儲電技術與成本 抑制印度煤電成長的關鍵 | 解讀《 2019年世界能源展望》報告2/3

CO2 emissions

In the STEPS, global CO2 emissions from energy would continue to rise from the record level they reached in 2018, putting the world on track for upwards of 2.7C of warming this century. This emissions trajectory is shown with the dashed black line in the chart, below.

In contrast, CO2 declines quickly in the SDS (thick red line) to 17% below 2010 levels by 2030, 48% by 2040 and 68% by 2050. According to the IEA, this is “on course for net-zero emissions by 2070” and corresponds to a 50% likelihood of limiting warming to 1.65C, or a 66% chance of 1.8C.

This trajectory is less ambitious than most pathways to 1.5C with no or limited overshoot (yellow lines, below). In its special report on 1.5C, the Intergovernmental Panel on Climate Change (IPCC) said this would need CO2 to fall 45% below 2010 levels by 2030 and to net-zero by 2050.

According to the IEA, the SDS charts “a path fully aligned with the Paris Agreement by holding the rise in global temperatures to ‘well below 2C…and pursuing efforts to limit [it] to 1.5C’”. It also offers two options for going beyond the SDS to keep warming below 1.5C.

This form of words implies either that “pursue” means to head towards a goal, without necessarily reaching it, or that the SDS is aligned with 1.5C – so long as it is accompanied by additional action.

Along with the WEO’s central focus on the STEPS pathway, the statement on Paris “alignment” is at the heart of criticism from a group of NGOs, scientists, business groups and others. In an April letter, they called for the IEA to develop a scenario with a 66% chance of limiting warming to 1.5C.

One of the letter’s authors, Dr Joeri Rogelj, a lecturer in climate change and the environment at the Grantham Institute at Imperial College London, says the SDS is “inconsistent with 1.5C and several aspects of the Paris Agreement”.

Rogelj was a coordinating lead author on chapter two of the IPCC special report on 1.5C and is a lead author for working group one on the IPCC’s forthcoming sixth assessment report.

He tells Carbon Brief that there are at least two potential interpretations of the Paris ambition to “pursue efforts towards 1.5C”. One is that of limiting peak warming to 1.5C and the other is overshooting this level before returning below 1.5C, Rogelj says: “Planning to simply miss it is not a reasonable interpretation for a scenario that wants to be fully aligned with the Paris Agreement.”

He also points to Article 4 of the deal, which commits to reaching a “balance” between human sources and sinks of all greenhouse gases. This goal is likely to require net-negative CO2, for which the SDS provides no detailed pathway.

Negative CO2 emissions could be provided via technological solutions, such as bioenergy with carbon capture and storage (BECCS), or using “natural climate solutions”, such as afforestation.

The IEA says that negative emissions do indeed offer one way that the SDS could become aligned to a 1.5C limit. A cumulative total of around 300bn tonnes of CO2 (GtCO2) would need to be removed to bridge this gap, it adds. There are concerns over the sustainability and deliverability of such extensive deployment, however, and these are acknowledged by the IEA.

The WEO says:

“[I]t would be possible in the light of concern about [negative emissions technologies] to construct a scenario that goes further than the Sustainable Development Scenario and delivers a 50% chance of limiting warming to 1.5C without any reliance on net-negative emissions on the basis of a zero carbon world by 2050.”

[Other groups have developed a limited number of scenarios that already do this, which are included in the IPCC’s 1.5C report and the figure above.]

To go beyond its SDS, the IEA says the world would need to tackle “hard to abate” sectors, such as aviation, heavy industry and heat for buildings. This would include near-universal building retrofits and the development and retrofitting of new technologies for industrial processes.

The IEA says this “would not amount to a simple extension” of the changes in the SDS, instead “pos[ing] challenges that would be very difficult and very expensive to surmount.” It adds that tackling some of these areas would require social acceptance and behavioural change:

“This is not something that is within the power of the energy sector alone to deliver. It would be a task for society as a whole…Change on a massive scale would be necessary across a very broad front, and would impinge directly on the lives of almost everyone.”

If the IEA were to develop a 1.5C scenario, despite the challenges it would present, then the agency’s modelling could be used by policymakers to inform their energy and climate choices. Such guidance would be pertinent as governments reconsider their climate pledges under the Paris Agreement, with a fresh round of “Nationally Determined Contributions” due in 2020.

Coal changes

The outlook includes various changes since last year’s edition, reflecting shifts in the base year – there was unusually strong growth in demand in 2018 – and new or amended policy.

As a result, the IEA has once again revised down its outlook for coal demand in the central STEPS pathway, as the chart below shows (red line). However, it has also raised its near-term outlook for coal, in part due to China’s renewed reliance on smokestack industries to prop up flagging growth.

Despite the near-term increase in expected demand, this year’s outlook affirms that coal use would remain below the global peak reached in 2014, if stated plans and policies are met as per the STEPS. Nevertheless, this would leave coal demand significantly above the level in its SDS, where warming is limited to well-below 2C (yellow line, above).

According to the STEPS, rising demand in India is one of the key factors holding global coal use steady, despite rapid falls in developed economies, such as the US and EU.

Part of the reason for this increase in India is a large expected buildout of new coal-fired power stations, with 232GW of capacity built by 2040 in the STEPS, roughly doubling its installed capacity and accounting for a third of global additions.

The IEA says India’s coal capacity growth could be cut “sharply”, if declines in the cost of battery storage are faster than expected. Solar and cheap storage could “reshape the evolution of India’s power mix”, the IEA says, offering a “very compelling economic and environmental proposition”.

It is also worth comparing the 232GW of new coal capacity expected by the IEA, with India’s current pipeline of just 85GW, of which a quarter has been frozen in construction for years.

Another 510GW of new coal has been cancelled since 2010 due to competition from cheaper renewables, financial distress at utility firms and public opposition.

In addition, the Indian government has repeatedly overestimated electricity demand growth, meaning existing coal capacity is running less than two-thirds of the time. Moreover, data for 2019 to date suggests India’s electricity generation from coal could be declining.

The Indian government recently announced a highly ambitious target for solar, wind and biomass capacity to reach 450GW, potentially as soon as 2030, when the IEA STEPS outlook sees just 344GW having been added. If this target is met, then wind, solar and other low-carbon sources could largely meet rising demand without new coal, according to recent Carbon Brief analysis.