The ABCs of Global Warming: Understanding the Essentials
Climate change presents a pressing global challenge that demands urgent attention. In preceding articles, we have touched upon climate change, yet we have yet to explore its foundational aspects. According to the Intergovernmental Panel on Climate Change (IPCC) (2014), climate change refers to alterations in the climate’s state, characterized by shifts in its mean and/or variability persisting over extended periods, typically spanning decades or more. Over the past five to six decades, there has been a noticeable acceleration in the increase of planetary surface temperatures, as noted by the IPCC.
Based on rigorous statistical analyses, the IPCC’s observations reveal alarming trends. For instance, the atmospheric temperature has surged notably over the last three decades, with the period from 1983 to 2012 identified as very likely the warmest 30-year span in the Northern Hemisphere over the past 800 years and likely the warmest in the last 1400 years. Additionally, ocean temperatures have risen by an average of 0.11 °C per decade from 1971 to 2010, while glaciers, snow and ice caps, polar sea ice, and permafrost soils have experienced significant melting. Furthermore, global mean sea levels have ascended by 0.19 meters between 1901 and 2010, primarily attributed to thermal expansion and the influx of water from melting ice. Such changes have intensified the frequency and severity of weather-related natural disasters, underscoring the profound impacts of climate change.
These developments prompt the fundamental question: What are the root causes of climate change?
The Greenhouse Effect
Climate change primarily arises from a phenomenon referred to as the “greenhouse effect”. As outlined by The National Aeronautics and Space Administration (NASA; 2024), the greenhouse effect entails the retention of heat close to the Earth’s surface by substances termed ‘greenhouse gases.’ Picture these gases akin to a snug blanket encircling our planet, aiding in preserving a higher temperature than it would naturally possess.
The atmospheric greenhouse effect, explored and understood since the early 19th century, is indispensable for sustaining life on Earth and has been a constant presence since the planet’s inception (Rosenbaum et al., 2017). Without it, the global average temperature of the atmosphere near the Earth’s surface would hover around −18 °C, starkly contrasting with the current 15 °C. Consequently, natural mechanisms and sources play a crucial role in maintaining this equilibrium, albeit occasional imbalances leading to natural occurrences such as ice ages. Alongside these natural drivers, human activities also contribute to intensifying this effect, resulting in global warming — an occurrence characterized by a gradual increase in surface temperatures across the planet over extended periods.
Fundamentally, there’s an equilibrium between solar radiation entering the Earth’s atmosphere and energy leaving it, maintaining a stable temperature (Rosenbaum et al., 2017). About 28% of incoming sunlight is reflected back into space, termed albedo, while the rest is absorbed by greenhouse gases (21%) and the Earth’s surface (50%). The absorbed energy warms the surface, emitting infrared radiation, some of which is trapped by greenhouse gases (GHGs), contributing to the greenhouse effect and rising atmospheric temperatures. As depicted in the image provided, GHGs are produced through natural life processes, capturing a portion of the sun’s warmth and averting planetary freezing. Conversely, the excessive release of CO₂ from fossil fuel combustion entraps surplus heat, leading to a rise in the Earth’s average temperature.
Earlier, we discussed the connection between the greenhouse effect and certain types of gases referred to as “greenhouse gases.” What exactly do these gases entail?
Greenhouse Gases
Numerous greenhouse gases occur naturally in the atmosphere, playing a role in the natural greenhouse effect. Among these, water vapor accounts for approximately 55%, while carbon dioxide (CO₂), ozone (O₃), methane (CH₄), and nitrous oxide (N₂O) contribute 39%, 2%, 2%, and 2%, respectively, to this effect. Notably, anthropogenic emissions of water vapor do not impact climate change, as its presence is dictated by atmospheric temperature and evaporation processes. However, human activities significantly contribute to increased CO₂, CH₄, and N₂O concentrations, amplifying the greenhouse effect beyond its natural levels. Additionally, emissions of industrial halocarbons such as chlorinated fluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), perfluoromethane, and sulfur hexafluoride (SF₆) also play a role. Ultimately, greenhouse gas emissions stem from various human activities, affecting the balance of greenhouse gases in the atmosphere.
The greenhouse gases exert varying degrees of influence on global warming. In order to gauge their respective impacts, the (Intergovernmental Panel on Climate Change, 2014) assessed each gas using the global warming potential (GWP) metric. These global warming potentials (GWPs) are calculated relative to carbon dioxide, the predominant greenhouse gas. Below are significant GWPs for several greenhouse gases:
Human activities have a significant impact on the release of greenhouse gases. Since 1750, the atmospheric concentration of carbon dioxide has surged by 43%, as Stocker et al. (2013) noted. Measurements at the Mauna Loa laboratory in June 2018 recorded 411 parts per million (ppm) of CO₂, contrasting starkly with the preindustrial level of about 280 ppm. The rate of atmospheric CO₂ growth has escalated from 0.85 ppm per year during the 1960–69 decade to 2.28 ppm per year over the recent 10-year period from 2008 to 2017. This dramatic shift in atmospheric composition is primarily attributed to our heavy reliance on fossil fuels for energy and widespread deforestation. Corresponding to this rise in CO₂ content, the mean global surface temperature has already increased by 0.85°C compared to the preindustrial era (Hansen et al., 2010; Shurpali et al., 2019). Additionally, global methane concentrations have increased from 722 parts per billion (ppb) in preindustrial times to 1834 ppb by 2013, an increase by a factor of 2.5 and the highest value in at least 800,000 years.
Climate Change Action
Amidst the global emergency of climate change, necessitating collaboration that transcends national borders, international cooperation is imperative. A pivotal moment unfolded on 12 December 2015, as world leaders convened at the UN Climate Change Conference (COP21) in Paris and achieved a historic breakthrough: the adoption of the Paris Agreement (United Nations Framework Convention on Climate Change, 2020). This landmark accord sets forth long-term objectives intended to guide all nations in substantially reducing global greenhouse gas emissions. It aims to limit the rise in global temperature to well below 2°C above pre-industrial levels, with efforts aimed at further constraining it to 1.5°C above pre-industrial levels, acknowledging the significant risk mitigation associated with this target. Additionally, the Agreement mandates regular evaluations of collective progress toward its objectives and long-term goals, alongside the provision of financial support to developing countries for climate change mitigation, resilience strengthening, and adaptation enhancement.
As a legally binding international treaty, the Paris Agreement officially entered into force on 4 November 2016, with 195 Parties (194 States plus the European Union) having joined to date. In pursuit of “Net-Zero” objectives, various sectors worldwide have implemented stringent measures, including the adoption of carbon capture technology — an area of discussion we have extensively addressed previously.
All In All…
Climate change is an urgent global challenge demanding immediate action. Human activities, notably fossil fuel use and deforestation, have significantly increased greenhouse gas emissions, driving up temperatures and altering atmospheric composition. The Paris Agreement, established at COP21, provides a crucial framework for international cooperation and emissions reduction. However, achieving “Net-Zero” goals requires concerted efforts across all sectors, such as the adoption of carbon capture technology. It is imperative that we work together to address this pressing issue and safeguard the planet for future generations.
References
Hansen, J., Ruedy, R., Sato, M., Lo, K., 2010. Global surface temperature change. Reviews of Geophysics 48. https://doi.org/10.1029/2010RG000345
Intergovernmental Panel on Climate Change, 2014. Climate Change 2014: Synthesis Report.
Rosenbaum, R.K., Hauschild, M.Z., Boulay, A.M., Fantke, P., Laurent, A., Núñez, M., Vieira, M., 2017. Life cycle impact assessment, in: Life Cycle Assessment: Theory and Practice. Springer International Publishing, pp. 167–270. https://doi.org/10.1007/978-3-319-56475-3_10
Shurpali, N., Agarwal, A.K., Srivastava, V.K., 2019. Introduction to Greenhouse Gas Emissions, in: Energy, Environment, and Sustainability. Springer Nature, pp. 1–5. https://doi.org/10.1007/978-981-13-3272-2_1
Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex, P.M. Midgley (eds.), 2013. Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge.
The National Aeronautics and Space Administration (NASA), 2024. What is the greenhouse effect? [WWW Document]. URL https://science.nasa.gov/climate-change/faq/what-is-the-greenhouse-effect/ (accessed 3.21.24).
United Nations Framework Convention on Climate Change (UNFCC), 2020. The Paris Agreement [WWW Document]. URL https://unfccc.int/process-and-meetings/the-paris-agreement (accessed 3.23.24).
