Geoengineering, the deliberate modification of the Earth’s climate on a planetary scale, is a topic emerging from the fringes of debate and receiving increased attention from scientists, policy-makers, and the public. Ideas, such as adding sulphates to the stratosphere to reflect out sunlight, or fertilizing the oceans with iron to promote the growth of plants that absorb carbon dioxide, were once considered science fiction. However with global temperatures rising, along with the fear that humanity is not going to make the emissions cuts required to avert dangerous climate change, some are calling for climate intervention techniques to be researched immediately. In September 2009 the Royal Society Science Policy Center published "Geoengineering Climate." This major science policy report assessed the potential benefits, drawbacks, and risks of the most prominent geoengineering proposals. In highlighting the range of political, social, and ethical questions raised by climate intervention, it brought to the fore the need for informed international debate and continued public engagement. This symposium will continue the discussion of if, when, and how research and deployment should proceed. It will review the numerous scientific challenges that remain and explore how deliberate intervention in the Earth’s climate should be governed.