Sources may be found in “Files” within “Homework_Four.” The four sources are drawn from the 1990s, the 2000s, and the 2010s, including one published earlier this week! Please read through them and compose a short response (300-500 words) drawing on them which addressess the question: “How does the threat to human survival from climate change relate to the changes in geology, biodiversity, and other natural systems which have been observed already and the changes in those systems that are projected to occur if we fail to limit global temperature change to 1.5 degree Celsius by llimiting greenhouse gas emissions?”
1. Paul J. Crutzen: Geology of Mankind–The Anthropocene. Nature, 415, 2002: 23 (crutzen2002.pdf, 5 pages).
Atmospheric chemist Paul J. Crutzen shared the Nobel Prize in Chemistry for working on the chemical reactions catalyzed by chluorofluoro carbons that break down ozone in the stratosphere leading to the ozone hole to form over the poles. In 2002 he wrote about the change in greenhouse gas concentration in the troposphere in the British journal Nature. Crutzen refers to these changes as a new age in the sense of geology: the anthropocene, or age of humankind.
2. Edward O. Wilson, The Diversity of Life (Harvard University Press, Cambridge, MA 1992, wilson1992.pdf, 8 pages) pgs. 222, 276-280.
American entomologist Edward O. Wilson started with ants in the hills near his home in Alabama. In school he learned of the changes in the diversity of life with time and later he worked to uncover the scaling law tying the number of species found in a geographic place, such as an island, to the surface area of that place. Here Wilson gives a graph showing the law in the case of some of the islands of the Carribean Sea and uses it to guess the human impact on the diversity of life, concluding as follows: “Clearly we are in the midst of one of the great extinction spasms of geological history.”
3. Elizabeth Kolbert, The Sixth Extinction (Henry Holt, New York, 2014, kolbert2014.pdf, 5 pages) pgs. 16-18.
Writer Elizabeth Kolbert sits on the Science and Security Board of the Bulletin of Atomic Scientists. Her 2014 book looks at the loss of diversity of life going on now in the context of the five massive losses of life in the geologic record known as mass extinctions. In this excerpt, we find a plot of the number of biological families in the marine fossil record showing five big dips in the past six hundred million years as well discussion of the loss of reptile and amphibian species. Kolbert traces the loss of diversity to “one weedy species:” humans.
4. Intergovernmental Panel on Climate Change, Special Report on 1.5 degree Celsius (sr15_spm-1.pdf 34 pages, sr15_headline_statements-1.pdf 2 pages).
The more that the temperature rises compared to pre-industrial levels, the more severe the impacts on human and natural systems, the IPCC notes in this special report released in preparation for the December 2018 meeting of the 196 countries that have joined the United Nations Framework Convention on Climate change. In particular, limiting the temperature change to 1.5 degrees celsius compared to 2.0 degrees celsius reduces the risks and improves the chances for survival in a significant way which they attempt to estimate. Of course the limits on greenhouse gas emissions must be much sharper to achieve the 1.5 degree celsius target, and the IPCC provides side-by-side comparisons of the changes in this case versus the more dangerous 2.0 degree celsius scenario.