We appear to be approaching the point at which it doesn't much matter whether warming is caused by humans.

Decreases in glacial ice are pretty well documented.

Ocean warming is reasonably indicated.

Droughts in several parts of the world are near the point of outstripping the loss of vegetation caused by clear cutting and burning forests for agriculture.

Permafrost is thawing.

We know that increased CO₂ will increase warming.

Melting of glaciers and winter ice are very likely to increase drought effects. The loss of vegetation due to drought and thawing of the permafrost may be near the tipping point where those two effects alone will release more sequestered CO₂ faster than current man generated amounts. If that point is reached, the warming will continue even if human kind is extinguished tomorrow, and no method is known for re-sequestering the CO₂ amounts that will be released, at a rate adequate to stop the rise.

Current analytical methods are not adequate to give estimates that don't allow some debate about how far up the curve we are already; but quite a few people now believe that "we ain't far from where it's out of our hands completely."

It is very likely that we are in a "positive feedback" acceleration, where the further (and faster) we go, the faster and further we will be driven by effects we can't turn off.

It may be time to teach the cockroaches how to write, if we wish to leave a history for whatever re-populates the neighborhood, although that may not be really necessary as nature doesn't really require literacy, and will continue quite happily with simpler critters who are less troublesome.

John