Science paper examines role of aerosols in climate change

Sep 05, 2008

A group of scientists affiliated with the International Geosphere-Biosphere Programme (IGBP) have proposed a new framework to account more accurately for the effects of aerosols on precipitation in climate models. Their work appears in the 5 September issue of Science magazine.

The increase in atmospheric concentrations of man-made aerosols—tiny particles suspended in the air—from such sources as transportation, industry, agriculture, and urban land use not only poses serious problems to human health, but also has an effect on weather and climate.

Recent studies suggest that increased aerosol loading may have changed the energy balance in the atmosphere and at the Earth's surface, and altered the global water cycle in ways that make the climate system more prone to precipitation extremes.

It appears that aerosol effects on clouds can induce large changes in precipitation patterns, which in turn may change not only regional water resources, but also may change the regional and global circulation systems that constitute the Earth's climate.

The proposed framework improves scientists' ability to simulate present and future climates by integrating, for the first time, the radiative and microphysical effects of aerosols on clouds. The radiative effects of aerosols on clouds mostly act to suppress precipitation, because they decrease the amount of solar radiation that reaches the land surface, and therefore cause less heat to be available for evaporating water and energizing convective rain clouds. Microphysical effects of aerosols can slow down the conversion of cloud drops into raindrops, which shuts off precipitation from very shallow and short-lived clouds.

Model simulations suggest that this delay of early rain causes greater amounts of cloud water and rain intensities later in the life cycle of the cloud. This suggests that rain patterns are shifting, leading to possible drought in one area and flooding downwind in another area. In addition, greater cooling below and heating above leads to enhanced upward heat transport. Model simulations have shown that greater heating in the troposphere enhances the atmospheric circulation system, shifting weather patterns due to changes convective activity.

Investigations of aerosol/precipitation effects are especially relevant to policy issues, as effects on the hydrological cycle may affect water availability, a great concern in many regions of the world. The IPCC, in its latest climate change assessment report, declared aerosols to be "the dominant uncertainty in radiative forcing (a concept used for quantitative comparisons of the strength of different human and natural agents in causing climate change)". Therefore, aerosols, clouds and their interaction with climate are still the most uncertain areas of climate change and require multidisciplinary coordinated research efforts.

To that end, authors of the Science article are participating in a new, international research project designed to study the connections between aerosols, clouds, precipitation and climate (ACPC project). The project will bring together an international multidisciplinary group of scientists from the areas of aerosol physics and chemistry, cloud dynamics, and cloud microphysics under theauspices of two international research programmes, the International Geosphere-BiosphereProgramme (IGBP) and the World Climate Research Programme (WCRP).

Source: International Geosphere-Biosphere Programme

Explore further: Five anthropogenic factors that will radically alter northern forests in 50 years

add to favorites email to friend print save as pdf

Related Stories

Clean air: Fewer sources for self-cleaning

12 hours ago

Up to now, HONO, also known as nitrous acid, was considered one of the most important sources of hydroxyl radicals (OH), which are regarded as the detergent of the atmosphere, allowing the air to clean itself. ...

Better climate predictions within grasp

Apr 14, 2014

that will improve our understanding of the consequences of climate change and could save the global economy up to $30 trillion - has received funding to develop a more detailed design of the technology and identify partners. ...

Slowdown of global warming fleeting

Apr 07, 2014

The recent slowdown in the warming rate of the Northern Hemisphere may be a result of internal variability of the Atlantic Multidecadal Oscillation—a natural phenomenon related to sea surface temperatures, ...

Recommended for you

US delays decision on Keystone pipeline project

10 hours ago

The United States announced Friday a fresh delay on a final decision regarding a controversial Canada to US oil pipeline, saying more time was needed to carry out a review.

New research on Earth's carbon budget

16 hours ago

(Phys.org) —Results from a research project involving scientists from the Desert Research Institute have generated new findings surrounding some of the unknowns of changes in climate and the degree to which ...

User comments : 0

More news stories

Magnitude-7.2 earthquake shakes Mexican capital

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

New research on Earth's carbon budget

(Phys.org) —Results from a research project involving scientists from the Desert Research Institute have generated new findings surrounding some of the unknowns of changes in climate and the degree to which ...

Impact glass stores biodata for millions of years

(Phys.org) —Bits of plant life encapsulated in molten glass by asteroid and comet impacts millions of years ago give geologists information about climate and life forms on the ancient Earth. Scientists ...