In this blog post, we will examine whether reducing carbon dioxide emissions is a sufficient response based on various theories surrounding the causes of global warming.
The world is experiencing extreme climate change, with summers becoming hotter and winters colder. Seasonal temperature differences are much more pronounced than in the past, and weather anomalies are no longer considered unusual. For example, in January 2025, North America experienced a record cold snap that was so severe it was aptly described as “nature’s freezer.” Minnesota, in particular, recorded an average temperature of -37°C, lower than the surface temperature of Antarctica or Mars, resulting in dozens of deaths across the United States and economic losses estimated at over $7 billion, including disruptions to air and road transportation.
Such climate disasters are not limited to North America. In the summer of 2024, Beijing and Sichuan Province in China were hit by record-breaking rainfall of 1,000 mm over two days, causing parts of the city to flood, landslides to occur, and hundreds of casualties.
In the same year, Europe experienced prolonged heatwaves exceeding 40 degrees Celsius, leading to a surge in heatstroke cases and significant crop damage. Meanwhile, large-scale wildfires in Australia and Brazil destroyed millions of hectares of forest. The extreme cold wave in North America mentioned earlier is believed to have been caused by the “polar vortex.”
The “polar vortex” is a very strong low-pressure system that appears in the stratosphere over the Arctic during winter. Under normal conditions, it is blocked by strong westerly jet streams and remains over northern Siberia without moving southward. However, due to global warming, the jet streams have weakened, allowing the cold low-pressure system known as the “polar vortex” to move southward as far as the central United States, causing the extreme cold wave.
Extreme heatwaves and floods in various regions are also attributed to global warming. While these extreme climate changes have diverse local causes such as the polar vortex and the formation of numerous rain clouds due to warmer sea temperatures, the underlying common cause is global warming.
These climate changes have intensified significantly over the past century, prompting humanity to recognize the urgency of the situation and devote efforts to identifying the causes of global warming, which is considered the primary driver of climate change. As a result, causes such as ozone layer depletion caused by CFCs and excessive greenhouse effects caused by greenhouse gases have been identified. Experts have identified carbon dioxide as the primary cause of global warming, citing its increasing emissions due to human industrialization and deforestation, as well as its strong correlation with rising global average temperatures. Therefore, countries around the world, recognizing the urgency of carbon dioxide emissions, proposed the Kyoto Protocol—an international agreement aimed at regulating and preventing global warming—in Kyoto, Japan, in December 1997. The protocol established carbon dioxide emission reduction targets tailored to each country’s economic and industrial levels and introduced systems such as carbon emissions trading to achieve global reductions in carbon dioxide emissions.
The author also agrees that the phenomenon of global warming is causing significant changes in the world’s climate. If the Earth’s average temperature continues to rise, Arctic glaciers will melt rapidly, reducing the amount of sunlight reflected back into space (albedo), causing the Earth to absorb more solar heat. Additionally, the solubility of greenhouse gases in the ground and water will decrease, leading to their release into the atmosphere and further warming of the Earth through a positive feedback loop. As a result, deserts may form in some regions, glaciers may melt and sea levels may rise, submerging and destroying low-lying areas, increased evaporation of water into the atmosphere may lead to more powerful typhoons and floods, and some regions may experience severe droughts. The climate changes that could occur due to global warming are clearly evident in the examples of cold waves, floods, and heavy snowfall mentioned earlier, leaving no doubt that global warming is rapidly altering the Earth’s climate.
Therefore, it is necessary to prevent global warming, which is changing the Earth’s climate and threatening many living things on Earth, and I believe that efforts to reduce carbon dioxide, which has been identified as the main cause of global warming, are also appropriate. However, I disagree with the leading theory that the increase in carbon dioxide concentrations caused by industrialization and green space development is solely responsible for global warming.
It is true that carbon dioxide concentrations have risen since industrialization, and this trend aligns with the rise in global average temperatures. Additionally, there is substantial research evidence supporting the claim that carbon dioxide warms the Earth, such as Svante Arrhenius’ 19th-century study titled “On the Influence of Carbon in the Atmosphere on the Temperature of the Earth’s Surface,” which quantitatively demonstrated that carbon dioxide influences temperature increases. Given this supporting evidence, it is understandable that the world has become so focused on reducing carbon dioxide emissions.
However, there is a significant leap in logic in concluding that carbon dioxide is the primary cause of global warming based solely on the fact that higher carbon dioxide concentrations are associated with the greenhouse effect and that carbon dioxide concentrations have increased since industrialization. While carbon dioxide is indeed a greenhouse gas that plays a role in warming the Earth, the rise in carbon dioxide concentrations and the rise in temperatures are merely correlated; they have not been proven to have a causal relationship. According to the book “The Age of Ice,” which analyzes climate change, 98% of the carbon dioxide on Earth is dissolved in the oceans. Additionally, we know that the solubility of gases in water is highly sensitive to temperature. Considering these factors together, it is also possible that other factors, rather than carbon dioxide, have caused global temperatures to rise, leading to a decrease in the solubility of carbon dioxide in the oceans and an increase in its concentration in the atmosphere, thereby creating the current correlation.
If that is the case, how can we explain the rise in temperature? In recent years, new warming theories have emerged to challenge the carbon dioxide theory and provide alternative explanations. The most prominent examples include the Milankovitch theory, the Dansgar-Oeschger theory, and the Heinrich theory. The Milankovitch theory posits that temperature changes are caused by external astronomical factors such as the Earth’s axial tilt and orbital eccentricity, rather than internal factors. According to this theory, the steeper the Earth’s axial tilt and the more elongated its elliptical orbit, the more extreme seasonal climates can become. Using this theory, one can partially explain the intensification of extreme summer heatwaves and winter cold snaps currently observed, even when excluding the effects of global warming caused by increased carbon dioxide emissions from industrialization. However, since the orbital eccentricity has a cycle of approximately 100,000 years and the tilt of the Earth’s rotational axis changes over about 40,000 years, this theory cannot adequately explain rapid temperature changes over short periods.
Therefore, by referencing the “Dansgar-Oeschger theory” and “Heinrich theory,” which suggest that Earth’s temperature can change drastically within relatively short periods of several decades to centuries, we can explain the short-term temperature increases not accounted for in the “Milankovitch theory.” The “Dansgaard-Oeschger theory” explains that there were periods of rapid temperature increases within very short time frames before the several ice ages that occurred in the past. This theory estimates the temperature changes at that time by analyzing the changes in the ratio of oxygen isotopes, which are related to temperature changes, found in ice cores deep within glaciers. Based on the fact that oxygen isotope ratios in ice cores from glaciers around the world changed significantly at similar times over the course of tens to hundreds of years before the ice age, it is possible to consider that extreme temperature changes could have occurred even without the industrialization-induced increase in carbon dioxide concentrations. The “Heinrich theory,” which infers temperature increases by identifying traces of glacial melting and movement during short periods before the Ice Age, also supports the validity of the “Dansgar-Oeschger theory.”
Of course, these theories have limitations in that they do not adequately explain the causes of temperature changes. However, through these theories, we can understand that the current trend of global warming has occurred multiple times in the past without factors such as the increase in carbon dioxide due to industrialization. Therefore, it cannot be conclusively stated that the increase in carbon dioxide due to industrialization is the primary cause of global warming. Moreover, according to the greenhouse effect theory based on carbon dioxide, the Earth’s temperature should have risen due to the massive increase in carbon dioxide. However, there is a critical counterexample where the global average temperature actually decreased during the period from 1940 to 1975, when industrialization was most advanced. From this perspective, it is insufficient to claim that carbon dioxide is the primary cause of global warming, as the correlation between carbon dioxide and global average temperature, as well as the validity of the greenhouse effect theory, are lacking. Moreover, even without the carbon dioxide theory, there are many other factors that could potentially warm the Earth. Therefore, there is concern that focusing too much attention on carbon dioxide, whose role as a definitive cause is still unclear, might lead us to overlook other factors that could have a greater impact on global warming. For this reason, I believe it is inappropriate to label the increase in carbon dioxide as the primary cause of global warming at this stage, when the exact cause has not yet been clearly identified.
There is no doubt that global warming is a major issue that can affect human life on a small scale and disrupt the Earth’s ecosystem on a large scale. Humans have proposed various theories to address this problem, but all remain theoretical, and decisive analysis is still lacking. However, the world is reacting as if reducing carbon dioxide emissions alone would achieve half the goal of halting global warming, blindly trusting the unproven theory that carbon dioxide causes global warming. Global warming could be caused by external factors, or even if it originates from within the Earth, it may be something humans cannot prevent. Given that the exact cause of global warming remains unknown, it is crucial to avoid hasty conclusions about its origins. Instead, we must engage in discussions about what other measures, besides reducing carbon dioxide emissions, can be taken to address the inevitable challenges posed by global warming.
