Is the weather actually becoming more extreme? - R. Saravanan

譯者: Regina Chu 審譯者: Marssi Draw

From 2016 to 2019,

從 2016 到 2019 年

meteorologists saw record-breaking heat waves around the globe,

氣象學家看到全球各地破紀錄的熱浪

rampant wildfires in California and Australia,

加州及澳洲的野火肆虐

and the longest run of category 5 tropical cyclones on record.

及史上持續最久的五級熱帶氣旋

The number of extreme weather events has been increasing for the last 40 years,

過去四十年，極端天氣事件不斷增加

and current predictions suggest that trend will continue.

目前的預報顯示這種趨勢將持續下去

But are these natural disasters simply bad weather?

但是這些天災只是壞天氣而已嗎？

Or are they due to our changing climate?

或是因為氣候變遷造成？

To answer this question

要回答這個問題

we need to understand the differences between weather and climate—

我們必須了解天氣與氣候的不同

what they are, how we predict them, and what those predictions can tell us.

這兩者是什麼，要怎麼預報 及這些預報能告訴我們什麼

Meteorologists define weather as the conditions of the atmosphere

氣象學家定義天氣

為大氣在某時某地的狀態

at a particular time and place.

Currently, researchers can predict a region’s weather for the next week

目前，研究人員可以預報 某一個區域下一週的天氣

with roughly 80% accuracy.

準確度大約是 80%

Climate describes a region’s average atmospheric conditions

氣候則描述某個區域的平均大氣狀態

over periods of a month or more.

通常是一個月或更長時間的平均值

Climate predictions can forecast average temperatures for decades to come,

氣候預報可以預測 未來數十年的平均溫度

but they can’t tell us what specific weather events to expect.

但是不能告訴我們具體的天氣為何

These two types of predictions give us such different information

這兩種預報會給我們大不相同的資訊

because they’re based on different data.

是因為它們以不同的數據為基礎

To forecast weather,

要預報天氣

meteorologists need to measure the atmosphere’s initial conditions.

氣象學家需要觀測大氣的初始條件

These are the current levels of precipitation, air pressure, humidity,

包括目前的降雨量、氣壓、濕度

wind speed and wind direction that determine a region’s weather.

風速及風向等等 這些都會決定某區域天氣的條件

Twice every day, meteorologists from over 800 stations around the globe

全球八百多個氣象站的 氣象學家會每天兩次

release balloons into the atmosphere.

釋放氣球進入大氣中

These balloons carry instruments called radiosondes,

這些氣球帶著稱作 無線電探空儀的儀器

which measure initial conditions

會觀測初始條件

and transmit their findings to international weather centers.

然後把結果傳輸到各個國際氣象中心

Meteorologists then run the data through predictive physics models

氣象學家再用預報物理模式跑數據

that generate the final weather forecast.

產生最終的天氣預報

Unfortunately, there’s something stopping this global web of data

可惜，有些東西會阻礙這個全球數據網

from producing a perfect prediction:

產生完美的預報：

weather is a fundamentally chaotic system.

天氣本身就是一個混沌系統

This means it’s incredibly sensitive and impossible to perfectly forecast

這意味著它非常敏感

如果沒有系統所有要素的絕對知識 不可能產生完美預報

without absolute knowledge of all the system’s elements.

In a period of just ten days,

在短短的十天內

even incredibly small disturbances can massively impact atmospheric conditions—

即使是極細微的干擾

也可以對大氣狀態產生極大的影響

making it impossible to reliably predict weather beyond two weeks.

無法準確預測兩週後的氣象

Climate prediction, on the other hand, is far less turbulent.

另一方面氣候預報就沒有這麼亂

This is partly because a region’s climate is, by definition,

部分原因是某地區的氣候按定義來說

the average of all its weather data.

是其所有氣象數據的平均值

But also because climate forecasts ignore

但也是因為氣候預報

會忽略目前大氣正在發生的事

what’s currently happening in the atmosphere,

and focus on the range of what could happen.

而專注在可能會發生什麼的範圍

These parameters are known as boundary conditions,

這些參數是所謂的邊界條件

and as their name suggests, they act as constraints on climate and weather.

如同字面所說

它們扮演氣候及氣象的限制條件

One example of a boundary condition is solar radiation.

邊界條件的一個例子就是日射

By analyzing the precise distance and angle between a location and the sun,

透過分析某位置和太陽之間的 精確距離及角度

we can determine the amount of heat that area will receive.

我們可以算出那個區域 會接收多少熱能

And since we know how the sun behaves throughout the year,

既然我們知道太陽一年的變化

we can accurately predict its effects on temperature.

我們就可以準確預測它對溫度的影響

Averaged across years of data,

把跨數年的數據取平均值

this reveals periodic patterns, including seasons.

就會揭示周期性的模式，包括季節

Most boundary conditions have well-defined values that change slowly, if at all.

大多數邊界條件都有明確定義的值 這些值如果有變化也非常緩慢

This allows researchers to reliably predict climate years into the future.

這讓研究人員能確實預報 未來幾年的氣候

But here’s where it gets tricky.

但這也是事情變得棘手的地方

Even the slightest change in these boundary conditions

即使這些邊界條件僅有細微的變化

represents a much larger shift for the chaotic weather system.

也會讓混沌的天氣系統產生大幅變化

For example, Earth’s surface temperature has warmed by almost 1 degree Celsius

例如，地球表面溫度

在過去 150 年已經暖化了 將近攝氏一度

over the last 150 years.

This might seem like a minor shift,

聽起來變化不大

but this 1-degree change has added the energy equivalent

但是這個一度的改變增加的能量當量

of roughly one million nuclear warheads into the atmosphere.

等於發射一百萬個核子彈頭進入大氣

This massive surge of energy has already led to a dramatic increase

這麼巨大的能量驟增已經導致

in the number of heatwaves, droughts, and storm surges.

熱浪、乾旱及風暴潮的數量急劇增加

So, is the increase in extreme weather due to random chance, or changing climate?

所以，極端天氣事件會增加 只是隨機發生還是因為氣候變化？

The answer is that—

答案是

while weather will always be a chaotic system—

雖然天氣永遠都是混沌系統

shifts in our climate do increase the likelihood of extreme weather events.

氣候變化的確會增加 極端天氣的可能性

Scientists are in near universal agreement that our climate is changing

科學家目前幾乎已達到共識 就是我們的氣候正在改變

and that human activity is accelerating those changes.

而人類的活動正在加速這些變化

But fortunately,

幸運的是

we can identify what human behaviors are impacting the climate most

我們可以找出什麼樣的人類行為 對氣候的影響最大

by tracking which boundary conditions are shifting.

方法是追蹤哪些邊界條件正在改變

So even though next month’s weather might always be a mystery,

所以即使下個月的天氣 可能永遠都是個謎

we can work together to protect the climate for centuries to come.

我們還是可以合作 保護未來數個世紀的氣候