8 things to know about black carbon

Although it warms the atmosphere 10,000s of times faster than CO₂, black carbon remains underappreciated as a climate change driver. Here are the crucial facts. 

1. Black carbon is a byproduct of burning fossil fuels 
   Black carbon, also known as soot, consists of tiny particles, about 1/100th the width of a human hair in size, that form when fossil fuels like coal, oil, and gas are burned incompletely. Among its sources are the exhaust pipes of trucks and other diesel-powered vehicles, industrial facilities like power plants, steel mills and brick kilns, and wood-burning cooking stoves. 
    

   
2. Black carbon drives climate change 
   Black carbon is a climate-forcing agent, meaning it contributes to global warming. When black carbon is emitted, the microscopic particles become suspended in the atmosphere. Because they are dark in color, they absorb energy from the sun. They radiate that energy back into the atmosphere in the form of heat.  
    
3. Black carbon outmuscles CO₂ – by a lot 
   As a driver of global warming, black carbon is up to 52,000 times more potent than carbon dioxide. That’s why, along with methane, HFCs and tropospheric ozone, it’s one of the “Big Four” non-CO₂ climate pollutants that are responsible for 45% of all manmade global warming. 
    
4. It stays around for just a few days…
   As opposed to CO₂, which lingers for centuries, black carbon doesn’t become “well-mixed” in the atmosphere. It falls back down to the surface or is washed out of the air by rain within five days. That’s why we call it a “short-lived climate pollutant.”  
    
5. …But we emit it every single day 
   No-one should be misled by the term “short-lived.” Since we emit black carbon in vast quantities every day, it’s a permanent problem. In 2019, the world emitted almost 6 million metric tons of black carbon. Totals have been decreasing slowly, but they remain stubbornly high, mainly in Asia, Africa and Latin America. 
    
6. Black carbon contributes to melting snow- and ice caps 
   When black carbon comes down from the atmosphere, it can settle on snow and ice, light-colored surfaces that reflect the sun’s heat back into space. Covered in black carbon, which absorbs heat, they begin to melt away, exposing darker rock and soil surfaces, which absorb even more heat. In this manner, black carbon pollution lowers the Earth’s albedo (its reflectivity), driving a vicious cycle of heat and melting.   
    
7. It can destroy your health 
   Because they are about 1/100th the width of a human hair, black carbon particles penetrate deep into the lungs. Black carbon is associated with a host of diseases including asthma, chronic obstructive pulmonary disease (COPD), heart attacks, strokes, and various pregnancy-related issues. It is a significant factor in the 8 million annual global deaths associated with air pollution caused by fossil fuel use. This is one of the reasons why the fights against climate change and air pollution are so closely interlinked.  
    
8. If we stopped emitting black carbon today… 
   Black carbon only stays aloft for a few days. That means that if we could zero out its emissions today, the return on investment would be immediate. Black carbon particles would be out of the atmosphere by next week, no longer trapping heat and causing people to get sick. All the more reason to step up our efforts to curb emissions, starting today.

Find out what you can do to assess or offset your own black carbon emissions.