热浪席卷全球 人体对高温的耐受临近极限

Extreme global temperatures are pushing the human body “close to thermal limits,” according to a climate scientist.

Record-breaking heat has swept through Europe last week with temperatures topping 40 degrees Celsius in a number of countries.

However, in places such as South Asia and the Persian Gulf, people are already enduring temperatures reaching up to 54 degrees Celsius.

Despite all the body’s thermal efficiencies, these areas could soon be uninhabitable, according to Loughborough University climate scientist Tom Matthews.

When air temperature exceeds 35 degrees Celsius, the body relies on sweating to keep core temperatures at a safe level. However, when the wet bulb temperature — which reflects the ability of moisture to evaporate — reaches 35 degrees Celsius, this system no longer works.

“The wet bulb temperature includes the cooling effect of water evaporating from the thermometer, and so is normally much lower than the normal (dry bulb) temperature reported in weather forecasts,” Matthews wrote.

“Once this wet bulb temperature threshold is crossed, the air is so full of water vapor that sweat no longer evaporates,” he said.

This means the human body cannot cool itself enough to survive more than a few hours.

“Without the means to dissipate heat, our core temperature rises, irrespective of how much water we drink, how much shade we seek, or how much rest we take,” he explained.

Some areas — which are among the most densely populated on Earth — could pass this threshold by the end of the century, according to Matthews.

With climate change starting to profoundly alter weather systems, rising temperatures could soon make parts of the world uninhabitable.

If electricity can be maintained, living in chronically heat-stressed conditions may be possible, but a power outage could be catastrophic.

In a recent paper published in Nature Climate Change, Matthews and his team looked at the probability of a “gray swan” event in the case of extreme heat coinciding with massive blackouts.

Heat-stressed countries are likely to see the largest absolute increases in humid-heat and they are often the least well-prepared to deal with the hazard. This could drive mass migration, which would make heat a worldwide issue — even for countries that are not experiencing scorching temperatures.

Words to Learn 相关词汇

【湿球温度】shīqiú wēndù

wet bulb temperature the lowest temperature that can be reached by evaporating water into the air

【驱散】qūsàn

dissipate disperse or scatter

一位气候科学家表示，全球极端气温正将人体推向“高温极限”。上周，破纪录的高温席卷欧洲，一些国家的气温超过40摄氏度。

然而，在南亚和波斯湾等地，人们忍受的高温已达54摄氏度。

拉夫堡大学气候科学家汤姆·马修斯说，尽管人体的热效率很高，但这些区域可能很快就不宜居住了。

当气温超过35摄氏度时，身体依靠流汗来将核心温度保持在安全水平。然而，当反映水分蒸发能力的“湿球温度”达到35摄氏度时，该机能就不再起作用了。

马修斯博士写道：“湿球温度包括温度计的水分蒸发冷却效果，因此通常比天气预报中的正常（干球）温度低得多。”

他说：“一旦湿球温度超过阈值，空气中就充满了水蒸气，汗水就不再蒸发了。”

这意味着人体不能自我降温，这种情况持续几个小时就能危及生命。

他解释说：“如果不能散热，人体的核心温度就会上升，不管我们喝了多少水，在阴凉地方呆了多久，或者休息了多长时间。”

马修斯说，地球上人口最密集的一些地区的湿球温度可能会在本世纪末突破这一阈值。

随着气候变化开始深度改变天气系统，不断上升的气温可能很快使部分地区不宜居住。

如果能维持电力供应，长期生活在高热状况下是可能的，但停电可能造成灾难性后果。

在最近发表在《自然气候变化》杂志上的一篇文章中，马修斯和他的团队研究了极端高温和大范围停电同时发生的“灰天鹅”事件的可能性。

高温国家很可能出现最严重的湿热绝对值增加，而这些国家应对这种危险往往准备最不充分。这可能会导致大规模的人口迁移，并将使高温成为全球性问题，即使对那些没有经历高温的国家也是如此。(Chinadaily.com.cn)