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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?

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

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DeBriefed 15 August 2025: Raging wildfires; Xi’s priorities; Factchecking the Trump climate report

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Welcome to Carbon Brief’s DeBriefed. 
An essential guide to the week’s key developments relating to climate change.

This week

Blazing heat hits Europe

FANNING THE FLAMES: Wildfires “fanned by a heatwave and strong winds” caused havoc across southern Europe, Reuters reported. It added: “Fire has affected nearly 440,000 hectares (1,700 square miles) in the eurozone so far in 2025, double the average for the same period of the year since 2006.” Extreme heat is “breaking temperature records across Europe”, the Guardian said, with several countries reporting readings of around 40C.

HUMAN TOLL: At least three people have died in the wildfires erupting across Spain, Turkey and Albania, France24 said, adding that the fires have “displaced thousands in Greece and Albania”. Le Monde reported that a child in Italy “died of heatstroke”, while thousands were evacuated from Spain and firefighters “battled three large wildfires” in Portugal.

UK WILDFIRE RISK: The UK saw temperatures as high as 33.4C this week as England “entered its fourth heatwave”, BBC News said. The high heat is causing “nationally significant” water shortfalls, it added, “hitting farms, damaging wildlife and increasing wildfires”. The Daily Mirror noted that these conditions “could last until mid-autumn”. Scientists warn the UK faces possible “firewaves” due to climate change, BBC News also reported.

Around the world

  • GRID PRESSURES: Iraq suffered a “near nationwide blackout” as elevated power demand – due to extreme temperatures of around 50C – triggered a transmission line failure, Bloomberg reported.
  • ‘DIRE’ DOWN UNDER: The Australian government is keeping a climate risk assessment that contains “dire” implications for the continent “under wraps”, the Australian Financial Review said.
  • EXTREME RAINFALL: Mexico City is “seeing one of its heaviest rainy seasons in years”, the Washington Post said. Downpours in the Japanese island of Kyushu “caused flooding and mudslides”, according to Politico. In Kashmir, flash floods killed 56 and left “scores missing”, the Associated Press said.
  • SOUTH-SOUTH COOPERATION: China and Brazil agreed to “ensure the success” of COP30 in a recent phone call, Chinese state news agency Xinhua reported.
  • PLASTIC ‘DEADLOCK’: Talks on a plastic pollution treaty have failed again at a summit in Geneva, according to the Guardian, with countries “deadlocked” on whether it should include “curbs on production and toxic chemicals”.

15

The number of times by which the most ethnically-diverse areas in England are more likely to experience extreme heat than its “least diverse” areas, according to new analysis by Carbon Brief.


Latest climate research

  • As many as 13 minerals critical for low-carbon energy may face shortages under 2C pathways | Nature Climate Change
  • A “scoping review” examined the impact of climate change on poor sexual and reproductive health and rights in sub-Saharan Africa | PLOS One
  • A UK university cut the carbon footprint of its weekly canteen menu by 31% “without students noticing” | Nature Food

(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)

Captured

Factchecking Trump’s climate report

A report commissioned by the US government to justify rolling back climate regulations contains “at least 100 false or misleading statements”, according to a Carbon Brief factcheck involving dozens of leading climate scientists. The report, compiled in two months by five hand-picked researchers, inaccurately claims that “CO2-induced warming might be less damaging economically than commonly believed” and misleadingly states that “excessively aggressive [emissions] mitigation policies could prove more detrimental than beneficial”80

Spotlight

Does Xi Jinping care about climate change?

This week, Carbon Brief unpacks new research on Chinese president Xi Jinping’s policy priorities.

On this day in 2005, Xi Jinping, a local official in eastern China, made an unplanned speech when touring a small village – a rare occurrence in China’s highly-choreographed political culture.

In it, he observed that “lucid waters and lush mountains are mountains of silver and gold” – that is, the environment cannot be sacrificed for the sake of growth.

(The full text of the speech is not available, although Xi discussed the concept in a brief newspaper column – see below – a few days later.)

In a time where most government officials were laser-focused on delivering economic growth, this message was highly unusual.

Forward-thinking on environment

As a local official in the early 2000s, Xi endorsed the concept of “green GDP”, which integrates the value of natural resources and the environment into GDP calculations.

He also penned a regular newspaper column, 22 of which discussed environmental protection – although “climate change” was never mentioned.

This focus carried over to China’s national agenda when Xi became president.

New research from the Asia Society Policy Institute tracked policies in which Xi is reported by state media to have “personally” taken action.

It found that environmental protection is one of six topics in which he is often said to have directly steered policymaking.

Such policies include guidelines to build a “Beautiful China”, the creation of an environmental protection inspection team and the “three-north shelterbelt” afforestation programme.

“It’s important to know what Xi’s priorities are because the top leader wields outsized influence in the Chinese political system,” Neil Thomas, Asia Society Policy Institute fellow and report co-author, told Carbon Brief.

Local policymakers are “more likely” to invest resources in addressing policies they know have Xi’s attention, to increase their chances for promotion, he added.

What about climate and energy?

However, the research noted, climate and energy policies have not been publicised as bearing Xi’s personal touch.

“I think Xi prioritises environmental protection more than climate change because reducing pollution is an issue of social stability,” Thomas said, noting that “smoggy skies and polluted rivers” were more visible and more likely to trigger civil society pushback than gradual temperature increases.

The paper also said topics might not be linked to Xi personally when they are “too technical” or “politically sensitive”.

For example, Xi’s landmark decision for China to achieve carbon neutrality by 2060 is widely reported as having only been made after climate modelling – facilitated by former climate envoy Xie Zhenhua – showed that this goal was achievable.

Prior to this, Xi had never spoken publicly about carbon neutrality.

Prof Alex Wang, a University of California, Los Angeles professor of law not involved in the research, noted that emphasising Xi’s personal attention may signal “top” political priorities, but not necessarily Xi’s “personal interests”.

By not emphasising climate, he said, Xi may be trying to avoid “pushing the system to overprioritise climate to the exclusion of the other priorities”.

There are other ways to know where climate ranks on the policy agenda, Thomas noted:

“Climate watchers should look at what Xi says, what Xi does and what policies Xi authorises in the name of the ‘central committee’. Is Xi talking more about climate? Is Xi establishing institutions and convening meetings that focus on climate? Is climate becoming a more prominent theme in top-level documents?”

Watch, read, listen

TRUMP EFFECT: The Columbia Energy Exchange podcast examined how pressure from US tariffs could affect India’s clean energy transition.

NAMIBIAN ‘DESTRUCTION’: The National Observer investigated the failure to address “human rights abuses and environmental destruction” claims against a Canadian oil company in Namibia.

‘RED AI’: The Network for the Digital Economy and the Environment studied the state of current research on “Red AI”, or the “negative environmental implications of AI”.

Coming up

Pick of the jobs

DeBriefed is edited by Daisy Dunne. Please send any tips or feedback to debriefed@carbonbrief.org.

This is an online version of Carbon Brief’s weekly DeBriefed email newsletter. Subscribe for free here.

The post DeBriefed 15 August 2025: Raging wildfires; Xi’s priorities; Factchecking the Trump climate report appeared first on Carbon Brief.

DeBriefed 15 August 2025: Raging wildfires; Xi’s priorities; Factchecking the Trump climate report

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New York Already Denied Permits to These Gas Pipelines. Under Trump, They Could Get Greenlit

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The specter of a “gas-for-wind” compromise between the governor and the White House is drawing the ire of residents as a deadline looms.

Hundreds of New Yorkers rallied against new natural gas pipelines in their state as a deadline loomed for the public to comment on a revived proposal to expand the gas pipeline that supplies downstate New York.

New York Already Denied Permits to These Gas Pipelines. Under Trump, They Could Get Greenlit

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Factcheck: Trump’s climate report includes more than 100 false or misleading claims

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A “critical assessment” report commissioned by the Trump administration to justify a rollback of US climate regulations contains at least 100 false or misleading statements, according to a Carbon Brief factcheck involving dozens of leading climate scientists.

The report – “A critical review of impacts of greenhouse gas emissions on the US climate” – was published by the US Department of Energy (DoE) on 23 July, just days before the government laid out plans to revoke a scientific finding used as the legal basis for emissions regulation.

The executive summary of the controversial report inaccurately claims that “CO2-induced warming might be less damaging economically than commonly believed”.

It also states misleadingly that “excessively aggressive [emissions] mitigation policies could prove more detrimental than beneficial”.

Compiled in just two months by five “independent” researchers hand-selected by the climate-sceptic US secretary of energy Chris Wright, the document has sparked fierce criticism from climate scientists, who have pointed to factual errors, misrepresentation of research, messy citations and the cherry-picking of data.

Experts have also noted the authors’ track record of promoting views at odds with the mainstream understanding of climate science.

Wright’s department claims the report – which is currently open to public comment as part of a 30-day review – underwent an “internal peer-review period amongst [the] DoE’s scientific research community”.

The report is designed to provide a scientific underpinning to one flank of the Trump administration’s plans to rescind a finding that serves as the legal prerequisite for federal emissions regulation. (The second flank is about legal authority to regulate emissions.)

The “endangerment finding” – enacted by the Obama administration in 2009 – states that six greenhouse gases are contributing to the net-negative impacts of climate change and, thus, put the public in danger.

In a press release on 29 July, the US Environmental Protection Agency said “updated studies and information” set out in the new report would “challenge the assumptions” of the 2009 finding.

Carbon Brief asked a wide range of climate scientists, including those cited in the “critical review” itself, to factcheck the report’s various claims and statements.

The post Factcheck: Trump’s climate report includes more than 100 false or misleading claims appeared first on Carbon Brief.

https://www.carbonbrief.org/factcheck-trumps-climate-report-includes-more-than-100-false-or-misleading-claims/

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