Countries have agreed to keep global temperature rise to “well-below 2°C, pursuing efforts to limit the temperature increase to 1.5°C”. As of writing, 172 countries had submitted their Nationally Determined Contributions (NDC), a national climate plan for all countries involved — many of which are informed by studies relying on large-scale global implementation of NETs.
NETs work by taking CO2 out of the atmosphere. The inclusion of NETs in 2°C pathway scenarios expand the available carbon budget — the maximum amount of CO2 humans can emit to keep global temperatures below an increase of 2°C. However, NETs such as Bioenergy Carbon Capture Storage (BECCS) have yet to be proven to be effective at scale and argued in this paper to be too speculative an assumption to be included in all 2°C pathway scenarios. In other words, many more scenarios without BECCS, illustrating alternative means of cutting CO2, should be analysed and published in academic literature than is currently the case. BECCS is a technology that involves sequestration of CO2 by plants, its use as bioenergy, and the capture of storage underground of the CO2 emitted during the bioenergy process. It is a technology which does not yet exist at scale and yet has been readily included in modeling solutions that reach the 2°C goal.
If countries do not rely on NETS such as BECCS, are their existing mitigation plans sufficient to reach the Paris goal? The short answer is no. According to this research, countries have yet to put in place mitigation plans commensurate with 2C.
“Most of the pathway scenarios that inform country commitments rely heavily on NETs, increasing the carbon budget while reducing the rates of CO2 emission mitigation needed to reach the 2 degree Paris goal. This poses a significant risk to the Paris Agreement. If countries are relying on technology that is currently still speculative, believing they have more CO2 to burn than they actually have, they risk missing the narrow window of opportunity to exploit the mitigation opportunities already available,” said lead researcher Professor Alice Larkin.
“In our research, we created different 2°C pathway scenarios exploring the importance of short-term mitigation by the top 25 largest carbon emitters as well as international aviation and shipping, in relation to the carbon budget. We also explicitly avoided including widespread NETs, unlike most 2°C scenarios. We found in these scenarios that short-term mitigation by a few big country emitters has a big impact on the rate of emissions reduction required for all. For example, if China can mitigate CO2 emissions in five years or sooner, other countries can reduce their CO2 emission reduction rates by 1% to 1.5% per year,” Larkin added.
The “Sustain” pathway represents a highly inequitable world successfully recovering from economic downturn, with limited efforts to implement new mitigation policy before 2020.
The “Immediate” pathway is similar to “Sustain”, illustrating a highly inequitable world where economic downturn resumes, but with more positive mitigation effort that materialises before 2020.
The “Development” scenario captures a more equitable distribution of mitigation effort where nations with low per-capita emissions expand fossil fuel energy systems for an extended period, to support development.
These scenarios also give greater attention than many others to very recent levels of CO2 and near-term CO2 growth rates. For instance, Japan’s emissions are expected to rise at a higher rate than pre-2011 if it continues to move away from nuclear power following Fukushima Similarly, Russia’s CO2 trends are uncertain due to factors such as falling oil prices, rising consumption of indigenous shale oil in the US, and a highly volatile Russian economy. China’s shifting economy also adds uncertainty to CO2 growth — with almost 30% of global CO2 from fossil fuel and industry, any short-term change in China’s CO2 growth rate has a significant impact on mitigation rates required for all countries, if limited to a stringent carbon budget. For example, China’s reduction in coal consumption has already influenced global CO2 growth. In addition, India’s CO2 growth rate might not be expected to fall for at least a decade, with rising demand for fossil fuel supporting development.
“Unfortunately, what stands out in this scenarios is that even with a weak consideration of equity, a reasonably high chance of avoiding 2°C (66%) becomes infeasible. This scenario requires mitigation rates of the order of 11% per year – pointing to a need for whole-system change. Even if there is no allowance for equity, avoiding 2°C with a reasonable chance is only achievable with deep and immediate mitigation,” says Larkin.
The research recommends that climate-focused policies in big country emitters to be urgently informed by three key factors: the equity principle of the Paris Agreement, the sensitivity of constrained carbon budgets to countries own short-term CO2 trend, and the climate risks societies face by unquestionably including widespread NETs within 2°C pathway scenarios.
As Glen Peters noted in his research, in the absence of CCS ‘there needs to be a radical reduction in the consumption of fossil fuels for a likely chance to keep global average temperatures below 2°C’. If big emitting countries fail to deliver immediate, deep, and absolute mitigation, the carbon budget will be beyond reach unless NETs are both proved to be viable at scale and urgently deployed.
Originally published at the Tyndall Centre for Climate Change Research