The Geoengineering Option
A Last Resort Against Global Warming?
By David G. Victor, M. Granger Morgan, Jay Apt, John Steinbruner, and Katharine Ricke
From Foreign Affairs , March/April 2009
Summary: As climate change accelerates, policymakers may have to consider "geoengineering" as an emergency strategy
to cool the planet. Engineering the climate strikes most as a bad idea, but it is time to start taking it seriously.

The odds that the global climate will reach a dangerous tipping point are increasing. Over the course of the twenty-first
century, key ocean currents, such as the Gulf Stream, could shift radically, and thawing permafrost could release huge
amounts of additional greenhouse gases into the atmosphere. Such scenarios, although still remote, would dramatically
accelerate and compound the consequences of global warming. Scientists are taking these doomsday scenarios seriously because the steady accumulation of warming gases in the atmosphere is forcing change in the climate system at rates so rapid that the outcomes are extremely difficult to predict.

The world's slow progress in cutting carbon dioxide emissions and the looming danger that the climate could take a
sudden turn for the worse require policymakers to take a closer look at emergency strategies for curbing the effects of global warming. These strategies, often called "geoengineering," envision deploying systems on a planetary scale, such as
launching reflective particles into the atmosphere or positioning sunshades to cool the earth. These strategies could cool
the planet, but they would not stop the buildup of carbon dioxide or lessen all its harmful impacts. For this reason,
geoengineering has been widely shunned by those committed to reducing emissions.

Originally posted by Hazelnut
They dissipate in a minute or less. Whatever you want to call the "trails" that remain for hours, spread out and co-mingle with other "trails" which eventually block out the sky are very real. never mind that the planes themselves are unmarked and fly at extremely high altitudes and make no sound whatsoever.

Depending on atmospheric conditions, contrails may be visible for only a few seconds or minutes, or may persist for many hours

The "trails" shine unnaturally, almost like an oil spill in the sky at sunset.