厄爾尼諾又要來(lái)了？今年會(huì)有多熱？｜科學(xué)60秒

夏天不可避免會(huì)越來(lái)越熱嗎

(資料圖片)

從地中海到南亞，世界各地都在打破高溫記錄，最近打破紀(jì)錄的，則是太平洋西北部和加拿大西部。

“在不列顛哥倫比亞省各地，居民正在應(yīng)對(duì)破紀(jì)錄的熱浪?！薄爸芰?7項(xiàng)溫度記錄被打破，加拿大西部大部分地區(qū)都發(fā)出了高溫警告。”“這不是一個(gè)平常的五月，這甚至不是一個(gè)極為干燥的五月，這過(guò)于異常了?！?/p>

有些地區(qū)的溫度達(dá)到了90年代中期的水平，也就是比正常情況下高出約10~14攝氏度。北半球已入夏，隨著氣候變暖，近幾年的炎熱夏季將成為我們余生中最涼爽的幾個(gè)夏季。

那么首先，熱浪是如何形成的？

當(dāng)一個(gè)高壓系統(tǒng)在同一個(gè)地區(qū)上空停留多天時(shí)，熱浪就會(huì)形成。在這些系統(tǒng)之下，空氣下沉導(dǎo)致云層無(wú)法形成。天空中沒(méi)有云意味著太陽(yáng)可以直接烘烤地表。想象一下坐進(jìn)在太陽(yáng)下暴曬過(guò)的轎車，大概就是這么一回事。

而這可能十分危險(xiǎn)。2021年6月，北美的超強(qiáng)熱浪導(dǎo)致了數(shù)百人死亡。隨著氣候的變化，像這樣的熱浪將發(fā)生得更加頻繁、持續(xù)時(shí)間更長(zhǎng)，而且隨著時(shí)間的推移，它們可能會(huì)變得更加強(qiáng)烈。高溫記錄更容易被打破，在某些情況可能會(huì)創(chuàng)下十分夸張的新高，通常而言，高溫記錄只會(huì)比此前高出零點(diǎn)幾度，但是不久前在加拿大哈德遜灣附近，一處仍被冬季冰雪所覆蓋的地方，新的高溫記錄比原來(lái)高出了7攝氏度，氣溫比平均水平上升了22攝氏度。

但是不一定非得等到創(chuàng)下高溫記錄我們才會(huì)感到難受，特別是在像太平洋西北部這樣空調(diào)不常見(jiàn)的地方，那里的人們對(duì)熱的適應(yīng)性較差，而在一年中的某些時(shí)候，比如5月，熱浪會(huì)讓日子變得十分難耐。對(duì)于老人、兒童和患有哮喘或心臟病等健康問(wèn)題的人來(lái)說(shuō)，熱浪也特別煎熬。構(gòu)成問(wèn)題的不僅僅是白天飆升的高溫，更高的夜間溫度意味著人體很難有機(jī)會(huì)降溫，特別是如果沒(méi)有空調(diào)。

濕度在我們對(duì)熱的體驗(yàn)中也扮演著重要的角色。夏天在戶外活動(dòng)過(guò)的人都知道，高溫會(huì)讓我們出汗，這實(shí)際上是身體的自然冷卻系統(tǒng)，因?yàn)楹顾谡舭l(fā)的過(guò)程中會(huì)讓我們的皮膚降溫。但是，當(dāng)濕度很高時(shí)，這種蒸發(fā)速度就會(huì)減慢，甚至停止。

隨著全球氣溫逐年升高，記憶中最強(qiáng)的熱浪和夏天將變得不值一提。1998年的夏天曾是有記錄以來(lái)最熱的夏天，這要?dú)w功于厄爾尼諾（El Ni?o）現(xiàn)象，但現(xiàn)在，它只能算是第十熱的年份。厄爾尼諾現(xiàn)象發(fā)生時(shí)，熱帶太平洋東部地區(qū)的海水溫度會(huì)比平時(shí)更高。釋放到大氣中的熱量使會(huì)讓影響全球天氣的大型空氣循環(huán)模式發(fā)生變化，這種熱量也導(dǎo)致全球氣溫升高。

根據(jù)美國(guó)國(guó)家海洋和大氣管理局（NOAA）在5月11日發(fā)布的預(yù)測(cè)，2023年有90%的可能性出現(xiàn)厄爾尼諾現(xiàn)象，而且可能……[查看全文]

Heat Waves Are Breaking Records.

Here"s What You Need to Know

Andrea Thompson:?As you might have heard, heat records are breaking all around the world from the Mediterranean to South Asia. Most recently, records fell in the Pacific Northwest and western Canada.

Newscaster:?Across British Columbia, residents are dealing with a record-breaking heat wave.

Newscaster:?Seventeen temperature records fell on Saturday with heat advisories falling across much of Western Canada.

Interviewee:?This is not a usual May. This is not even an abnormally dry May. This is something exceptional.

Kelso Harper:?A few places saw temperatures in the mid-90s. For context–that’s about 20 to 25 degrees Fahrenheit above normal.

Thompson:?Today we’re talking about heat. It’s nearly summer in the Northern Hemisphere, and with climate change, today’s hot summers will be among the coolest of the rest of our lives.

Thompson: I’m?Scientific American’s earth and environment editor, Andrea Thompson.

Harper:?I’m Kelso Harper, a SciAm multimedia editor, and you’re listening to?Science, Quickly.

Harper: So, Andrea, first things first. How does a heat wave even happen?

Thompson: Heat waves happen when a high pressure system parks itself over an area for several days. Under these systems, air sinks, which keeps clouds from forming. And if you don’t have clouds in the sky—that means the sun can really bake the surface. Imagine getting into your car after it’s been sitting in the sun, and you get the picture.

Harper: Right, and this can be really dangerous. In June of 2021, a particularly strong heat wave in the same area contributed to hundreds of deaths.

Thompson: With climate change, heat waves like this are happening more often, they’re lasting longer and they’re likely to become more intense as time goes on.

Harper: And heat records are more likely to be broken and in some cases completely shattered. Normally, heat records are broken by a few tenths of a degree. But last week in Canada near Hudson Bay—which is still covered in winter ice—a heat record was broken by a huge 7 degrees Celsius, or more than 12 degrees Fahrenheit. The temperature shot up 40 degrees Fahrenheit over the average.

Thompson:?But a heat wave doesn’t have to set records to feel miserable. Especially in places like the Pacific Northwest, where air conditioning isn’t as prevalent and where people are less adjusted to heat. And at times of the year—like May—when people aren’t expecting them.

Harper:?Heat waves are also particularly tough on the elderly, young children and people with health conditions like asthma or heart disease.

Thompson:?And it’s not just the soaring high temperatures of the day that pose a problem. Higher nighttime temperatures mean people don’t have a chance to cool down, particularly if they lack air conditioning.

Harper:?And humidity plays a role in our experience of heat, right?

Thompson:?Yeah, as anyone who’s stepped outside on a summer day knows, high temperatures cause us to sweat. That’s actually the body’s natural cooling system, because the sweat cools our skin as it evaporates. But when the humidity is high, that evaporation slows down and can eventually stop.

Harper:?And with global temperatures rising higher every year, it sounds like the heat waves and summers that are among the hottest in memory today are going to be left in the dust.

Thompson: Yeah, the summer of 1998 was by far the hottest summer on record at the time, thanks to a?blockbuster?El Ni?o event, but it’s now the 10th hottest.

Harper:?Speaking of El Ni?o, forecasters are expecting one to develop this year. Can you remind us what an El Ni?o actually is?

Thompson: An El Ni?o happens when ocean waters in the eastern part of the tropical Pacific are hotter than usual. The heat that releases into the atmosphere shifts around some of the big air circulation patterns that influence weather all over the world. That heat also amps up global temperatures.

Harper: And how likely is it that we’ll see one this year?

Thompson:?There’s about a 90 percent chance right now, and it’s looking like...[full transcript]

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