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火山喷发对科学家及其气候模型构成了根本性挑战。

众所周知,剧烈的火山喷发会导致地表气温突然下降,多次喷发则会在几十年乃至几个世纪的时间尺度上影响气候变率。

当火山喷发将二氧化硫注入平流层时,会形成气溶胶,从而阻挡阳光到达地球表面。

与人类对气候变化的影响不同,后者发生缓慢且可以在各种社会经济情景下被纳入气候模型进行考量。火山喷发具有突发性,这给气候预测带来了挑战。

目前科学家尚无法预测火山喷发的发生时间、地点以及二氧化硫的排放量。

那么,在进行未来气候预测时,如何考虑火山喷发对气候的影响呢?

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在我们最近发表于《通讯-地球与环境》(Communications Earth & Environment)的研究中,我们表明火山喷发对全球气温预测的不确定性产生了重大影响。

我们的研究结果发现,如果将偶发的火山喷发纳入气候预测,突破《巴黎协定》所设定的1.5C升温上限的时间会略有延迟,但与此同时,未来几十年也将出现更多快速升温和降温的时期。

气候预测中的火山强迫

气候科学家将火山喷发对气候的影响——主要是通过释放出二氧化硫气体进入大气——称为“火山强迫”(volcanic forcing)。

当前的气候模型在进行未来预测时采用一个恒定的火山强迫值,该值是根据1850年至今的历史平均强迫值计算得出的。

国际耦合模式比较计划(CMIP)也是如此,这项全球模型工作为政府间气候变化专门委员会(IPCC)发布的重要评估报告提供基础数据。

然而,这种方法存在显著局限。

首先,历史平均强迫值无法表示火山爆发的偶发性。

大规模火山喷发呈零星分布——有时好多事件集中发生在某几个十年内,有时两个事件之间则可能相隔上百年。

此外,与数千年尺度的记录相比,从1850年至今的参考时期中,发生过的大规模喷发事件 ——指排放超过3太克(Tg)二氧化硫的喷发事件——相对较少。

最后,早期国际耦合模式比较计划气候模型中所使用的火山强迫重建数据并未包含排放量少于3太克二氧化硫的中小规模喷发。

这是因为这些喷发在1980年卫星时代开始之前大多未被探测到。然而,这些体量较小但发生频率更高的喷发事件,在长期火山强迫中贡献了30%至50%。

采取新方法

传统上,气候科学家认为气候预测中主要存在三种不确定性来源:内部变率、模型不确定性和情景不确定性。

其中,“内部”变率是指气候系统内部自然产生的波动,如厄尔尼诺现象;模型不确定性是指不同气候模型之间结果的差异;情景不确定性则涉及未来几十年全球可能的发展路径。

我们的研究结果表明,火山喷发应被明确视为气候预测中第四个重要的不确定性来源。

为了探究在考虑火山强迫不确定性的情况下,气候预测会发生怎样的变化,我们的研究采用了一种概率方法,这一方法建立在Bethke等人于2017年提出的研究基础之上。

为此,我们构建了“随机强迫情景”,其本质是1000种延续至本世纪末的火山活动可能时间线预测。

这些情景基于冰芯中记录的过去1.15万年火山活动历史,以及卫星观测和地质证据。每个情景都呈现了不同的喷发强度、地点、时间和频率的组合。

(在数学中,“随机”系统是指结果包含随机性或不确定性的系统,因此不可预测;这与“确定性”系统相对,后者的结果可以通过初始条件和一套规则或方程完全预测。)

随后,我们利用2015至2100年期间的随机火上强迫和历史平均火山强迫模拟气候预测,研究共享社会经济路径(SSPs)中三种不同排放情景下的升温变化:低排放情景(SSP1-1.9)、与现行气候政策相符的中等排放情景(SSP2-4.5)、非常高排放情景(SSP5-8.5)。

在这一步中,我们使用了一种称为FaIR的简化气候模型,也称“模拟器”。

通过模拟1000种不同的火山未来情况,我们发现在21世纪未来时期火山喷发所引起的气候不确定性,可能超过同期气候系统本身的内部变率。

我们还发现,到2030年代,火山喷发可能占全球气温预测总不确定性的三分之一以上。

下图中能看到这些结果。图中展示了不同来源对总不确定性的影响。火山为橙色、内部变率为深蓝色、气候模型响应为黄色,未来人类排放情景为绿色。

Chart: Annual mean contribution of uncertainties

对1.5C临界值的意义

我们的模拟结果表明,在气候预测中纳入可能的火山活动时间线后,短期内突破《巴黎协定》设定的1.5C升温上限的概率略有下降。

根据不同的排放情景,相较于使用恒定火山强迫的预测,模拟发现超过1.5C升温上限的概率下降了4%至10%。

尽管这一结果听起来似乎令人鼓舞,但未来的火山活动并不能在长期缓和由人类引起的全球变暖。

1815年坦博拉火山的喷发事件就是一个强有力的例证。这次喷发使全球气温平均下降了约0.8C,带来了“无夏之年”,导致欧洲、北美和中国大范围的作物歉收和饥荒。

火山喷发带来的降温效应是短暂的,通常只持续几年,其并不会改变由人类排放所导致的长期变暖趋势。

我们的研究发现,即使考虑多种可能的未来火山活动,在除了最低排放路径以外的所有情景中,全球变暖仍将在几十年内超过1.5C。

即便21世纪火山活动频繁,其对全球变暖的抵消作用也仅占很小一部分——这意味着减排对于实现长期气候目标仍然至关重要。

下方图表展示了在三种排放情景下,使用随机火山强迫(实线)与恒定火山强迫(虚线)时超过1.5C的概率(上图),以及两种强迫方式之间的概率差异(下图)。

Charts: Probability of exceeding 1.5C

十年尺度的气温变率

我们的研究提供的另一个重要发现是:一旦将火山强迫的变率纳入考虑,将更有可能出现极端温暖和寒冷的十年期。

在中等排放情景下,我们发现出现负向十年期趋势——即全球表面温度在某个十年内平均下降——的概率增加了10%到18%。

与此同时,出现极端温暖十年期的概率也随之增加,这反映出火山强迫的变率会同时提高变暖和变冷极端事件发生的可能性。

这一结果凸显了火山喷发如何在十年时间尺度上对全球气温趋势带来显著的波动。

迈向更完善的气候预测

了解火山对气候的影响,对于全面评估农业、基础设施和能源系统在未来所面临的风险至关重要。

使用全面的地球系统模型运行数千种火山情景并不切实际,因为这需要极高的计算资源。但与此同时,当前的方法也存在上文提到的显著局限。

不过,在未来的气候模型工作中,仍有折中方案可行。

即将开展的下一阶段气候建模实验——即CMIP7情景模式比较计划——可以采用更具代表性的“平均”火山强迫基线,这一基线纳入了历史记录中常被遗漏的小型喷发事件的影响。这一偏差现已在用于下一代气候模型模拟的历史火山强迫数据集中得到纠正。

此外,建模团队还应额外运行包含高频和低频未来火山活动的情景,以全面捕捉火山不确定性对气候预测的影响范围。

虽然人类导致的温室气体排放仍是气候变化的主导因素,但若能妥善考虑火山活动的不确定性,将有助于我们获得更全面的未来气候图景及其对社会的潜在影响。

The post 嘉宾来稿:探究火山喷发如何影响气候预测 appeared first on Carbon Brief.

嘉宾来稿:探究火山喷发如何影响气候预测

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Island nations fight to save cultural heritage from climate change

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Farmers and fishermen in the Maldives have long relied on an ancient calendar to guide their daily lives.

The Nakaiy system divides the year into 27 distinct periods, each named after a star or constellation in the night sky.

Any one period in the calendar tells you about expected weather and tidal patterns, navigational routes, and fishing conditions. The Nakaiy was created through centuries of careful observation and local knowledge, passed down through families as an essential tool for survival.

But things are now changing. The climate crisis is leading to more extreme weather events across the Indian Ocean island nation and upending the Nakaiy calendar.

“When you go and speak to communities and ask them what kind of impacts they are facing, a lot of elders will tell you that the weather, it doesn’t follow the calendar anymore,” explained Aishath Reesha Suhail, a programme officer in the Maldives’ Ministry of Tourism and Environment.

As the effects of climate change worsen, it is a real prospect that the Nakaiy may be abandoned by local people, representing a major cultural loss to the Maldives.

‘Systemic and growing threat’

With extreme weather becoming the norm, communities are observing a domino effect of consequences in their everyday lives. The slow onset of heritage loss is now being seen across continents, but notably among small islands in remote parts of the ocean.

“Climate change represents a systemic and growing threat to cultural heritage worldwide,” a UNESCO spokesperson told Climate Home, adding that the World Heritage Committee has identified climate change as “one of the most significant long-term risks affecting properties across all regions.”

UNESCO, the UN body for education, science and culture, defines the loss of cultural heritage as “the erosion of traditional knowledge systems, craftsmanship, social practices and identity, particularly where communities are displaced or livelihoods disrupted”. A clear example is historical sites and even entire islands washed into the ocean as a result of rising sea levels and coastal erosion. 

The Maldives is dealing with such a situation now. The Koagannu Cemetery is a 900-year-old resting place, located on the country’s southernmost atoll, a mere 50 metres from the shoreline. The monument’s intricate coral gravestones are being actively threatened by the encroaching Indian Ocean. 

The government and local community have responded to this challenge with emergency protection measures. Sandbags and concrete structures have been installed along the coastline, complemented by large numbers of palm trees to create a seawall. A wider solution is ‘beach nourishment’, a common practice in the Maldives where sand from elsewhere is brought in to replace what has been lost through erosion. Taken together, these solutions have so far protected the cemetery.

Pacific islands push back against growing climate threats

Among the many issues climate change creates, cultural heritage is not always front of mind. In the Maldives, one of the main barriers people face is awareness. “Most of what we are dealing with relates to the erosion of our islands along with areas such as fisheries… but we are quite limited in our capacity to do something about it,“ Suhail said.

“We don’t understand the full breadth of the issue at present because we haven’t been able to do extensive research on the matter,” she added. However, assessing the extent of the damage – and how to respond effectively – is a key priority for the government, outlined in its latest climate plan, known as a Nationally Determined Contribution, and as part of its National Adaptation Plan process.

Fishing is at the core of the country’s culture and identity, employing thousands of people. Most dishes include fish – “we have it for breakfast, lunch and dinner,” Suhail noted – but the climate crisis and overfishing are shifting how and when communities can fish. Tuna makes up 98% of all fish caught in the Maldives, but warmer ocean temperatures are changing migratory patterns, pushing the species into deeper, colder waters.

As a critical economic and cultural resource, the government has outlined a range of solutions to protect the fisheries sector in its first Biennial Transparency Report to the UN. These include using real-time tracking data to improve the efficiency of fishing operations; investing in canneries to increase fish storage; and diversifying away from tuna through marine farming.

Koagannu Cemetery, a 900-year-old resting place in the Maldives, is threatened by rising sea levels in the Indian Ocean. (Image: Ashwa Faheem) 

Koagannu Cemetery, a 900-year-old resting place in the Maldives, is threatened by rising sea levels in the Indian Ocean. (Image: Ashwa Faheem) 

Culture and nature go hand-in-hand

The same pattern is playing out elsewhere.

Palau and the Maldives are not close to one another. The two states are separated by around 4,000 miles and sit in different corners of the ocean. But both are experiencing very similar climate challenges, based on their position as a set of scattered, low-lying islands surrounded by an imposing body of blue water.

In the same way as the Maldives, Palau’s cultural heritage is closely tied to “land, coastlines and traditional food systems,” according to Toni Soalabla, at the Palau Office of Climate Change.

“Many of the places that hold stories, history and identity of our communities are located along the coast and are increasingly exposed to erosion and sea level rise,” she said.

One of these places is Ngerutechei village, reportedly the oldest in Palau, and home to ancient stone paths and carvings. The village provides a glimpse into the past social values and culture of the people in this western Pacific nation.

How Vanuatu is facing up to rising climate risks

As part of the development of Palau’s National Adaptation Plan, the government has worked with local leaders to identify similar sites of cultural significance. The plan encourages communities to use their own knowledge to create protective measures for these sites.

Climate change is also prompting communities to take up traditional land and food practices again. These include cultivating taro, a stable food source that has historically supported water, soil and food security on the islands. 

“These systems developed over generations in response to local environmental conditions, so strengthening them today is both a climate adaptation measure and a way of maintaining cultural knowledge that might otherwise fade,” said Soalabla.

Cultural practices in Palau have developed alongside the natural ecosystems that people rely on to survive. It is within this context that researchers believe adaptation policies should be created. Recognising this relationship “can strengthen both community identity and environmental resilience at the same time”, according to Soalabla.

Taro farming is making a return to Palau as a traditional source of food security. (Image: Kiara Worth / IISD / Palau Office of Climate Change)

Taro farming is making a return to Palau as a traditional source of food security. (Image: Kiara Worth / IISD / Palau Office of Climate Change)

An ancient monolith in Ngerutechei village is being protected against coastal erosion. (Image: Kiara Worth / IISD / Palau Office of Climate Change).

An ancient monolith in Ngerutechei village is being protected against coastal erosion. (Image: Kiara Worth / IISD / Palau Office of Climate Change).

Heritage on the global stage

The issue of cultural loss has not gone unnoticed in international climate negotiations. 

Small island states such as the Maldives have used their role at the UN to push for greater awareness and action, with some key successes.

In 2015, the Paris Agreement established a Global Goal on Adaptation (GGA) which recognised that countries needed to do something about climate change now and not later. However, it took six years before a framework and a set of adaptation targets were agreed at the UN climate summit in Glasgow to pursue this goal. 

From this came the establishment of seven overall themes – from poverty eradication to access to health – to guide adaptation action and a set of around 60 indicators to measure progress against the targets.

World leaders invited to see Pacific climate destruction before COP31

Emilie Beauchamp, an adaptation specialist at the International Institute for Sustainable Development (IISD), said that “cultural heritage was highlighted as one of the global priorities [of the GGA Framework] and is one of the seven themes, so it is considered very important by the international community.”

The much-debated set of indicators, only finalised in Belém at last year’s COP30, include five related to cultural heritage with a focus on preserving cultural practices and important sites that are “guided by traditional knowledge, Indigenous Peoples’ knowledge and local knowledge systems”. A spokesperson for UNESCO said the inclusion of heritage indicators “marks an important recognition that climate impacts extend beyond economic losses”. 

While critics said the set of final indicators was rushed through by the Brazilian presidency, they now serve as guidance for national governments that wish to implement plans to protect their common heritage. The missing piece of the puzzle remains how to finance these plans – something notably absent from the Belém text, which made clear that the adaptation indicators “do not create new financial obligations or commitments, nor liability or compensation”.

The lack of financial commitments proved disappointing for many small states grappling with how to prevent their cultural history from being entirely forgotten, especially at a time when adaptation finance remains below requirements. A recent UNEP report found that developing nations would need an estimated US$310 billion per year in 2035 to adapt to climate change, while current public financing was around $26 billion.

At these low levels “only a small percentage of what the framework outlines could be implemented,” according to Beauchamp.

Recent research from WRI and UNESCO found 73% of non-marine World Heritage Sites are threatened by at least one severe water risk.

Recent research from WRI and UNESCO found 73% of non-marine World Heritage Sites are threatened by at least one severe water risk.

The challenge of cultural heritage

When looking at low-lying islands on a map, they can appear as specks of land amid a vast ocean. Many of the stories from these remote places go unnoticed. But the specks represent millennia of human culture that is slowly being lost to the ocean.

While the international community has now recognised the problem and solutions exist, the recurring issue of scarce finance may prevent governments from taking sustained action. Island communities have already been forced to move home as sea levels rise, leaving behind their cultural connections to a place.

The value of any cultural asset, or of human heritage, can be judged by how it is engaged with over generations. Without human intervention, many historical sites, language, cuisine and other local customs would become a forgotten part of history. The rapid onset of climate change brings the role of cultural heritage into sharp relief, challenging communities to decide in real time what they value, what deserves saving, and how to achieve that.

Stories of cultural loss are not confined to small islands but it is here where the challenge is presenting most acutely. The experiences of these vulnerable nations in protecting their heritage will provide the litmus test for effective adaptation responses elsewhere.

Adam Wentworth is a freelance writer based in Brighton, UK.

(Main image: The Isdhoo Havitha is an ancient Buddhist monastery in the Maldives, located moments from the shoreline. Photo: Ashwa Faheem) 

The post Island nations fight to save cultural heritage from climate change appeared first on Climate Home News.

Island nations fight to save cultural heritage from climate change

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The Wabanaki Basketmakers’ Plans to Save Maine’s Ash Trees

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The invasive emerald ash borer, native to northeast Asia, has spread to 37 states over the past quarter century, killing nearly all of the ash trees it infests. But in Maine, a coalition of basketmakers, scientists and government officials are plotting a future for their trees.

Each strip of wood in Richard Silliboy’s hands started as a year of an ash tree’s life.

The Wabanaki Basketmakers’ Plans to Save Maine’s Ash Trees

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Toxic Ocean Crisis in Papua New Guinea Sparks Mass Marine Die-Off and Public Health Emergency

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Thousands of dead fish are washing ashore and people are falling ill too, as officials investigate possible sources of contamination.

It started in December, when dead fish began washing ashore New Ireland—a mountainous island in Papua New Guinea’s New Ireland Province, flanked by the Pacific Ocean and the Bismarck Sea.

Toxic Ocean Crisis in Papua New Guinea Sparks Mass Marine Die-Off and Public Health Emergency

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