scientists have proposed a solution that sounds like science fiction.

科學家們提出了一個聽起來像科幻小說的解決方案。

If the water doesn't come during the winter in the form of snowfall, and doesn't come during the spring in the form of rain...

如果水在冬天不以降雪的形式出現，而在春天不以雨水的形式出現......

what if we just make it rain? Literally?

如果我們只是讓它下雨呢？從字面上看？

While this may seem like a far-fetched fix, this idea is actually based on technology that's been around since the 1940s.

雖然這可能看起來像一個牽強的解決方案，但這個想法實際上是基於自20世紀40年代以來一直存在的技術。

It's called cloud seeding, and it is what it sounds like:

這被稱為 "雲播種"，和它聽起來一樣。

Tiny particles are released into the air, either by an aircraft or an automated machine.

微小的顆粒被釋放到空氣中，可以由飛機或自動機器來完成。

This technique relies on the answer to one key question: where do clouds come from?

這種技術依賴於對一個關鍵問題的回答：雲從哪裡來？

The simple answer is that clouds have nuclei, but not the kind that atoms have.

簡單的答案是，雲有核，但不是原子的那種核。

Water evaporates into the atmosphere as part of the water cycle.

作為水循環的一部分，水會蒸發到大氣中。

That evaporated water accumulates around micro-scale solid or liquid particles made of dust or pollen...or even bacteria.

蒸發的水積聚在由灰塵或花粉......甚至是細菌組成的微觀規模的固體或液體顆粒周圍。

These are called condensation nuclei.

這些被稱為凝縮核。

As more and more water vapor clings onto a condensation nucleus, it starts to form a cloud droplet.

隨著越來越多的水蒸氣附著在凝結核上，它開始形成一個雲滴。

Once the droplets get big and heavy enough, they fall from the cloud in the form of precipitation—

一旦液滴變得足夠大和重，它們就會以降水的形式從雲中落下。

that can be rain, snow, even hail!

可以是雨，可以是雪，甚至可以是冰雹!

The scientists who came up with the idea of cloud seeding assumed that the limiting factor to how big clouds get

提出雲播種想法的科學家們認為，限制雲層變大的因素是什麼？

or how likely it is they'll precipitate is these condensation nuclei.

或者說它們沉澱的可能性有多大，就是這些凝結的核。

So, they decided to add some.

是以，他們決定增加一些。

They chose silver iodide particles because their crystal structure is assumed to be very similar to that of real ice,

他們選擇了碘化銀顆粒，因為他們的晶體結構被認為與真正的冰非常相似。

providing a scaffold for water to cling to.

為水提供一個腳手架，使其附著在上面。

Adding these particles to growing clouds helps water vapor freeze around the nuclei at higher temperatures than it would naturally,

將這些顆粒添加到成長中的雲中，有助於水蒸氣在核周圍以比自然界更高的溫度結冰。

making precipitation come faster.

使降水來得更快。

And after its invention, cloud seeding was widely adopted.

而在其發明之後，雲播種被廣泛採用。

It was put to work by the U.S. government—most notably during the Vietnam War, with the goal of flooding enemy supply routes.

它被美國政府投入使用--最引人注目的是在越南戰爭期間，其目的是淹沒敵人的供應路線。

But in the 70s, the UN adopted a resolution to ensure that all its member states would only use weather modification—

但在70年代，聯合國通過了一項決議，以確保其所有成員國只使用天氣改變--

like cloud seeding—for peaceful purposes from then on.

像雲播種一樣--從那時起就用於和平目的。

So, it may sound like a simple and effective solution:

是以，這聽起來可能是一個簡單而有效的解決方案。

Just make more clouds to make more rain, right?

只要製造更多的雲來製造更多的雨，對嗎？

But there are four main pitfalls that mean we gotta switch the faucet off on that excitement.

但是，有四個主要的陷阱，意味著我們必須關閉這種興奮的水龍頭。

One: we still don't really know if it works.

一：我們仍然不知道它是否真的有效。

Or if it does work, how effective it is.

或者，如果它確實有效，它的效果如何。

See, once you've seeded a cloud, it's tough to say how much precipitation that cloud would have yielded if you didn't seed it.

你看，一旦你在雲中播種，就很難說如果你不播種，那片雲會產生多少降水。

One recent study DID find that some seeding produced snow where it would not have fallen otherwise...

最近的一項研究發現，一些播種產生了雪，否則它不會落下。

but the amount of snow was negligible.

但雪的數量可以忽略不計。

And in areas where precipitation was expected, it's still hard to say if seeding made a difference either way

而在預計會有降水的地區，仍然很難說播種是否產生了不同的效果。

in what would have fallen naturally.

在本來自然落下的東西。

We also don't actually know HOW water vapor forms around condensation nuclei into cloud droplets in the first place—

我們實際上也不知道水蒸氣是如何在凝結核周圍形成雲滴的。

although there's a lot of interesting research into this right now too, so...

雖然現在也有很多有趣的研究，所以...

there are just a LOT of unknowns.

只是有很多未知的因素。

Problem two: You can only seed clouds that are already there—

問題二：你只能對已經存在的雲進行播種--

you can't make clouds appear out of thin air.

你不可能讓雲彩憑空出現。

There has to be enough water vapor in the air already for cloud seeding to work,

空氣中必須有足夠的水蒸氣才能使雲播種發揮作用。

so in extremely dry areas already devastated by drought,

所以在已經受到乾旱破壞的極度乾旱地區。

this isn't much of a fix.

這並不是什麼好的解決辦法。

Three: We don't yet fully understand the implications of adding seeding chemicals to our water cycle.

三。我們還沒有完全理解在我們的水循環中加入播種化學品的影響。

Take silver iodide, for example.

以碘化銀為例。

Silver is toxic to many aquatic organisms in large doses, so we need to monitor the levels of these compounds

大劑量的銀對許多水生生物是有毒的，所以我們需要監測這些化合物的水準

that may make their way into the water cycle.

可能會使它們進入水循環。

And while dry ice, potassium chloride, and more can also be used for cloud seeding, depending on the situation,

而乾冰、氯化鉀等也可用於雲層播種，具體視情況而定。

the environmental effects of these will need to be considered too.

也需要考慮這些的環境影響。

And four: Does cloud seeding upset the balance of nature even more than climate change-induced drought already has?

還有四點。雲播種會不會比氣候變化引起的乾旱更加破壞大自然的平衡？

Some scientists worry that increasing the volume of clouds in one place will pull moisture from another area,

一些科學家擔心，增加一個地方的雲量會從另一個地區拉走水分。

interrupting rain that could have fallen there instead…but again.

導致原本可以落在那裡的雨水被打斷......但又是這樣。

The dynamics at play in clouds are so complex that it's really hard to say where rain would have fallen if we had left everything alone.

在雲中起作用的動力是如此複雜，以至於很難說如果我們不理會一切，雨水會落在哪裡。

The fact remains that by 2030, almost half the world's population will live in highly water-stressed areas due to climate change.

事實是，到2030年，由於氣候變化，世界上幾乎一半的人口將生活在水資源高度緊張的地區。

And at least 52 countries all over the world—including the U.S., China, India, and Russia—

而全世界至少有52個國家--包括美國、中國、印度和俄羅斯--都是如此。

have invested in weather modification technologies in the hope of bending the weather to their will.

他們投資於改變天氣的技術，希望能使天氣適應他們的意願。

So, while we investigate if and how cloud-seeding could help,

是以，在我們調查雲播種是否有幫助以及如何幫助時。

it's important to remember that it's really just a band-aid.

重要的是要記住，這真的只是一個Ok繃。

Experts say that if these strategies are seriously considered as a drought solution,

專家說，如果認真考慮將這些戰略作為乾旱的解決方案。

they must be part of a larger plan that involves smart water management.

它們必須是涉及智能水管理的更大計劃的一部分。

And even if things like cloud-seeding will help, they treat a symptom, not the cause.

而且，即使像雲播種這樣的事情會有幫助，它們也是治標不治本。

To ensure long-lasting solutions to droughts worldwide, change that will actually make a fundamental difference,

為了確保長期解決全世界的乾旱問題，改變將真正帶來根本性的變化。

we have to address the root causes of the climate crisis too.

我們也必須解決氣候危機的根本原因。

If this video left you thirsty for more info on clouds, check out this other video on cloud complexity here,

如果這段視頻讓你渴求更多關於雲的資訊，請看這段關於雲複雜性的其他視頻。

and let us know down in the comments what else you're interested in learning about weather modification.

並在評論中告訴我們，你還想了解哪些關於天氣變化的資訊。

Subscribe to Seeker to keep up with all your news on weather and climate, and as always, thanks for watching.

訂閱Seeker以瞭解所有關於天氣和氣候的新聞，並一如既往地感謝您的關注。

I'll see ya next time.

下次見。