The planet Earth is composed by living creatures as well as non-living elements like rocks, water, air, etc. All parts are connected and interact with each other. There are many ways of interaction, and many of these interactions are critical for survival. For example, one category of interaction is how the organisms obtain their food. Some organisms can make their own food, others need to eat other organisms to obtain their nutrients. Another interaction is symbiosis. It describes a close long-term relationship between 2 organisms from different species. Sometimes, symbiosis can be mutually beneficial for both organisms.
One of the biggest and complex ecosystems are coral reefs, these had become affected by subtle changes in the sea water temperature and ocean acidification. In this article, I will try to explain the science behind this process.
Approximately 25% of the marine species use the coral reefs as habitats. Scientists have observed that an increase of 1 °C in the water for 4 weeks can trigger the bleaching process in corals reefs. The process occurs when coral polyps expel the algae that live inside their tissue. These algae provide up to 90% of coral's energy. If coral dies, it will affect the whole ecosystem and will affect the species that depend on it for, shelter, food, habitat, etc.
Humans are also affected. Coral reefs bleaching socio-economic impact
- Degraded coral reefs may not be able to provide shoreline protections for human communities.
- The change in fish communities also will affect food supply and associated economic activities.
- Coral reefs are valuable source for important medicinal resources. Drugs to treat heart disease, cancer, and other illnesses.
On the Left a healthy coral and in the right a bleached coral.
DIOXIDE CARBON CO2
The CO2 measurement begun in March 1958 at the Mauna Loa in Hawaii. Charles Keeling measured for the first time 313ppm (particles per million). Since then, the keeling curve is a daily record of global atmospheric carbon dioxide concentration. As of the January 2022 the reading is 417.69ppm, (updated measure here) it doesn't look a big change in 64 years, however the perspective is different when we compare CO2 data from 800,000 years ago. This has been possible by extracting the data from the air trapped between the ice layers at different depths in Antarctica.
There is an interesting correlation between the glacial periods - warmer periods and the variations of earth orbit around the sun. It worth to mention that the highest CO2 concentration: 300ppm was 350,000 years ago.
In the origin, the Earth was covered by rocks and a dense atmosphere composed by dioxide carbon (CO2), hydrogen (H) and water vapour (H2O). The Earth temperature decreased, and the water from vapour condensation and the rain created the oceans. At this point the predominant gas was the CO2 and the estimation indicates the density of the atmosphere was 30 times denser than today. The CO2 balance, to make the life possible, started when the CO2 and the water begun to interact to each other to produce carbonic acid.
The carbonic acid does not dissolve in the water and sinks to the seabed. It then interacts with the rocks and forms carbonate, which is basically a salt of carbonic acid (CO2-;3). Later, the carbonate interacts with other elements like calcium (Ca), magnesium (Mg) and iron (Fe). Eventually, the tectonic plates movement buries the carbonate until it’s translated to the continental crust. The carbonate is liberated again into the atmosphere through the magma pool and volcanoes.
For a single CO2 molecule, this process lasts one hundred million years. And after billions of years the planet found the right balance between the CO2 in the atmosphere and the carbonate in the ground, which made the life possible to evolve.
H2O + CO2 = H2CO3 (carbonic acid)
THE CO2 EQUILIBRIUM
The equilibrium value in the planet earth for the carbonate is 600 gigaton (Gt) in the biosphere and 600 Gt in the atmosphere(1 Gt represents 1,000,000,000 tons). There is 1,800 Gt of carbonate in the ground and 1,000 Gt in the ocean surface in contact with the atmosphere. Finally in the seabed there is 37,000 Gt of carbonate. The carbonate from the CO2 is recycled: from the atmosphere, biosphere, ground, and ocean.
The red box on central park represents a gigaton. Central park is 4Km long and 0.8Km wide. A gigaton wild extend 341mt high.
In 1 Year...
- The biosphere absorbs 120 Gt of carbonate. 60 Gt are going to the ground and 60 Gt are released to the atmosphere in the form of CO2.
- 90 Gt are exchanged between the atmosphere and the ocean surface.
- 35 Gt are added to the atmosphere every year by humans. In the last seventy years, the human activity has contributed to 400 Gt of carbon to the atmosphere. Which is around 2/3 of the previously existent CO2 in the atmosphere in the last million years. If the same emission levels continue, in 150 years the human activity had been add to the atmosphere between 1,000 Gt to 4,000 Gt.
The carbon dioxide (CO2) molecules floating in the atmosphere vibrate when they are hit by infrared radiation coming from the sun. The vibration produces energy and since the molecules are constantly in motion and colliding with other molecules, this energy is transferred during the collision. That’s why CO2 molecules absorb the infrared radiation and raises the temperature of the gases in the atmosphere. The temperature of a gas is measured by speed of the molecules in the gas. The faster the vibration the higher temperature.
Earth's atmosphere is composed mainly of oxygen (O2) and Nitrogen (N2) since they are simple components they are not affected by infrared radiation. In the other hand, CO2 molecules vibrate in ways the nitrogen and oxygen cannot. Other significant greenhouse gases include water vapour (H2O), methane (CH4), nitrous oxide (N2O) and ozone (O3).
In the above image you can see the molcule structure of green gases is more complex than oxigen and nitrogen. The vibration of green gases molecules is slower than others, and is affected by low frequencies like infrarred radiation.
THE WATER LEVEL
Without the greenhouse gases and greenhouse effect the Earth’s temperature would be -18° C. In contrast, current mathematical models calculate an increase of the average surface temperature by 1.3° C from the year 1900, considering only the CO2 factor: From 300ppm to 417.69ppm. Global warming is a direct consequence of the increased CO2 level and other greenhouse gases. One effect is the current increased temperature in the Artic and in the long term, the rise of the temperature in Antarctica. These two areas hold about 90% of the freshwater that exists on the Earth. Predicting the future of Greenland and Antarctica is critical to understand the impact and the possible direct and indirect consequences if the temperature continues to increase.
The thermal dilatation of water is the main factor in the rise of the level water. And this expansion is inevitable to continue because the heat stored in the oceans. The second cause is the shrink of the glaciers in Greenland, for many years this effect was secondary, but new data collected shows the opposite.
The diagram on the left shows the ice mass reduction from 1992 to 2018. the difference is a reduction of 4,040 Gt. The diagram on the right shows the increment of sea level in mm from the same range of years, total of 11.22mm.
The latest mathematical models predict by the year 2,100 an increment, almost sure, of 2°C before the end of this century. Greenland ice melt will contribute to 5cm to the sea level. Nevertheless, the ice sheet melt has been duplicated, in comparison to the original prevision, and the current models suggest a contribution between 10cm to 16cm to the sea level. Antarctica, by the same year will contribute to 12cm.
|Contribution||Sea Level in meters|
|Sea water dilatation||~ 0,23 ± 0,09 meters|
|Other Glaciers||~ 0,37 ± 0,02 meters|
|Greenland ice melt (current ice melt speed)||~ 0,16 meters|
|Antarctic ice melt (current ice melt speed)||~ 0,12 meters|
|TOTAL :||~ 0,88 ± 0,12 meters|
Cummulative sea level increase by the year 2,100 (in 78 years).
The pictures in the left, Antarctica, is the difference of ice between 10 days in the past January. This area is called Larsen B. The diagram on the right, shows how the icebergs are separated from the ice shelf. The grounding line is the point where the ice and the ground are in contact.
THE ACID OCEAN
For million years, the Earth's ecosystem found a fragile balance between the CO2 in the atmosphere and the production of carbonic acid H2CO3. Oceanographic measures have proved a consistent reduction in the seawater pH for over a decade. The process of carbonate concentration in the ocean is called ocean acidification (OA). And the current models estimates that by 2100 the ocean surface water could have the acid level nearly 150 percent higher, resulting in a pH that the oceans haven't reached for more than 20 million years.
Calcium carbonate minerals are the bricks for shells skeleton of many marine organisms. The continued acidification causes decrease of these minerals in the oceans. Currently, the OA process has been shown a significant reduction the ability of reef-building corals to produce their skeletons as well as oysters and molluscs.
THE EMERGENT SYSTEM (Conclusions)
A simple entity like a neuron, molecule of CO2 or a human being interacting each other creates complex and unpredictable behaviours. The interaction rules are quite simple. For example, the CO2 molecule vibrates when is hit by infrared photons and the vibration produce heat. The complexity emerges when all entities in the system continuously affect each other.
Predict all the climate change consequences in the short term is extremely difficult because the planet Earth is a very complex system. Nevertheless, the current mathematical models suggest drastic changes in the planet by 2,100 if we keep the current CO2 emissions. In addition, the same models can accurately predict temperatures from 400,000 years ago. From my point of view, this is unmistakable evidence that predictions are correct. Its also necessary to consider that different research arrives to similar conclusions.
I hope these notes will force you to rethink your relationship with the climate change. We are the only entities in this ecosystem we can change our actions and we have the responsibility to do it. The CO2 molecules will continue vibrating and producing heat when hit by infrared photons.
The physics of climate change by Lawrence Krauss // A must read, the inspiration fo this article.
Nasa: visualizing the quantities of climate change // Nasa provides many resources and information.
Ice melt on West antartic ice sheet // Pay attention to the video.
CO2 Emissions // All kind of data visualizations, Our world in data.
Larsen Ice Shelf // There is also Larsen A, C and D.
Climate Change and ecosysem impacts // From the university of minnesota, Ecosystems and global changes.
Coral reef bleaching // Reef Resilience Network. All about coral reefs and the bleaching process.
Ocean acidification // The National Oceanographic and Atmospheric Administration (NOAA)
Data for cumulative changes in ice mass in Greenland // School of Earth and Environment, The University of Leeds
Greenland ice sheet // The Arctic program from NOAA, Arctic Report Card: Update for 2021
Global Temperature Anomalies - Graphing Tool // NOAA and Climate.gov