The discussion on climate change has now more than ever become very important; and as to how much humans have played a role in this phenomenon is even more intriguing. “It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together” (Hansen, 2015). The important roles greenhouse gases play in giving us the ‘just right’ amount of temperature we need cannot be stressed enough. Nonetheless, too much of these gases in the atmosphere could be cataclysmic in the long run. The Intergovernmental Panel on Climate Change (IPCC) describes the period from 1983 to 2012 as likely the warmest 30-year period of the last 1400 years in the Northern Hemisphere (IPCC, 2014). ‘Human influence has warmed the climate at a rate that is unprecedented in at least the last 2000 years’ (IPCC, 2021). But is climate change really anthropogenic and how do we know? There have been lots of cutting-edge research among scientists over the years to evidently demonstrate human involvement in the climate change phenomenon. Firstly, the elementary evidence of anthropogenic causes of climate change is basic physics or science in general. Basic physics paints the picture of how the atmosphere works and how it responds to mutations. There is the need therefore to appreciate the nomenclature of our atmosphere to be able to understand how it affects our climate. The atmosphere is a mixture of gases made up of primarily oxygen and nitrogen. Some of these atmospheric gases act as a greenhouse structure in effect; trapping energy and regulating the temperature here on earth. Greenhouse gases are the earths blanket that absorb outgoing solar radiation from the earth’s surface to keep our environment warm. Our planet would be downright freezing without naturally occurring greenhouse gases such as carbon dioxide (The Climate Reality Project, 2019). Nevertheless, injecting more greenhouse gases than needed into the atmosphere means there would be more greenhouse gases to absorb more outgoing solar radiation thereby defying the temperature balance needed to survive on earth and to a very large extent causing the planet to get warm rapidly. This phenomenon is known as global warming. Human activities result in the emission of four principal greenhouse gases: carbon dioxide (CO2), besides emanating from biota respiration, mainly from industrial processes and the burning of fossil fuel, methane (CH4) mainly owing to agricultural activities and the emission of coal, nitrous oxide (N2O) emanating from landfills and industrial emissions, and halo-carbons (a group of gases containing fluorine, chlorine, and bromine) from the use of chlorofluorocarbons (IPCC, 2007).
It is rather unfortunate that the global surge in temperatures have been met with the cutting down of trees (deforestation). “Deforestation - cutting down trees on a large scale for fuel, land, or other purposes - leads to more greenhouse gases in the atmosphere as more trees are burned and fewer are in the ground to absorb excess carbon dioxide” (Climate Reality Project, 2018). Trees are natural sinks for carbon dioxide; hence reduced trees imply reduced capacity to absorb carbon dioxide from the atmosphere. There has been a surge in the atmospheric concentrations of anthropogenic greenhouse gases and aerosols since the beginning of the industrial era.
Figure 1 IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu and B. Zhou (eds.)]. Cambridge University Press. In Press.
Figure 1 illustrates a change in global surface temperature (decadal average) as reconstructed (1 - 2000) and observed (1850 - 2020) and a change in global surface temperature (annual average) as observed and simulated using human & natural and only natural factors (both 1850 - 2020).
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https://escholarship.org/content/qt1pw524ws/qt1pw524ws_noSplash_4a741dd3d9388f5da28b82f776ed5d47.pdf
https://www.ipcc.ch/
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