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Does the necessary Carbon Dioxide need to be in the atmosphere for mammals?

Does the necessary Carbon Dioxide need to be in the atmosphere for mammals?


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In the answers to this question, we've learnt that carbon dioxide is necessary for mammalian life, but is it necessary in the atmosphere/to breathe it in?

Or does the act of respiration give a human (or other animal) enough carbon dioxide to fulfill all of the functions that carbon dioxide is needed for?

Or, phrased another way, if you put an animal in a carbon-dioxide-free atmosphere, and continually removed the carbon-dioxide that they generate upon respiration/exhalation, would they get enough carbon dioxide to fulfill these requirements:

  • fatty acid biosynthesis (FAS)
  • mammalian/bacterial biotin-dependent carboxylation reactions.
  • blood pH regulation

No it isn't necessary to breathe in CO2 from the atmosphere. For the buffer system your brain detects the amount of CO2 (H+ which is an indicator of excess or too little CO2) and adjusts your breathing automatically to compensate so that your blood's pH stays normal. No outside CO2 is needed. Your kidneys also play a similar role but the lungs are what provide a rapid response.


No, mammals need not take in CO2 from atmosphere. The body's homeostatic function will maintain its composition by checking the amount of CO2 released out by lungs. So certainly animals would survive if put in a CO2 free atmosphere.


It is unneccessary for a mammal to breath in CO2, though our bodies are able to expel unneeded gasses easily. However, if there were no CO2 in the atmosphere, animals would all die, as no oxygen could be produced by plants. In other words, we don't need to breath in CO2, but we need it to be plentiful.


Temperature Change and Carbon Dioxide Change

One of the most remarkable aspects of the paleoclimate record is the strong correspondence between temperature and the concentration of carbon dioxide in the atmosphere observed during the glacial cycles of the past several hundred thousand years. When the carbon dioxide concentration goes up, temperature goes up. When the carbon dioxide concentration goes down, temperature goes down. A small part of the correspondence is due to the relationship between temperature and the solubility of carbon dioxide in the surface ocean, but the majority of the correspondence is consistent with a feedback between carbon dioxide and climate. These changes are expected if Earth is in radiative balance, and they are consistent with the role of greenhouse gases in climate change. While it might seem simple to determine cause and effect between carbon dioxide and climate from which change occurs first, or from some other means, the determination of cause and effect remains exceedingly difficult. Furthermore, other changes are involved in the glacial climate, including altered vegetation, land surface characteristics, and ice sheet extent.

Other paleoclimate proxies help us understand the role of the oceans in past and future climate change. The ocean contains 60 times more carbon than the atmosphere, and as expected, the changes in carbon dioxide in the atmosphere were paralleled by changes in carbon in the ocean over the past several hundred thousand years. While the ocean changes much more slowly than the atmosphere, the ocean played an essential role in past variations in carbon dioxide, and it will play a role in the future over thousands of years.

Finally, paleoclimate data reveal that climate change is not just about temperature. As carbon dioxide has changed in the past, many other aspects of climate changed too. During glacial times, snow lines were lower, continents were drier, and the tropical monsoons were weaker. Some of these changes may be independent others tightly coupled to the changing level of carbon dioxide. Understanding which of these changes might occur in the future, and how large those changes might be, remains a topic of vigorous research. NOAA's Paleoclimatology Program helps scientists document the changes that have occurred in the past as one approach to understanding future climate change.


Respiration

Respiration is the process during which organic food, mainly glucose that is present in the cell, breaks down into simpler substances and liberates carbon dioxide and energy. The energy released during respiration is chemical energy. There are two types of respiration- aerobic and anaerobic respiration.

Aerobic Respiration

Aerobic means &lsquowith air&rsquo. This type of respiration requires oxygen, so it is called aerobic respiration. During aerobic respiration, complete oxidation of carbohydrates takes place. Glucose is broken down by oxygen to release energy, while carbon dioxide and water are the by-products of the reaction. The released energy is used to make a special energy molecule called Adenosine triphosphate (ATP). ATP is where the energy is stored for later use by the body. Aerobic respiration occurs in plants as well as animals and takes place in the mitochondria.

The word equation for aerobic respiration is:

Anaerobic Respiration

Anaerobic means without air. Sometimes there is not enough oxygen around for animals and plants to respire, but they still need energy to survive, so they carry out respiration in the absence of oxygen to produce the energy they require. As the respiration takes place in the absence of oxygen, incomplete oxidation of food occurs and much less energy is released. However, carbon dioxide is still produced. This is called anaerobic respiration and the process occurs in the cytoplasm.


Does the necessary Carbon Dioxide need to be in the atmosphere for mammals? - Biology

All of this extra carbon needs to go somewhere. So far, land plants and the ocean have taken up about 55 percent of the extra carbon people have put into the atmosphere while about 45 percent has stayed in the atmosphere. Eventually, the land and oceans will take up most of the extra carbon dioxide, but as much as 20 percent may remain in the atmosphere for many thousands of years.

The changes in the carbon cycle impact each reservoir. Excess carbon in the atmosphere warms the planet and helps plants on land grow more. Excess carbon in the ocean makes the water more acidic, putting marine life in danger.

Atmosphere

It is significant that so much carbon dioxide stays in the atmosphere because CO2 is the most important gas for controlling Earth&rsquos temperature. Carbon dioxide, methane, and halocarbons are greenhouse gases that absorb a wide range of energy&mdashincluding infrared energy (heat) emitted by the Earth&mdashand then re-emit it. The re-emitted energy travels out in all directions, but some returns to Earth, where it heats the surface. Without greenhouse gases, Earth would be a frozen -18 degrees Celsius (0 degrees Fahrenheit). With too many greenhouse gases, Earth would be like Venus, where the greenhouse atmosphere keeps temperatures around 400 degrees Celsius (750 Fahrenheit).

Rising concentrations of carbon dioxide are warming the atmosphere. The increased temperature results in higher evaporation rates and a wetter atmosphere, which leads to a vicious cycle of further warming. (Photograph ©2011 Patrick Wilken.)

Because scientists know which wavelengths of energy each greenhouse gas absorbs, and the concentration of the gases in the atmosphere, they can calculate how much each gas contributes to warming the planet. Carbon dioxide causes about 20 percent of Earth&rsquos greenhouse effect water vapor accounts for about 50 percent and clouds account for 25 percent. The rest is caused by small particles (aerosols) and minor greenhouse gases like methane.

Water vapor concentrations in the air are controlled by Earth&rsquos temperature. Warmer temperatures evaporate more water from the oceans, expand air masses, and lead to higher humidity. Cooling causes water vapor to condense and fall out as rain, sleet, or snow.

Carbon dioxide, on the other hand, remains a gas at a wider range of atmospheric temperatures than water. Carbon dioxide molecules provide the initial greenhouse heating needed to maintain water vapor concentrations. When carbon dioxide concentrations drop, Earth cools, some water vapor falls out of the atmosphere, and the greenhouse warming caused by water vapor drops. Likewise, when carbon dioxide concentrations rise, air temperatures go up, and more water vapor evaporates into the atmosphere&mdashwhich then amplifies greenhouse heating.

So while carbon dioxide contributes less to the overall greenhouse effect than water vapor, scientists have found that carbon dioxide is the gas that sets the temperature. Carbon dioxide controls the amount of water vapor in the atmosphere and thus the size of the greenhouse effect.

Rising carbon dioxide concentrations are already causing the planet to heat up. At the same time that greenhouse gases have been increasing, average global temperatures have risen 0.8 degrees Celsius (1.4 degrees Fahrenheit) since 1880.

With the seasonal cycle removed, the atmospheric carbon dioxide concentration measured at Mauna Loa Volcano, Hawaii, shows a steady increase since 1957. At the same time global average temperatures are rising as a result of heat trapped by the additional CO2 and increased water vapor concentration. (Graphs by Robert Simmon, using CO2 data from the NOAA Earth System Research Laboratory and temperature data from the Goddard Institute for Space Studies.)

This rise in temperature isn&rsquot all the warming we will see based on current carbon dioxide concentrations. Greenhouse warming doesn&rsquot happen right away because the ocean soaks up heat. This means that Earth&rsquos temperature will increase at least another 0.6 degrees Celsius (1 degree Fahrenheit) because of carbon dioxide already in the atmosphere. The degree to which temperatures go up beyond that depends in part on how much more carbon humans release into the atmosphere in the future.

Ocean

About 30 percent of the carbon dioxide that people have put into the atmosphere has diffused into the ocean through the direct chemical exchange. Dissolving carbon dioxide in the ocean creates carbonic acid, which increases the acidity of the water. Or rather, a slightly alkaline ocean becomes a little less alkaline. Since 1750, the pH of the ocean&rsquos surface has dropped by 0.1, a 30 percent change in acidity.

Some of the excess CO2 emitted by human activity dissolves in the ocean, becoming carbonic acid. Increases in carbon dioxide are not only leading to warmer oceans, but also to more acidic oceans. (Photograph ©2010 Way Out West News.)

Ocean acidification affects marine organisms in two ways. First, carbonic acid reacts with carbonate ions in the water to form bicarbonate. However, those same carbonate ions are what shell-building animals like coral need to create calcium carbonate shells. With less carbonate available, the animals need to expend more energy to build their shells. As a result, the shells end up being thinner and more fragile.

Second, the more acidic water is, the better it dissolves calcium carbonate. In the long run, this reaction will allow the ocean to soak up excess carbon dioxide because more acidic water will dissolve more rock, release more carbonate ions, and increase the ocean&rsquos capacity to absorb carbon dioxide. In the meantime, though, more acidic water will dissolve the carbonate shells of marine organisms, making them pitted and weak.

Warmer oceans&mdasha product of the greenhouse effect&mdashcould also decrease the abundance of phytoplankton, which grow better in cool, nutrient-rich waters. This could limit the ocean&rsquos ability to take carbon from the atmosphere through the fast carbon cycle.

On the other hand, carbon dioxide is essential for plant and phytoplankton growth. An increase in carbon dioxide could increase growth by fertilizing those few species of phytoplankton and ocean plants (like sea grasses) that take carbon dioxide directly from the water. However, most species are not helped by the increased availability of carbon dioxide.

Plants on land have taken up approximately 25 percent of the carbon dioxide that humans have put into the atmosphere. The amount of carbon that plants take up varies greatly from year to year, but in general, the world&rsquos plants have increased the amount of carbon dioxide they absorb since 1960. Only some of this increase occurred as a direct result of fossil fuel emissions.

With more atmospheric carbon dioxide available to convert to plant matter in photosynthesis, plants were able to grow more. This increased growth is referred to as carbon fertilization. Models predict that plants might grow anywhere from 12 to 76 percent more if atmospheric carbon dioxide is doubled, as long as nothing else, like water shortages, limits their growth. However, scientists don&rsquot know how much carbon dioxide is increasing plant growth in the real world, because plants need more than carbon dioxide to grow.

Plants also need water, sunlight, and nutrients, especially nitrogen. If a plant doesn&rsquot have one of these things, it won&rsquot grow regardless of how abundant the other necessities are. There is a limit to how much carbon plants can take out of the atmosphere, and that limit varies from region to region. So far, it appears that carbon dioxide fertilization increases plant growth until the plant reaches a limit in the amount of water or nitrogen available.

Some of the changes in carbon absorption are the result of land use decisions. Agriculture has become much more intensive, so we can grow more food on less land. In high and mid-latitudes, abandoned farmland is reverting to forest, and these forests store much more carbon, both in wood and soil, than crops would. In many places, we prevent plant carbon from entering the atmosphere by extinguishing wildfires. This allows woody material (which stores carbon) to build up. All of these land use decisions are helping plants absorb human-released carbon in the Northern Hemisphere.

Changes in land cover&mdashforests converted to fields and fields converted to forests&mdashhave a corresponding effect on the carbon cycle. In some Northern Hemisphere countries, many farms were abandoned in the early 20th century and the land reverted to forest. As a result, carbon was drawn out of the atmosphere and stored in trees on land. (Photograph ©2007 Husein Kadribegic.)

In the tropics, however, forests are being removed, often through fire, and this releases carbon dioxide. As of 2008, deforestation accounted for about 12 percent of all human carbon dioxide emissions.

The biggest changes in the land carbon cycle are likely to come because of climate change. Carbon dioxide increases temperatures, extending the growing season and increasing humidity. Both factors have led to some additional plant growth. However, warmer temperatures also stress plants. With a longer, warmer growing season, plants need more water to survive. Scientists are already seeing evidence that plants in the Northern Hemisphere slow their growth in the summer because of warm temperatures and water shortages.

Dry, water-stressed plants are also more susceptible to fire and insects when growing seasons become longer. In the far north, where an increase in temperature has the greatest impact, the forests have already started to burn more, releasing carbon from the plants and the soil into the atmosphere. Tropical forests may also be extremely susceptible to drying. With less water, tropical trees slow their growth and take up less carbon, or die and release their stored carbon to the atmosphere.

The warming caused by rising greenhouse gases may also &ldquobake&rdquo the soil, accelerating the rate at which carbon seeps out in some places. This is of particular concern in the far north, where frozen soil&mdashpermafrost&mdashis thawing. Permafrost contains rich deposits of carbon from plant matter that has accumulated for thousands of years because the cold slows decay. When the soil warms, the organic matter decays and carbon&mdashin the form of methane and carbon dioxide&mdashseeps into the atmosphere.

Current research estimates that permafrost in the Northern Hemisphere holds 1,672 billion tons (Petagrams) of organic carbon. If just 10 percent of this permafrost were to thaw, it could release enough extra carbon dioxide to the atmosphere to raise temperatures an additional 0.7 degrees Celsius (1.3 degrees Fahrenheit) by 2100.


What's in the Air?

By volume, the dry air in Earth&rsquos atmosphere is about 78.09 percent nitrogen, 20.95 percent oxygen, and 0.93 percent argon.

A brew of trace gases accounts for the other 0.03 percent, including the greenhouse gases carbon dioxide, methane, nitrous oxide and ozone. Yet while these greenhouse gases make up just a tiny percentage of our atmosphere, they play major roles in trapping Earth&rsquos radiant heat and keeping it from escaping into space, thereby warming our planet and contributing to Earth&rsquos greenhouse effect.

The largest greenhouse gas by volume is actually the one most people tend to overlook: water vapor, whose concentration varies significantly depending on temperature. As the temperature of the atmosphere increases, the amount of humidity in the atmosphere also goes up, further heating our planet in a vicious cycle.

Tiny solid or liquid particles known as aerosols, which are produced both naturally and by human activities, are also present in variable amounts, along with human-produced industrial pollutants and natural and human-produced sulfur compounds.


Effects of Changing the Carbon Cycle

All of this extra carbon needs to go somewhere. So far, land plants and the ocean have taken up about 55 percent of the extra carbon people have put into the atmosphere while about 45 percent has stayed in the atmosphere. Eventually, the land and oceans will take up most of the extra carbon dioxide, but as much as 20 percent may remain in the atmosphere for many thousands of years.

The changes in the carbon cycle impact each reservoir. Excess carbon in the atmosphere warms the planet and helps plants on land grow more. Excess carbon in the ocean makes the water more acidic, putting marine life in danger.

Atmosphere

It is significant that so much carbon dioxide stays in the atmosphere because CO2 is the most important gas for controlling Earth&rsquos temperature. Carbon dioxide, methane, and halocarbons are greenhouse gases that absorb a wide range of energy&mdashincluding infrared energy (heat) emitted by the Earth&mdashand then re-emit it. The re-emitted energy travels out in all directions, but some returns to Earth, where it heats the surface. Without greenhouse gases, Earth would be a frozen -18 degrees Celsius (0 degrees Fahrenheit). With too many greenhouse gases, Earth would be like Venus, where the greenhouse atmosphere keeps temperatures around 400 degrees Celsius (750 Fahrenheit).

Rising concentrations of carbon dioxide are warming the atmosphere. The increased temperature results in higher evaporation rates and a wetter atmosphere, which leads to a vicious cycle of further warming. (Photograph ©2011 Patrick Wilken.)

Because scientists know which wavelengths of energy each greenhouse gas absorbs, and the concentration of the gases in the atmosphere, they can calculate how much each gas contributes to warming the planet. Carbon dioxide causes about 20 percent of Earth&rsquos greenhouse effect water vapor accounts for about 50 percent and clouds account for 25 percent. The rest is caused by small particles (aerosols) and minor greenhouse gases like methane.

Water vapor concentrations in the air are controlled by Earth&rsquos temperature. Warmer temperatures evaporate more water from the oceans, expand air masses, and lead to higher humidity. Cooling causes water vapor to condense and fall out as rain, sleet, or snow.

Carbon dioxide, on the other hand, remains a gas at a wider range of atmospheric temperatures than water. Carbon dioxide molecules provide the initial greenhouse heating needed to maintain water vapor concentrations. When carbon dioxide concentrations drop, Earth cools, some water vapor falls out of the atmosphere, and the greenhouse warming caused by water vapor drops. Likewise, when carbon dioxide concentrations rise, air temperatures go up, and more water vapor evaporates into the atmosphere&mdashwhich then amplifies greenhouse heating.

So while carbon dioxide contributes less to the overall greenhouse effect than water vapor, scientists have found that carbon dioxide is the gas that sets the temperature. Carbon dioxide controls the amount of water vapor in the atmosphere and thus the size of the greenhouse effect.

Rising carbon dioxide concentrations are already causing the planet to heat up. At the same time that greenhouse gases have been increasing, average global temperatures have risen 0.8 degrees Celsius (1.4 degrees Fahrenheit) since 1880.

With the seasonal cycle removed, the atmospheric carbon dioxide concentration measured at Mauna Loa Volcano, Hawaii, shows a steady increase since 1957. At the same time global average temperatures are rising as a result of heat trapped by the additional CO2 and increased water vapor concentration. (Graphs by Robert Simmon, using CO2 data from the NOAA Earth System Research Laboratory and temperature data from the Goddard Institute for Space Studies.)

This rise in temperature isn&rsquot all the warming we will see based on current carbon dioxide concentrations. Greenhouse warming doesn&rsquot happen right away because the ocean soaks up heat. This means that Earth&rsquos temperature will increase at least another 0.6 degrees Celsius (1 degree Fahrenheit) because of carbon dioxide already in the atmosphere. The degree to which temperatures go up beyond that depends in part on how much more carbon humans release into the atmosphere in the future.

Ocean

About 30 percent of the carbon dioxide that people have put into the atmosphere has diffused into the ocean through the direct chemical exchange. Dissolving carbon dioxide in the ocean creates carbonic acid, which increases the acidity of the water. Or rather, a slightly alkaline ocean becomes a little less alkaline. Since 1750, the pH of the ocean&rsquos surface has dropped by 0.1, a 30 percent change in acidity.

Some of the excess CO2 emitted by human activity dissolves in the ocean, becoming carbonic acid. Increases in carbon dioxide are not only leading to warmer oceans, but also to more acidic oceans. (Photograph ©2010 Way Out West News.)

Ocean acidification affects marine organisms in two ways. First, carbonic acid reacts with carbonate ions in the water to form bicarbonate. However, those same carbonate ions are what shell-building animals like coral need to create calcium carbonate shells. With less carbonate available, the animals need to expend more energy to build their shells. As a result, the shells end up being thinner and more fragile.

Second, the more acidic water is, the better it dissolves calcium carbonate. In the long run, this reaction will allow the ocean to soak up excess carbon dioxide because more acidic water will dissolve more rock, release more carbonate ions, and increase the ocean&rsquos capacity to absorb carbon dioxide. In the meantime, though, more acidic water will dissolve the carbonate shells of marine organisms, making them pitted and weak.

Warmer oceans&mdasha product of the greenhouse effect&mdashcould also decrease the abundance of phytoplankton, which grow better in cool, nutrient-rich waters. This could limit the ocean&rsquos ability to take carbon from the atmosphere through the fast carbon cycle.

On the other hand, carbon dioxide is essential for plant and phytoplankton growth. An increase in carbon dioxide could increase growth by fertilizing those few species of phytoplankton and ocean plants (like sea grasses) that take carbon dioxide directly from the water. However, most species are not helped by the increased availability of carbon dioxide.

Plants on land have taken up approximately 25 percent of the carbon dioxide that humans have put into the atmosphere. The amount of carbon that plants take up varies greatly from year to year, but in general, the world&rsquos plants have increased the amount of carbon dioxide they absorb since 1960. Only some of this increase occurred as a direct result of fossil fuel emissions.

With more atmospheric carbon dioxide available to convert to plant matter in photosynthesis, plants were able to grow more. This increased growth is referred to as carbon fertilization. Models predict that plants might grow anywhere from 12 to 76 percent more if atmospheric carbon dioxide is doubled, as long as nothing else, like water shortages, limits their growth. However, scientists don&rsquot know how much carbon dioxide is increasing plant growth in the real world, because plants need more than carbon dioxide to grow.

Plants also need water, sunlight, and nutrients, especially nitrogen. If a plant doesn&rsquot have one of these things, it won&rsquot grow regardless of how abundant the other necessities are. There is a limit to how much carbon plants can take out of the atmosphere, and that limit varies from region to region. So far, it appears that carbon dioxide fertilization increases plant growth until the plant reaches a limit in the amount of water or nitrogen available.

Some of the changes in carbon absorption are the result of land use decisions. Agriculture has become much more intensive, so we can grow more food on less land. In high and mid-latitudes, abandoned farmland is reverting to forest, and these forests store much more carbon, both in wood and soil, than crops would. In many places, we prevent plant carbon from entering the atmosphere by extinguishing wildfires. This allows woody material (which stores carbon) to build up. All of these land use decisions are helping plants absorb human-released carbon in the Northern Hemisphere.

Changes in land cover&mdashforests converted to fields and fields converted to forests&mdashhave a corresponding effect on the carbon cycle. In some Northern Hemisphere countries, many farms were abandoned in the early 20th century and the land reverted to forest. As a result, carbon was drawn out of the atmosphere and stored in trees on land. (Photograph ©2007 Husein Kadribegic.)

In the tropics, however, forests are being removed, often through fire, and this releases carbon dioxide. As of 2008, deforestation accounted for about 12 percent of all human carbon dioxide emissions.

The biggest changes in the land carbon cycle are likely to come because of climate change. Carbon dioxide increases temperatures, extending the growing season and increasing humidity. Both factors have led to some additional plant growth. However, warmer temperatures also stress plants. With a longer, warmer growing season, plants need more water to survive. Scientists are already seeing evidence that plants in the Northern Hemisphere slow their growth in the summer because of warm temperatures and water shortages.

Dry, water-stressed plants are also more susceptible to fire and insects when growing seasons become longer. In the far north, where an increase in temperature has the greatest impact, the forests have already started to burn more, releasing carbon from the plants and the soil into the atmosphere. Tropical forests may also be extremely susceptible to drying. With less water, tropical trees slow their growth and take up less carbon, or die and release their stored carbon to the atmosphere.

The warming caused by rising greenhouse gases may also &ldquobake&rdquo the soil, accelerating the rate at which carbon seeps out in some places. This is of particular concern in the far north, where frozen soil&mdashpermafrost&mdashis thawing. Permafrost contains rich deposits of carbon from plant matter that has accumulated for thousands of years because the cold slows decay. When the soil warms, the organic matter decays and carbon&mdashin the form of methane and carbon dioxide&mdashseeps into the atmosphere.

Current research estimates that permafrost in the Northern Hemisphere holds 1,672 billion tons (Petagrams) of organic carbon. If just 10 percent of this permafrost were to thaw, it could release enough extra carbon dioxide to the atmosphere to raise temperatures an additional 0.7 degrees Celsius (1.3 degrees Fahrenheit) by 2100.


Moral Hazard

Beyond conversations about “how” one might capture carbon, there is also a real debate about how much carbon we “should” be trying to capture. This isn’t about climate change skepticism, but the incentives we use to structure the economy.

Imagine all the world governments decided to implement no changes to address global warming other than building carbon capture from atmosphere plants. To keep warming under 1.5°C, the IPCC has said we need to reduce global CO2 emissions from 36.6 billion tons of CO2 per year in 2018 to 15 billion tons CO2 per year by 2030. To achieve this, we would need to build at least 20,000 carbon capture plants, costing trillions of dollars. Not only that, we would need to construct hundreds of additional plants per year to keep up with growth in CO2 emissions across the world. It is simply not a sustainable strategy to implement on such a large scale.

Unless there are some astonishing breakthroughs in the technology, it seems unlikely that carbon capture alone will be enough to stop global warming. This strategy will need to happen alongside reduced carbon emissions. Some worry that attention and resources used on carbon capture will lead to underinvestment in decarbonizing our economy.

This may all sound hypothetical, but it is worth mentioning that some of the most active sponsors of carbon capture research are oil companies like Chevron and BP. Some activists are concerned that these companies are using carbon capture to delay the transition away from fossil fuels or that big oil is attempting to profit from cleaning up their own mess. Alternatively, this could be seen as a good faith effort to fix their mistakes and find a new business model that is more sustainable. There are broader questions about how fossil fuel companies fit into the future economy, which is complicated for entirely legitimate reasons.

One way or another, we will need to utilize carbon capture initiatives to avoid substantial warming. Hopefully, regulation and policy will incentivize the right mix of emissions reductions and CO2 offsets, allowing the carbon capture sector to play a major role in the economy soon.

This article was originally published on Ecosolver.


Is It Time for an Emergency Rollout of Carbon-Eating Machines?

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The climate emergency demands that we dramatically and rapidly cut emissions. There’s no substitute for that, full stop. But it also demands a technological revolution to reverse years of out-of-control emissions: The UN’s Intergovernmental Panel on Climate Change notes that if we want to meet the Paris climate agreement’s most optimistic goal of limiting warming to 1.5 degrees Celsius above preindustrial levels, we have to deploy some sort of negative emissions technologies.

One promising technique is known as direct air capture (DAC), machines that scrub the atmosphere of CO2. Early versions of these facilities already exist: One firm called Carbon Engineering has been developing the technology for over a decade. DAC facilities use giant fans to suck in air, which then passes over special plastic surfaces, where it reacts with a chemical solution that binds to the CO2. The air leaves the facility minus the carbon.

But what might the wide-scale deployment of DAC look like? In a recent paper in the journal Nature Communications, a team of researchers crunched the numbers, arguing that it’s feasible for humanity to embark on a wartime-style crash deployment of a global network of machines that sequester carbon. “We think there's sort of a dearth of conversation generally, but also in the academic literature, around emergency responses to the climate crisis,” says Ryan Hanna, an energy systems researcher at the UC San Diego and lead author on the paper.

Typically, climate scientists run big, complicated models about the most economically optimal ways to decarbonize. “That envisions this very technocratic, manicured, highly granular transition,” Hanna says, “which doesn't really reflect the way transitions actually occur in reality.” So Hanna and his colleagues sketched out an alternate vision: Imagine what would happen if humanity invested in DAC like we’d invest in another world war.

The researchers broke their modeling into three parts. The first was an estimate of how much governments would need to pay for DAC plants. This would include appropriating crisis-level funding to pay private firms to build the facilities, and to pay the companies for storing the carbon they’d be capturing. The second piece of the modeling looked at how fast the plant rollout could scale using already-existing energy supplies like hydropower. (You wouldn’t want to use fossil fuels to run them, obviously.) And the last part was a climate model, representing the entire Earth system, including oceans and the atmosphere. This showed how global temperatures would change if a mass deployment of DAC facilities turned down the amount of CO2 hanging around in the atmosphere.

The WIRED Guide to Climate Change

The researchers found that with an annual investment of between 1 and 2 percent of the global gross domestic product, humanity could scale up a DAC network to remove around 2.3 gigatons of CO2 annually by the year 2050. (For perspective, total global emissions are currently around 40 gigatons a year.)

That’s about 400 times the amount of CO2 humanity currently sequesters, so we’re talking about a massive scale-up. Still, “relative to what the integrated assessment models tell us we should do by 2050, it's actually quite small,” says Hanna. We need to remove something like 5 to 9 gigatons of CO2 per year by 2050 to meet the Paris agreement’s 1.5 degrees C goal. “What that tells us is that we need more than just a single means of negative emissions,” Hanna adds. For instance, we could also bolster wetlands and plant trees to naturally sequester carbon.

The DAC facilities themselves will need to scale as quickly as possible. To be able to remove a mere 2 to 2.5 gigatons of carbon a year by 2050—a fraction of the amount that will help get us to the Paris goals—we’d need around 800. But to truly make a dent in the skyrocketing CO2 levels, we’d need to build them much faster. We’re talking 4,000 to 9,000 plants by the year 2075, and beyond 10,000 by the end of the century, at which point we could theoretically be sequestering up to 27 gigatons of carbon a year. “It shows, in effect, that you have a really long, slow, gradual scale-up as the industry grows through 2050,” says Hanna. “Then once it sort of grows to a massive size, then it's really easy to add a lot of plants quickly, because you have this huge industrial base for the industry.”

But there are some important caveats to consider, because Hanna and his colleagues are modeling a nascent technology rife with unknowns. For instance, they have to make informed assumptions about how much energy the future plants might use, which determines their operation costs. “The other big unknown,” Hanna says, “is how the performance of the system could actually improve, and how the costs of the systems would decline over time, given firms’ experience with building the technology.”

Plus, global politics could make a mess of DAC’s rollout: If all humans share the same atmosphere, why would one country pay to research and deploy the technology if their neighbor doesn’t pay a penny? “It's nice to approach things about climate change as if they're just technological problems—if we get the cost right, if we get the technology right,” says Louisiana State University environmental scientist Brian Snyder, who wasn’t involved in this new work. “But they are inherently political problems, and we've got to solve that simultaneously.” (In their paper, Hanna and his colleagues call for help from political scientists to study the challenges of international cooperation here.)

Yet another outstanding question: What do you do with that carbon once you’ve captured it? One option is to pump it underground, sealing it away forever. Economically, that’s a bit fraught, because you’re spending money to run your facility, but then throwing away your product instead of selling it. That means DAC will require government subsidies to be economically feasible. A nation could assign an inherent value to capturing carbon and slowing climate change, and dedicate some of its own funding to taking a financial loss—at least in the near term—for an environmental good.

Researchers are also working on turning captured carbon into new fuels, which could make that initial government investment in DAC lucrative. That sounds, well, counterproductive, since we’d be burning the fuel and putting the carbon right back into the atmosphere. But the idea is to use such a fuel to make hard-to-decarbonize industries carbon-neutral. Airliners and cargo ships, for instance, are too massive to run on current solar technologies. Making them essentially reburn fuel that’s on its second life means there’s less demand for fossil fuels pulled right out of the ground.

If these industries burn fuels made from captured CO2, they’ll still pollute, but at least they’ll be polluting with carbon that was previously in the atmosphere. “The real effective role of negative emissions is for this long tail of hard-to-decarbonize sectors,” says Zeke Hausfather, a climate scientist and the director of climate and energy at the Breakthrough Institute, which advocates for climate action. (He wasn’t involved in this new research.) “Aviation, agriculture—things where we're still going to be emitting carbon well into the 2050s, and perhaps after that.”


The unexpected ingredient necessary for life

From microbes to marsupials, life abounds on Earth. But even if you stripped the planet of all its inhabitants, Earth would still "live".

Its molten core churns, generating a magnetic field that envelops the planet. Erupting volcanoes spew gases and pave new lands with fresh lava. Earth's surface is a jigsaw puzzle of continent-sized rocky plates that push, rub, and clash against one another &ndash powerful processes that build mountains and reshape landscapes.

Earth is not just a vessel for life the planet itself is alive. But its geological metabolism &ndash and especially the dynamism of its tectonic plates &ndash is also responsible for making it a habitable world. If the planet were a cold, dead, and inert space rock, life as we know it probably could not exist. At least on today's Earth, geology and biology go hand in hand.

Of all planets, Earth is the only one known to have plate tectonics. It is also the only one known to harbour life. But whether that means plate tectonics is required for life, no one knows for sure.

Astronomers have discovered thousands of planets beyond the Solar System, some of which could be habitable. And plate tectonics could boost the likelihood for life &ndash especially for more complex organisms. If aliens do in fact exist, then they might also live on an active planet, rife with ground-shifting geological activity just like on Earth.

But as spacecraft exploring the Solar System have discovered, Earth is not unique when it comes to geological activity. Even though neither the moon nor Mars has plate tectonics, both worlds experience "moonquakes" and "marsquakes."

Some of Jupiter's moons have active volcanoes and geysers. Mercury has a magnetic field, suggesting at least part of its core is molten. Even Pluto &ndash once thought to be a relatively dormant ice world &ndash turns out to be full of towering ice mountains and glaciers, a landscape more dynamic than scientists expected.

Subduction can dig deep ocean trenches or induce volcanic eruptions

Still, geological activity alone is not the same as plate tectonics. Earth is the only planet in the Solar System with an outer crust broken into several plates like a cracked eggshell. These rigid tectonic plates, extending a couple of hundred kilometres deep at most, float on the more malleable mantle below.

Other worlds in the Solar System have ancient surfaces that are pockmarked with craters millions or even billions of years old. But on Earth, tectonic plates shift and slide, constantly renewing the surface. At mid-ocean ridges, rising magma forms new crust as it pushes two plates apart.

When two plates press into each other, one can get subsumed underneath. This process of subduction can dig deep ocean trenches or induce volcanic eruptions. Sometimes, like in the Himalayas, continental plates thrust themselves into each other, and with nowhere to go but up, they build mountains.

This is all essential for life on Earth.

These processes carry carbon in and out of Earth's interior, and by doing so, regulate the amount of carbon dioxide in the atmosphere. Carbon dioxide is a greenhouse gas: too much of it, and the atmosphere traps too much heat.

"The surface temperature increases and Earth eventually becomes a planet like Venus," says Jun Korenaga, a geophysicist at Yale University, US. Too little, and all the heat would escape, leaving Earth inhospitably cold.

Plate tectonics helps keep volcanism active for a long time

The carbon cycle therefore acts as a global thermostat, regulating itself when needed (although it does not take into account the excess carbon dioxide that is driving human-caused climate change). A warmer climate also results in more rain, which helps extract more carbon dioxide out of the atmosphere.

The gas is dissolved in raindrops, which fall on exposed rock. Chemical reactions between the rainwater and rock release the carbon and minerals like calcium from the rock. The water then flows through rivers and streams, eventually reaching the ocean, where the carbon forms carbonate rocks and organic objects like seashells.

The carbonate settles on the bottom of the ocean, on a tectonic plate that gets subducted, carrying the carbon into Earth's interior. Volcanoes then belch the carbon back into the atmosphere as carbon dioxide.

After hundreds of millions of years, the cycle is finally complete.

Plate tectonics plays a part in every aspect of this cycle. Not only does subduction deliver carbon back into Earth's mantle, but tectonic activity brings fresh rock to the surface. That exposed rock is crucial for the chemical reactions that release minerals. Mountains, formed from plate tectonics, channel air upward, where it cools, condenses, and forms raindrops &ndash which help extract carbon from the atmosphere.

Plate tectonics could have created diverse environments that sparked evolution

Then there are the volcanoes. "Plate tectonics helps keep volcanism active for a long time," says Brad Foley, a geophysicist at Penn State University, US. "If we didn't have volcanism sending back carbon dioxide into the atmosphere, then the planet could get very cold. It would freeze over."

Maintaining a warm climate is key for a habitable planet. But plate tectonics contributes other things as well. For example, research has suggested that erosion and weathering processes remove elements like copper, zinc, and phosphorous from rock and carry them to the sea.

These elements are important nutrients for organisms like plankton. In the past, they could have been responsible for bursts in biodiversity, such as the Cambrian explosion 540 million years ago. Evidence also suggests that periods with little erosion &ndash and therefore fewer available nutrients in the ocean &ndash coincided with mass extinction events.

By moving continents around, plate tectonics could also have created diverse environments that sparked evolution. Over millions of years, continents drift across Earth's surface, going from one climate zone to another. Without plate tectonics, Earth would not have its diverse geography, which provides a wide range of habitats.

The engine that generates the magnetic field is a churning, molten core of iron

Plate tectonics is also responsible for hydrothermal vents on the ocean floor. Near a plate boundary, seawater can seep into cracks, where magma heats it to hundreds of degrees, ejecting the hot water back into the ocean. Hydrothermal vents, discovered in the late 1970s, are home to diverse ecosystems, and some scientists have suggested that similar vents gave rise to the first life on Earth.

The constant plate motions may even play a role in Earth's magnetic field. The field might have acted as a shield that prevented the solar wind from stripping away the atmosphere &ndash another possible requirement for life. The engine that generates the magnetic field is a churning, molten core of iron. Those turbulent motions are due to a process called convection, in which the hotter liquid rises while the cooler stuff sinks. Whether or not convection takes place in Earth's core &ndash and so whether it creates a magnetic field &ndash depends on the planet's cooling rate.

"If you have plate tectonics, then that tends to cool the interior faster than if you didn't have it," says Peter Driscoll, a geophysicist at the Carnegie Institution of Washington. A faster cooling rate allows for convection and, in turn, a magnetic field. Mars and Venus, for example, do not have plate tectonics. Nor do they have liquid cores, magnetic fields, or life &ndash that we know of, anyway.

But while plate tectonics is important for life on Earth today, what about extraterrestrial life?

Astronomers estimate that as many as a hundred billion planets populate the galaxy. This includes plenty of Earth-sized ones within the so-called habitable zone of their star, the region where it is not too hot nor too cold for liquid water to potentially exist on the surface. They have even found such a planet around Proxima Centauri, the closest star to the Solar System.

Being in the habitable zone and having liquid water are the most important factors for whether life could exist on a planet. But after that, plate tectonics, among other features, come into play.

It can slowly drip downward like molasses, dropping carbon deep into the interior

"Plate tectonics is extremely helpful for life," says Norm Sleep, a geophysicist at Stanford University, US. If a planet had plate tectonics, he says, "habitability would be greatly enhanced."

Of course, any discussion of habitability on other planets is inherently speculative. There is only one known example of a habitable world, and that is Earth.

"Plate tectonics is critical for the life we know and love as humans," says Lindy Elkins-Tanton, a planetary scientist at Arizona State University, US. But "it's not necessarily required for life in a broader sense."

On Earth, for instance, plate tectonics' most important role is regulating the carbon cycle. But on another planet, plate tectonics might not be necessary to maintain such a cycle.

Some volcanoes, such as the ones that make up the Hawaiian Islands, do not require tectonic activity.

"With that volcanism, there's still a way to have carbon dioxide added to the atmosphere," Foley says. "That volcanism is also creating fresh rock that can weather, so you have the ability to do both parts of the carbon cycle."

Still, returning that carbon back into the planet's interior without subduction gets tricky. A planet without plate tectonics, called a stagnant-lid planet, is encased in a rigid crust that locks in carbon. However, the deeper layers of the crust are warmer and softer. It is also denser than the mantle, so if it is soft enough, it can slowly drip downward like molasses, dropping carbon deep into the interior, where it can be expelled again via volcanoes.

You have to take any prediction of the early Earth with a grain of salt

But even if some sort of carbon cycle is possible, it might not last as long, and the planet will have a shorter window for habitability. Without plate tectonics, Foley says, volcanism might die out sooner.

Some researchers say that, even on Earth, life might not have needed plate tectonics. In 2016, Craig O'Neill, a planetary scientist at Macquarie University in Sydney, developed computer models that suggest Earth did not have plate tectonics in the distant past &ndash even when life first appeared 4.1 billion years ago. If life emerged on Earth without plate tectonics, then that would imply tectonic activity is not required for life.

But that conclusion is premature, other researchers say. "You have to take any prediction of the early Earth with a grain of salt," says Foley. Different assumptions with the model can give completely different answers.

In the end, researchers agree that plate tectonics could help coax life into existence. But no one can say for sure whether it is necessary. "We don't understand enough about plate tectonics to understand whether it's critical for habitability," Elkins-Tanton says. Scientists did not develop the theory until the latter half of the 20th Century, and they do not fully understand it on Earth, let alone on other planets.

We could barely detect it on our planet, and we're standing right on it

One complicating factor on Earth is the intimate relationship between plate tectonics and life. "These geological cycles are making the Earth more habitable," Sleep says, but biology is also important. "Life has had four billion years to evolve traits that adapt itself to being able to live on a planet with plate tectonics." Maybe life on Earth came to rely on plate tectonics simply because evolution steered it that way.

Even if plate tectonics were required for life, astronomers probably would not be able to tell whether a planet has plate tectonics in the first place. Planets outside the Solar System are far away, and even the best telescopes can only tease out the chemical composition of planetary atmospheres, which is already a remarkable feat. But short of interstellar travel, it is virtually impossible to measure plate tectonics on another planet.

"We could barely detect it on our planet, and we're standing right on it," Elkins-Tanton says.

Plate tectonics is just one of many factors that may influence habitability. Scientists may not determine the formula for life until they actually discover ET. For now, Earth will remain the only world that is truly alive.


Carbon Dioxide

Carbon dioxide (CO2) is an important heat-trapping (greenhouse) gas, which is released through human activities such as deforestation and burning fossil fuels, as well as natural processes such as respiration and volcanic eruptions. The first graph shows atmospheric CO2 levels measured at Mauna Loa Observatory, Hawaii, in recent years, with average seasonal cycle removed. The second graph shows CO2 levels during the last three glacial cycles, as reconstructed from ice cores.

Over the past 171 years, human activities have raised atmospheric concentrations of CO2 by 48% above pre-industrial levels found in 1850. This is more than what had happened naturally over a 20,000 year period (from the Last Glacial Maximum to 1850, from 185 ppm to 280 ppm).

The time series below shows global distribution and variation of the concentration of mid-tropospheric carbon dioxide in parts per million (ppm). The overall color of the map shifts toward the red with advancing time due to the annual increase of CO2.


Respiration

Respiration is the process during which organic food, mainly glucose that is present in the cell, breaks down into simpler substances and liberates carbon dioxide and energy. The energy released during respiration is chemical energy. There are two types of respiration- aerobic and anaerobic respiration.

Aerobic Respiration

Aerobic means &lsquowith air&rsquo. This type of respiration requires oxygen, so it is called aerobic respiration. During aerobic respiration, complete oxidation of carbohydrates takes place. Glucose is broken down by oxygen to release energy, while carbon dioxide and water are the by-products of the reaction. The released energy is used to make a special energy molecule called Adenosine triphosphate (ATP). ATP is where the energy is stored for later use by the body. Aerobic respiration occurs in plants as well as animals and takes place in the mitochondria.

The word equation for aerobic respiration is:

Anaerobic Respiration

Anaerobic means without air. Sometimes there is not enough oxygen around for animals and plants to respire, but they still need energy to survive, so they carry out respiration in the absence of oxygen to produce the energy they require. As the respiration takes place in the absence of oxygen, incomplete oxidation of food occurs and much less energy is released. However, carbon dioxide is still produced. This is called anaerobic respiration and the process occurs in the cytoplasm.


Watch the video: Kohlenstoffdioxid in der Atmosphäre (October 2022).