National Plans – 3.2°C (5.8°F) – No change after national contribution pledge period.
<2.0°C Path – 1.8°C (3.3°F) – All countries peak by 2030 and then reduce steadily, with rates in the post-2030 period faster in the developed countries (5%/yr) than in the developing countries (3.5%/yr).
1.5°C Path – 1.5°C (2.8°F) – All developed countries peak by 2025 and then reduce steadily at 10%/yr; all developing countries peak no later than 2030 and then reduce steadily at 8%/yr.
In order to assess the cumulative impact of all the pledges and offer
a projected temperature in 2100, we had to make some assumptions that
are highlighted below. Many points are also explained in our FAQs.
We only include Nationally Determined Contributions (NDCs), Intended
Nationally Determined Contributions (INDCs), and Long-Term
Strategies submitted to the UNFCCC that are unconditional.
For the “National Plan” scenario, which is the one displayed on the
Scoreboard, we assume no continued reductions by developed countries and
no further action from developing countries beyond the timeframe of
their plans. Specifically, there are four primary types of pledges, and
we make the following assumptions for them:
Absolute reductions – For countries that are making
absolute emissions reductions, we assume that emissions stay constant
after 2025-2030 (the end of the pledge period), unless an NDC states
otherwise. For example, Australia has offered to reduce their greenhouse
gas emissions 26% below 2005 levels by 2030. After that, given there is
no formal post-2030 pledge, we assume that Australia’s emissions do not
increase nor continue to decrease, but stay constant at that new level.
Relative to a reference scenario – For countries that are
reducing emissions from a reference scenario or business as usual (BAU)
level, we assume they stay at the target level below the reference
scenario after the pledge period. For example, Kenya has pledged to
reduce their emissions 30% below their BAU by 2030. After 2030, we
assumed that the emissions would continue to stay 30% below their
Reference Scenario. Since the Reference Scenario is increasing, however,
emissions increase at the same rate as the Reference Scenario.
Peaking – Emissions grow until year target peak year. For
example, China has said they will peak their CO2 emissions by 2030. We
assumed that the rate of growth in emissions would slow starting in
2015, approaching a flat trajectory gradually. After the peaking date,
emissions would stay level. (Note: other greenhouse gas emissions
continue to increase given they were not covered by China’s pledge).
Emissions intensity reduction – Change in emissions
relative to the GDP of the country. For example, India reducing
emissions intensity 40% (we took the low end of the pledge, which was
35-40%) by 2030. Up to 2030, we calculate emissions by using the GDP
growth. After 2030, emissions intensity stays 40% below the growing GDP.
In the <2°C and 1.5°C scenarios, we assume continued action and reductions after the period when the current NDCs end.
The regional distribution of emissions reductions in the <2°C and
1.5°C scenarios is one representation of many possible approaches. We
assume that developed countries move faster than developing countries.
We assume that proposals will be fully implemented, in accordance with the dates specified in the plans.
Some countries have made proposals for specific actions (rather than
for emissions targets). If we don’t have a good estimate for the impact
of those actions on emissions then we don’t include the action in our
We assume emission reductions cover all greenhouse gas emissions
unless specified otherwise. In some cases for smaller countries, the
structure of the model requires us to assume that they take proportional
action on other greenhouse gases.
The C-ROADS reference
scenario (also called “business as usual”) accounts for the UN’s medium
fertility population projections, historical GDP per capita rates
that converge over time to be consistent with other integrated
assessment models, and GHG per capita projections for each gas that
reflect trends over the last decade for CO2 and follow the IPCC’s RCP8.5 for the non-CO2 greenhouse gases.
C-ROADS uses a climate sensitivity of 3 (that is 3°C of temperature increase for a doubling of CO2 concentration.)
There are positive feedback loops in the real climate system that are not modeled in the current version of C-ROADS.
C-ROADS allows inputs of emissions reductions targets for 12
countries (U.S., Japan, Russia, Canada, Australia, South Korea, China,
India, Brazil, Mexico, South Africa, Indonesia) and three blocs of
countries (EU, “other developed” and “other developing”). For the 12
countries with individual controls, we adjust that country’s modeled
emissions from a reference scenario (based on the IPCCs RCP 8.5
NDCs accounted for in “other developed” or “other developing” were
calculated in accordance with that country’s percentage of emissions
from the entire group. In other words, each nation’s proposals are
scaled to their actual share of emissions within their bloc.
We are fortunate to have many colleagues in the field of adding up climate mitigation proposals to assess their sufficiency, aggregate their contributions, and see what more is needed. Explore other climate trackers.