较快增长。
光电和风电满足需求增长
企稳的电力部门排放量值得关注，因为电力需求继续以7.4%高速增长，而受长期干旱的影响，水电利用率低于长期平均水平。
过去几年，工业用电推动电力需求迅速增长。3月，工业需求增长放缓，但服务业的反弹维持了整体需求的增长。
近一半的用电需求增长来自工业，其中有色金属、化工、机械和电子等行业是最主要的需求增长的领域。服务业贡献了需求增长的三分之一，主要源自批发和零售贸易，另有六分之一来自家庭用电。
在2022年历史性的热浪引发一波空调购买潮的推动下，家庭用电需求在过去几年也出现了激增，尤其是在以前没有空调的低收入家庭。
尽管电力需求快速增长，但由于分布式光伏电站的大规模部署，规模以上工业发电量增速放缓至3%。
（与大型集中式太阳能发电场相比，分布式光伏电站指的是装机规模较小的发电系统，通常安装在家庭和企业的屋顶上。）
总体而言，由于2023年光电和风电装机的创纪录增长，光电和风电发电量占比已达到22%，并在3月实现了近90%的同比增长。非化石燃料发电量占比从去年的32.6%上升至36.2%。
分布式光伏对发电的贡献越来越大，但这在一定程度上被中国月度电力数据的报告方式所掩盖。国家统计局只发布大型光伏和风力发电站的月度发电量。它还系统性地上修了前几年的数据，这表明其没有实时捕捉新进入市场的企业的发电量。
由于去年创纪录的光伏新增装机容量中有45%是分布式发电，对小型光伏装机的排除对这些数字的影响比以往大得多。
这在中国和海外引起很多困惑，特别是报告的用电量数据远大于发电量数据，这显然是不可能的，彭博社甚至称其为“数据缺失问题”。
然而，用电量和规模以上工业发电量之间不断扩大的差距表明，分布式光伏在满足用电需求方面的贡献越来越大。
与月报数据不同，中国的年度统计公报中没有“缺失”的数据，因为年度统计包括所有电厂，无论其规模。例如，2023年的年度统计公报显示，光伏发电量是月度统计的两倍，风电发电量则多出了10%。
事实上，如果按照月度数据中的装机容量和利用小时数来计算发电量，得到的数据与年度报告数据非常接近。这清楚地表明，尽管统计局的月度数据中没有纳入分布式光伏的发电量，但其的确为满足电力需求做出重大贡献。
清洁能源热潮继续
去年光电和风电新增发电装机容量约300吉瓦（GW），这推动了3月份碳排放量的下降。这种热潮在2024年前三个月加速，与去年相比增长了40%。
太阳能发电新增装机容量46吉瓦，同比增长36%；风电新增装机容量16吉瓦，同比增长50%。
通常来说，第一季度的新增装机容量增速一般较低，而且由于报告滞后，相当多的新增装机在年底才被报告。
强劲的同比增长表明，对新项目能否成功并网的担忧并未影响新增装机容量增加的步伐。即便今年剩下时间里增速会有所放缓，但迄今为止的数据表明，去年创纪录的增速可能会在2024年持续。
今年1月至3月，太阳能电池板产量在去年的高基数上又增长了20%，表明中国和海外的需求强劲。
电动汽车产量增长了29%，汽车总产量恢复了下降趋势，这使得电动汽车占比持续快速攀升，在第一季度达到了31%，而去年同期为26%。
由于光电和风电项目的经济效益显著，对新增装机的主要限制来自并网。因担心无法消纳新增发电量，去年多个省级电网运营商已开始限制新增光电和风电项目。
这凸显了中国电网运营上的短板，因为风电和光电占中国总发电量的份额仍然有限，仅为15%。相比之下，两者在欧盟电力系统中的占比为27%，德国、西班牙和希腊达到40%。
中国已开始采取行动解决该问题。国家发改委已开始放宽光电和风电并网的要求。这将增加风光项目投资者的不确定性，但提高了电网运营商的消纳能力，从而支持发电装机和发电量的增长。
国家发改委还发布了一项推动储能发展的政策，承诺到2027年，电力系统将能够支撑新增风光装机容量，同时将因电网问题而浪费的发电量比例保持在较低水平。
虽然光电和风电已开始满足大部分或全部用电需求的增长，但煤电投资仍在继续。第一季度，火电装机的新增速度同比略有放缓，但各省2024年的“重点项目清单”中包括超过200吉瓦的火电项目，其主要是燃煤电厂。
未来仍充满变数
中国3月份碳排放量的下降可能标志着自2020年以来碳排放的强劲增长出现了转折点。正如 Carbon Brief 去年秋天发布的一篇分析所述，目前清洁能源的增长率有可能使该国提前实现碳达峰。
因此，清洁能源增长是否会持续，是影响中国未来排放路径的关键问题。但是，外界对于未来风电和光电的发展速度仍存在很大分歧。
中国光伏行业协会在其“保守”情景中预测，2024年至2030年间年均新增装机容量为225吉瓦，比2023年的217吉瓦略有增加。在“乐观”情景下，这一数字将加速至每年280吉瓦。根据该协会预测，中国的太阳能总装机容量将从目前的660吉瓦，到2030年增加到2200至2600吉瓦。
据风电行业数据，要实现2060年碳中和目标，中国需要在2021年至2025年间每年新增超过50吉瓦的风电装机。从2026年起，每年新增装机超过60吉瓦。这是一个相对适中的轨迹，因为2023年风电新增装机容量已经达到76吉瓦。
另一方面，国家能源局局长章建华在最近一篇文章中写道，清洁能源的新增装机容量应保持在每年100吉瓦以上，但这不到2023年实际水平的一半。这意味着他认为最近的加速增长是反常的，可能难以持续。
与之类似，在国家能源局2024年的工作计划中，从总发电装机容量和非化石能源发电容量占比，可以推算出非化石能源新增装机的目标在170吉瓦左右。（尽管2023年工作计划的目标是160吉瓦，但实际新增接近300吉瓦。）
下图展现了对于光电和风电发展的不同愿景。深蓝色线代表了章建华的预期，即年新增装机容量将回落到2020年至2022年水平；浅蓝色和红色线是可再生能源行业预测的增长趋势，其大致保持在2023年的水平，或稳步增长。
到2030年，光伏行业协会和国家能源局就光电和风电的装机目标差距为1400至1800吉瓦。如果新增的清洁能源发电量在2030年能够取代煤电，那么碳排放量将比当前水平下降10至15%。到2035年，随着风电和光电进一步发展，碳排放量将比当前水平下降20至25%。
章建华在文章中指出了一些挑战，以解释为何他认为清洁能源新增发电容量水平较低，包括储能价格机制尚未健全，能源转型政策合力亟待加强，以及集中连片新能源发展用地、用海空间不足等。
尽管如此，减缓光电、风电和相关储能的新增装机速度将给中国经济泼上一盆冷水，因为这些清洁能源行业已成为经济增长的一个关键来源。
此外，最近对这些行业生产能力的大量投资，只有在清洁能源设备需求持续增长的情况下才能得到利用和回报。
政府雄心的减弱也反映在今年设定的较为保守的官方目标上。根据环保部最近设定的目标，2024年碳强度（每单位GDP的排放量）的目标降幅为3.9%。
尽管这一目标超过过去三年碳强度年均仅下降1.5%的水平，但考虑到GDP增速目标是“约5%”，该碳强度目标实际将允许碳排放量增长逾1%。
在2021年至2023年碳排放量快速增加之后，中国已经严重偏离了2025年和2030年的碳强度目标，而2024年的年度目标未能缩小这一差距。
3.9%正是实现“十四五”规划中碳排放强度下降18%的目标所需的年均下降幅度。因此，该目标避免了落后幅度进一步扩大，但对弥补迄今为止的进展滞后毫无作用。
国家发改委还设定了一个相对保守的目标，即到2024年将“化石能源强度”降低2.5%，这将允许碳排放量增加2%以上。
章建华还认为，在2026至2030年期间，清洁能源应满足70%的能源消费增长，这一目标也与清洁能源新增装机容量放缓的趋势一致。
这意味着，能源消费增长的30%仍将通过增加化石燃料的使用来满足，因此CO2排放量也将继续增加。
持续增长的碳排放量意味着中国将面临无法实现2030年的碳强度承诺的风险，而这是中国在《巴黎协定》下提交的国际气候承诺的一部分。因为假设GDP年均增长5%或更低，根据这一承诺，从2023年到2030年，能源部门的CO2排放量没有增加的空间。
因此，中国能否实现其气候承诺，取决于清洁能源增长是否会继续显著超过中央政府制定的目标，亦或是这些目标在未来是否会提高。
数据来源
本分析数据来源于中国国家统计局、国家能源局、中国电力企业联合会、中国海关官方发布的数据以及行业数据提供商WIND资讯。
电力行业煤炭消费量是根据煤炭发电量和燃煤电厂每月平均发热量来估算的，以避免官方煤炭消费量影响近期数据的问题。煤炭发电量根据火力发电总量和燃煤、燃气、生物质电厂报告容量和利用小时数计算，以得到综合火力发电数据。
当数据来自多个来源时，本文交叉引用不同来源并尽可能使用官方来源，调整总消费数控，以匹配国家统计局报告的消费增长和能源结构变化。
2024年第一季度的数据进行了调整，以匹配国家统计局初步官方数据中报告的整个季度的同比增长率。但无论有没有这种调整，三月份排放量下降的结论都成立。
二氧化碳排放量估算基于国家统计局默认的 2018 年燃料热值和中国最新国家温室气体排放清单中的排放因素。水泥二氧化碳排放基于截至 2023 年的年度估算。
对于石油消耗量，表观消耗量是根据炼油厂吞吐量计算，减去石油产品的净出口量。
The post 分析：月度碳排放量下降或表明中国已在2023年碳达峰 appeared first on Carbon Brief.
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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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