Table 1 Pathway ‘what-if’ assumptions

Baseline

Follows emissions until 2030, consistent with a successful implementation of the current NDC submitted by individual countries under the Paris Agreement, adapted from Rogelj et al.¹⁵. Emissions continue after 2030, assuming no significant strengthening in climate action.

The data are adapted from Rogelj et al.¹⁵ and represents a central estimate of the range of estimates presented therein. This pathway also falls centrally in the range identified by the 2019 UNEP Emissions Gap Report³⁰.

Two-year blip

Reflecting potential SARS-CoV-2 transmission dynamics²², this case explores 66% of the June 2020 lockdown persisting until the end of 2021, then emissions linearly recover to baseline by the end of 2022.

This implies a persistent necessity of partial lockdowns until the end of 2023 but with no lasting effect of SARS-CoV-2.

Fossil-fuelled recovery

Follows the two-year blip pathway until the end of 2021, then emissions recover in a way similar to the recovery after the 2008/9 global recession, rebounding to 4.5% above the baseline at the end of 2022. Stimulus packages are designed with strong support for fossil-fuel energy supply, resulting in more fossil investment than a pre-COVID-19 current-policy scenario (+1%) and considerably less in low-carbon alternatives (−0.8%). Resulting emissions are 10% higher in 2030 than the baseline scenario, a trend that is assumed to continue thereafter³¹.

2030 data taken from Climate Action Tracker³¹, ‘rebound to fossil-fuel scenario’ with the relative increase in emissions compared to baseline continued thereafter.

Moderate green stimulus

Follows the two-year blip pathway until end of 2021, then emissions recover slightly, until the end of 2022 but never reach the baseline projections. Governments choose recovery packages to target specifically low-carbon energy supply and energy efficiency, and do not support bailouts for fossil firms. The resulting investment differential (+0.8% for low-carbon technologies and −0.3% for fossil fuels relative to a current-policy scenario) begins to structurally change the emissions intensity of economic activity, resulting in about a 35% decrease in GHG emissions by 2030 relative to the baseline scenario, a trend that is assumed to continue thereafter³¹, consistent with meeting global net-zero CO₂ by 2060.

Short-term benefits come from changes to the norms of behaviour, then green incentives to decarbonize all sectors of the economy.

Strong green stimulus

As for the moderate green stimulus with investment differentials (+1.2% for low-carbon technologies and −0.4% for fossil fuels relative to a current-policy scenario), resulting in a slightly more than 50% decrease of GHG emissions by 2030 relative to the baseline scenario. This trend is continued thereafter, consistent with meeting global net-zero CO₂ by 2050.

This has >50% chance of limiting the 2050 temperature rise to 1.5 ^oC above pre-industrial.