Connect with us

Published

on

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?

上微信关注《碳简报》

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

Continue Reading

Climate Change

How clean energy can boost business for Africa’s food producers

Published

on

Despite millions of dollars in grants and technical help for African businesses to power farming and other food production activities with renewable energy, most efforts remain stuck at the early stages because they struggle to find the investors, markets and expertise they need to grow.

This was the message from a coalition of global institutions working on energy, water and agriculture at this month’s Africa Food Systems Forum in Kigali, Rwanda.

“Energy, agriculture, water and nutrition actors rarely design solutions together,” the Agri-Energy Coalition said in a Call to Action on powering food systems with clean energy.

Using more renewables – especially solar power – to drive food systems would reduce food losses, ensure year-round availability and affordability of healthy foods, and improve productivity, income and resilience among farmers, food processors and other small enterprises, the coalition added.

In an interview with Climate Home News at the forum, Olamide Niyi-Afuye, CEO of the Africa Minigrid Developers Association (AMDA) – a body representing private-sector developers of small-scale, off-grid electricity systems across the continent – said its members are starting to recognise this interdependence and are increasingly considering businesses that combine energy with agricultural activities.

    This, Niyi-Afuye added, could lead to greater supply and use of clean power for key processes like irrigation, food processing and storage, creating new sources of revenue for both sectors.

    CHN: Conversations at the Africa Food Systems Forum highlighted how organisations working in energy and agriculture often operate in silos. What has hampered their collaboration, and how has that affected Africa’s economic development?

    A: Most mini-grid companies in Africa were primarily incentivised to achieve connections. If you look at some ongoing projects, you see a cost-per-connection model [of revenue]. When a subsidy is tied to achieving a connection, regardless of whether it is a productive connection, you might not notice the problem until five years down the line, when you realise the cash flows are not what you projected.

    Despite African walkout, fractious land COP ends without drought deal

    So now we’re in a “come-to-Jesus moment” as an industry, where we’re righting the wrongs and adjusting our business models to make sure companies do not go bust and there is some level of sustainability over the long term.

    The saying is not wrong that we’ve been working in our own silos because we’ve focused on the smaller things instead of the helicopter view. There needs to be cross-pollination [between the energy and agriculture sectors] because, if we are thinking about industrialisation, energy is a key driver of industrialisation. We will not achieve that if we’re not in the room and part of those conversations.

    CHN: Productive use of energy is intended to ensure electricity access goes beyond lighting homes to improving livelihoods, creating jobs and powering equipment. But what happens when farmers cannot afford the equipment they need to do that? How can energy, agriculture and equipment players work together to make the transition more accessible?

    A: That’s why we’re having conversations with companies set up to de-risk the agriculture sector. By leveraging that connection, we’re able to aggregate potential energy needs and develop instruments that make equipment more affordable through bulk procurement.

    We can have arrangements that make it easier for farmers and food producers to lease equipment and eventually own it over a period. There’s no real pressure to recover the capital very quickly because you’re looking at scale.

    Rice farmer Danjuma Okuwa adjusts his newly installed electric rice milling machine at his compound in Rukubi, Nasarawa, Nigeria, September 27, 2022. (Thomson Reuters Foundation/Afolabi Sotunde)

    Rice farmer Danjuma Okuwa adjusts his newly installed electric rice milling machine at his compound in Rukubi, Nasarawa, Nigeria, September 27, 2022. (Thomson Reuters Foundation/Afolabi Sotunde)

    There is a whole lot across the agricultural value chain that needs energy, from farming and harvesting to food processing and value-addition. We need to understand the energy needs across the value chain and bring our members in to provide solutions.

    Developers do not necessarily need to provide every productive-use solution themselves. They can partner with equipment suppliers, financiers, agribusinesses and other service providers to enable customers to use electricity productively. The objective is simple: do not just electrify communities; enable economic activity that uses that electricity.

    CHN: When Africa’s industrialisation is discussed, you hear things like renewables cannot provide enough baseload, while some food processors are sceptical about switching to renewable energy because of these concerns about reliability. What is your response?

    A: It’s not a controversial statement to say that a typical baseload is usually from the grid, and it’s usually from multiple sources including renewable energy. For large-scale operations, we can look at blending multiple sources of energy. But how do we solve the problem of a mid-sized farmer? We can solve it with a mini-grid using renewable energy.

    Comment: Every country needs a model to help optimise its energy transition

    If you go to a small farmer in a rural area, they don’t care about what source of energy they’re getting. They just want something that can help them get from A to B. If you look at the direct energy needs of farmers and food processors, I’m sure 90 percent of their consumption can be solved by renewable energy. Let’s start with that problem first. Then, as they scale, they might need to ramp up, and we can start talking about a bigger baseload.

    CHN: How much agricultural value is lost because farmers and food businesses lack reliable, affordable electricity?

    A: If you look at, for example, the fact that we need to maybe plant tomatoes or strawberries in Jos before it gets to Lagos [Nigeria], which most likely is by road, I can assure you that a good chunk, if not stored properly, would be bad by then. So the fact that we do not have energy is in itself a lost opportunity to maximise the potential of the agriculture sector. So until we’ve solved the energy problem, we will not salvage waste – and for me that is a lost opportunity.

    CHN: AGRA, an institution focused on scaling agricultural innovations to help smallholder farmers, estimates a massive shortfall between current investments in the continent’s food systems and what is actually needed to build a resilient, profitable agricultural economy – to the tune of $180 billion per year. Can integrating energy into food systems help bridge that gap?

    A: Yes – if energy can help unlock the potential to earn more money, investors will follow the money. Investments go where there is certainty, and until there is certainty around cash flow and revenue, investment will be limited.

    My vision is to see more Power Purchase Agreements (PPAs) being signed between energy players and the agriculture sector. We can start by getting people into the room, understanding their pain points, crafting a framework and documentation that works for both parties, and then seeing deals happen.

    This interview was shortened and edited for clarity.

    The post How clean energy can boost business for Africa’s food producers appeared first on Climate Home News.

    How clean energy can boost business for Africa’s food producers

    Continue Reading

    Climate Change

    Human security relies on adapting to the world’s new climate reality

    Published

    on

    Cristina Rumbaitis del Rio is a senior advisor on adaptation and resilience with the United Nations Foundation and Mattias Söderberg is global climate lead at Danish NGO DanChurchAid.

    Recent extreme events – from wildfires and heatwaves in Europe to flash flooding following a glacier collapse in Nepal – have shocked and devastated communities, bringing years of warnings about such climate impacts to the doorstep of communities around the world.

    One thing is certain: the new climate reality is here – and the adaptation strategies designed for yesterday’s world are no longer sufficient.

    Attribution science has since shown that the hotter and more frequent heatwaves we’re experiencing around the world would have been virtually impossible without today’s high concentrations of greenhouse gases in the atmosphere. Climate shocks are now so severe that they reverberate through supply chains, food and water systems, financial markets and the movement of people.

      They must be a catalyst for a new way of thinking about adaptation and resilience, and how we finance solutions that work. A failure to invest in adaptation in one region can create costs far beyond it, which is why the concept of shared resilience is critical for leaders to grasp.

      Investment not charity

      At the UN General Assembly (UNGA 81) this month, leaders have an opportunity to translate today’s urgency into concrete commitments on adaptation and loss and damage finance ahead of COP31.

      Those commitments are needed to underpin global stability, shared prosperity and human security. Governments should use this moment to show what a new response looks like: finance that reaches communities faster, supports locally grounded solutions, strengthens national systems, and helps countries prepare before the next shock arrives.

      If we want sustained economic growth, food and water security, and resilient and prosperous societies across every region, adaptation must be at the heart of today’s development and security agenda. It cannot be just a future planning consideration or a narrow issue for climate ministries. Adaptation is now everyone’s business – and it must be financed fast and fair.

      UN Secretary-General António Guterres has repeatedly framed climate finance as an investment rather than charity, warning that “a world in climate chaos cannot be a world at peace” and describing human security as freedom from the chronic and sudden disruptions that climate change multiplies.

      What’s more, adaptation delivers a real return-on-investment, with researchers estimating that every dollar invested produces $10 in benefits, saving lives, protecting livelihoods, and reducing the costs of future disasters.

      Hitting adaptation limits

      The urgency to scale adaptation systematically is growing. The newly released “Limiting Overshoot” report from the UN Environment Programme (UNEP) confirms what scientists have long warned: exceeding global warming of 1.5C is now unavoidable under current policies. Yet, how high temperatures rise – and how long the world remains above the 1.5C threshold – will determine whether communities, economies and entire ecosystems can keep pace.

      There are limits to adaptation. When we breach those limits, lives and livelihoods are lost, and people and ecosystems suffer greatly. We cannot simply build yesterday’s infrastructure a little stronger and assume it will be enough.

      Nepal flood destruction shows “limits to adaptation”, scientists say

      We need to fundamentally change the systems that determine how societies anticipate, absorb and recover from both immediate and evolving non-linear climate shocks. This includes transforming physical systems, such as infrastructure, and the governance systems that affect where and how we live to how we maintain our health and wellbeing.

      Finance today is nowhere near the scale of the challenge.

      The UNEP “Adaptation Gap Report 2025” estimates the shortfall in adaptation finance in developing countries at $284 billion–$339 billion a year – roughly 12 to 14 times current international public flows of around $26 billion. That gap is a development, economic and human security problem, especially for the most vulnerable populations who have contributed the least to causing the climate crisis.

      Building resilience into financial systems

      There are already signs of what a more systemic adaptation response could look like. Communities around the world are delivering practical solutions at local level, even as adaptation finance remains notoriously, and appallingly, difficult to access. Cyclone-resistant homes, local forecasting capacities, drought-resistant crops, heat insurance for pregnant informal workers and mangrove restoration are rooted in local knowledge and lived experience, while delivering benefits far beyond the communities where they originate from.

      But local innovation alone is not enough; the systems around it need to be resilient too.

      Jamaica offers one example. The country has built a multi-layered disaster-risk financing framework, including a catastrophe bond and contingency funds, through sustained fiscal discipline and proactive investment. Its debt-to-GDP ratio fell from around 147% in 2012 to around 62% in 202-25. That groundwork matters when disaster strikes.

      Hurricane Melissa’s destruction shows need for climate resilience push

      Following Hurricane Melissa, Jamaica was able to secure billions of dollars in reconstruction financing from multilateral banks – finance that might otherwise have been much harder to access. The lesson is clear: resilience can be built into the financial architecture of a country before a crisis arrives. That is the shift we now need to make at scale.

      The foundations already exist – in Kingston’s fiscal reforms, in early-warning systems from the Sahel to the Pacific, and in every community that adapted before disaster struck. What is still missing is the political will, and the finance, to take what works and put it to work everywhere, at the speed our world’s new climate reality demands.

      To hear more on this issue from high-level officials and experts, sign up for this event during Climate Week NYC, at 8am EDT on September 24 (in person or online), moderated by Climate Home News Editor Megan Rowling: Adapting to the New Climate Reality: Why Accelerating Impacts Demand New Responses.

      The post Human security relies on adapting to the world’s new climate reality appeared first on Climate Home News.

      Human security relies on adapting to the world’s new climate reality

      Continue Reading

      Climate Change

      Framing the climate science debate as a binary battle isn’t just wrong – it’s dangerous

      Published

      on

      Lidy Nacpil is the coordinator of Asian Peoples’ Movement on Debt and Development (APMDD).

      Recent reporting on international climate negotiations has highlighted a sharpening divide within civil society and multilateral diplomacy. A troubling, simplistic narrative has taken root: that the UN climate process is witnessing a binary struggle between defenders of science and those attacking it.

      This framing is not only inaccurate; it is dangerous. Characterising a substantive methodological and political debate in these terms misdiagnoses the stakes and stirs conflict instead of clarity.

      No one disputes that climate action must rest on science. Science tells us what has led us to the climate crisis – the accumulation of historical emissions – and how much carbon budget remains if we are to keep temperature rise below 1.5C. It tells us how much global emissions must drop, and how fast. Science is also essential in assessing each country’s historical contribution to the accumulation of greenhouse gases in the atmosphere.

      Responsibility, however, must also be based on capacity. For those who generated the largest share of historical emissions, that capacity includes the enormous wealth and economic power accumulated through the same fossil-fuel-intensive development that generated those emissions.

      As science comes under attack at UN talks, climate movement splits over how to respond

      While principles that should guide human action aren’t scientific questions – they are matters of values – applying them to real-world problems requires scientific grounding. Equity recognises the scientifically established reality of differentiated responsibilities among countries and within societies. Putting equity into practice demands scientific rigour.

      Scrutiny of IPCC models

      Today, critics are scrutinising the assumptions and frameworks behind the Intergovernmental Panel on Climate Change’s Integrated Assessment Models (IAMs), used to project future scenarios and map global mitigation pathways. These concerns centre squarely on equity and justice.

      The economic, technological and policy assumptions used in IAM scenarios are normative choices rather than scientifically prescribed or neutral facts. These include choices about discount rates, economic growth, energy demand, technology costs, carbon prices, land availability and the regional location of mitigation. Many IAM scenarios reproduce existing global inequalities rather than transform them. Questions about transparency, representativeness and diversity in the scientific process are deeply urgent.

      Most IAM scenarios are built primarily around global cost-effectiveness – directing emissions reductions to places where mitigation is modelled as cheapest rather than allocating effort according to historical responsibility, capacity and development needs.

      The resulting pathways allow developed countries to retain disproportionately high levels of energy and fossil-fuel consumption while requiring developing countries to undertake substantial mitigation and carbon removal, including land-based measures that threaten food security and local development.

      Northern models often assume uniform access to cheap financing. In reality, Global South economies face far higher capital costs, driving up the price tag of rapid infrastructure shifts.

      Constraints on development space

      Scenario constraints also limit the development space poorer nations need without guaranteeing adequate climate finance. When models treat profoundly unequal starting points as uniform baselines, policy pathways lock in global inequality under the banner of scientific objectivity.

      Pointing out these structural flaws isn’t rejecting science. It is essential scientific scrutiny aimed at producing stronger, fairer, and more actionable results.

      Science ‘under attack’ from fossil fuel interests at UN climate talks

      The fight is not about whether we want to keep temperature rise below 1.5C, but about how we get there. A pathway can be technically compatible with 1.5C or 2C while still being deeply unequal in who gets to consume energy, who must reduce emissions, and whose development is constrained. Temperature compatibility alone does not make a pathway fair.

      Critiquing IAM scenarios from an equity perspective is neither an attack on the Intergovernmental Panel on Climate Change (IPCC) nor an attack on science. Rigorously examining IPCC reports – their substance, assumptions, and processes – is an acknowledgement of the IPCC’s importance and entirely consistent with scientific method.

      Tensions over AR7 timing

      There is a separate but related tension over the cycle and timeline of the IPCC’s Seventh Assessment Report (AR7). Some governments and civil society voices advocate completing its Working Group reports in time to feed directly into the UN’s Second Global Stocktake in 2028.

      The motivation makes sense: policymakers need timely science. But several developing-country negotiators and researchers have warned that meeting that deadline could severely disadvantage the Global South.

      Funding gap threatens next round of IPCC climate science reports, chair warns

      Global North authors and institutions remain disproportionately represented in the research underlying IAM assessments. Developing-country researchers often work with fewer institutional resources, smaller research budgets, and less administrative support. Accelerated publishing and assessment schedules can further limit their ability to generate, submit, and peer-review research in time for inclusion.

      The AR7 timeline concerns boil down to inclusivity, representation, and equity. Requiring the IPCC to meet tight political calendars without ensuring meaningful support and participation for developing-country researchers risks reproducing the very inequalities being challenged.

      Cooperation requires equity

      Political interests are indeed at work in UNFCCC negotiations and must be surfaced. Bad-faith actors seek to evade fossil-fuel phase-outs or shirk climate-finance obligations. Many developed country parties are guilty of both, including those who style themselves as “Friends of Science.”

      We must not lump legitimate scientific critiques raised by several Global South researchers and many civil society organisations concerning representation, economic assumptions and fair-share accounting together with obstructionism. Doing so risks misrepresenting and delegitimising critical scientific work and Global South equity and justice perspectives.

      The climate movement is strongest when it aligns rigorous science with global equity and justice. Achieving the Paris Agreement’s goals requires robust science that fully integrates the experiences, economic realities and academic contributions of the Global South. Effective climate action also requires international cooperation, and without equity, such cooperation cannot be sustained. We do not have to choose between science and equity. We need both.

      The post Framing the climate science debate as a binary battle isn’t just wrong – it’s dangerous appeared first on Climate Home News.

      Framing the climate science debate as a binary battle isn’t just wrong – it’s dangerous

      Continue Reading

      Trending

      Copyright © 2022 BreakingClimateChange.com