The Washington Post-Warming oceans are fueling destructive hurricanes earlier study finds
September 27, 2023 4 min 777 words
这篇报道揭示了一个令人担忧的趋势：大型飓风形成的时间正在比几代人之前明显提前。这一趋势的主要驱动因素是由人类活动引起的气候变化所导致的海洋变暖。根据研究，这种情况对气象预测和社会有着深远的影响。 研究将“强烈热带气旋”定义为最大持续风速超过127英里/小时的飓风、台风和其他热带系统，本质上是高端3级或更严重的飓风。研究发现，强烈热带气旋的形成日期在北半球每十年提前3.7天，南半球每十年提前3.2天。换句话说，自1981年以来，北半球高纬度地区的强烈飓风发生时间提前了大约15.5天，而南半球的提前幅度略低于两周。 这对我们来说具有双重警示意义，因为较早季节形成的强烈热带气旋更容易导致严重的洪水。极端降雨事件最常见于夏季，当空气最温暖且能容纳最多水分时。而历史上，强烈热带气旋更常见于秋季，当时海洋最温暖。现在，高峰期的强烈热带气旋活动逐渐延伸到夏季，这意味着高峰期的极端降雨季节与强烈热带气旋之间的重叠更大，从而可能导致洪水灾害更加普遍。 研究的作者回顾了1981年至2017年之间的全球热带气旋，这段时间卫星数据可获得。他们使用了一组公开可用的数据集，使用卫星技术估计热带气旋的强度，然后确定了每场风暴达到其“生命周期最大强度”的日期。尽管对于所有强度的热带气旋进行了分析，但研究人员发现强烈热带气旋的形成时间趋势最为显著。这表明强烈热带气旋更加敏感于海表温度的升高，而由于人为气候变化，这种升温预计将继续下去。 此研究还发现，风暴的迅速强化事件也在季节上呈现出提前的趋势，北半球每十年提前约3.6天，南半球每十年提前约4.1天。迅速强化是指一场风暴在24小时内至少强化35英里/小时或更多的过程。绝大多数强烈热带气旋在其生命周期中至少迅速强化一次；很少有风暴在没有迅速强化的情况下达到强烈飓风的状态。 这个趋势令人担忧，因为经历迅速强化的风暴往往更难以预测，通常造成更大的破坏，给应急规划和应对带来挑战。这篇研究加入了越来越多的文献，显示了在变暖的世界中，热带气旋正在发生变化。它们不仅形成得更早，迅速强化的频率更高，而且研究还表明它们的强度高峰达到的地点比以前更北，降雨更重，停滞时间更长。 总的来说，这篇报道强调了气候变化对于极端气象事件的影响，并提醒我们采取行动来减缓气候变化，以应对未来可能更加频繁和严重的飓风和洪水事件。这是一个紧迫的问题，需要国际社会共同努力来解决。
2023-09-27T14:15:08.708Z
Major hurricanes — which cause devastating damage on the planet’s coastlines and often well inland — are forming “significantly” earlier in the year than they did generations ago, according to a study published in the journal Nature Wednesday. Warming ocean waters, boosted by human-caused climate change, are thought to be a primary driver of the trend, which has both forecasting and societal implications.
The study defined “intense tropical cyclones” as hurricane, typhoons and other tropical systems having maximum sustained winds over 127 mph — essentially a high-end Category 3 hurricane or worse. The authors, made up of a group of researchers from China and the United States, found that the formation dates of intense tropical cyclones are shifting 3.7 days earlier per decade in the northern hemisphere, and 3.2 days per decade earlier in the southern hemisphere.
In other words, since 1981, which the study’s analysis began, the incidence of intense hurricanes has lurched forward some 15.5 days north of the equator. In the southern hemisphere, the shift is just under two weeks.
A first: Category 5 storms have formed in every ocean basin this year
Intense tropical cyclones are disproportionately responsible for the overwhelming majority of economic and human losses associated with tropical systems.
The increasing tendency of intense tropical cyclones earlier in the season is of particular concern because it predisposes them to have a greater risk of causing serious flooding, the study authors assert.
Extreme rainfall events are most common in the summertime, when the air is warmest and can hold the most moisture. Intense tropical cyclones, historically, were more common in the autumn, when oceans are the warmest. The inching of peak intense tropical cyclone activity into the summertime means a greater overlap between peak extreme rainfall season and intense tropical cyclones, suggesting that flood disasters may be made more common.
What the researchers did
Researchers reviewed all global tropical cyclones between 1981 and 2017, during which satellite data was readily available. They drew upon a publicly available data set that estimates tropical cyclone strength using satellite techniques. Then they determined what date each storm achieved its “lifetime maximum intensity.”
The researchers found the greatest tendency for earlier-forming intense tropical cyclones was in the Northwest Pacific east of the Philippines, Taiwan and Japan, the western South Pacific east of Australia and in the Gulf of Mexico. Parts of the Southern Indian Ocean and northeast Pacific south of the Baja Peninsula are also seeing an uptick in early-season intense tropical cyclone activity.
Curiously, despite robust trends in shifts for intense tropical cyclones, the researchers found little change in the timing when they analyzed tropical cyclones of all strengths. That suggests that intense tropical cyclones are more sensitive to increases in sea surface temperature, which are expected to continue because of human-caused climate change.
Previous studies have also demonstrated that most intense tropical cyclones (Category 3 and higher) have exhibited increases in strength in a warming world.
“It is likely that the global proportion of major (Category 3—5) tropical cyclone occurrence has increased over the last four decades,” the Intergovernmental Panel on Climate Change concluded in its most recent assessment.
The Nature study team also found that storm rapid intensification events are trending earlier in the season too — about 3.6 days per decade in the northern hemisphere, and 4.1 days per decade in the southern hemisphere.
Rapid intensification describes the process by which a storm strengthens by at least 35 mph or more in 24 hours. The vast majority of intense tropical cyclones rapidly intensify at least once in their lifetime; few storms reach major hurricane status without rapidly intensifying at some point.
Just two weeks ago, Hurricane Lee intensified by 80 mph in 24 hours from a low-end Category 1 to a solid Category 5 — the third most quickly-intensifying hurricane on record in the Atlantic. The other seven Category 5 Atlantic hurricanes that have formed since 2016 all underwent rapid intensification.
Hurricane Idalia’s rapid intensification is becoming the norm for gulf storms
Storms that undergo rapid intensification are the most difficult to predict and often cause greater destruction, posing challenges for emergency planning and response.
The study joins a growing literature showing changes in tropical cyclones in a warming world. Not only are they forming earlier and rapidly intensifying more frequently, but studies have shown they are also reaching their peak intensity farther north than they used to, producing heavier rain, slowing down and staying stronger over land.
Jason Samenow contributed to this report.