Black Carbon : Its Impact on Global warming

BLACK CARBON:

• Black Carbon consists of pure carbon in several linked forms.
• It is formed through the incomplete combustion of fossil fuels, biofuel, and biomass, and is emitted in both anthropogenic and naturally occurring soot.
• In climatology black carbon is a climate forcing  Black carbon warms the Earth by absorbing heat in the atmosphere and by reducing albedo, the ability to reflect sunlight, when deposited on snow and ice.
• Black carbon stays in the atmosphere for only several days to weeks, whereas carbon dioxide (CO₂) has an atmospheric lifetime of more than 100 years.
• The first indications of the role of black carbon in a larger, global context came from studies of the Arctic Haze phenomena.
  • Black carbon was identified in the Arctic haze aerosolsand in the Arctic snow.
  • In general, aerosol particles can affect the radiation balance leading to a cooling or heating effect.

• Unlike carbon dioxide and other greenhouse gases that remain in the atmosphere for years, Black Carbon takes roughly 10 days to be cleaned out from the atmosphere.
• Despite its short life span, black carbon has claimed 1.15 million lives worldwide.
• While domestic emissions from inefficient fuel such as firewood has been considered the major contributor, experts said that black carbon emitted from diesel have impacted 75 % of the people affected by short-lived pollutants.
• People living in rural Asia, especially in India and China, suffer the most as there is slow improvement in switching to better fuels, such as cooking gas, from solid fuels such as wood or coal.
• The particulate matter, which also comprises black carbon, is highest in Asia.

• Black carbon emissions, especially from domestic sources, increase the aerosol radiative forcing.
• Radiative forcing is essentially related to absorption and reflection of sun rays due to the presence of certain particles. The process either cools the atmosphere or warms it.
• Black carbon from diesel warms up the atmosphere significantly.

BACKGROUND:

• Developed countries were once the primary source of black carbon emissions, but this began to change in the 1950s with the adoption of pollution control technologies in those countries.
• Today, the majority of black carbon emissions are from developing countriesand this trend is expected to increase.
• The largest sources of black carbon are Asia, Latin America, and Africa.
• China and India together account for 25-35% of global black carbon emissions.
• Black carbon emissions are highest in and around major source regions.This results in regional hotspots of atmospheric solar heating due to black carbon.
• Hotspot areas include:
  • The Indo-Gangetic plains of India
  • Eastern China
  • Most of Southeast Asia and Indonesia
  • Equatorial regions of Africa
  • Mexico and Central America
  • Most of Brazil and Peru in South America.
• Approximately 3 billion people live in these hotspots.
• Biomass burning in the country contributes to 30 % of black carbon.
• Inefficient burning of firewood in brick kilns also emits black carbon.

IMPACTS:

• Black carbon is a form of ultrafine particulate matter, which when released in the air causes premature human mortality and disability.
• In addition, atmospheric black carbon changes the radiative energy balance of the climate system in a way that raises air and surface temperatures, causing a variety of detrimental environmental impacts on humans, on agriculture, and on plant and animal ecosystems.
• Black carbon causes significantly higher warming over the Arctic due to a combination of the warming effect in the atmosphere and melting of Arctic snow and ice.

Figure: Black carbon is in the air and circulates the globe.

MITIGATION:

• Existing and well-tested technologies used by developed countries, such as clean diesel and clean coal, could be transferred to developing countries to reduce their emissions.
• Many countries have existing national laws to regulating black carbon emissions, including laws that address particulate emissions. Some examples include:
  • banning or regulating slash-and-burn clearing of forests and savannas;
  • mandating fuel standards for ships seeking to dock at port;
  • requiring regular vehicle emissions tests, including penalties for failing to meet air quality emissions standards, and heightened penalties for on-the-road “super-emitting” vehicles;
  • banning or regulating the sale of certain fuels and/or requiring the use of cleaner fuels for certain uses;
  • limiting the use of chimneys and other forms of biomass burning in urban and non-urban areas;
  • requiring permits to operate industrial, power generating, and oil refining facilities and periodic permit renewal and/or modification of equipment; and
  • requiring filtering technology and high-temperature combustion (e.g. super-critical coal) for existing power generation plants, and regulating annual emissions from power generation plants.
• One of the ways to mitigate this is to give access to better and efficient cooking fuel and technologies to the poor.