A flashback from Geography class in school will remind you that the key to mitigating climate change for a sustainable planet for all living things is to reduce the emission of greenhouse gases (GHGs) in the atmosphere.
Since the atmospheric release of carbon dioxide surpasses all other such gas emissions in abundance and longevity, it is paramount to address this issue earnestly and collectively. Now that the concentration of carbon dioxide in the atmosphere is higher than it has ever been in the last 800,000 years, it is hard to see the rays of hope for a sustainable planet for all living things.
GHGs are expressed in parts per million (PPM) and the safe threshold is known to be 350 ppm. During the pre-industrial era, carbon dioxide levels remained at 280 ppm for almost 6,000 years of civilization. In April 2022, it was recorded to be 418.82 ppm and within a year it galloped to 423.06 ppm.
The scorching increase of carbon dioxide in the atmosphere in the last 60 years has been about 100 times faster than previous surges. Based on air bubbles trapped in mile-thick ice cores and other paleoclimate evidence, it is estimated that during the ice age cycles of the past million years, atmospheric carbon dioxide never exceeded 300 ppm. In 2021, carbon dioxide was estimated to be responsible for about two-thirds of the total heating influence amongst all the GHGs.
What is carbon sequestration, carbon capture, and carbon sinks?
Carbon sequestration and carbon capture are tools to reduce the amount of carbon emitted into the atmosphere.
Carbon sequestration is the process of capturing, securing, and storing carbon dioxide from the atmosphere. In biological carbon sequestration, carbon is stored in natural carbon reservoirs such as forests, grasslands, soils, and waterbodies. Geological carbon sequestration is an artificial process of carbon capture where the captured carbon is compressed into a liquid form that is stored in underground geologic formations. Carbon capture is a process of containing carbon before it can even enter the atmosphere.
In the same vein, carbon sinks are natural or artificial reservoirs that absorb more carbon dioxide from the atmosphere than they can release. Protecting carbon sinks is crucial to impeding the pace of current global warming, however, we have already over stretched its value. Amazon has more than one-third of the trees across the tropics and is an important carbon sink. Forestation such as mangroves, seagrass beds, and salt marshes absorb 10 times more carbon dioxide from the atmosphere than terrestrial trees. The oceans which cover a sizable portion of our planet contribute to half the absorption of atmospheric carbon.
There is no planet B, yet humans have destroyed natural carbon sinks through deforestation as well as released an enormous amount of carbon over centuries by the usage of materials such as coal, oil, natural gas, methane hydrate, and limestones.
How is carbon dioxide affecting the biodiversity in the oceans? What changes are happening in the oceans?
Oceans are a utopian wonder as they routinely balance the carbon cycle -- the natural flow of carbon between the atmosphere, ocean, rocks, fossil fuels and living organisms. These immeasurably massive water bodies have high heat storing capacity. For instance, 90% of the heat generated by the warming effects over the past decades have been absorbed by the oceans. The top few meters of the ocean store as much heat as Earth's entire atmosphere.
Seawater has the capacity to absorb excessive carbon dioxide which combines with carbonates in seawater to form carbonic acid, leading to ocean acidification. The souvenir we gained from historic levels of global industrialization is the decrease in average surface ocean pH from 8.2 to about 8.1.
Sea organisms like phytoplankton, corals, shellfish, mollusks, fishes, algae, and other bacteria play a role in marine biodiversity balance. For example, mollusks and corals convert calcium and carbonate internally to form calcium carbonate which ultimately becomes an ingredient of limestone rocks present in deep sea.
When carbonates are used up to absorb the atmospheric carbon dioxide, it makes less carbonate available for making the outer shells and skeletons of these organisms. The bad news is that the levels of ocean acidification make their shells dissolve more easily.
Phytoplankton use atmospheric carbon for photosynthesis to form energy for themselves and they also use silica to build their dense outer walls which help them to sink and bury the carbon in the deep sea. There is an echo of concern as they have become less effective at burying carbon. This is because the acidic seawater renders these organisms to evolve to form less dense walls, and hence they turn into lighter species which do not sink fast.
Ocean acidifications are also lowering deep-sea coral calcification and causing “reef flattening.” Corals produce coral reefs that provide protection to marine animals, but the flattening is lowering this support. Unfortunately, coral reefs are vital sources of medicine and protection from storms.
What is the cause of sea-level rise?
Polar ice melting might seem like an obvious guess, but in reality, expanding water due to heat is responsible for almost half of the rise in global sea level. A new record was documented in 2021, where it was found that sea levels have been rising an average of 4.5 millimeters per year over the period 2013 to 2021. The heated sea and high sea level are increasing the frequency of deadly storms, tropical cyclones, and coastal hazards like flooding, erosion, and landslides. In addition, the incidence of extensive, intense marine heatwaves have led to coral bleaching and reef flattening.
The average global temperature has risen by at least 1.1 degree Celsius since 1880. 60% of the world's marine ecosystems have already been degraded, and a temperature rise of 1.5 degrees will destroy 70 to 90% of coral reefs and marine biodiversity.
What are the effects of GHG emissions in the long term?
The limits of carbon sinks are also limiting our optimism when it comes to climate change. A study published in MIT suggested that if all carbon dioxide emissions were to be eliminated by 2050, half the emissions that have already been released into the atmosphere would still persist even 750 years later.
Sadly, the effects of greenhouse gases like sea water expansion and rising sea levels can last for centuries even if the gases cease to be released. Mother nature itself has been quite self-sufficient for centuries but our relentless exploitation of the environment has been detrimental to the global ecosystem.
On one hand, the continued damage to the environment is becoming increasingly drastic; on the other hand, the prolonged impact on future generations is also something that needs to be considered as nations across the world forge ahead towards better climate action policies.
Maliha Mannan Ahmed is an entrepreneur and a public health communicator. She is the Founder and Managing Director of Organikare Limited- a personal health, hygiene, and wellness brand.
Shaniz Chowdhury is an associate of YPF Environment Policy Team and currently majoring in Economics. This is the second part of a series of articles on Politics and Policies of Climate Change, produced by YPF.
