Air conditioners are a modern wonder: they've saved countless lives during heat waves, cooled giant servers to essentially make the Internet possible, and in general made life in warm places more comfortable.

冷氣是現代奇蹟，它們在熱浪來襲時拯救無數人，冷卻巨大的伺服器、讓網際網路得以成真，並且讓炎熱地區的生活舒適許多。

But keeping our indoor climate cool has, ironically, made the outdoor climate much warmer, and fixing the planet-warming effect of air conditioners is going to be one of the major challenges of the 21st century.

不過諷刺的是，室內涼爽的同時，室外溫度卻在提升，解決冷氣帶來的地球暖化將會是 21 世紀的一大挑戰。

For now, heating buildings is still a larger overall contributor to climate change than air conditioners because more people use heat for more hours.

目前為止，暖氣還是比冷氣更大程度地影響氣候變遷，因為比較多人會長時間使用暖氣。

But air conditioning heats the planet in nefarious and subtle ways that are going to be harder to address.

不過更難解釋的是，冷氣才是悄悄地對地球暖化下毒手。

For example, to heat our buildings, we burn fossil fuels, which releases heat and heat trapping CO2.

舉個例子，暖氣仰賴於燃燒化石燃料，過程中會釋放熱氣，熱氣困住二氧化碳。

But air conditioning also burns fossil fuels (just out of sight), and that's not their only problem.

但是冷氣也會燃燒化石燃料，只不過藏在眼皮子底下，而且這還不是唯一的問題。

The way that air conditioners cool buildings is by moving heat from inside to outside.

冷氣藉由將熱氣移至室外來保持室內的涼爽。

They can pump out enough heat to warm an entire city by a few degrees.

它們排出的熱氣足以讓整座城市升溫幾度。

And on top of that, when we get rid of our old air conditioners, most of their chemical refrigerants leak out and evaporate.

不僅如此，當舊的冷氣機被丟棄，裡頭的化學冷媒會洩出然後蒸發。

And while only a small overall amount leak out, it just so happens that the refrigerants we use are thousands of times more powerful than CO2 at trapping the Earth's heat.

雖然只有洩出一小部分，但其實冷媒比二氧化碳要擅於困住地球熱氣好幾千倍。

So they warm the Earth nearly 60% extra on top of the warming from the CO2 released to run the air conditioners.

所以除了運轉過程釋出的二氧化碳，它們還替地球暖化貢獻了額外 60%。

Then, as the earth gets warmer, we use more air conditioning, which warms the earth even more in a vicious feedback cycle that's only going to get worse over time and as developing countries get richer and more people have access to air conditioners.

然後隨著地球越來越熱，我們就使用更多的冷氣，惡性循環下地球變得更熱，而且當發展中國家富裕起來、越來越多人使用冷氣機，這情況還只會越來越糟。

Compared to today, we're going to be using 4 times as many air conditioners in 2050.

相比今日，我們在 2050 年將會使用四倍多的冷氣機。

And at some point we're going to be using more energy for air conditioning than for heating.

到了某階段，我們花在冷氣上的石油燃料將多過暖氣。

To avoid the immense global impact this will have, we'll need to use the most efficient air conditioners, and generate electricity in a way that doesn't release heat or CO2.

為了避免這種地球困境，我們必須改用效率高的冷氣機，並且使用製造過程中不會產出熱氣或二氧化碳的電力。

When we get rid of our old air conditioners, we'll need to recycle or destroy their refrigerants, rather than - y'know - letting them leak out everywhere.

當丟棄老舊冷氣機時，我們必須把其中的冷媒回收或是銷毀，而不是 …… 你知道的，丟在路邊讓它到處洩。

And we'll have to switch over to refrigerants that, even if they do leak, won't trap heat.

我們也必須改用即使洩出也不會困住熱氣的冷媒。

We'll also have to figure out how to use less air conditioning, some of which we can do by using fans until it gets too hot, and some of which we'll have to do by building buildings that are naturally cooler.

我們也要找到減少使用冷氣的辦法，幾種替代方案是在一定溫度內優先使用電風扇，或是建築本身使用能提升涼感的建材。

Buildings with shiny white roofs that reflect heat or "green" roofs that reflect, insulate, and evaporate; buildings with rooms that have windows on opposite sides so air can easily flow through, creating a natural breeze.

建築頂部加裝亮白色屋頂反射熱度，或是植物屋頂不僅反射和隔絕熱度還能蒸發；房內兩側裝上窗戶，空氣就能輕易對流、形成自然微風。

And buildings with wall materials that can absorb lots of heat in the walls without letting it inside - to keep people cool in the day - and then release it overnight.

以及可以吸收熱氣的墻壁材質，確保白天室內涼爽，夜間才會釋放熱氣。

And we'll need to go even further, by redesigning our entire cities to include more green spaces with trees that can provide shade, encourage hot air to mix with cool air, and cool the air themselves through evaporation.

我們甚至應該做得更廣，重新規劃整個市容，種更多樹就能有更多的遮陰、混合不同溫度的空氣、並且透過蒸發降低空氣溫度。

Or, we could do nothing.

或者，我們可以攤手不管。

But that definitely wouldn't be cool.

但那樣肯定涼不起來。

This video was sponsored by the University of Minnesota, where students, faculty and staff across all fields of study are working to solve the Grand Challenges facing society.

本影片由明尼蘇達大學贊助，各領域的學生和職員合作解決社會面臨的大挑戰。

These challenges include adapting to a changing world and ensuring we have clean water and sustainable ecosystems.

這些挑戰包括適應世界變遷、確保乾淨的飲用水以及維護生態系統。

And part of the solution is to reimagine some of the fundamental structures of modern life, like buildings.

其中一個解決辦法是重新構想現代生活的基礎建設，例如建築。

Professors Richard Graves at the Center for Sustainable Building Research and Bonnie Keeler at the Humphrey School of Public Affairs are researching how to move from "green design," where we make buildings more efficient (or less bad), towards "regenerative design," where we make buildings that positively contribute to the local communities and ecosystems of which they are a part.

永續建築研究中心的 Richard Graves 教授以及漢弗萊斯學院的 Bonnie Keeler 正在研究如何從「綠色設計」( 也就是提升、優化建築效率 ) 進步到「再生設計」，後者對地方社群以及生態系統貢獻良多。

Thanks, University of Minnesota!

感謝明尼蘇達大學！