Dare to Doubt: 20 Climate Change Facts for Deniers

  1. Carbon dioxide is rising as a component of Earth’s atmosphere (NOAA, 2017).
  2. The level of carbon dioxide in the atmosphere has not been this high for the past 5 million years (Stap et al. 2016).
  3. Beginning about 10,000 years ago and extending to the advent of the Industrial Revolution, carbon dioxide in the atmosphere was roughly constant, indicating that natural sources were well-balanced by removals from the atmosphere (Fluckiger et al. 2002).
  4. The current rise in carbon dioxide is due to human activities, especially combustion of fossil fuels (Hofmann et al. 2009).
  5. Carbon dioxide is a “greenhouse” gas, inasmuch as it absorbs heat radiation leaving the Earth’s surface (Tyndall, 1865).
  6. There is a natural greenhouse effect on Earth, which keeps its temperature above freezing (Houghton 1986).
  7. Water vapor, methane and nitrous oxide also act “greenhouse gases” in the atmosphere, but the human impacts are greatest for CO2 (Schmidt et al. 2010).
  8. Past period of high CO2 have been unusually warm (Luthi et al. 2008, Parrenin et al. 2013; Triparti et al. 2009).
  9. 2016 was the hottest year on record (Science 355: 331, 2017).
  10. Rising CO2 will affect the mean annual (not necessarily daily) temperature on Earth (Trenberth 1992).
  11. Mean annual temperature is an essential feature of climate (von Humboldt 1860).
  12. Different climate regions on Earth determine what crops we can grow, what diseases we experience, and how much water is available (von Humboldt 1860).
  13. Past changes in global climate have determined the position of sea level (Grant et al. 2012).
  14. Higher levels of CO2 in Earth’s atmosphere increase the acidity of seawater, making it difficult for shellfish to synthesize their shells (Ekstrom et al. 2014).
  15. CO2 is an essential component for plant photosynthesis, and it should increase the rate of growth of most plants—both crops and weeds—when other conditions are favorable (Taiz and Zeiger 1998).
  16. Measured increases in plant growth during the past few decades have been rather modest (Long et al. 2006; Groenendijk et al. 2015).
  17. Higher plant growth does not equate with greater carbon storage on land, as a way to mitigate rising CO2 in the atmosphere (Wieder et al. 2015).
  18. Higher temperatures are associated with greater occurrence of drought, which lowers plant growth (Rind et al. 1990).
  19. Drought is directly correlated to and a determinant of forest fires.
  20. Drought, famine, and losses of soil fertility are implicated in the downfall of several historical civilizations (deMenocal 2001).



deMenocal, P.B. 2001.  Cultural response to climate change during the late Holocene.  Science 292: 667-673.

Ekstrom, J.A. and 16 others.  2014. Vulnerability and adaptation of US shellfisheries to ocean acidification.  Nature Climate Change  doi: 10.1038/NClimate2508.

Fluckiger, J., E. Monnin, B. Stauffer, J. Schwander, T.F. Stocker, J. Chappellaz, D. Raynaud, and J.M. Barnola. 2002.   High-resolution Holocene N2O ice-core record and its relationship with CH4 and CO2.  Global Biogeochemical Cycles 16:

Grant, K.M., E.J. Rohling, M. B. Matthews, A. Ayalon, M. M. Elizalde, C.B. Ramsey, C. Satow, and A.P. Roberts. 2012.  Rapid coupling between ice volume and polar temperature over the past 150,000 years.  Nature 491: 744-747.

Groenendijk, P., P. van der Sleen, M. Vlam, S. Bunyavejchewin, F. Bongers and P.A. Zuidema. 2015.   No evidence for consistent long-term growth stimulation of 13 tropical tree species: Results from tree-ring analysis.  Global Change Biology doi: 10.111/gcb.12955.

Houghton, J.T. 1986.  The Physics of Atmospheres. 2nd ed., Cambridge University Press.

Long, S.P. Long, E.A. Ainsworth, A.D.B. Leakey, J. Nosberger, and D.R. Ort. 2006.  Food for thought: Lower-Than-Expected Crop Yield Stimulation with Rising CO2 Concentration.  Science 312: 1918-1921.

Luthi, D., M. Le Floch, B. Bereiter, T. Blunier, J.M. Barnola, U. Siegenthaler, D. Raynaud, J. Jouzel, H. Fischer, K. Kawamura, and T.F. Stocker. 2008.  High-resolution carbon dioxide concentration record 650,000-800,000 years before present.  Nature 453: 379-382.

NOAA.  2017.  https://www.esrl.noaa.gov/gmd/ccgg/trends/full.html

Parrenin, F., V. Masson-Delmotte, P. Kohler, D. Raynaud, D. Paillard, J. Schwander, C. Barbante, A. Landais, A. Wegner, and J. Jouzel. 2013.  Synchronous change of atmospheric CO2 and Antarctic temperature during the last deglacial warming.  Science 339: 1060-1063.

Rind, D., R. Goldberg, J. Hansen, C. Rosenzweig, and R. Ruedy. 1990.   Potential evapotranspiration and the likelihood of future drought.  Journal of Geophysical Research 95: 9983-10004.

Schmidt, G.A., R.A. Ruedy, R.L. Miller, and A.A. Lacis. 2010. Attribution of the present-day total greenhouse effect.  Journal of Geophysical Research 115:

Stap, L.B., B. de Boer, M. Ziegler, R. Bintanja, L.J. Lourens, and R.S.W. van de Wal. 2016.  CO2 over the past 5 million years: Continuous simulation and new δ11B-based proxy data.  Earth and Planetary Science Letters 439: 1-10.

Taiz, L. and E. Zeiger. 1998.  Plant Physiology. 2nd ed., Sinauer Associates Publishers, MA

Trenberth, K.E. 1992.  Climate System Modeling. Cambridge University Press.

Tripati, A.K., C.D. Roberts, and R.A. Eagle. 2009.   Coupling of CO2 and ice sheet stability over major climate transitions of the last 20 million years.  Science 326: 1394-1397.

Tyndall, J. 1865. Heat: A Mode of Motion.  D. Appleton and Co., New York.

von Humboldt, A.  1860. Cosmos: A Sketch of the Physical Description of the Universe (translated and reprinted by Johns Hopkins Univ. Press, Baltimore, 1997)

Wieder, W.R., C.C. Cleveland, W.K. Smith, and K. Todd-Brown. 2015.  Future productivity and carbon storage limited by terrestrial nutrient availability.  Nature Geoscience 8: 441-445