Among the basic systems phenomena that seems to escape economists is hysteresis.
It is entirely possible that by waiting ten years we will reach a
condition where some desired state that we might have reached in the
foreseeable future becomes entirely inaccessible. For example, if the
Greenland or West Antractic ice sheets warm up enough fail
mechanically, restoring them will not be feasible without a severe
cooling. Restrained warming will not be enough.
I think the right way to think about it is that there are multiple
tipping points in the system.
Based on what we have read here and elsewhere of late we will lose the
perennial Arctic ice very shortly. It is probably already be too late
to prevent this; even if we were to succumb to a vast epidemic and
disappear from the earth next month, hence not just clamp emissions
levels but actually stop emitting altogether, it seems likely that
perennial Arctic sea ice will vanish within decades due to the forcing
already in place. This will remove a summer temperature maximum of 0 C
at the Arctic surface and may have consequences for the entire
circulation of the atmosphere and the ocean.
Had we heeded early warnings twenty years ago, perhaps we might have
avoided this fate, but it's likely too late now. Reducing emissions
will never reverse this. We must actually remove carbon to allow sea
ice to the familiar configuration.
On 9/17/06, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
> Hansen may be a climate science expert, but this particular argument
> hasn't much to do with climate science as such and is awfully weak. If
> we start ten years later, we'll just have to reduce emissions more
> steeply to get to the same end result. It won't be too late, rather
> it'll require a greater effort to get to the same end goal.
To state such a thing without proof is inadequate when you are
questioning an expert in a discipline distinct from your own. In the
present case your assertion appears to me entirely and
straightforwardly incorrect.
mt
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