Backgrounds and methods
Some context
In signing up to the Paris Agreement, Governments agreed to pursue efforts to limit warming to 1.5°C, and set out their near-term emissions reduction pledges in so-called Nationally Determined Contributions (NDCs). The first set of NDCs put the world on track for around 3°C of warming by 2100, with warming continuing to rise into the next century. This level of warming would be devastating.
To limit warming to 1.5°C, the emissions pathways assessed by the Intergovernmental Panel on Climate Change (IPCC) in its Special Report on Global Warming of 1.5°C show that global emissions in 2030 need to be about 45% lower than they were in 2010.
As governments bring forward updated NDCs, a key question is: how much stronger to they need to be to keep the 1.5°C limit within reach? In 2019 we showed that holding warming to 1.5°C would require emissions in 2030 to be about half of the level implied by current pledges. A truly transformational ramping up of climate action for the period to 2030 and beyond is required.
What does this mean at the country level? This tool allows users to explore the effect that strengthening different governments’ climate pledges for 2030 could have on global warming levels and climate change impacts.
Country selection
To give a global coverage, we have selected the largest economies and emitters from each of five major global regions. Action by these governments alone will not be sufficient to limit warming to 1.5°C, so users can also change the aggregated strength of the NDCs of other countries within each major grouping of countries (OECD, Asia, Latin America and the Caribbean, Africa and the Middle East, former Soviet Union).
Current pledges scenario
Our reference scenario, “current pledges”, reflects our best guess of the global emissions levels and warming consequences implied by the first set of Nationally Determined Contributions, taking into account the fact that some countries are on track to overachieve these NDC targets. These estimates are based on assessments made by the
Climate Action Tracker (CAT) of the NDCs submitted in 2016 (see the
NDC Updates tab for more details). Where there is uncertainty in the emissions level associated with a country’s NDC, we take the upper end of this range to provide a conservative estimate.
Our baseline is the ambition level set by countries five years ago on ratification of the Paris Agreement. Some countries have brought forward updated NDCs, although few demonstrate a significant increase in ambition, and the UNFCCC Secretariat recently highlighted the enormous shortfall in ambition that remains in its
NDC Synthesis Report . The
NDC Updates tab contains information on the updated NDCs that have already been submitted, and provides an estimate of the change in the strength of each, based on the CAT’s
Climate Target Update Tracker assessments.
It is worth noting that the starting point of different countries in terms of their 2016 NDCs varies substantially. Some countries are already set to overachieve their pledges through the implementation of existing policies (e.g. India, South Africa, Russia). This anticipated overachievement is indicated on the country sliders with red numbering. NDCs also differ in the extent to which they constitute a “fair share” to mitigation climate change – see the CAT’s assessments for more information.
The 2030 emissions gap
The emissions gap in 2030 is the gap between the global emissions level for a median 1.5°C (low or no overshoot) pathway from the IPCC’s SR1.5 (26 GtCO2e/yr) and the emissions level for the user selected scenario.
Emissions pathways after 2030
After 2030, the emissions projection for the user’s chosen scenario assumes a continued level of mitigation effort that is consistent with the ambition of the NDC. Baseline estimates of emissions from international aviation, marine activities and land-use, land-use change and forestry (LULUCF) are also included, following the Climate Action Tracker’s methodology (for more information, see our 2019 report,
here).
When a country or region’s slider is moved to x%, the emissions of that country / region in 2030 decline are reduced to x% below the reference scenario value. We assume that a consistent level of climate action continues beyond 2030.
Our analysis is based on model scenarios produced by Integrated Assessment Models, which are taken from the IPCC’s Fifth Assessment Report (AR5) database. Scenarios that limit warming to 1.5°C by the end of the century show rapid emissions reductions to reach net zero around or shortly after mid-century, and go net negative after that. A mitigation target in 2030 alone is therefore not sufficient to ensure that emissions follow a trajectory that is compatible with the Paris Agreement’s long-term temperature goal, and our analysis assumes that a given level of climate action by 2030 will be followed by equivalent mitigation efforts over the rest of the century. To do so, a scenario is constructed from the available AR5 scenarios to best represent the user’s selected NDC targets on the regional level. This scenario is used as an approximation of the same ambition level performed throughout the century.
For 1.5°C compatible pathways, this means that some level of carbon dioxide removal is deployed. For information on the challenges associated with governing large-scale carbon dioxide removal, see our
publication on the topic.
The pathways constructed by the tool are limited by the set of modelled pathways available in the IPCC’s AR5 database. This means that at very high levels of ambition, some regions may hit an artificial ceiling in the level of ambition that the tool can process. For example, if sliders for both the EU and the USA are moved to 80% (i.e. their emissions are 80% below the NDC baseline level), a change in the strength of other OECD countries’ NDCs does not make a difference to the warming level in the tool because the most ambitious OECD pathway available has already been selected. This does not mean that a chosen combination is infeasible, but instead reflects a limitation in the pathway dataset used for this tool.
Estimating warming levels for each scenario
We calculate the levels of global warming associated with different levels of climate action for each scenario using the linear relationship between the cumulative emissions released over the century and the warming level reached in 2100. The warming ranges shown indicate the “likely” level of warming – in other words, there is a 66% chance that the warming level will fall within this range. The median warming level indicates that we have a 50% chance of staying at or below that level (or a 50% chance of exceeding it).
Some scenarios reach their peak warming level before the end of the century, with temperatures declining gradually afterwards so that the warming level in 2100 is lower than the peak level. Peak temperature level estimates are especially important with regards to tipping points and are required for assessing climate impacts. We therefore also estimate the peak warming level, which is derived using the (non-linear) relationship between cumulative emissions from 2011 over the century and the level of peak warming. The relationship is calibrated using MAGGIC6 runs for many variations (see our
2019 report for more details).
In this analysis, GMT values are estimated based on the simplified climate model MAGICC6 (Meinshausen et al., 2011). The simplified version allows only to project global temperature levels that are sufficiently accurate for this analysis. For this tool to work in real-time and for a wide range of user-options, we interpolate certain temperature responses. Thus, determined GMT levels do not exactly match e.g. data provided by the
Climate Action Tracker.
Connecting a level of climate action in 2030 with the level of warming achieved in the longer term requires a number of assumptions to be made regarding climate action beyond 2030. As described above, we use pathways assessed by the IPCC to project emissions out to 2100. An important caveat to our warming estimates is the role of negative emissions in many high ambition scenarios. The IPCC’s SR1.5 found that all scenarios that limit end-century warming to 1.5°C, and most that limit warming to 2°C, require some level of carbon dioxide removal, or negative emissions, to make up for a lack of progress to-date in reducing emissions, and to balance residual emissions that are challenging to mitigate. In some cases, carbon dioxide removal is used to reduce warming levels after a peak. For information on the challenges associated with governing large-scale carbon dioxide removal, see our
publication on the topic.
Climate impacts
For the level of warming that corresponds to a user’s selection, the
Overview tab shows the corresponding severity of risks at the global level for five ‘reasons for concern’, as assessed by the IPCC in its
Special Report on Global Warming of 1.5°C.
Climate change impacts vary from place to place. Sub-regional climate change impacts for the level of warming that corresponds to a user’s selection are shown in the Impacts tab. Users can choose from three different impacts:
- Hottest temperature of the year
- Heat wave severity index (a measure of heat wave duration)
- Heat wave frequency index
The data for these impacts is taken from the latest simulations produced by global climate models (GCMs) under the
Coupled Model Inter-comparison Project (CMIP6). These serve as the primary source of information for the upcoming IPCC’s Assessment Report (AR6). For each impact, the change against the reference period 1990-2010 is shown. During this period, global temperatures had risen by 0.85°C above pre-industrial levels
In this tool we show an area average for each sub-region, but it is important to remember that climate impacts can vary substantially within countries and sub-regions.
Pathway extension method - further detail
Connecting near-term climate action with global temperature rise requires an emissions pathway consistent with climate pledges in 2030 to be extended to the end of the century. We use the constant quantile extension method (
Gütschow et al. (2018)), which is based on the assumption that the relative ambition level of climate policy is kept constant over the century. The extension is done using a database of emission scenarios from integrated assessment models (IAMs) included in the IPCC’s Fifth Assessment Report (AR5) (Clarke et al., 2014). For each region, the emissions level in 2030 that we estimate as being consistent with the NDCs in that region defines the selection of IAM scenarios used to extend the pathway until the end of the 21st century. This ensures that that the long-term projection of a region is as consistent as possible with near-term pledges. See
Geiges et al. (2020) for more detailed information.
Sources
- Clarke, L., Jiang, K., Akimoto, K., Babiker, M., Blanford, G., Fisher‐Vanden, K., Hourcade, J., Krey, V., Kriegler, E., Löschel, A., McCollum, D., Paltsev, S., Rose, S., Shukla, P. R., Tavoni, M., van der Zwaan, B., van Vuuren, D. P., Böttcher, H. K. C., Daenzer, K., den Elzen, M., Dhar, S., Eom, J., Hoeller, S., Höhne, N., Hultman, N., Irvine, P., Jewell, J., Johnson, N., Kanudia, A., Kelemen, A., Keller, K., Kolp, P., Lawrence, M., Longden, T., Lowe, J., Lucena, A., Luderer, G., Marangoni, G., Moore, N., Mouratiadou, I., Petermann, N., Rasch, P., Riahi, K., Rogelj, J., Schaeffer, M., Schäfer, S., Sedlacek, J., Sokka, L., von Stechow, Christoph Sue Wing, I., Vaughan, N., Wiertz, T., and Zwickel, T.: Assessing Transformation Pathways, in: Climate Change 2014: Mitigation of Climate Change., edited by: Edenhofer, O., Pichs-Madruga, R., Sokona, Y., Farahani, E., Kadner, S., Seyboth, K., Adler, A., Baum, I., Brunner, S., Eickemeier, P., Kriemann, B., Savolainen, J., Schlömer, S., von Stechow, C., Zwickel, T., and Minx, J., Cambridge University Press, 2014.
- Geiges, A., Nauels, A., Parra, P. Y., Andrijevic, M., Hare, W., Pfleiderer, P., Schaeffer, M., and Schleussner, C.-F.: Incremental improvements of 2030 targets insufficient to achieve the Paris Agreement goals, Earth Syst. Dynam., 11, 697–708, https://doi.org/10.5194/esd-11-697-2020, 2020.
- Gütschow, J., Jeffery, M. L., Schaeffer, M., and Hare, B.: Extending Near-Term Emissions Scenarios to Assess Warming Implications of Paris Agreement NDCs, Earth’s Future, 6, 1242–1259, https://doi.org/10.1002/2017EF000781, 2018.
- Meinshausen, M., Raper, S. C. B., and Wigley, T. M. L.: Emulating coupled atmosphere-ocean and carbon cycle models with a simpler model, MAGICC6 – Part 1: Model description and calibration, Atmos. Chem. Phys., 11, 1417–1456, https://doi.org/10.5194/acp-11-1417-2011, 2011. a, b