Particles and Rainfall – the Drips but no Drops!

[DougHaigh_JenMercer]

An article written by Assoc Prof Kearney and sent by Aron Gingis, Australian Management Consolidated Pty. Ltd.

Associate Professor of University of Sydney, Dr. Ray Kearney has just prepared this copy of his article prepared for local paper in Sydney.

Recent headlines ‘Rain in all the wrong places’ and ‘Deserts have taken our rain’ highlight the current trends that will bring dramatic ecological changes in Australia – greener for the desert and the Kimberley but browner for southern Australia. Why the doubling of rainfall in unpopulated areas and halving of rainfall in the industrial urbanised areas? Frightening satellite images confirm large swathes of our continent are now half as green as before.
Why has the vast cropping areas of Australia endured a decade-long dry spell? Is this recent phenomenon totally explained by the headlines ‘Greenhouse gas effect’ and the ‘Largest hole in the ozone layer yet’? Or is there another reason that has been swept under the carpet, unwanted and unseen for political and corporate expediency? Have alleged breaches of scientific probity corrupted climate science in this country?

For decades, scientists have debated whether urban air pollution alters a region's rainfall. Because numerous factors can influence precipitation, documenting pollution's effect on rainfall levels is difficult.
However, recent compelling evidence shows that clouds of fine particle pollution from power plants and combustion of fossil fuel as well as from other sources are inhibiting precipitation in many regions of the world, including Australia. In some cases these fine particles, of the size in tail-pipe exhaust, can choke rain clouds and eliminate almost all rain and snow produced by clouds, according to recent multinational studies. The presence of these atmospheric particles (aerosols) is seen as they scatter and absorb sunlight. Their scattering of sunlight can reduce visibility (haze) and redden sunrises and sunsets.

As a direct effect, the aerosols scatter sunlight directly back into space. As an indirect effect, aerosols in the lower atmosphere can modify the size of cloud particles, changing how the clouds reflect and absorb sunlight, thereby affecting the earth's energy budget.
Aerosols also can act as sites for chemical reactions that lead to the destruction of stratospheric ozone.
Daniel Rosenfeld, an atmospheric scientist at Hebrew University of Jerusalem, has reported in the journal Science that satellite data show plumes of pollution from industrial sites in Australia, Canada and Turkey persist downwind for hundreds of kms. Moisture in the air condenses on these particles, but never forms droplets big enough to fall to the ground as rain or snow.
Before Rosenfeld et al.'s research, confirmed independently in 2006, many scientists thought that airborne dust particles would speed the formation of rain by forming giant cloud condensation nuclei and larger cloud droplets. Not so, it seems! Dust and other particles in the air cause water droplets in clouds to be smaller, leading to decreased rain. More airborne dust is not necessarily a result of decreased rainfall but rather its cause. These startling findings are the opposite of what the scientists expected.
In the study, satellite images were used to simultaneously track pollution from coal-burning power plants and measure the precipitation and structure of clouds over large expanses of sky in Australia and overseas. They showed that weather changes can spread hundreds of kms downwind of large industry's plumes of pollution. The scientists reported that it is a physical process, rather than a chemical one, that blocks formation of rain and snow. Industrial plants spew particles, formed by fuel combustion, that are much smaller than the water droplets normally found in clouds. The small pollution particles inhibit the cloud's water droplets from coalescing into larger drops to create rain. Smaller water droplets are also slower to freeze, reducing the ice particles in clouds. In types of clouds that are short-lived, the lack of larger droplets reduces, or even eliminates, the precipitation, the report claimed.

The research also showed dust actually amplifies the process of creating deserts. Activities that expose and disrupt topsoil, such as grazing and agricultural cultivation, can increase the amount of dust blown into the air. In other words: Dust begets dust!
Rosenfeld has used NASA's Tropical Rainfall Measuring Mission (TRMM) spacecraft captured images in two other recent studies to show that aerosols from biomass-burning smoke and urban air pollution also reduce rainfall. Combined with the negative impact of desert dust, Rosenfeld believes the aerosol rainfall-suppression effect can have a major impact on regional and global climate.
These recent observations of the impact on precipitation of all kinds of aerosols, each with a major human contribution, show a dramatic climate change issue that has nothing to do with greenhouse gases. This is perhaps the climate-change effect with the greatest socio-economic impact on water-scarce areas.
In contrast, the addition of highly efficient larger aerosol particles however, typically soluble particles, such as salt crystals, can cause preferential droplet nucleation on these particles and actually lead to enhanced coalescence and production of rain. It is just this process that leads to the eventual clarification of air over the oceans. The total effect of added atmospheric aerosols therefore depends both on the materials and upon the general structure of the clouds to which they are added.
What is now emerging in this country is the anomalous role taken by the CSIRO because of its affiliation with the Commonwealth Government and the alleged offenders in the corporate sectors, especially those in the oil and coal industry. Whilst some researchers in the relevant CSIRO Atmospheric Science Division concede that the confirmed Rosenfeld’s investigation shows that industrial effluent plumes can indeed affect cloud properties and rainfall for a significant distance downwind of the source, CSIRO have had the temerity, apparently in the interests of political patronage and institutional survival, to debunk such observations. See link:
http://www.casanz.org.au/pdf/%20G.%20Ayers%20May%202005.pdf

A subsequent refereed response by Professor Rosenfeld and colleagues clearly established that the CSIRO’s claims are based on rudimentary scientific errors. CSIRO’s conclusions and advice to the State and Federal Governments as well as to the water authorities have been seriously flawed and misleading. See link:

http://www.earth.huji.ac.il/data/pics/06_226_CAS_May_06_rosenfeld2.pdf

This alleged breach of scientific probity by CSIRO is not uncommon or isolated. Similar conduct was observed during deliberations of the 2005 Biofuels Taskforce on which CSIRO had representation. Prior to interviews, the CSIRO posted, on the website of the Biofuels Taskforce, a flawed critique of fuel’s expert Dr Whitten who found that 10% ethanol added to petrol reduced fine particles by a qualified 50%. CSIRO failed to concurrently post on the website the rebuttal by Dr Whitten to CSIRO’s bias and prejudicial critique. Not surprising, the recommendations of the Biofuels Taskforce in its Report favoured the oil cartels and limited the opportunities of the clean alternative fuels industry while CSIRO stood to become a major beneficiary of the research the Report recommended.

While there is confirmatory evidence that fine-particle pollution generated from industry, unfiltered coal-burning power stations and motor vehicles powered by petrol and diesel can affect the droplet size and very likely the precipitation from certain types of clouds up to several hundred kms downstream from the source, politicians must now act in a non-partisan way to urgently implement preventive measures. This includes the adoption of cleaner fuels and filtration of fine toxic particles from their various sources.

For too long, governments have been emasculated by powerful energy and industry cartels who in turn have helped corrupt science and plunder earth’s life-support systems to augment profit and shift the cost of health impacts and environmental degradation to the taxpayer. We urgently need more useful drops but demand many fewer useless ‘drips’.

Dr Ray Kearney
Chairman,
Lane Cove Tunnel Action Group Inc

Ass. Prof. Kearney could be contacted on
rkearney@infdis.usyd.edu.au
rkearney@med.usyd.edu.au
(also posted in "Media Watch")