Saturday, April 05, 2008

Global Dimming

Concern over global warming has literally reached a fever pitch. And while no one is denying that addressing this critical issue may very well be key to our planet's survival, it is not the only major problem that needs our immediate attention. Earth's biosphere is an interconnected system where everything influences everything else. By focusing so much attention on global warming we are ignoring other critical issues at our peril.

Consider the little known phenomenon called global dimming. Scientists first began documenting this anomaly more than a quarter of a century ago, but it has languished in obscurity until last year when the BBC science program Horizon featured a documentary on the subject.

The story, which has more twists and turns than a Dan Brown novel, began in Israel in the 1950s when British scientist Dr. Gerald Stanhill was developing an irrigation system. He carefully measured the amount of radiation that was reaching Israeli soil in order to calculate how much irrigation would be required. Some 20 years later, Dr. Stanhill repeated his measurements to make sure that his original calculations were still valid. He was astounded to discover that there had been a 22 percent drop in measurable solar radiation.

While Dr. Stanhill's subsequent report of his findings was almost totally ignored by the scientific community, it did capture the attention of German scientist Dr. Beate Liepert. Dr. Liepert studied journals and other data from 1950 to the early 1990s and concluded that the phenomenon of reduced radiation wasn’t limited to Israel. Dr. Liepert discovered that the amount of solar radiation reaching the Earth’s surface during the study period had decreased 9 percent in Antarctica, 10 percent in the United States, 30 percent in Russia and16 percent in parts of Britain.

Once again, these findings were dismissed, largely because they contradicted the growing body of evidence about climate change. Logically, if less energy from the sun was reaching the Earth’s surface then the temperature should be getting cooler, not warmer.

Meanwhile in Australia, Dr. Michael Roderick and Dr. Graham Farquhar were gathering data about pan evaporation rates. For more than a hundred years outdoor evaporation rates have been measured for agricultural purposes. What the two scientists discovered was that despite the increase in global temperatures, pan evaporation rates have been declining since the1990s.

What their data led them to conclude was that contrary to popular scientific belief, the rate of evaporation is not determined by temperature, but rather by photons of sunlight knocking molecules of water out of the pan and into the atmosphere. Subsequent Russian research confirmed that the drop in the evaporation rate corresponded directly with the drop in solar radiation.

Using their collective data, Indian scientist Dr. V. Ramanathan conducted an atmospheric study over the Maldives Islands in the Indian Ocean. What he discovered was that the decline in solar radiation was caused by billions of tiny particles produced by the burning of fossil fuels. This particulate matter was turning the clouds into giant mirrors, reflecting the sunlight back into space. These same particles were also acting like giant umbrellas, shielding the Earth from the sun's heat.

Dr. Leon Rotstayn from the CSIRO Atmospheric Research Institute took the Maldives data and made an astounding conclusion. Exhaust pipes and power stations in Europe effectively caused the dimming that was ultimately responsible for altering the monsoons over Africa. This led to a 20-year famine in Ethiopia, claiming over one million lives and impacting 50 million more.

Even more shocking was his conclusion that the change to the African Monsoon was just a taste of things to come. The Asian Monsoon brings rainfall to 3.6 billion people, more than half the world’s population. Alterations to the Asian Monsoon could create a famine beyond our comprehension.

Until recently, global dimming, caused by airborne particulate, has actually protected us from the potential climate changing impacts of less toxic gases such as carbon dioxide and methane. While we have made significant strides in reducing deadly airborne emissions thanks to the widespread use of catalytic converters on cars and scrubbers and other pollution control devices on power plants, so-called greenhouse gas emissions continue to rise.

Here is the terrible Catch-22. Without the protection of global dimming, global temperatures could rise twice as quickly as currently predicted with catastrophic results.

If there is any good news is all of this, it is that the burning of fossil fuels is the root cause of both climate change and global dimming. This new evidence makes is even more critical to break our oil addiction and create a carbon-free energy economy before we catastrophically and irreversibly change our Earth.


Take the time to watch the 40-minute 2007 Horizon documentary entitled, Global Dimming. It is available at


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