May 16, 2012 – Vol.17 No.9
PLANET TOO HOT? PAINT IT WHITE.
by Bruce Mulliken, Green Energy News
It’s any climate scientist’s best guess as to when the irreversible tipping point for global warming will come. (Heck, we may already have passed it.) When the tipping point comes, planetary warming will accelerate no matter what efforts are made to cut greenhouse gas emissions. At that point we run for cover, barricade our shore lines against the ever rising seas and make serious attempts to cool off the planet through some kind of geoengineering scheme so the human race can survive.
Already, there are some minor efforts underway to either absorb carbon dioxide or reflect sunlight. There are tree planting programs to absorb carbon over decades, but trees grow rather slowly and it’s hard to keep up the pace of tree planting with deforestation in parts the world. White roofs on buildings to reflect sunlight are being encouraged to reduce the heat island effect in urban areas and bring temps down, at least locally.
If those efforts don’t help, some have suggested deploying giant mylar mirrors in space to reflect sunlight off our little planet. However, space shades may not be necessary.
It has long been thought that nanoscale particles of air pollution actually help cool the earth by blocking sunlight. It sounds odd but dirty air makes us cooler. Some climate scientists lately think that as Asia cleans its air of pollutants, the global temperature will go up as the continent’s brown cloud disappears.
In 1991 nature gave climate scientists a real-life experiment as to how well pollutants can block sunlight and lower global temperatures.
That year Mount Pinatubo in the Philippines erupted spewing an estimated 20 million tons of sulfur dioxide into stratosphere forming a fine mist of sulfuric acid particles which scattered a small portion of incoming sunlight (about 1 percent) for about two years. The result was fabulous orange-purple sunsets as well as global temperature dropping nearly one degree F (or about half a degree C).
In the UK, researchers were taking the first steps to inject Pinatubo-like pollutants into the upper atmosphere, but for now they’ve stopped in their tracks. The Stratospheric Particle Injection for Climate Engineering (Spice) project had been planned as a testbed for pumping minute sulfate particles into the stratosphere with the help of a balloon. (Water was to be used in the testing.) The project has been temporarily scrubbed for legal problems over intellectual property with the technology they are considering.
Adding sulfur pollutants to the stratosphere would make environmentalist squeamish. But according to Peter Davidson, a former UK government advisor and chemical engineer, a similarly sized and benign particle, Titanium Dioxide (TiO2) would do the same, if not better job of reflecting sunlight.
A press release from the Institute of Chemical Engineers says it best:
Titanium Dioxide (TiO2), mankind’s most commonly-used pigment. It is stable in air, nontoxic and seven-times more effective at scattering light than sulfuric acid. Titanium is abundant in the earth’s crust and five million tonnes a year of pigment is produced currently so supply appears feasible. If you are reading this on a printed page the ink and the paper probably both have a TiO2 pigment in them.
With a candidate particle identified, the next challenge is devising a system to effectively and economically lift and disperse millions of tons of particles some 20 km (~ 65,000 feet) up into the stratosphere, so they stay up for a couple of years and do not immediately get rained out.
Davidson says: “The impact of global warming is predicted to be most severe on the world’s poorest peoples, both because of their lack of resources and because of where they happen to be living. I would hope we could ensure that these peoples have a stake in decision-making and the opportunity to have their voice heard, alongside the richer countries, and appropriate NGO’s (for example environmentalists), as well as other bodies.
“Ideally an independent charitable trust funded by a variety of stakeholders from around the world would research not only the technology but suitable governance, legal and ethical frameworks,” adds Davidson.
The total capital cost of the balloon, tethers, ultra high pressure pumps, and the production and transport of the particles is estimated to be GBP 500m ($800 million) plus GBP 600m ($950 million) in annual operating costs in a paper to be published by the Royal Society. These costs are perhaps thirty times lower than the next best technologies considered, such as large numbers of very sophisticated jet aircraft, and do not have the same carbon footprint. “Space mirrors on the scale needed and 20 km tall towers are likely to be for the 22nd century not this one.”
Very approximate estimates are that we’d need to disperse over a million tonnes of titanium dioxide per year to keep planetary temperatures constant if CO2 levels in the atmosphere double. If such an insurance policy was needed we would have to do this for 50 to 150 years. Ocean acidification would be a worry but this might be still worse if such temperature control did not keep methane emissions from melting arctic tundra or seas under control.
At current prices, supplying these particles would cost around GBP 3 billion (nearly $5 billion) per year or around 50p (80 cents) per person per year.
Davidson says: “Creating a suitable insurance policy for climate remediation is a vital task. It will not do to underestimate the challenges. Much research and work on governance is still needed, but a vision is now on offer for debate, and development where potential means of solving some of the most difficult technical challenges have been identified. It would be shortsighted to put-off research of such a safety-device – like trying to develop a lifejacket when you’re swept out to sea and struggling in the water.”
Davidson says his plan is an insurance policy if nothing else succeeds in cooling us off. So far efforts to stem global warming range from timid to nonexistent. If we haven’t yet crossed over the tipping point, each day that goes by we get closer.
Five tethered balloons would loft 1.5 million tonnes of titanium dioxide particles into the stratosphere each year. The balloon size is far larger than any launched to date to avoid ‘blow over’ from the fierce winds that the tether will experience 10 km above the Earth. The cost of the technology is significantly cheaper than other proposed stratospheric particle injection systems such as aircraft, artillery, and even tall towers. (Picture credit: IChemE/A Revell)
Peter Davidson explains how using balloons to lift and disperse stratospheric aerosols that scatter the sun’s light back into space could work as a “plan B’ for climate remediation.
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