Black Carbon

Black Carbon (BC) is a major contributor to global climate change, possibly second only to CO₂ as the main driver of change. Black carbon is formed by the incomplete combustion of fossil fuels, wood and other fuels. Complete combustion would turn all carbon in the fuel into carbon dioxide (CO₂), but combustion is never complete and CO₂, carbon monoxide, volatile organic compounds, and organic carbon and black carbon particles are all formed in the process. The complex mixture of particulate matter resulting from incomplete combustion is often referred to as soot.

• BC particles strongly absorb sunlight and give soot its black color.
• BC is produced both naturally and by human activities as a result of the incomplete combustion of fossil fuels, biofuels, and biomass.
• Primary sources include emissions from diesel engines, cook stoves, wood burning and forest fires.
• Reducing CO₂emissions is essential to avert the worst impacts of future climate change, but CO₂ has such a long atmospheric lifetime that it will take several decades for CO₂ concentrations to begin to stabilize after emissions reductions begin.
• In contrast, BC remains in the atmosphere for only a few weeks, so cutting its emissions would immediately reduce the rate of warming, particularly in the rapidly changing Arctic.

Impacts

• Black carbon is an important contributor to warming because it is very effective at absorbing light and heating its surroundings. Per unit of mass, black carbon has a warming impact on climate that is 460-1,500 times stronger than CO₂.
• When suspended in the atmosphere, black carbon contributes to warming by converting incoming solar radiation to heat. It also influences cloud formation and impacts regional circulation and rainfall patterns.
• When deposited on ice and snow, black carbon and co-emitted particles reduce surface albedo (the ability to reflect sunlight) and heat the surface. The Arctic and glaciated regions such as the Himalayas are particularly vulnerable to melting as a result.
• Black carbon and its co-pollutants are key components of fine particulate matter (PM2.5) air pollution, the leading environmental cause of poor health and premature deaths.
• At 2.5 micrometres or smaller in diameter, these particles are, many times smaller than a grain of table salt, which allows them to penetrate into the deepest regions of the lungs and facilitate the transport of toxic compounds into the bloodstream.
• 5 has been linked to a number of health impacts including premature death in adults with heart and lung disease, strokes, heart attacks, chronic respiratory disease such as bronchitis, aggravated asthma and other cardio-respiratory symptoms. It is also responsible for premature deaths of children from acute lower respiratory infections such as pneumonia.
• Each year, an estimated 7 million premature deaths are attributed to household and ambient (outdoor) PM2.5 air pollution.
• Black carbon can affect the health of ecosystems in several ways: by depositing on plant leaves and increasing their temperature, dimming sunlight that reaches the earth, and modifying rainfall patterns.
• Changing rain patterns can have far-reaching consequences for both ecosystems and human livelihoods, for example by disrupting monsoons, which are critical for agriculture in large parts of Asia and Africa.

Black carbon’s short atmospheric lifetime, combined with its strong warming potential, means that targeted strategies to reduce emissions can provide climate and health benefits within a relatively short period of time.

Blue Carbon

• Blue carbon is the carbon stored in coastal and marine ecosystems.
• Sea grasses, mangroves, and salt marshes along our coast “capture and hold” carbon, acting as something called a carbon sink.
• Coastal ecosystems such as mangroves, tidal marshes and seagrass meadows sequester and store more carbon per unit area than terrestrial forests and are now being recognised for their role in mitigating climate change.
• These ecosystems also provide essential benefits for climate change adaptation, including coastal protection and food securityfor many coastal communities.
• However, if the ecosystems are degraded or damaged, their carbon sink capacity is lost or adversely affected, and the carbon stored is released, resulting in emissions of carbon dioxide (CO₂) that contribute to climate change.
• Dedicated conservation effortscan ensure that coastal ecosystems continue to play their role as long-term carbon sinks. 

Brown Carbon

• Brown carbon is brown smoke released by the combustion of organic matter.
• It coexists with black carbon when released in the atmosphere.
• Known for its light brownish color, absorbs strongly in the ultraviolet wavelengths and less significantly going into the visible.
• It is one of the significant warming factors as it disturbs the temperature pattern of the atmosphere and the cloud forming process. It also changes the solar absorption pattern and the nature of clouds.

Brown carbon contributes +0.25 W m^-2 or about 19% of the total atmospheric absorption by anthropogenic aerosols, while 72% is attributed to black carbon and 9% is due to the coating effect of sulfate and organic aerosols on black carbon. Brown carbon needs to be considered in global climate simulations.

A study of IIT Kanpur has highlighted that Brown Carbon has the potential to warm atmosphere by absorbing light. When compared to Black Carbon, Brown Carbon has 10 times more mass; Black Carbon has 50 times more absorption capacity than BrC. Both of them are absorbers, contributing in the warming of atmosphere. 

Green Carbon

• Green carbon is the carbon stored in the plants and soil of natural ecosystems and is a vital part of the global carbon cycle.
• Currently, international rules are blind to the colour of carbon so that the green carbon in natural forests is not recognised, resulting in perverse outcomes including ongoing deforestation and forest degradation, and the conversion of extensive areas of land to industrial plantations.

* Red carbon is the newest colour in the carbon spectrum. “In its broadest context, it includes all living biological particles on snow and ice that reduce albedo to survive”.

Climate change mitigation

• Conserving and restoring terrestrial forests, and more recently peatlands, has been recognised as an important component of climate change mitigation.
• Several countries are developing policies and programmes in support of sustainable development through initiatives that reduce the carbon footprint associated with the growth of their economies.
• These include actions to conserve and sustainably manage natural systemsrelevant to the United Nations Framework Convention on Climate Change (UNFCCC), including through the reducing emissions from deforestation and forest degradation in developing countries (REDD+) mechanism and Nationally Determined Contributions (NDCs).
• To incorporate coastal wetlands into the carbon market through the buying and selling of carbon offsets.
• This approach creates a financial incentive for restoration and conservation projects by helping to alleviate federal and state carbon taxes aimed at discouraging the use of fossil fuels.
• When fewer greenhouse gases are emitted, less pollution is created. When there is less pollution to tax, the process benefits not only the environment but also the financial well-being of the community doing the restoration.