Global Warming: The Ocean Fever and the Urgent Call for Environmental Protection

In recent years, global greenhouse gas emissions have continuously reached new heights, accelerating the process of global warming.

A paper published in the prestigious academic journal "Earth System Science Data" in June 2023 highlighted that over the past decade, global greenhouse gas emissions have soared to a historical peak, with annual carbon dioxide emissions reaching 54 billion tons. Professor Piers Forster from the University of Leeds, one of the authors, emphasized that although global warming has not yet surpassed the 1.5°C threshold set by the Paris Climate Agreement, at the current rate of carbon emissions, the remaining carbon budget of approximately 250 billion tons of carbon dioxide is likely to be rapidly depleted in the coming years. The research team urged for the adoption of stricter emission reduction targets and measures at the COP28 conference in 2023. In May 2023, a report released by the World Meteorological Organization stated that due to the combined effects of greenhouse gases and the El Niño phenomenon, it is very likely that within the next five years (2023-2027), the global temperature will exceed the 1.5°C threshold above pre-industrial levels for the first time, with at least one year having a 98% chance of being the hottest year on record.

Global climate is a cohesive community, where any change in one climate factor can have profound impacts on other climate elements. Traditionally, attention has been focused on how climate warming triggers extreme weather events on land, such as heatwaves, droughts, and floods. However, with advancements in climate monitoring technology, it has been discovered that global warming also induces a phenomenon known as "ocean fever". Since 2023, meteorological institutions in Europe, the United States, and other regions have observed phenomena of unusual warming in the surface waters of regional or global oceans. In June 2023, data released by the UK Met Office showed that the surface water temperature of the North Atlantic in May reached the highest record since 1850, 1.25°C higher than the average level of the same period from 1961 to 1990, especially around the UK and Ireland where the seawater temperature was over 5°C higher than the long-term average.

Currently, British meteorological scientists have categorized this year's ocean heatwave as an extreme level IV or V. In mid-June 2023, a research report released by the National Oceanic and Atmospheric Administration (NOAA) in the United States showed significant warming of seawater in many parts of the world since the beginning of 2023. On April 1, the global sea surface temperature reached a record high of 21.1°C, which, although it decreased to 20.9°C afterward, was still 0.2°C higher than the highest temperature record in 2022. By June 11, the surface water temperature of the North Atlantic reached 22.7°C, the highest recorded temperature for the region, with expectations that the sea surface temperature will continue to rise, reaching its peak by the end of August or September.

Due to ocean warming, it is expected that by October, more than half of the world's oceans will experience ocean heatwaves. On July 14, the Copernicus Climate Change Service of the European Union detected that the seawater temperature in the North Atlantic and the Mediterranean Sea had set new records over several months, with ocean heatwaves occurring in the Mediterranean region, and seawater temperatures off the southern coast of Spain and along the North African coast exceeding the average reference values by more than 5°C, indicating an ongoing escalation of ocean heatwaves. In July 2023, NOAA measured seawater temperatures of 36°C near the southwestern coast of Florida, USA, the highest temperature recorded by satellite monitoring of ocean temperatures since 1985.

Meteorological monitors pointed out that in the past two weeks, the seawater temperature here was a full 2°C higher than the normal range. Seawater temperature is not only an environmental element of the marine ecosystem but also a basic component of the Earth's climate system. The continuous rise in seawater temperature has led to increasingly frequent extreme warm water events in the ocean, posing a significant threat to the health of marine ecosystems.

Ocean Heatwaves Threaten Marine Ecosystems Ocean heatwaves, defined as extreme warm water events where ocean surface water temperatures abnormally rise, typically last from several days to several months and can stretch thousands of kilometers. Ocean heatwaves directly harm marine ecosystems in a blunt and simple manner, including directly killing fish, forcing fish to migrate to cooler waters, causing coral bleaching, and even potentially leading to marine desertification. For marine ecosystems, ocean heatwaves are a thorough disaster.

Specifically, the harm of ocean heatwaves manifests in the following two aspects:

1. **Forcing Tropical Marine Life to Migrate to Mid and High Latitudes:**

Generally, the equatorial region is the most abundant area for marine life resources, with a large amount of seagrass, coral, and mangroves, serving as a paradise for most marine creatures.

However, over the past 50 years, the seawater temperature at the equator has risen by 0.6°C, forcing a large number of tropical marine creatures to migrate to cooler mid and high latitudes for refuge. A study published in the journal Nature in April 2019 found that global warming has the most significant impact on marine life, with the number of species forced to migrate in the ocean being twice that on land, especially in equatorial waters. The paper estimated that currently, nearly a thousand species of fish and invertebrates are fleeing tropical waters.

In August 2020, scientists from the National Oceanic and Atmospheric Administration published research in Nature, finding that ocean heatwaves cause "thermal displacement," with displacement distances ranging from several tens to thousands of kilometers. To adapt to these changes in ocean heat, a large number of marine creatures also have to move the same distance to avoid high temperatures, leading to a "redistribution" of marine life. In March 2022, Australian scientists discovered a decline in the number of species in tropical oceans after reviewing nearly 50,000 records of marine life distribution since 1955, with the 30°N and 20°S latitudes replacing the equatorial region as the most abundant areas for marine species.

Not only is the marine environment changing, but the food chain in equatorial waters is also changing. Plankton plays a significant role in the complex marine food chain network, but in recent years, scientists have discovered that due to global warming, the number of plankton, represented by foraminifera, is rapidly declining in equatorial waters. This means that in terms of nutritional levels, equatorial waters are no longer able to support as rich marine life as before. Unsuitable marine environments and reduced food sources are accelerating the migration process of equatorial marine life. The mass migration of tropical marine life will trigger a series of chain reactions, causing the stable marine ecosystems formed over millions of years of geological and biological evolution to gradually become disordered and even collapse.

The migration of a large number of tropical marine species to subtropical marine ecosystems means that many invasive species will enter these areas, and the new predatory species will engage in intense food competition with native species, leading to the decline or even extinction of some species. This phenomenon of ecosystem collapse and species extinction has occurred during the Permian and Triassic geological periods.

2. **Causing the Death of a Large Number of Marine Creatures:**

Cold water contains far more oxygen than warm water. The continuous rise in seawater temperature and the increasing frequency of ocean heatwaves in recent years have significantly increased the phenomenon of hypoxia and low oxygen in coastal waters. Scientists point out that due to the rise in seawater temperature, the oxygen content in the ocean has decreased by 2% to 5% over the past 50 years, leading to the death of a large number of fish due to breathing difficulties. Some high-oxygen-consuming large fish may even become extinct.

In June 2023, thousands of kilometers of dead fish appeared in the waters near Chumphon Prefecture in southern Thailand and in the Gulf of Mexico in the United States, caused by fish trapped in shallow waters suffocating to death due to ocean heatwaves. The mass death of fish will further affect seabirds that feed on them. From 2013 to 2016, the warming of the Pacific surface waters off the west coast of North America led to a tragic incident where about 1 million seabirds died due to a lack of food. Ocean heatwaves also lead to coral bleaching.

Coral reefs, known as the "forests of the sea," provide habitats, foraging, and breeding grounds for about a quarter of marine life, making them one of the most biodiversity-rich ecosystems on Earth. The formation of coral reefs cannot be separated from the symbiotic relationship between corals and zooxanthellae, which provide each other with nutrients. Zooxanthellae are algae that are very sensitive to temperature. When seawater temperature rises, their photosynthesis weakens, and they produce harmful oxygen free radicals to corals. To protect themselves, corals have to expel zooxanthellae, breaking the symbiotic relationship.

Without zooxanthellae, corals gradually return to their original gray-white color. If zooxanthellae do not return for a long time, corals will lose their nutrient source and eventually die. This is the phenomenon of coral bleaching. Currently, the Great Barrier Reef in Australia is the most severely affected by coral bleaching. In recent years, due to global warming, the seawater temperature near the Great Barrier Reef has continued to rise, and between 1998 and 2017, there were at least four large-scale coral bleaching events.

At the beginning of 2020, Australia experienced record high temperatures, with wildfires lasting for half a year on land and the most severe coral bleaching event on record in the ocean, affecting about a quarter of the coral reefs. Currently, more than half of the Great Barrier Reef has bleached. With global warming, coral bleaching events will become more frequent and severe. Scientists have found that since 1985, the frequency of global coral bleaching has increased from once every 27 years to once every four years, and by the end of the 21st century, more than three-quarters of the world's corals are expected to bleach or become diseased. Coral bleaching and death will cause a large number of fish to lose their habitats, foraging, and breeding grounds, further affecting fish population development.

In recent years, the frequency and range of ocean heatwaves have been continuously increasing and expanding. In March 2019, researchers from the Marine Biological Association of the United Kingdom published an academic paper in the journal Nature Climate Change, finding that the annual average number of days with ocean heatwaves from 1987 to 2016 increased by 50% compared to 1925-1954. Moreover, scientists have also observed ocean heatwave phenomena in the deep sea. In March 2023, researchers from the National Oceanic and Atmospheric Administration published a study in Nature Communications, finding that ocean heatwaves also exist in the deep sea. Through simulation of observational data, it was found that in the areas surrounding the North American continental shelf, deep-sea ocean heatwaves last longer and may have a stronger warming signal than surface waters.

The increase in the frequency and range of ocean heatwaves means that marine ecosystems will face greater harm in the future. Ocean Acidification Threatens the Development of Marine Species The increase in atmospheric carbon dioxide concentration not only causes the greenhouse effect and accelerates global warming but also leads to ocean acidification, threatening the survival and reproduction of marine life. The ocean is constantly exchanging gases with the Earth's atmosphere, and almost any gas that enters the atmosphere can dissolve in seawater. As an important component of the atmosphere, carbon dioxide can also be absorbed by seawater. Ocean acidification is essentially the phenomenon where the ocean absorbs excessive carbon dioxide, leading to an increase in acidic substances in seawater and a decrease in pH.

According to estimates, about one-third of the carbon dioxide emitted by humans into the atmosphere is absorbed by the ocean. As the concentration of carbon dioxide in the atmosphere continues to increase, the rate of absorption and dissolution is also intensifying. Currently, the ocean absorbs 1 million tons of carbon dioxide per hour, meaning that ocean acidification is accelerating.

Scientific research has found that due to excessive carbon dioxide emissions by humans over the past two centuries, the global ocean's pH value has dropped from 8.2 to 8.1, increasing the actual acidity of seawater by about 30%. According to the current rate of carbon dioxide emissions by humans, by the end of the 21st century, the pH of the global ocean surface water will drop to 7.8, making the acidity of seawater 150% higher than in 1800. In 2003, the term "ocean acidification" first appeared in the world-renowned academic journal Nature. In 2005, scientists pointed out that 55 million years ago, there was a mass extinction event in the ocean due to ocean acidification, estimated to have dissolved 4.5 trillion tons of carbon dioxide into the ocean, after which it took the ocean 100,000 years to gradually return to normal levels. In March 2012, a paper published in the journal Science argued that the Earth is currently experiencing the fastest ocean acidification process in 300 million years, with many marine species facing a survival crisis.

In April 2015, a study published in the American journal Science pointed out that 250 million years ago, violent volcanic eruptions in Siberia released a large amount of carbon dioxide, causing the pH of seawater to drop sharply over the following 60,000 years, leading to the death of a large number of highly calcified marine organisms. Scientists estimate that this ocean acidification event ultimately led to the extinction of 90% of marine life and more than 60% of terrestrial life. The study also pointed out that during the mass extinction event 250 million years ago, the amount of carbon dioxide released into the atmosphere each year was only about 2.4 billion tons, while currently, humans emit about 35 billion tons of carbon dioxide into the atmosphere each year, far exceeding the emissions during the mass extinction period.

Ocean acidification severely affects the normal growth and reproduction of marine life, threatening the survival and development of species. On the one hand, ocean acidification threatens and inhibits the survival of calcifying organisms. Ocean acidification leads to a continuous decrease in carbonate ions in the ocean, which are important materials for many marine organisms (such as crabs, scallops, corals, etc.) to form shells.

Ocean acidification will severely threaten the growth and development of these calcifying organisms. In addition, acidified seawater can directly dissolve some marine organisms. Mollusks are an important food source for salmon, and scientists predict that by 2030, acidified seawater will have a corrosive effect on marine mollusks, leading to their reduction or disappearance in some marine areas, further affecting the development of salmon populations.

On the other hand, ocean acidification also damages the sensory systems of fish. Sensory systems such as smell, hearing, and vision help marine fish efficiently forage, find safe habitats, and avoid predators. Once damaged, it will directly threaten the survival of fish. In June 2011, researchers from the University of Bristol in the UK incubated clownfish eggs in seawater with four different concentrations of carbon dioxide. After comparative research, it was found that young fish hatched in high-concentration carbon dioxide seawater were very slow to respond to predator sounds.

This means that in acidic seawater, the auditory sensitivity of young fish significantly decreases. In March 2014, a study published in Experimental Biology found that high concentrations of carbon dioxide in seawater can interfere with various types of gamma-aminobutyric acid in fish nerve cells, reducing their visual and motor abilities, ultimately making it difficult for them to forage or avoid predators. In July 2018, a study published in Nature Climate Change found that ocean acidification can cause fish to lose their sense of smell, disrupt their central nervous system, and reduce their brain's information processing ability.

In addition to the direct harm to marine species, ocean acidification can further enhance the negative effects of marine pollutants and toxins. Research has found that ocean acidification can continuously increase the bioavailability of heavy metals such as mercury, lead, iron, copper, and zinc, meaning that these heavy metals can be more easily absorbed by marine organisms and more easily accumulate in marine organisms. Eventually, these pollutants will be transferred to higher organisms through the food chain, threatening their health. Moreover, ocean acidification can also change the abundance and chemical composition of harmful algae, allowing these toxins to be transferred to shellfish, producing paralytic and neurotoxic toxins, ultimately threatening human health.

Global Efforts to Protect Marine Biodiversity Currently, the global ocean average temperature has risen by about 0.9°C compared to the 20th century and by 1.5°C compared to pre-industrial levels. The past ten years have been the warmest decade for ocean temperatures on record. The El Niño phenomenon formed in 2023, and scientists predict that in the coming months, the global sea surface temperature will rapidly increase by 0.2 to 0.25°C. This means that marine ecosystems will face more severe high-temperature threats in the future, and marine life will face greater survival challenges. Faced with the increasingly severe marine ecological crisis, countries around the world are also actively taking action to protect marine ecosystems. On December 19, 2022, the second phase of the 15th Conference of the Parties to the Convention on Biological Diversity adopted the "Kunming-Montreal Global Biodiversity Framework." The framework set the "30x30" target, aiming to protect at least 30% of the world's land and ocean by 2030.

To ensure the smooth implementation of the agreement, the content of the agreement also established clear and strong financial guarantees. This framework will lead the international community to work together to protect biodiversity and strive towards the great goal of harmonious coexistence between humans and nature by 2050. Over the past few decades, a large number of shipping, seabed mining, and distant-water fishing activities have been carried out on the high seas. Although there are relevant international institutions regulating these activities, the lack of necessary communication and coordination between different institutions has led to a fragmented state of ecological monitoring and protection of the high seas, failing to effectively curb marine environmental pollution and biodiversity loss.

In June 2023, the United Nations adopted the "Agreement on the Conservation and Sustainable Use of Marine Biological Diversity of Areas Beyond National Jurisdiction under the United Nations Convention on the Law of the Sea." The "Agreement" proposes new mechanisms and content for marine environmental assessment, marine technology transfer, benefit-sharing of marine genetic resources, and marine protected areas. United Nations Secretary-General António Guterres pointed out that this "Agreement" is crucial for addressing threats such as climate change, overfishing, ocean acidification, and marine pollution, ensuring the sustainable development and use of more than two-thirds of the world's oceans, and has milestone significance for protecting marine biodiversity.