控制暖化不超過2°C 燃煤電廠需大規模改建更新 | 解讀《 2019年世界能源展望》報告1/3

環境資訊中心外電;姜唯 翻譯;林大利 審校;稿源:Carbon Brief

國際能源署(IEA)13日發表《 2019年世界能源展望》報告。報告中指出,全球能源系統正在進行「深層更新」,但儘管如此,除非積極度再提升,否則全球的二氧化碳排放量還是會繼續增長數十年。

今年810頁版本的特點在於「承諾政策情境(Stated Policies Scenario, STEPS)」(以前稱為「新政策情境」),反映政府已經說出口的政策的效果。風能和太陽能的激增將使再生能源滿足全球能源需求的大部分成長。但是煤炭的平穩發展,加上對石油和天然氣的需求不斷增加,全球排放量在到2040年的展望期內將繼續上升。

相對地,報告的「永續發展情境(Sustainable Development Scenario, SDS)」描繪出有50%機率將升溫限制在1.65°C內所需的條件,IEA表示這是「完全符合巴黎協定」的情況。

報告說,SDS需要投資「大量重新分配」,從化石燃料轉向效率和再生能源、淘汰全球約一半的燃煤電廠,以及全球經濟的其他變化。

IEA今年還探討了將升溫限制在工業化前1.5°C內(即巴黎協定的理想目標)所需條件,不過沒有建立詳細模型。

未來情境

《世界能源展望》(WEO)是這個主題的年度出版物中審查最嚴格的報告之一。長達數百頁的分析以世界各國政府的數千個資料庫和IEA的世界能源模型為基礎。

IEA表示報告沒有對前景預測。相反地,它以二氧化碳排放量和其他資料形式呈現了特定能源選擇的後果。該報告說明道:

「《世界能源展望》的目的不是提供一個關於2030年或2040年世界能源將在何處的觀點。這將取決於未來的各種重大選擇。 WEO-2019的目的是,提供決策者制訂新政策、考慮新投資或以其他方式塑造能源未來時所需的資訊。透過探索各種可能的未來、實現的方式、不同選擇的後果以及一些關鍵的不確定性來做到這一點。」

引言中介紹了三種可能的「前景」,在報告發表前,部落格文章「了解WEO情境」也提前對此做了說明。

展望報告的中心觀點是「STEPS」,它的目的是「在不預期未來有所改變的情況下,讓政策制定者好好審視自己的計畫和積極度會有何表現」,包括政府做出的巴黎氣候承諾。不過,IEA並不認為所有政策目標都會實現:

「積極度不會自動被納入情境中:徹底落實不是理所當然的,因此政策落實的前景和時機是以我們對相關監管、市場、基礎建設和財務限制的評估為基礎。」

承諾政策包括零排放淨目標,如英國的目標。 IEA表示,已商定或討論中的類似目標(包括歐盟)涵蓋了全球排放量的12%。就解決全球排放而言,這些目標很重要,但不是決定性的。IEA表示,為實現零排放目標而開發的技術和方法可能會產生更大的連鎖反應,這可能有助於其他國家減少排放。

WEO的第二個未來情境是「永續發展情境(SDS)」。這個情境從能源獲取、空氣污染和碳排放方面的永續發展目標開始,探討達到目標所需的條件。

最後,在「當前政策情境(Current Policies Scenario, CPS)」中,政府放棄其承諾目標和意圖,能源系統僅以已經制定好的政策和法律為指導。

今年的報告文字、圖表和數據將繼續提到CPS,只是重要性較低,「當前政策情境」這個詞在810頁中僅使用了102次,遠少於STEPS的793次和SDS的535次。報告也說明,CPS就是不採取行動的後果,可看出STEPS情境所需的額外努力。

(2010年《世界經濟展望》 中,CPS被提及了340次,而當時的中心觀點NPS出現981次,「450種情境」出現745次。)

需求上升

IEA表示,根據全球已承諾的計畫和政策,到2040年,全球能源需求將繼續每年增長1%,相當於中國目前的總需求量。

根據國際貨幣基金組織(IMF)的預測,人口增加(根據聯合國的「中等」預測,2040年將達到90億人口)和經濟持續擴大(全球GDP每年增加3.4%)推動了這個成長。

IEA表示,由於產業轉向低能耗,能源效率的提高和「飽和效應」(如汽車需求封頂),2019年能源需求的成長率大約是2000年以來平均2%的一半。

如下圖中的紅線所示,STEPS中再生能源將滿足約49%的需求增長。天然氣的使用也預期將迅速增加(藍色),超過煤炭成為僅次於石油的第二大能源,並滿足總體需求增長的三分之一。


1990年至2040年全球各類型能源需求量,單位是數百萬噸石油當量。未來需求預測以STEPS為基礎。其他再生能源包括太陽能、風能、地熱能和海洋能。資料來源:國際能源署《 2019年世界能源展望》。Carbon Brief使用Highcharts繪製圖表。

與天然氣和再生能源的快速發展相比,IEA STEPS情境預測煤炭使用量將達到平穩,然後從今日的水平略降(上方黑線)。這呼應去年的分析,即全球煤炭需求在2014年達到頂峰。

IEA現在還建議,由於汽車燃油效率的提高和電動汽車(EV)的增加,到2030年(橙色線)石油需求將開始趨於穩定,這將使汽車的石油需求在2020年代末期達到峰值。報告說,由於電動汽車成本下降,傳統汽車的未來將是值得深思的問題。

IEA表示,貨運、航運、航空和化學產品的石油需求「持續增長」,SUV因日益普及,成為另一個潛在的需求支撐因素。(值得注意的是,阿拉伯國家石油公司的股票銷售文件也顯示,全球石油需求將從2035年左右開始趨於穩定。)

根據IEA STEPS,到2040年,全球能源需求增長的三分之二來自亞太地區。印度成為世界上人口最多的國家,其能源需求成長一倍,成為全球需求成長的最大貢獻者,佔成長總量的四分之一以上。

在這一總數中,STEPS預測亞洲國家對煤炭的需求增加抵消了美國和歐洲的大幅減少。IEA說:

「煤炭需求來自大多數亞洲發展中國家:在煤基礎設施方面的新投資決策已顯著放緩,但是現有的煤電廠和用煤工廠還是很多……為煤炭提供了可觀的發展動力。」

比例變動

STEPS之下,到2040年,再生能源的興起體現了IEA所形容的「深層更新」,但同時也指出了全球能源系統「變動緩慢」的特性,如煤炭長期的需求高原。

需求成長的比例變化顯示在下面圖表中,煤炭、石油和天然氣(藍色色塊)滿足了能源史上的大部分成長(最左欄)。

儘管STEPS之下,再生能源能滿足2040年需求成長一半,而且成長速度因為經濟因素和能源效率變化而放慢(中間欄),但它仍然遠遠沒有限制全球碳排放量(參閱下文)。

如果要阻止全球氣溫上升,需要有更具決定性的變化,如實現IEA SDS(最右欄)。


全球能源需求年均變化量,以百萬噸石油當量為單位。左:歷史變化。中:IEA STEPS。右:IEA SDS。資料來源:國際能源署《 2019年世界能源展望》 。Carbon Brief使用Highcharts繪製。

在STEPS之下可見再生能源所能滿足的需求成長越來越多,化石燃料在全球能源用量的比例將從2018年的81%下降到2040年的74%,SDS之下則下降到58%。

從STEPS到SDS的需要大規模的變革,其中大多數已經在決策者的議程中很久了。報告解釋:

「2018年化石燃料消費補貼的全球價值,幾乎是再生能源和電動汽車補貼以及全球碳定價計畫收入總和的兩倍。這種不平衡使排放儘早達到峰值的任務變得十分複雜。」

SDS之下,2030年代無碳捕集的化石燃料投資將減少至2014年到2018年平均的一半,再生能源、電網和核能方面的投資將翻倍,而在能源效率上的支出將翻兩倍。

IEA表示,這反映了一個事實,即能源效率是解決排放的最重要因素,這表示SDS下2040年的總體需求會略低於今日的水平。

IEA說「提高能源效率很有機會讓全世界實現永續能源目標」,它召集了「全球能源效率緊急行動委員會」來促成進展。

某種程度上這是對數據的回應,數據顯示效率的改善正在放緩,2018年的效率成長率是2010年以來最低的,這「疲軟的氣力」直得「深切關注」。IEA表示「新能源效率政策和加強現有措施的努力相對缺乏」。

較低的需求會帶來連鎖反應,特別是加上再生能源的快速成長。值得注意的是,在SDS之下,對煤炭、石油和天然氣的需求逐漸下降,而煤炭減幅特別大(上方最右欄中的灰色部分)。

在這個總數中,IEA說,電業的煤炭用量受影響最大。到2040年,超過一半的當前燃煤電廠將退役,規模大於全中國目前的容量。

有半數的退役發生在壽命結束之前,如果將升溫保持在2°C以下,那麼投資於全球現有煤電廠的10億美元中,有部分將面臨風險。歐洲222GW燃煤中有約98%、美國276GW中約88%將關閉。

IEA說,在SDS之下,剩餘的燃煤電廠大部分必須「改建或翻新」。他們得在需求高峰和再生能源產出低谷期間運作有限的時間,不然就得大量投資碳捕集與封存(CCS)技術來減排。

今年的展望報告包含了對煤炭開採過程中釋放的甲烷的新分析。分析結果說明,與航空和航運業相比,煤炭開採的暖化效應更大。(1/3,繼續閱讀下篇

'Profound shifts' underway in energy system, says IEA World Energy Outlook (1/3)
by Simon Evans

The world's CO2 emissions are set to continue rising for decades unless there is greater ambition on climate change, despite the "profound shifts" already underway in the global energy system.

That is one of the key messages from the International Energy Agency's (IEA) World Energy Outlook 2019, published today. This year's 810-page edition is notable for its renamed central "Stated Policies Scenario" (STEPS), formerly known as the "New Policies Scenario".

In this scenario, which aims to mirror the outcome of policies already set out by governments, a surge in wind and solar power would see renewable sources of energy meeting the majority of increases in global energy demand. But a plateau for coal, along with rising demand for oil and gas, would mean global emissions continue to rise throughout the outlook period to 2040.

In contrast, the report's "Sustainable Development Scenario" (SDS) sets out what would be required to give a 50% chance of limiting warming to 1.65C, which the IEA describes as "fully in line with the Paris Agreement".

It says the SDS would require a "significant reallocation" of investment away from fossil fuels towards efficiency and renewables, as well as the retirement of around half the world's fleet of coal-fired power stations and other changes across the global economy.

The IEA has this year also explored, but not modelled in detail, what it would take to limit warming to no more than 1.5C above pre-industrial temperatures, the aspirational goal of the Paris Agreement.

Future scenarios

The World Energy Outlook (WEO) is one of the most heavily scrutinised documents in the annual calendar of publications on the topic. Its hundreds of pages of analysis are based on thousands of datapoints, drawn from governments around the world, as well as the IEA's World Energy Model.

The IEA says that it does not make forecasts in its outlook. Instead, it presents the consequences of societal energy "choices" in terms of CO2 emissions and other outcomes. The report explains:

"The World Energy Outlook does not aim to provide a view on where the energy world will be in 2030 or 2040. This will depend on hugely important choices that lie ahead. What the WEO-2019 does aim to do is to inform decision-makers as they design new policies or consider new investments or shape our energy future in other ways. It does so by exploring various possible futures, the ways that they come about, the consequences of different choices and some of the key uncertainties."

The outlook spans three alternative "futures", set out in the introduction and described in a blog, published ahead of the report's release, on "understanding the WEO scenarios".

The outlook's central scenario is STEPS, which has "the intention to ‘hold up a mirror' to the plans and ambitions announced by policymakers without trying to anticipate how these plans might change in future". This includes the Paris climate pledges made by governments. The IEA does not assume that all policy goals will be met, however:

"[A]mbitions are not automatically incorporated into the scenario: full implementation cannot be taken for granted, so the prospects and timing for their realisation are based upon our assessment of the relevant regulatory, market, infrastructure and financial constraints."

Stated policies include some net-zero emissions goals, such as the UK's. Similar goals agreed or under discussion, including in the EU, cover 12% of global emissions, the IEA says. This makes the targets significant, but not decisive, in terms of tackling the global emissions. But the IEA says there could be larger knock-on effects due to the technologies and approaches developed to meet net-zero targets, which could help others to also cut emissions.

The second WEO future is the "Sustainable Development Scenario" or SDS. This is a different type of scenario that starts from sustainable development goals on energy access, air pollution and CO2 emissions before working backwards to show what would be needed to reach them.

Finally, the "Current Policies Scenario" (CPS) would see governments renege on their stated goals and intentions, with the energy system guided only by policies and laws that are already in place.

This year's outlook continues to feature the CPS in its text, charts and data. But it is afforded lower priority, with the phrase "current policies scenario" used 102 times over 810 pages – far less often than the 793 mentions of the STEPS or the 535 for the SDS. The outlook says the CPS highlights the consequences of inaction and the level of effort required to meet even the STEPS pathway.

(For comparison, the CPS is mentioned 340 times in the WEO 2010, against 981 uses of the then-central NPS and 745 mentions of the "450 scenario".)

Rising demand

On the basis of stated plans and policies around the world, the IEA says that global energy needs will continue to rise by 1% per year until 2040, adding demand equivalent to China's current total.

This growth is driven by a rising population – based on the UN's "medium" projections to reach 9 billion people by 2040 – and an expanding economy, with global GDP increasing by 3.4% a year, per International Monetary Fund projections.

The rate of energy demand growth is around half the average rate of 2% seen since 2000, the IEA says, due to shifts towards less energy-intensive industries, energy efficiency gains and "saturation effects" – for example, where demand for cars reaches a peak.

Some 49% of demand growth would be met by renewables in the STEPS, as shown with the red line in the chart, below. Gas use is also expected to rise rapidly (blue), overtaking coal to become the second-largest source of energy after oil and meeting a third of the rise in overall demand.

Global primary energy demand by fuel, millions of tonnes of oil equivalent, between 1990 and 2040. Future demand is based on the STEPS. Other renewables includes solar, wind, geothermal and marine. Source: IEA World Energy Outlook 2019. Chart by Carbon Brief using Highcharts.

In contrast to the rapid gains for gas and renewables, the IEA STEPS sees coal use plateau and then decline slightly from today's levels (black line above). This confirms last year's analysis that global coal demand peaked in 2014.

The IEA now also suggests that oil demand will start to level off by the 2030s (orange line) as a result of vehicle fuel-efficiency gains and the rise of electric vehicles (EVs), which see passenger car oil demand peak in the "late 2020s". There are "profound questions" over the future of conventional cars, it says, given falling costs for EVs.

Oil demand for freight, shipping, aviation and chemicals "continues to grow", the IEA says, with the growing popularity of SUVs another potential factor propping up demand. (Notably, documentation for the Saudi Aramco share sale also has global oil demand levelling off from around 2035.)

Some two-thirds of the increase in global energy demand to 2040 comes from the Asia Pacific region, under the IEA STEPS. India becomes the world's most populous country and its energy demand doubles, making it the single largest contributor to global growth and accounting for more than a quarter of the total increase.

Within this total, the STEPS sees rising coal demand from Asian countries offset large declines in the US and Europe. The IEA says:

"Coal is the incumbent in most developing Asian countries: new investment decisions in coal-using infrastructure have slowed sharply, but the large stock of existing coal-using power plants and factories…provides coal with considerable staying power in the STEPS."

Shifting shares

The rise of renewables anticipated under the STEPS to 2040 is demonstrative of the "profound shifts" described by the IEA, yet it also points to the "slow moving" nature of the global energy system, as exemplified by the long, high plateau in demand for coal.

These shifting shares of demand growth are shown in the chart, below, with coal, oil and gas (shades of blue) having met most of the historical increases in energy use (leftmost columns).

While the STEPS maps a future where renewables meet half of the increase in demand to 2040, and the pace of growth slows due to shifting economic factors and energy efficiency (central columns), it remains well short of putting a cap on global CO2 emissions (see discussion below).

If increases in global temperatures are to be stopped, then even more decisive changes will be required, as shown in the example of the IEA SDS (rightmost columns).

Average annual change in global energy demand, by fuel, million tonnes of oil equivalent. Left: historical changes. Centre: IEA STEPS. Right: IEA SDS. Source: IEA World Energy Outlook 2019. Chart by Carbon Brief using Highcharts.

The rising portion of demand growth met by renewables sees the fossil fuel share of global energy use decline from 81% in 2018 to 74% in 2040 under the STEPS, or 58% under the SDS.

Moving from the STEPS to the SDS will require a wide range of changes, most of which have long been on the agenda for policymakers. As the report explains:

"The global value of fossil fuel consumption subsidies in 2018 was almost double the combined value of subsidies to renewable energy and electric vehicles and the revenue from carbon pricing schemes around the world. This imbalance greatly complicates the task of achieving an early peak in emissions."

By the 2030s, investment in fossil fuels without carbon capture would halve in the SDS, relative to the average during 2014-2018. At the same time, investment in renewables, electricity networks and nuclear would roughly double and spending on energy efficiency would nearly quadruple.

This reflects the fact that energy efficiency is the single most important factor in tackling emissions, the IEA says, meaning that overall demand in 2040 under the SDS is slightly below today's levels.

It says "the potential for efficiency improvements to help the world meet its sustainable energy goals is massive" and it has convened a Global Commission for Urgent Action on Energy Efficiency to boost progress.

In part, this is a response to data showing that efficiency improvements are drying up and 2018 saw the slowest rate since 2010, with this "faltering momentum" a cause for "deep concern". It cites "a relative lack of new energy efficiency policies and of efforts to tighten existing measures".

Lower demand has knock-on consequences, particularly when combined with more rapid growth from renewables. Notably, demand for coal, oil and gas progressively declines under the SDS, with coal facing particularly large reductions (grey chunks in the rightmost columns, above).

Within this total, the IEA suggests that coal use in the power sector would be hardest hit. It says that more than half of current coal-fired power stations would retire by 2040 in the SDS, representing a fleet larger than China's current capacity.

With half of retirements coming before the end of their useful lives, some of the $1tn of capital invested in the world's existing coal fleet would be put at risk, if warming is kept below 2C. Some 98% of the 222 gigawatts (GW) of coal in Europe and 88% of the 276GW in the US would close.

Under the SDS, the remaining coal plants would mostly need to be "repurposed or retrofitted", the IEA says. This means they would either operate limited hours, during peaks in demand and troughs in renewable output, or would face substantial investments to fit carbon capture and storage (CCS) technology to prevent their CO2 emissions.

This year's outlook contains new analysis on the methane released during coal mining, which it suggests has a greater warming impact than aviation and shipping combined.

※ 全文及圖片詳見:Carbon BriefCC BY-NC-ND 4.0

作者

姜唯

如果有一件事是重要的,如果能為孩子實現一個願望,那就是人類與大自然和諧共存。

林大利

於特有生物研究保育中心服務,小鳥和棲地是主要的研究對象。是龜毛的讀者,認為龜毛是探索世界的美德。

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