Sunday, July 8, 2012

Are humans too insignificant to affect climate?

Are humans really so tiny and insignificant that their activity makes no difference on climate? Some people say so but, if you are of this opinion, you might change your mind once you read how much human activities affect the Earth's crust. For instance, the amount of rock and soil we move every year would fill the whole Grand Canyon in about 50 years.

An excerpt from Ugo Bardi's "Depleting the Earth," a book being prepared in collaboration with the Club of Rome.  

The amounts of minerals extracted nowadays is immense and it becomes even larger if consider as “mining” the use of fertile soil in agriculture which is consumed by the process called erosion. It is estimated that about 4 billion tons of agricultural soil are eroded in the United States alone and dumped into the oceans every year (1). In the whole world, the total amount has been estimated as 75 billion tons per year by Pimentel et al. (2) and as 120 billion tons per year by Hooke (3). These amounts dwarf those created by natural erosion, at least one order of magnitude smaller. 

To this amount related to agriculture we must add the amount of rock and sand moved by the construction industry. From the USGS data, we find that the worldwide production of sand and gravel may exceed 15 billion tons per year. The total world production of concrete in 2008 has been of 2,8 billion tons. China, alone, produces more than a billion tons per year, that is about 450 kg per person on the average. 

According to Bruce Wilkinson (4) we can visualize the total amount of rock and soil yearly moved by humans considering that these amounts are “ca. 18,000 times that of the 1883 Krakatoa eruption in Indonesia, ca. 500 times the volume of the Bishop Tuff in California and about 2 times the volume of Mount Fuji in Japan. At these rates, this amount of material would fill the Grand Canyon of Arizona in ca. 50 years.

1 Azimut, 29 Jun 2011, John Baez (Accessed 12 Aug 2011)
2 David Pimentel; C. Harvey; P. Resosudarmo; K. Sinclair; D. Kurz; M. McNair; S. Crist;. L. Shpritz; L. Fitton; R. Saffouri; R. Blair. 1995, Science, New Series, Vol. 267, p. 1117-1123
3 Hooke, R.L.B., 2000, On the history of humans as geomorphic agents, Geology, v. 28 p 843-846
4 Wilkinson, Bruce, 2005, “Humans as geologic agents: a deep-time perspective”, Geolog, 22 pp 161-164


  1. When people deny that humans can change climate, because we're "too small", I point out that it was microscopic bacteria that created our current environment. And that the waste they created (oxygen) was toxic to them.

  2. Divide the population into the land surface of Earth. Each persons living space is a square only 150 metres on a side within which all of their activities, resource extraction, pollution etc notionally takes place. Do people really think "they are so small" they cannot affect 150 metres square?

  3. Of course, that is a rhetorical question. Yes we are significant, see e.g. Russia on fire as of today!




Ugo Bardi is a member of the Club of Rome and the author of "Extracted: how the quest for mineral resources is plundering the Planet" (Chelsea Green 2014). His most recent book is "The Seneca Effect" to be published by Springer in mid 2017