Even if every country in the world reduced their emissions to Koyoto levels (1990), I think it would be too late to avoid either abrupt climate change or runaway global warming:

Leemans and Eickhout (2004) found that ecosystem adaptive capacity decreases rapidly with an increasing rate of climate change.

If the rate should exceed 0.4 C/decade, all ecosystems will be quickly destroyed.

According to the Intergovernmental Panel on Climate Change (IPCC), the global average temperature today is increasing by 0.2 C/decade.

This incease is caused by greenhouse gases we put into the atmosphere decades ago, due to the lag time between emission and temperature rise.

We have emitted nearly double the greenhouse gas since then, and are increasing our emissions at a rate of over 3% per year.

Therefore, in the next couple of decades we are facing the quick destruction of all the world's ecosystems, which will result in abrupt climate change (I suggest reading the Pentagon's alarming report on this subject).

Reference: Leemans og Eickhout, 2004, Another reason for concern: regional and global impacts on ecosystems for different levels of climate change, Global Environmental Change 14, 219-228.

Instead, the any feasible strategy for planetary rescue must include a method of removing the excess CO2 from the air.