Decarbonization Around the World

• CO₂: Energy Institute Statistical Review of World Energy — every figure and the calculator on this site covers CO₂ from fossil fuel combustion specifically (oil, gas, coal), not full CO₂e and not other sources of CO₂ or other greenhouse gases (land use, cement process emissions, methane, N₂O, etc.). Manually updated annually (~June). Same source for both the Intensity and Per Capita figures.
• GDP (CO₂ Intensity figure): World Bank — constant 2015 US$ (NY.GDP.MKTP.KD, MER, market-exchange-rate based) and constant 2021 international $ (NY.GDP.MKTP.PP.KD, PPP, purchasing-power-parity based). World Bank's PPP series only starts in 1990 for almost every country — lines in PPP mode begin there, not at 1965, even though MER and CO₂ both go back further.
• MER vs. PPP: MER converts each country's local-currency GDP to US dollars using observed market exchange rates — it reflects a country's economic weight as valued by currency markets, but says nothing about what that money actually buys at home. PPP instead converts using a conversion factor that equalizes purchasing power across countries, correcting for the fact that a dollar buys more goods and services in lower-income countries than in higher-income ones. In practice, PPP GDP runs higher than MER GDP for most developing economies (and roughly comparable for high-income ones), so a country's CO₂ intensity looks higher under MER and lower under PPP for the identical physical CO₂ output — MER isn't "wrong," it's just answering a different question (financial/trade weight in the global economy) than PPP (real domestic output, more comparable to a genuine efficiency measure). Energy and climate analyses more often lean on PPP for that reason, but reasonable people differ on which is the more meaningful basis for this specific chart — hence the toggle, rather than picking one and hiding the other.
• Population (Per Capita figure and calculator): World Bank's total-population indicator (SP.POP.TOTL), itself sourced from the UN Population Division's World Population Prospects (midyear estimates).
• Energy (calculator): Energy Institute Statistical Review — total primary energy supply, exajoules. Same workbook and same annual update cycle as CO₂.
• Coverage gaps: Taiwan has no World Bank GDP or population series and is excluded from both figures. Venezuela has no World Bank PPP series (MER only). Two regions (Africa, S.&Cent. America) include countries not individually broken out in the CO₂/energy source data — this understates their GDP denominator in the Intensity figure and overstates their per-capita CO₂ and per-capita energy (real totals divided by an undercounted population) in the Per Capita figure and calculator. Flagged on the Per Capita page's chart, and in the calculator, when one of these regions is selected.
• Kaya identity: a standard climate-policy decomposition (Yoichi Kaya, 1990) splitting emissions into population × GDP per capita × energy per unit of GDP × CO₂ per unit of energy. This calculator isolates just the last factor — carbon intensity of energy — by working entirely in per-capita terms (emissions = energy × carbon intensity of energy), so the implied rate depends only on the target %, the target year, and the assumed energy-growth rate, not on the entity's actual per-capita levels. This same decomposition, and what it really implies for emissions targets, is the subject of Roger Pielke Jr.'s book The Climate Fix — see the Bibliography below.
• Physical buildout (calculator): illustrative, not an engineering plan. The emissions target is applied to the entity's whole 2025 CO₂ (not per-capita, and with no separate population-growth assumption), retired coal-first-then-gas-then-petroleum using each fuel's EI consumption series and IPCC 2006 default CO₂ intensities (coal 94.6, gas 56.1, petroleum 73.3 kg CO₂/GJ). All retired fossil energy is treated as electricity-displacing, which overstates the buildout needed for non-power uses (transport, heat, industry). The fossil-retirement figures depend only on the target and today's baseline, not on the assumed energy-growth rate; the new clean capacity needed does also scale with that rate, since growing demand has to be met by new clean capacity too, on top of whatever replaces retired fossil fuel. New capacity is sized against reference units (nuclear: 1 GW, 90% capacity factor; wind: 3 MW turbine, 35% capacity factor) -- both shown as alternatives ("or"), not summed. The share image also expresses the retired coal and gas the same way, as a plant count against a reference unit (coal: 600 MW, 55% capacity factor; gas: 500 MW, 50% capacity factor) -- no petroleum reference, since most petroleum use isn't power generation.
• Waste heat: a toggle in the buildout calculator. Off (default): retired fossil energy is replaced 1-for-1 with new clean capacity, EJ for EJ. On: retired fossil energy is first discounted to a typical fossil power-plant's actual electrical output (coal/oil ~38%, gas ~50% thermal efficiency) before sizing replacement capacity, since a wind turbine or reactor doesn't need to replace the ~50-60% of fossil fuel input that was never converted to useful energy in the first place — only the fossil plant did.
• Regions: EU/EEA/G7/G20/BRICS are built from constituent countries (BRICS is the original 5: Brazil, Russia, India, China, South Africa; G20 is its 19 individual country members).

Bibliography

1. Energy Institute. Statistical Review of World Energy (2026 edition), CO₂ from energy and total energy supply data. energyinst.org/statistical-review.
2. World Bank. World Development Indicators — GDP, MER (NY.GDP.MKTP.KD), GDP, PPP (NY.GDP.MKTP.PP.KD), and total population (SP.POP.TOTL). data.worldbank.org.
3. United Nations, Department of Economic and Social Affairs, Population Division. World Population Prospects. population.un.org/wpp.
4. Intergovernmental Panel on Climate Change. 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Volume 2 (Energy), Table 2.2 — default CO₂ emission factors used in the calculator's fossil-retirement buildout. ipcc-nggip.iges.or.jp/public/2006gl.
5. Kaya, Yoichi (1990). Impact of Carbon Dioxide Emission Control on GNP Growth: Interpretation of Proposed Scenarios. Presented to the IPCC Energy and Industry Subgroup, Response Strategies Working Group, Paris. See also: Kaya identity.
6. Pielke Jr., Roger (2010). The Climate Fix: What Scientists and Politicians Won't Tell You About Global Warming. Basic Books. The decarbonization arithmetic behind this whole site — the Kaya identity, emissions targets, and what they really require — is discussed there in far more depth than a website footnote can manage. Archived at thehonestbroker.org/climatefix.

Thanks

This site runs entirely on data that the Energy Institute, the World Bank, and the UN Population Division publish openly and free of charge. None of them built this site, vetted its analysis, or endorse anything on it — but without their open data, none of it would exist. Thank you.