Thomas & Calvin lecture at the University of Texas at San Antonio College of Architecture at 6pm on January 28th, 2009 in the Buena Vista Building

Slashdot just ran a post pointing out that The Independent just finished polling leading climate scientists and found growing support for geoengineering as a supplement to CO2 reduction to confront global warming.  So what is geoengineering exactly?

As human populations grow and technology spreads, measurable changes in the Earth are becoming more apparent. The current geological time period is known as the Anthropocene, as man’s activities are now a major driving force on the Earth’s biology and climate. Anthropogenic land use, accelerated since the industrial revolution, has led to the alteration of between one-third and one-half of the Earth’s land surface. Levels of atmospheric CO₂ have increased by approximately 30 percent over the last two centuries. More atmospheric nitrogen is fixed by humanity than by all natural terrestrial sources combined. And, more than half of all accessible surface fresh water is put to use by humans. The consequence of this is that humans have been radically altering the Earth for thousands of years, and geoengineering is usually proposed as an attempt to reverse the harmful side-effects of these changes, rather than to effect an ‘improvement’ upon nature. Typical projects are proposed to deal with recent climate change caused by greenhouse gas emissions, rather than to attempt to alter the effects of pre-industrial human civilisations and activity.

Although many geo-engineering projects have been proposed (see below), large-scale CO₂-storage through biomass creation (e.g. tree-plantations) is the only universally-accepted means to decrease greenhouse gas concentrations. However, some geoengineering techniques seek to reduce carbon in the atmosphere directly (e.g. CO₂-scrubbing ‘Fake Plastic Trees’) or indirectly (e.g. ocean iron fertilization). Other techniques, such as Solar Radiation Management, attempt to mitigate the warming effects of global warming without influencing CO₂ and other greenhouse gases directly. Techniques that do not reduce greenhouse gas concentrations can only address the warming effects of these gases. They and cannot address other problems linked to increasing levels of CO₂ and other greenhouse gases in the atmosphere (such as ocean acidification).

Many members of the scientific and technical communities fear that the full effects of various geoengineering schemes are not fully understood. The failure of the ambitious Biosphere 2 facility is one example of a complex project that was unsuccessful because scientists still have a limited understanding of how earth systems work together.

Performance of the systems may become ineffective, unpredictable or unstable as a result of external events, such as volcanic eruptions, phytoplankton blooms, El Nino, solar flares, etc., potentially leading to profound and unpredictable disruption to the climate system.

It may be difficult to predict the effectiveness of projects, with models of techniques giving widely varying results. In the instances of systems which involve tipping points, this may result in irreversible effects. Climate modelling is far from an exact science even when applied to comparatively well-understood natural climate systems, and it is made more complex by the need to understand novel and unnatural processes which by definition lack relevant observation data

A piece of technology decades ahead of its time