Black carbon contributes to droughts and floods in China

September 26, 2002

A new NASA climate study has found large amounts of black carbon (soot) particles and other pollutants are causing changes in precipitation and temperatures over China and may be at least partially responsible for the tendency toward increased floods and droughts in those regions over the last several decades.

In a paper appearing in the September 27 issue of SCIENCE, Surabi Menon of NASA and Columbia University, New York, and her colleague, James Hansen of NASA's Goddard Institute for Space Studies, New York, indicate black carbon can affect regional climate by absorbing sunlight, heating the air and thereby altering large-scale atmospheric circulation and the hydrologic cycle.

Using the NASA Goddard Institute for Space Studies climate computer model and aerosol data from 46 ground stations in China, Menon and Hansen conducted four sets of computer simulations to monitor the effects of black carbon on the hydrologic cycle over China and India. The aerosol data from the Chinese ground stations were provided by Yunfeng Luo, a co-author on the study from the Institute of Atmospheric Physics, Chinese Academy of Sciences.

In the four numerical simulations, Menon and Hansen isolated specific factors such as sea surface temperature, other greenhouse gases and aerosols, and analyzed whether changes in those factors would be responsible for hydrologic cycle changes.

Out of the four scenarios, the effect of increased amounts of soot (over southern China) created a clear tendency toward the flooding scenario that has been occurring in southern China and the increasing drought over northern China that has persisted over the last several years.

"If our interpretation is correct, then reducing the amount of black carbon or soot may help diminish the intensity of floods in the south and droughts in the northern areas of China, in addition to having human health benefits," Hansen said. Currently research is being conducted to verify a similar pattern over India.

Black carbon or soot is generated from industrial pollution, traffic, outdoor fires and household burning of coal and biomass fuels. Soot is a product of incomplete combustion especially of coal, diesel fuels, biofuels and outdoor biomass burning. Emissions are large in China and India because cooking and heating are done with wood, field residue, cow dung, and coal, at a low temperature that does not allow for complete combustion. These resulting soot particles absorb sunlight, just as dark pavement becomes hotter than light pavement in the summertime.

When soot absorbs sunlight it heats the air and reduces the amount of sunlight reaching the ground. The heated air makes the atmosphere more unstable, creating rising air (convection), which forms clouds and brings rainfall to regions that are heavily polluted.

The increase of rising air in southern China is balanced by an increase of sinking air (subsidence) and drying in northern China. When air sinks, clouds and thus, rain cannot form, creating dry conditions. For example, deserts are places where subsidence occurs.

In recent years, northern China has suffered from an increased severity of dust storms, while southern China has had increased rainfall that is thought to be the largest change in precipitation trends since the year 950. Menon and Hansen believe that human-made sunlight-absorbing aerosols may be responsible.

This research continues long-term observations of global climate change and was funded by NASA's Earth Science Enterprise and the National Science Foundation. NASA's Earth Science Enterprise is dedicated to helping us to better understand and protect our home planet.

NASA/Goddard Space Flight Center

Related Black Carbon Articles from Brightsurf:

Black hole or no black hole: On the outcome of neutron star collisions
A new study lead by GSI scientists and international colleagues investigates black-hole formation in neutron star mergers.

U.S.-born Black women at higher risk of preeclampsia than Black immigrants
Black women born in the United States have a higher risk of developing high blood pressure during pregnancy, a condition known as preeclampsia, compared to Black women who immigrated to the country.

The biggest trees capture the most carbon: Large trees dominate carbon storage in forests
A recent study examining carbon storage in Pacific Northwest forests demonstrated that although large-diameter trees (21 inches) only comprised 3% of total stems, they accounted for 42% of the total aboveground carbon storage.

The black hole always chirps twice: New clues deciphering the shape of black holes
A team of gravitational-wave scientists led by the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) reveal that when two black holes collide and merge, the remnant black hole 'chirps' not once, but multiple times, emitting gravitational waves--intense ripples in the fabric space and time--that inform us about its shape.

Carbon-carbon covalent bonds far more flexible than presumed
A Hokkaido University research group has successfully demonstrated that carbon-carbon (C-C) covalent bonds expand and contract flexibly in response to light and heat.

Metal wires of carbon complete toolbox for carbon-based computers
Carbon-based computers have the potential to be a lot faster and much more energy efficient than silicon-based computers, but 2D graphene and carbon nanotubes have proved challenging to turn into the elements needed to construct transistor circuits.

For black girls, attitudes about being black affect risk of depression
A new study suggests that the messages Black girls hear at home about being Black, and about being Black women in particular, can affect their risk of exhibiting the symptoms of depression.

'Black nitrogen'
In the periodic table of elements there is one golden rule for carbon, oxygen, and other light elements.

Tracking Southern Hemisphere black carbon to Antarctic snow
Biomass burning represents around 80% of all BC emitted to the atmosphere in the Southern Hemisphere, which means that the fires happening in Australia, New Zealand and South America ultimately leave a mark in Antarctic snow.

Black hole team discovers path to razor-sharp black hole images
A team of researchers have published new calculations that predict a striking and intricate substructure within black hole images from extreme gravitational light bending.

Read More: Black Carbon News and Black Carbon Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to