The world’s coastlines are at the forefront of climate change. That’s because they’re constantly changing, and respond quickly to changes in climate. They’re particularly important because around 70% of the world’s population live within 100km of the coast, and 90% of the world’s trade passes through ports on the coast.
世界海岸線處於氣候變遷的最前沿。那是因為，它們不斷變遷中，且對氣候中的諸多變遷，做出快速反應。它們特別重要，因為世界上大約70%的人口，居住在距離海岸100公里以內，且世界上90%貿易透過海岸上的港口。
The global economy relies on our coastal systems functioning because of the volume of trade and commerce that takes place at or through the coastal zone.
全球經濟依賴我們的沿海體系運作，因為在沿海地區或透過沿海地區，發生的貿易及商業量。
Change and disruption do not fall evenly across the globe, however. Our new research is the first to find a group of coastal locations around the world highly vulnerable to one specific climate-driven change: stronger waves, or waves coming from a different direction, which may cause widespread coastal erosion.
然而，變遷及混亂並非均勻分佈於全球各地。我們的新研究是首度，於世界各地發現一群沿海地區，極易受到一種特定氣候驅動之變遷影響的研究：更強的海浪，也就是來自不同方向、可能導致廣泛海岸侵蝕的海浪。
These changes will affect major ports and coastal cities such as Lima, Cape Town, Durban and Mombasa, as well as broadly affecting the Pacific-facing east coasts of Peru and Chile, the Atlantic-facing west coasts of Namibia and South Africa, and the southeast coast of Kenya down to South Africa.
此些變遷，除了廣泛影響秘魯及智利面向太平洋的東海岸、納米比亞及南非面向大西洋的西海岸及肯亞下至南非的東南沿海之外，也會影響諸如利馬、開普敦、德班及蒙巴薩等，主要港口及沿海城市。
Many of these locations are in developing nations with low GDP, making it harder to adapt or reduce damage from these changes. While some areas will be able to respond better than others, the combined GDP of countries most affected is only about one percent of global GDP. This speaks to how climate change can act as an inequality amplifier, hitting the Global South the hardest.
其中諸多地區位於GDP較低的發展中國家，使其更難適應或減少，來自此些變遷的損害。儘管某些地區將能，比其他地區做出更好的反應，不過受影響最嚴重國家的總和GDP，僅佔全球GDP的1%左右。這證明，氣候變遷如何能充當一種，打擊全球南方(指非洲、拉丁美洲及亞洲發展中地區)最為嚴重的不均衡擴大器。
圖1. 倘若排放物繼續不減少，像肯亞蒙巴薩的沿海城市，可能面臨來自新波浪模式之意想不到的海岸侵蝕。 (圖援用自原文)
Our previous work found climate change is already making waves more powerful, particularly in the Southern Hemisphere.
我們先前的研究發現了，氣候變遷已經使得波浪更為加強大，特別是在南半球。
How? Ocean waves are generated by winds blowing along the ocean surface. If the sea surface becomes warmer, wind patterns change as well. In turn, this can alter the wave conditions across the world’s oceans.
為何？海浪是由沿著海面吹的風所產生。倘若海面變得較暖和，風的模式也改變。依序，這會改變世界海洋各地的波浪狀況。
But due to reasons such as the fact that oceans are heating at different rates in different places, wave conditions are not changing at the same rate everywhere. Some areas will be worse affected than others.
不過，由於諸如在不同地方，海洋以不同速率變熱之事實等原因，波浪狀況並非在所有地方，以相同速率改變。因此，有些地區會比其他地區遭到更嚴重影響。
Why does this matter for humans on dry land? Because waves have shaped Earth’s coastlines for millions of years. Even small, sustained changes in waves can have long term consequences for our coasts and the people who rely on them.
為何這對陸地上的人類有重大關係？因為，數百萬年來，海浪已經塑造了地球的海岸線。即使在波浪上微小、持續的改變，對我們的海岸及仰賴它們的人們，也會有長期影響。
That’s because waves control how much sand is moved along the coast, and where it is deposited. Changes to local wave climates could dramatically increase erosion in some areas, for instance, threatening human and natural use of the coasts as well as infrastructure and houses.
那是因為，波浪控制著多少沙子，沿著海岸被移動，及沙子沉積何處。在某些地區，致使局部波浪氣候的改變會顯著增強某些地區的侵蝕。譬如，除了基礎設施及房屋之外，也威脅到人類及此些海岸的自然益處。
圖2. 海浪沿著海灘移動沙子。 (圖援用自原文)
To find out where they are changing the most, we applied wave tracking algorithms to models of future wave conditions. To model ocean waves in the future, we used numerical wave models driven by atmospheric conditions such as wind and air pressure, taken from global climate models used by the Intergovernmental Panel on Climate Change.
為了找出何處它們改變最大，我們將波浪追蹤演算法，應用於未來波浪狀況的模型。為了模擬於未來的海浪，我們使用了，取自由政府間氣候變遷專門委員會使用之全球氣候模型，由諸如風及氣壓等，大氣條件驅動的數值波浪模型。
Our work builds on years of research developing a method to track different wave conditions (or “wave climates”) globally. For example, the Southern Ocean wave climate is characterised by big, powerful waves with long wave periods as they circumnavigate the globe west to east.
我們的研究以多年研究開發一種，追蹤全球不同波浪狀況(也就是“波浪氣候”)的方法為基礎。譬如，南大洋(也稱為南極洋，是世界海洋最南端的水域)波浪氣候是以，具有長波浪週期之大、強有力的波浪為特徵。因為，它們西向東環繞地球。
By comparison, the wave climate of equatorial regions is typically lower energy, shorter wave period, and travels west to east. The characteristics of each wave climate is what we call their “signature” and this is what we track.
相較之下，赤道地區的波浪氣候，通常是能量較低、波浪週期較短，及西向東移動。每種波浪氣候的特徵，是我們所稱它們的“識別標誌”，因此這是我們所追蹤的。
We use data from the last 19 years to identify the signature for each wave climate, and track how they will change under different emissions scenarios by the end of the century. By comparing the differences between present and future conditions across the world’s oceans, we can identify the areas likely to see the greatest changes in wave conditions.
我們使用來自過去19年的數據，來確認每種波浪氣候的特徵，並追蹤到本世紀末，它們在不同排放腳本下，會如何改變。藉由比較世界海洋各地，當前與未來狀況之間的差異。在波浪狀況上，我們能確認可能出現最大改變的區域。
Until recently, most of the focus on coastal climate change impacts has been on sea level rise, which will affect low-lying areas and cities. In the next few decades, however, changes in wave conditions are likely to be more important than sea level rise along millions of kilometres of the world’s sandy coastlines.
直到最近，對於沿海氣候變遷影響的大部分關注一直著重於，會影響處於低窪之地區及城市的海平面上升上。然而，在接下來的幾十年中，波浪狀況的改變，很可能比沿著世界數百萬公里之沙質海岸線的海平面上升更為重要。
By itself, sea level rise does not cause erosion. Waves do. As the sea rises, waves can expand the reach and eat away at the beach and beyond. The net effect of wave power increasing and sea level rise will vary locally, however, because changes in wave conditions can either boost or dampen the effect of sea level rise on the coast, depending on how much sand is available and where it is moved to.
就其本身，海平面上升並不會造成侵蝕。波浪則會。隨著海平面上升，波浪會擴大影響所及範圍，而侵蝕掉海灘及更遠處。然而，波浪力量增強及海平面上升的淨效應，會有地區性差異。因為，波浪狀況的改變，會增強或減弱海平面上升，對海岸的影響。這取決於多少沙子可資使用，及被移動到何處。
圖3. 在某些地方，更強的波浪結合了海平面上升，會引發重大的侵蝕。 (圖援用自原文)
Our modelling explored two scenarios. The first was a high emissions future world with little to no carbon emissions reduction, leading to global temperatures rising by over 4℃ by the end of the century compared to pre-industrial levels.
我們的模型製作探索了兩種腳本。第一是一種，具有鮮少到沒有減少碳排放之高排放的未來世界，導致到本世紀末全球溫度，相較於工業化前的水平，上升達4℃以上。
The second was a low emissions scenario, where global warming is kept below 2℃ by 2100, which requires deep and immediate reduction in global carbon emissions.
第二是一種，到2100年，全球暖化保持在2℃以下，在全球碳排放上，需要強烈且立即減少的低排放腳本。
We found reducing emissions can have a significant impact on how much wave conditions change in the future. By keeping warming under 2℃, we found there would be almost no change in wave conditions for many of the coastal locations which we identified as particularly at risk in a 4℃world.
我們發現，減少排放對未來多少波浪狀況的改變，會有重大影響。藉由保持暖化於2℃以下，我們發現，對諸多我們確認為，在上升4℃的世界中，特別冒有風險之沿海地區的波浪狀況，幾乎不會有改變。
It is still not too late to avoid the worst impacts of climate change, but the window of opportunity is closing fast. We hope this research will help direct funding for coastal adaptation and resilience to the areas which will need it most.
現在避免氣候變遷的最壞影響，為時尚不晚。不過機會之窗，正迅速關閉中。我們期盼，該項研究能有助於，將提供沿海之適應及復原力的資金，引導到最需要它的地區。
圖請參閱原文
網址：https://theconversation.com/climate-fuelled-wave-patterns-pose-an-erosion-risk-for-developing-countries-184064
翻譯：許東榮
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