Investigating the Causes of Climate Change

11/17/20222 min read

Generally, climate variations or climate change may be explained by natural internal processes, and/or by changes in external influences (which may in turn have natural or anthropogenic origins) (Hegerl et al, 2007).

An example of a natural internal process is changes in the temperature carried by ocean currents around the earth, which manifests in phenomena such as El Niño (Hegerl et al, 2007; BGS). As “Earth’s dominant source of interannual climate variability”, El Niño “has varied considerably since the Last Glacial Maximum (21,000 years ago)” and there may have been “a gradual intensification… over the past ~6,000 years” (Liu et al, 2014).

External influences owing to natural causes include the strength of the Sun; changes in the Earth’s orbit, axial tilt, and procession; plate tectonics and volcanic eruptions; and meteorite impacts (BGS). Deforestation and the burning of fossil fuels are the main reasons for anthropogenic influence on climate variations, also known as global warming or human-induced climate change (Houghton, 2015).

Deforestation leads to reduced vegetation cover, resulting in increased albedo and decreased absorption of carbon at the surface. When fossil fuels such as coal, natural gas, and oil undergo combustion, there is a rise in the atmospheric concentration of greenhouse gases, “increasing global temperatures, causing ocean acidification, and disrupting the planet’s ecosystems” (NOAA).

According to Hegerl et al (2007), when researchers used climate models to compare temperature changes using “only natural forcings”, and using “both natural and anthropogenic forcings”, simulations using the former method failed to produce the warming patterns actually observed on earth, while the latter method was able to do so.

References:

  • Hegerl, G.C., F. W. Zwiers, P. Braconnot, N.P. Gillett, Y. Luo, J.A. Marengo Orsini, N. Nicholls, J.E. Penner and P.A. Stott, ‘Understanding and attributing climate change’ in Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds) Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge: Cambridge University Press, 2007), pp.702–703

  • Liu., Z., Lu, Z., Otto-Bliesner, B.L., Timmermann, A., and Cobb, K.M. (2014) ‘Evolution and Forcing Mechanisms of El Nino over the Past 21,000 Years’. Nature (Vol. 515, Issue 7528). Nature Publishing Group.

  • British Geological Survey (‘BGS’). ‘What Causes The Earth’s Climate To Change?’ https://www.bgs.ac.uk/discovering-geology/climate-change/what-causes-the-earths-climate-to-change/

  • National Ocean and Atmospheric Administration (‘NOAA’). ‘What Is The Carbon Cycle?’ https://oceanservice.noaa.gov/facts/carbon-cycle.html