The article was basically unsurprising, because I've long understood the Earth's environment to be a chaotic system. I would expect that an overall warming trend would inject more energy into the atmosphere and oceans, inducing more instability, and thus larger excursions above and below the average.

A chaotic system can rest for a long time in a metastate, and then suddenly leave the metastate, gyrate wildly for a bit, then settle down into a new and different metastate. That's what the article's describing (even though the word "chaotic" appears only once):

The evidence also shows that Earth’s climate system has sensitive thresholds. Pushed past a threshold, the system can jump quickly from one stable operating mode to a completely different one...

I agree with the article, and I like the way that it clearly states the most fundamental danger from climate change: Instability and unpredictability. If the average global temperature rise were distributed equally and the environment simply scaled linearly (a global "hothouse"), we'd have few problems adjusting, and plenty of time to adjust. It's the likelihood of being blindsided by sudden dramatic change that's so worrisome.

Gagosian describes the North Atlantic Conveyor as "Earth's Achilles Heel", and he may be right. It's shut down several times in the past, and could shut down rapidly, in less than a decade, dropping average temperatures around the North Atlantic 3-5°.

It would produce winters twice as cold as the worst winters on record in the eastern United States in the past century. In addition, previous Conveyor shutdowns have been linked with widespread droughts throughout the globe.

The question of who's to blame for global warming is a rather large red herring. It's not a binary thing, guilty or not guilty--humans are making a contribution, and it's moot whether we are making the crucial contribution. If we can help slow global warming by reducing our own input, we're protecting ourselves, 100% guilty or not.

The most strident deniers of global climate change and the human contribution thereto seem to be trying to protect the American/Western Way of Life from criticism and blame, and the economic system which provides it from loss of profits. That's clear from the common charge that scientists and advocates concerned about global warming "hate capitalism" or "hate business" or "hate America" and are trying deliberately to destroy those things by making up the problem.

Those ideological blinders could kill us all, and I only hope that the recent apparent softening of opposition on the Right isn't too little, too late. It's a mixed blessing that Bush has stopped trying to out-and-out block remediation, because he seems to have switched to the classic strategy of pretending to address the problem while implementing change as slowly as possible. The danger is that the gullible will accept go-slow policies and slacken pressure for real solutions.

We're facing a heap o'trouble, and just because scientists can't exactly predict its form doesn't mean there's no danger. The fundamental danger is the increasing unpredictability and the damage we'll take each time we're caught unawares.