Global Warming and Human Activity (Academic)

Global warming is one of the major concerns in the 21st century. The debates on global warming are numerous and interwoven around the sciences, media, and politics. Although the scientific community is said to have reached a consensus on this matter, the debate is not yet settled as what the public might wish to believe. Dissenting voices from the scientific community are still often heard in the media. In 2012, 16 scientists wrote to the Wall Street Journal, rejecting the mainstream view on human-induced global warming (WSJ, 2012). Indeed, the debate is not as simple as yes or no, and both sides of the debate have reasonable arguments. In this essay, I contend that global warming is largely caused by human activity. To argue for my stance, I will firstly explore the correlation between atmospheric carbon dioxide and global warming. Secondly, I will discuss humans’ contribution to global warming. Lastly, I will explain the philosophy of science and the meta-analysis of global warming studies to indicate the level of certainty on human-induced global warming.

One of the most questioned views on the cause of global warming is the correlation between atmospheric carbon dioxide and global warming. “There is no scientific proof of causation between the anthropogenic increase in atmospheric CO2 and the recent global warming trend” wrote Patrick Moore, a co-founder of Greenpeace, in an open letter to the UK’s Royal Society (Moore, 2006). To understand this statement and the relationship between CO2 and temperature rise, it is better to start from understanding the effect of greenhouse gases. Greenhouse gases, such as water vapour, carbon dioxide, and methane are the fundamental part of greenhouse effect which acts as a thermal blanket for the Earth (NASA, 2016a). It absorbs and returns energy from the sun, and reflects heat to the earth. CO2 is, following water vapour, the second largest contributor to greenhouse effect (Kiehl and Trenberth, 1997). According to the data from the U.S. National Oceanic & Atmospheric Administration (NOAA), the global average concentration of CO2 is 403.42 ppm by March 2016. The current CO2 level has doubled the amount of pre-industrial level, and is 40% higher than the highest natural level over the past 800,000 years (see figure 1). As mentioned ealier, the increased concentration of CO2 in the atmosphere will cause temperature rise by retaining more heat from the sun and reflecting back to the earth. There is clear evidence of anthropogenic increase in atmospheric CO2, but how does human contribute to this increase, and how does the climate response?

Figure 1: Combined Data for Historical Global Average Atmospheric CO2 Concentration from 800 kyBCE to 2014 (NOAA, 2014).

Humans contribute to atmospheric CO2 increase by primarily two actions: 89% of total emission comes from fossil fuel combustion and 11% from land-use change (Le Quéré et al., 2013). Although our observations do clear indicate that global temperature and CO2 concentration both present an uprising trend (see figure 2), the relationship between human activity and global warming is not as crystal-clear as we might think. According to a U.S. Senate Minority Report, there are over 700 international scientists rejecting the human-caused global warming claim (Morano and Dempsey, 2009). The reason for this is the complex nature of our climate system. Many factors can affect global temperature, such as the earth’s orbit, sun’s intensity, changes in the reflectivity of earth’s atmosphere and surface, and changes in greenhouse effect. NASA (2016a) clearly states that the sun is not responsible for global warming according to their 30 years of data and observation. In addition, UN’s Intergovernmental Panel on Climate Change (IPCC) states that “human influence has been detected in warming of the atmosphere and the ocean… and it is extremely likely to have been the dominant cause of the observed warming since the mid-20th century” (IPCC, 2014). IPCC’s standard of certainty of “extremely likely” is larger than 95% probability. However, it is not clear how other natural drivers, for example the orbit of the earth and the reflectivity of earth’s atmosphere and surface are not responsible for global warming. As for now, we still do not have the certainty as in that the earth is warming since the late-20th century, to defy scientists who reject human-induced global warming. To understand the divide in the science community, and to comprehend this complicated relationship between human activity and global warming, we need to apprehend a little bit of the background philosophy of science and venture into the meta-analysis of the global warming debate in the science community.

Figure 2: Atmospheric CO2 Growth Rate (NOAA, 2016) and Surface Air Temperature Change (NASA, 2016b) from 1959 to 2013.

Scientists are not always right. In fact, science works by designing hypotheses, making observations, correcting falsehood, and putting forward the best available explanation. Therefore, it is irresponsible to call an immature science studying the earth’s climate as settled. There are many evidences suggesting that human activity plays an important part in causing global warming, but there are also many questions that we still cannot answer. For example, we are not certain whether the increase in atmospheric CO2 concentration causes global temperature rise or the contrary, as the Vostok ice-core records (~240,000 years before present) suggest that increase in atmospheric CO2 delays 800 years after global temperature rise (Caillon et al., 2003). However, this does not mean that humanity has fallen into an endless black hole of science. There is still ground that we can stand on: the level of certainty. We can consider the following meta-analysis studies: Liu et al. (2015) learn that “in the US congressional global warming and climate change hearings, 78% of scientists indicate that it is caused, at least to some degree, by human activity”. Anderegg et al. (2010) meta-analysis shows that 97-98% of climate researchers agreed to the consensus that global warming is largely caused by human activity. NASA’s website cites Cook et al. (2016) meta-analysis indicating a similar result, as well as a collective agreement from 18 scientific associations. We allow the space for skepticism in science, because that is how science advance, but our collective efforts voice a consistent result: global warming is largely caused by human activity.

Conclusion:

In this essay, we have discussed the correlation between CO2 and global warming, human’s contribution to global warming, the philosophy of science, and the meta-analysis of global warming studies. It is understood that CO2 is one of the greenhouse gases which plays a vital part in warming the earth. It is understood that human emission of CO2 has been considerable and growing since industrial revolution. And it is observed that both atmospheric CO2 concentration and global temperature show a trend of increase. Although the causal relationship between CO2 and global temperature is still not clear, and a number of scientists are still disapproving the consensus, the majority in the science community has produced a result with about 97-98% certainty that current global warming is primarily caused by human activity.

Works Cited:

Anderegg, W. R., Prall, J. W., Harold, J., & Schneider, S. H. (2010). Expert credibility in climate change. Proc Natl Acad Sci U S A, 107(27), 12107-12109. doi:10.1073/pnas.1003187107

Caillon, N., Severinghaus, J. P., Jouzel, J., Barnola, J.-M., Kang, J. & Lipenkov, V. Y. 2003, 'Timing of atmospheric CO2 and Antarctic temperature changes across Termination III', Science, 299, 1728.

IPCC 2014, 'Climate Change 2014 Synthesis Report', In: TEAM, C. W., PACHAURI, R. K. & MEYER, L. (eds.) Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change ed.

Kiehl, J. T. & Trenberth, K. E. 1997, 'Earth’s Annual Global Mean Energy Budget', Bulletin of the American Meteorological Society, 78, 197-208.

Le Quéré, C., Andres, R. J., Boden, T., Conway, T., Houghton, R. A., House, J. I., Marland, G., Peters, G. P., van der Werf, G. R., Ahlström, A., Andrew, R. M., Bopp, L., Canadell, J. G., Ciais, P., Doney, S. C., Enright, C., Friedlingstein, P., Huntingford, C., Jain, A. K., Jourdain, C., Kato, E., Keeling, R. F., Klein Goldewijk, K., Levis, S., Levy, P., Lomas, M., Poulter, B., Raupach, M. R., Schwinger, J., Sitch, S., Stocker, B. D., Viovy, N., Zaehle, S. & Zeng, N. 2013, 'The global carbon budget 1959–2011', Earth System Science Data, 5, 165-185.

Moore, P. 2006, Royal Society Release, viewed April 28 2016, <http://greenspiritstrategies.com/royal-society-release/#more-551>.

Morano, M. & Dempsey, M. 2009, 'U. S. Senate Minority Report: More Than 700 International Scientists Dissent Over Man-Made Global Warming Claims Scientists Continue to Debunk “Consensus” in 2008 & 2009': U.S. Senate Environment and Public Works Committee (Minority).

NASA 2016a, A blanket around the Earth NASA, viewed May 8 2016, <http://climate.nasa.gov/causes/>.

NASA 2016b, GISS Surface Temperature Analysis: NASA Goddard Institute for Space Studies, viewed May 9 2016, <http://data.giss.nasa.gov/gistemp/graphs_v3/>.

NOAA 2014, 'History of atmospheric carbon dioxide from 800,000 years ago until January, 2014. '.

NOAA 2016, Trends in Atmospheric Carbon Dioxide: Earth System Research Laboratory Global Monitoring Division, viewed May 9 2016, <http://www.esrl.noaa.gov/gmd/ccgg/trends/global.html#global_data>.

WSJ 2012, No Need to Panic About Global Warming: The Wall Street Journal, viewed May 8 2016, <http://www.wsj.com/articles/SB10001424052970204301404577171531838421366>.

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