It has become very difficult for anyone to argue that observed global warming is natural variability. We have good reason for being able to say that the world will be warmer by about a quarter of a degree in the next decade. It's the same reason we had 10 years ago when we said that the 1990s would be warmer than the 1980s: The planet is out of equilibrium.

If we fail to act, we will end up with a different planet.

There is still time to act and avoid a worsening climate but we are wasting precious time.

The United States did not sign Kyoto, yet its emissions are not that different from the countries that did sign it.

...the global surface albedo [surface whiteness] and greenhouse gas changes account for practically the entire global climate change.

If humanity wishes to preserve a planet similar to that on which civilisation developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO₂ will need to be reduced from its current 385 ppm [parts per million] to at most 350 ppm... If the present overshoot of this target CO₂ is not brief, there is a possibility of seeding irreversible catastrophic effects.

Imagine a giant asteroid on a direct collision course with Earth. That is the equivalent of what we face now with climate change, yet we dither.