By Victor Miguel Ponce

 Documented Version 


  1. The Earth was formed about 4,540,000,000 years ago.

  2. In the beginning, the Earth's atmosphere contained very little oxygen (less than 1% oxygen pressure).

  3. Early plants started to develop more than 2 billion years ago, probably about 2,700,000,000.

  4. Through photosynthesis, plants uptake carbon dioxide into the biosphere as organic matter, and release oxygen as a byproduct.

  5. Through geologic time, oxygen accumulated gradually in the atmosphere, reaching a value of about 21% of atmospheric gases at the present time.

  6. Through geologic time, surplus organic matter has been sequestered in the lithosphere as fossil organic materials (coal, petroleum, and natural gas).

  7. Early animals (the first organisms with external shells) started to develop around 635,000,000 years ago.

  8. Animals operate in the opposite way than plants: they take up oxygen, burn organic matter (food), and release carbon dioxide as a byproduct.

  9. Early humans (Australopithecus anamensis) began to develop about 4,100,000 years ago.

  10. Cool climatic conditions have prevailed during the past 1,000,000 years. The species Homo sapiens evolved under these climatic conditions.

  11. Homo sapiens dates back to more than 400,000 years.

  12. Estimates for the variety Homo sapiens sapiens, to which all humans belong, range from 130,000 to 195,000 years old.

  13. The last Ice Age began to recede about 22,000 years ago.

  14. The concentration of carbon dioxide in the atmosphere was as low as 190 ppm about 21,000 years ago, near the end of the last Ice Age.

  15. The agricultural revolution, where humans converted forests and rangelands into farms, began to develop about 12,000 years ago.

  16. The agricultural revolution caused a reduction in standing biomass in the biosphere and reduced the uptake of carbon dioxide in midlatitudinal regions, indirectly contributing, however so slightly, to global warming.

  17. The concentration of carbon dioxide in the atmosphere increased gradually from a low of 190 ppm 21,000 year ago, to about 290 ppm in the year 1900, i.e., at an average rate of 4.87 ppm per millennium.

  18. The industrial revolution, where humans developed machines (artificial animals, since they consume fuels, which are mostly organic matter), began in England about 260 years ago.

  19. In October 2011, the world's population reached 7,000,000,000, which is 2.5 times that of 1956.

  20. The world's population is currently increasing at the rate of about 80,000,000 per year (about 1.13 %).

  21. The current world population is 7,800,000,000 (December, 2020).

  22. The global fleet of motor vehicles (cars and trucks) is estimated at approximately 1.42 billion. (2020).

  23. The global fleet of motor vehicles (vehicles registrations) has been recently growing at the rate of 40,000,000 per year.

  24. Motor vehicles (cars, trucks, buses, and scooters) account for 80% of all transport-related energy use.

  25. The concentration of carbon dioxide in the atmosphere, which was at 290 ppm in the year 1900, rose to 316 ppm in 1959, or at an average 0.44 ppm per year.

  26. Measurements of the concentration of carbon dioxide since 1959 (316 ppm) have revealed an increase to 414 ppm in 2020, or at an average 1.51 ppm per year.

  27. The concentration of carbon dioxide has increased an average of about 2.0 ppm per year over the past two decades.

  28. The concentration of carbon dioxide increased 2.87 ppm in 1997-98, more than in any other year of record.

  29. According to NASA, the ten hottest years of record have occurred in the past eighteen-year period (1998-2015). The warmest year of record is last year, 2015.

  30. About 91% of the annual increase in atmospheric carbon dioxide is due to the burning of fossil fuels.

  31. The remaining 9% is attributed to anthropogenic changes in land use, which have the effect of reducing the net uptake of carbon dioxide.

  32. Anthropogenic changes in land use occur when forests are converted to rangelands, rangelands to agriculture, and agriculture to urban areas.

  33. Land degradation (deforestation, overgrazing, overcultivation, urban sprawl, desertification, and salinization) reduce the net uptake of carbon dioxide, indirectly contributing, however slightly, to global warming.

Victor Miguel Ponce is professor of civil and environmental engineering at San Diego State University. His specialty is hydrology, environmental science, and sustainable development.

See also The global warming predicament.