📐 Methodology

At a glance

Newleaf brings together public data on people, food, land, wealth, energy, greenhouse gases, climate in one table: every indicator for every country, year by year, with projections up to 2100. Most of the data is collected through Our World in Data, which gathers and harmonises the statistics of the UN, the World Bank, the FAO and many other institutions.

Data collection

Every source is fetched from Our World in Data's chart and explorer pages, and every column becomes one indicator, with its unit. Three inputs come from elsewhere:

• Monthly surface temperature by country (Copernicus ERA5, also through Our World in Data), from which we derive the yearly average, the coldest and hottest months and their spread.
• Country boundaries from Natural Earth, which also give each country its continent and sub-region.
• Published factors from the scientific literature: lifecycle emissions of each source of electricity, the land, water and emissions footprint of foods, the carbon footprint of income groups, and the physical constants of the climate model.

Cleaning and harmonising

• The world is the sum of its countries. World values are recomputed from the countries in the database (sums for totals, population-weighted averages for rates), so a world line always matches the countries under it.
• Gaps. Missing years between two observations are interpolated linearly. A series that stops early is extended with its last yearly change, damped.
• Per person first. Totals are turned into values per person before they are projected, and back into totals afterwards: a country's emissions grow because each person emits more and because there are more people, and the two are kept apart.
• Regions. Countries are grouped in 10 regions: Europe, OECD Pacific, Greater China, North America, Latin America, Sub-Saharan Africa, Middle East & North Africa, South East Asia, North East Eurasia, Indian Subcontinent.
• Income groups follow GDP per capita, with thresholds at 1,500, 5,000, 15,000 and 45,000 dollars a year.

Projections to 2100

Projections go year by year from 2026 to 2100. For some indicators the sources do not cover 2023–2025 yet: those years are estimated with the same method, so that every indicator reaches today. The projections are built in two passes, and the main indicators are linked to each other up to global warming:

1. Each indicator on its own

About a hundred indicators — GDP per capita, energy and electricity by source, emissions by sector, land by type, food, the income of the richest and the poorest — are projected country by country with the same rule. Each year's change is the sum of two terms:

• The country's own momentum: its average yearly growth over the previous five years, damped, with implausible jumps discarded and a maximum yearly rate per indicator.
• A baseline trend: a small yearly push, the same for every country, that fades linearly to zero by 2100 — for example the expansion of solar and wind or the decline of coal.

That change is then multiplied by a saturation factor that slows growth as the indicator approaches its ceiling.

2. Closing the accounts

The second pass makes the indicators agree with each other, year by year:

• Population starts from the UN medium-variant birth, death and migration rates: each year's population is last year's plus births, minus deaths, plus net migration, with migration rebalanced so that it sums to zero worldwide. Age groups, fertility, life expectancy and median age follow the UN projections, adjusted when the population differs from the UN's.
• Totals are rebuilt from values per person times population, and summed into the world.
• Land cannot exceed the country: if urban, grazing, crop and forest land add up to more than 95% of its area, they are scaled down, and what is left is “other”.
• Electricity emissions are the generation of each source times its lifecycle emission factor. Emissions from land use follow the change in forest area: about 50,000 tonnes of CO₂ for every km² of forest lost, and as much absorbed for every km² regained.
• Incomes: the income of the poorest 90% and of the richest 1% are projected; the richest 10% get what is left of GDP. The wealth shares of the richest move with their income.

Logistic curves

Nothing grows forever at the same rate, so every projected change is multiplied by how far the indicator still is from its ceiling K:

x_t+1 = x_t · (1 + g_t · (1 − x_t / K))

where g is the yearly growth described above. Far from the ceiling growth goes on as before; near it the curve flattens — the discrete form of the logistic curve. The ceiling depends on the indicator and on the country.

The climate model

Warming is computed from emissions with a chain of standard, simplified relationships, the same in the pipeline and in the Scenarios tool:

1. Emissions. Fossil CO₂ is population × GDP per person × energy per dollar of GDP × CO₂ per unit of energy, plus CO₂ from forest loss.
2. Concentration. CO₂ in the air is the pre-industrial 280 ppm plus a fixed fraction of cumulative emissions. Methane and nitrous oxide accumulate and decay, with lifetimes of about 12 and 109 years.
3. Radiative forcing. For CO₂, 5.35 W/m² × ln(C / 280); for methane and nitrous oxide, proportional to the square root of the concentration above pre-industrial.
4. Warming. The forcing of each gas times its sensitivity, summed over the three gases, calibrated on the observed warming of recent years.
5. Countries. Each country's contribution to warming is its share of cumulative CO₂; its local temperatures move by the same proportion as global warming.

Scenarios

The baseline is the projection above: it is the scenario shown everywhere on the site.

The Scenarios tool goes further. Five indicators drive the climate chain — population, GDP per capita, energy per GDP, CO₂ per energy and forest share — and each has two levers:

• World trend shifts the yearly growth rate of every country by the same amount, compounded from today.
• Low/high income countries adds growth to the poorest countries and takes it from the richest, in proportion to their rank by income.

The range of each lever is set so that, alone, it can at most halve or double the world value in 2100. Taking each of the five indicators at its baseline, its lowest and its highest gives 3⁵ = 243 combinations: the grey bundle around the warming line is those 243 runs of the climate chain, and the range quoted next to it holds 90% of them. They show how sensitive the result is to each assumption, not how likely it is.

Models on the website

• Income distributions. For each country, income by percentile is rebuilt from GDP per capita, the income shares of the poorest 90%, the richest 10% and the richest 1%, and the share of people in extreme poverty: a log-normal curve up to the 90th percentile and a Pareto tail above it. Its average equals GDP per capita by construction. The world curve is built the same way from world values.
• The tax simulator on Wealth distribution applies the chosen rates to these curves, bracket by bracket, and hands the revenue back to the chosen groups.
• Live counters run between the yearly values of the database, at the pace of the current year.
• Billionaires. The number and wealth of billionaires come from published rankings; they calibrate the extreme tail of the distribution.

Limitations

Some recent years are estimates.

For some indicators the sources have no data yet for 2023–2025: those years are estimated, not measured. From 2026 on every value is a projection, including the live counters on the homepage.

Projections are trends, not forecasts.

They extend each country's recent path with a growth rate that slows down and a ceiling it cannot pass. They do not model wars, pandemics, recessions, new technologies or policy changes, and they do not know about events after the latest data.

Few feedbacks between indicators.

Population, energy and land drive emissions, and emissions drive warming. Warming does not feed back into GDP, harvests, health or migration: climate damages are not part of the model.

The climate model is simplified.

It reproduces the observed warming but is far simpler than the models used by the IPCC: no aerosols, no ocean heat uptake, no carbon-cycle saturation, and only three gases. Country temperatures scale with global warming instead of being modelled region by region.

Gaps are filled.

Missing years inside a series are interpolated, and series that stop early are extended. Countries with patchy statistics therefore carry more modelled values than countries with complete ones.

168 countries, not all of them.

Very small states and territories are left out because most indicators do not cover them. World totals are the sum of the countries in the database, so they can differ slightly from the world figures published by the sources.

Income distributions are modelled.

Curves of income by percentile are rebuilt from a few published shares and poverty rates; the richest fraction of a percent is extrapolated from the shape of the top of the distribution.

Borders are not statements.

Maps use Natural Earth boundaries, chosen for their coverage. They imply no position on disputed territories.

Sources and licence

Most of the data on Newleaf comes from Our World in Data. Data produced by Our World in Data is published under the Creative Commons BY 4.0 licence, which allows reuse with attribution. The rest is collated by Our World in Data from third-party providers, under their own terms: we cite each of them below and, under every chart, the provider of that chart's data and the processing it went through — by Our World in Data, and the projections and modelling by Newleaf.

Newleaf is independent and is not affiliated with or endorsed by Our World in Data or any of the providers above. Errors in processing, projections and modelling are ours. If you spot one, please tell us.