Dear Presidents and Prime Ministers, Kings and Queens:

Once every generation or so, you're asked to step outside your national mindset and collectively figure out how to safeguard the planet and all its inhabitants. I grant you this: it's no easy task.

The media often describes geoengineering — large-scale deliberate interference in the climate system — as Plan B for the planet, a last resort should political negotiations to curb greenhouse gas emissions fail.

Almost by default this makes the UN’s Rio+20 summit in June Plan A for Planet Earth. So, is Plan A any good?

In order to reach the visionary ideal of a green economy, we'll need a Clean Revolution across the globe. At the Rio+20 Earth Summit in June this year, top-level politicians will be called upon to help catalyse the global transition to a green economy, alleviate poverty and create stable economic prosperity for all. Despite the huge advances made by the UN Commission on Sustainable Development (CSD) since its inception at the original Rio Earth Summit in 1992, it is clear that this transition needs to be quicker, ambitions greater, and actions stronger.

Setting humanity on a sustainable course will require striking a balance between the use of natural resources and their conservation.  A widespread but often overlooked doctrine called the Public Trust Doctrine (PTD) provides a legal foundation and implementation framework for achieving sustainable resource use.  Two key topics at Rio+20 in particular could be clarified by applying the PTD: 1) protecting the rights of future generations to functioning ecosystems and 2) governing resources beyond national jurisdiction.  We recommend that the notion of the ‘Public Trust’ be incorporated into the conversations regarding institutional frameworks for sustainable development at Rio+20.