IB Geography 2.1.3 the Enhanced Greenhouse Effect and Variations in Emissions Notes

The Enhanced Greenhouse Effect: More Gas, Slower Heat Loss, Warmer Surface

1. The natural greenhouse effect occurs when greenhouse gases absorb outgoing longwave radiation and return part of it to the ground as back radiation.
   1. The enhanced greenhouse effect is what happens to that same mechanism when human emissions raise the concentration of those gases above their pre-industrial levels.
   2. Adding more of these gases makes the atmosphere less transparent to longwave radiation at the wavelengths they absorb.
   3. The surface then loses energy more slowly and settles at a higher temperature.

1. The NOAA Global Monitoring Laboratory measured a global mean carbon dioxide concentration of 422.80 parts per million in 2024, against a 1750 baseline of 278.3 parts per million.
2. Friedlingstein and others, publishing the Global Carbon Budget 2025, projected atmospheric carbon dioxide at 425.6 parts per million for 2025, which they put 53 percent above the pre-industrial level.
3. Radiative forcing measures the size of the energy imbalance these gases create, in watts per square metre.
   1. NOAA's 2024 index attributes 2.33 W/m2 to carbon dioxide, which is 66 percent of the forcing from long-lived greenhouse gases.

Four Groups of Gas: Carbon Dioxide Dominates the Total, the Others Dominate per Molecule

1. The IPCC Sixth Assessment Report puts net anthropogenic greenhouse gas emissions at 59 GtCO2eq in 2019, which is the most recent year the report breaks down by gas.
2. Carbon Dioxide
   1. Fossil fuel combustion and industry produced 38 GtCO2eq in 2019, about 64 percent of the total.
   2. Land-use change added a further 6.6 GtCO2eq, about 11 percent.
3. Methane
   1. Livestock digestion, manure, flooded rice paddies, landfill and leaks from coal mines, gas wells and pipelines produced 11 GtCO2eq in 2019, about 19 percent of the total.
   2. The IPCC gives fossil methane a 100-year global warming potential of 29.8 and a perturbation lifetime of 11.8 years.
   3. Methane released from thawing permafrost is a climate feedback rather than a direct human emission.
4. Nitrous Oxide
   1. Nitrogen fertilizer applied to farmland, together with manure and some industrial processes, produced 2.7 GtCO2eq in 2019, about 5 percent of the total.
   2. Its 109-year atmospheric lifetime gives it a 100-year global warming potential of 273 and behaviour closer to carbon dioxide than to methane.
5. Fluorinated Gases
   1. Hydrofluorocarbons, perfluorocarbons, sulphur hexafluoride and nitrogen trifluoride produced 1.4 GtCO2eq in 2019, about 2 percent of the total.
   2. Refrigeration, air conditioning, electrical switchgear, semiconductor manufacture and primary aluminium smelting are the sources of almost all of them, since only the perfluorocarbons have any natural background.
   3. The IPCC gives HFC-134a a 100-year global warming potential of 1,530 and sulphur hexafluoride 24,300.
6. Water vapour is absent from this list because its concentration is set by temperature and not by emissions, which makes it a feedback rather than a driver.

Sources by Sector: Energy Supply and Use Accounts for Nearly Three Quarters

1. The sector split below is Climate Watch data for 2016, compiled by Our World in Data, on a total of 49.4 GtCO2eq.
   1. Each sector lists its largest items rather than its full breakdown, so the sub-figures do not sum to the sector total.
2. Energy supplies 73.2 percent, split between use in industry at 24.2 percent, buildings at 17.5 percent and transport at 16.2 percent, of which road transport alone is 11.9 percent.
3. Agriculture, forestry and land use account for 18.4 percent, with livestock and manure at 5.8 percent, agricultural soils 4.1, crop burning 3.5 and deforestation 2.2.
4. Industrial processes account for 5.2 percent, of which cement is 3 percent, released by the reaction that turns limestone into clinker and not by the kiln fuel.
5. Waste accounts for 3.2 percent, from landfill at 1.9 percent and wastewater treatment at 1.3.

Total Emissions: Four Emitters Produce Around Three Fifths of the World's Fossil Carbon Dioxide

1. The Global Carbon Budget 2025 projected global fossil carbon dioxide emissions of 38.1 GtCO2 for 2025, a record, plus 4.1 GtCO2 from land-use change.
   1. The two together give 42.2 GtCO2 of human-caused carbon dioxide emissions in 2025.
2. The Global Carbon Budget 2025 gives the shares of global fossil emissions for 2025 as China 32 percent, the United States 13 percent, India 8 percent and the European Union 6 percent.
   1. Those four together account for around 59 percent of global fossil emissions, though not of the larger total that includes land-use change.
3. In absolute terms for 2024, Our World in Data's compilation gives China 12.29 GtCO2, the United States 4.90, India 3.19 and the EU27 2.43, against a world total of 38.6.
   1. That series runs about 0.8 GtCO2 above the Global Carbon Budget headline, because it does not net off the cement carbonation sink.

Per Capita Emissions: The Ranking Rearranges Once You Divide by Population

1. The figures below are production-based fossil carbon dioxide per person for 2024, from Our World in Data's compilation of the Global Carbon Budget, against a world average of 4.73 tonnes.
2. Oil and Gas Exporters
   1. Qatar emitted 41.27 tonnes per person, Kuwait 26.25, Saudi Arabia 20.38 and the United Arab Emirates 20.13.
   2. Extraction, processing and liquefaction are energy-intensive operations divided across small populations.
3. High-Income Industrial Economies
   1. Australia emitted 14.48 tonnes per person, the United States 14.20 and Canada 13.42.
   2. The EU27 average of 5.39 shows that the high-income group is far from uniform.
4. Emerging Industrial Economies
   1. China emitted 8.66 tonnes per person, above the EU27 average and above Germany's 6.77.
5. Low-Income Economies
   1. Ethiopia emitted 0.14 tonnes per person and the Democratic Republic of the Congo 0.05, which puts Qatar at roughly 300 times the Ethiopian figure.

Cumulative Emissions: A Third Ranking, Because Carbon Dioxide Stays for Centuries

1. Carbon dioxide is removed from the atmosphere over centuries, which means what a country emitted in 1900 still contributes to today's forcing.
2. Carbon Brief's analysis puts cumulative emissions since 1850, counting fossil fuels, cement and land use, at 2,607 GtCO2 by the end of 2024.
   1. The United States leads that record on 537 GtCO2, about a fifth of the whole.
   2. China's cumulative total reached 312 GtCO2 in 2023, passing the European Union's 303 GtCO2 for the first time.
3. Carbon Brief's cumulative figures per person to the end of 2024 reverse that comparison, at 1,570 tonnes for the United States, 682 for the European Union and 227 for China.
   1. China has therefore overtaken the EU on the cumulative total while sitting at a third of the EU figure per person.

Development: Emissions Track Energy Use and Energy Mix, Not Income by Itself

1. The Kaya identity, set out by the energy economist Yoichi Kaya in 1990, expresses a country's carbon dioxide emissions as population multiplied by GDP per person, by energy intensity and by carbon intensity.
   1. Population multiplies whatever the per-person figure is, which is why India ranked third on fossil carbon dioxide emissions in 2024 while emitting only 2.20 tonnes per person that year.
   2. GDP per person rises with industrialization and urbanization, which add car ownership, appliances, air conditioning and more meat in the diet.
   3. Energy intensity, the energy used per unit of output, falls as an economy shifts from heavy industry towards services.
   4. Carbon intensity, the carbon dioxide released per unit of energy, depends on the electricity mix and produces the widest divergence between countries at similar incomes.
2. Carbon intensity is where the widest gap opens, because France emitted 3.97 tonnes per person in 2024 while Germany emitted 6.77 at a similar income level.
   1. Nuclear supplied about 67 percent of French electricity in 2024 and low-carbon sources reached 95 percent for the first time, on RTE's figures.
3. At the other end of the range, the IEA reported that 730 million people still had no access to electricity in 2024.
   1. About eight in ten of them live in sub-Saharan Africa, the world region with the lowest emissions per person.
4. The Global Carbon Budget 2025 counted 35 countries that cut their fossil carbon emissions over the past decade while their economies grew.
   1. Part of that fall is a genuine change in the energy mix, while part is production moving abroad, which the trade section separates.

Globalization: Splitting Production Across Borders Moves Emissions Between Countries

1. Globalization broke manufacturing into stages that can sit in different countries, which is why a single finished product now draws on factories across several continents.
   1. Each stage is counted where the factory stands, which places the emissions of a Chinese-made component in China's national total even when the finished good is sold in Germany.
2. UNCTAD's Review of Maritime Transport 2024 put seaborne trade at 12.3 billion tonnes in 2023, carrying over 80 percent of world trade by volume.
3. Transnational corporations locate energy-intensive stages where energy, labour or land is cheapest, and sometimes where environmental regulation is loosest.
   1. Smelting, cement production and textile finishing move more readily than design or marketing, because they are the stages that use the most energy per unit of output.
   2. Because the decision is made by the firm and not by either government, neither country's emissions figure reflects a choice its own electorate made.
4. Worked Illustration: Samsung in Bac Ninh and Thai Nguyen
   1. Samsung runs six manufacturing plants in Vietnam, with its two largest complexes in Bac Ninh and Thai Nguyen.
   2. The company told The Investor that its Vietnamese exports were worth 54.4 billion dollars in 2024, or 13.4 percent of the country's total exports.
   3. The energy used to assemble those phones is counted against Vietnam, while the phones themselves are used in Europe, North America and Korea.
   4. Our World in Data's share of emissions embedded in trade puts Vietnam's net exports of embodied carbon at 29 percent of its territorial emissions in 2023, the latest year that series covers.
   5. Vietnam is used here because these figures are published, not because the IB requires this country.
5. Ember reported that fossil fuels supplied 58 percent of China's electricity in 2025, which gives a tonne of Chinese steel a higher carbon intensity than the same tonne made on a nuclear or hydro grid.
6. Globalization also moves low-carbon technology, which means the flow does not run in only one direction.
   1. The IEA reported in 2022 that China's share of every manufacturing stage of solar panels, from polysilicon to modules, exceeds 80 percent.

Trade: Consumption-Based Accounting Reassigns Emissions to the Buyer

1. Production-Based Accounting
   1. This method counts every tonne emitted inside a country's borders, whoever buys the product.
2. Consumption-Based Accounting
   1. This method subtracts the emissions embodied in a country's exports and adds those embodied in its imports, which assigns the tonnes to the country where the finished product is bought.
   2. Its figures lag the territorial ones by a year or two, because they need an input-output model of world trade.
3. Carbon Leakage
   1. This term describes a fall in one country's territorial emissions that happens because production moved abroad and not because output stopped.
   2. The global total is unchanged by the move.
   3. It can even rise, if the new location runs on a more carbon-intensive electricity supply.
4. Peters and others (2011), in the Proceedings of the National Academy of Sciences, traced carbon dioxide embodied in international trade from 4.3 GtCO2 in 1990, which was 20 percent of global emissions, to 7.8 GtCO2 in 2008, or 26 percent.
5. On Our World in Data's 2023 figures the United Kingdom produced 4.48 tonnes of carbon dioxide per person and consumed 7.09, a net import equal to 58 percent of its territorial total.
6. China produced 8.56 tonnes per person and consumed 7.63, which puts about 11 percent of its territorial emissions into goods sent abroad.
7. India produced 2.13 and consumed 1.77, a net export of about 17 percent.
8. The adjustment does not remove the gap, because a clean electricity grid lowers both figures at once.
   1. France consumed 6.13 tonnes per person in 2023 against 4.07 produced.
   2. Sweden consumed 5.85 against 3.48 produced, a wider proportional gap than the United Kingdom's.
9. Worked Illustration: The United Kingdom's Two Emissions Figures
   1. UK territorial emissions fell 50 percent between 1996 and 2023, while the consumption-based footprint fell 15 percent over the same years.
   2. Emissions embodied in imports made up 53 percent of that footprint in 2023.
   3. The gap between a 50 percent territorial fall and a 15 percent footprint fall is where offshored manufacturing sits.
   4. The United Kingdom is used here because Defra publishes both figures in full, not because the IB requires this country.

Explaining a Country's Emissions: Development, Globalization and Trade Together

1. Development sets how much energy a population uses and what that energy is generated from.
2. Globalization decides where in the world the energy-intensive stages of production physically happen.
3. Trade decides whether those emissions are counted against the producer or the buyer.
4. Any single country needs all three before its figure makes sense.
   1. China's 32 percent share of global fossil emissions in 2025 rests on an electricity supply that Ember put at 58 percent fossil in the same year, and on its position as the assembly point for global manufacturing.
   2. On the 2023 consumption-based data it exported about 11 percent of its territorial emissions inside goods.