Don't tell Andrew Bolt

Less Ice In Arctic Ocean 6000-7000 Years Ago

Andrew Bolt and others have been posting a lot about the Arctic ice melt (and apparent recent rapid re-freeze), so he's bound to take encouragement from this article that suggests that the Arctic ocean had much less ice 7,000 years ago too, before our modern CO2 increase, of course.

My general impressions are as follows:

* the issue of the coming and going of Arctic ice is clearly not fully understood.

* of course there are AGW advocates who leap too quickly onto anything that appears to prove greenhouse warming. Those who wildly overstate the case as to the short term effects of AGW (such as Tim Flannery, Al Gore, etc) are usually not the scientists themselves.

* most climate scientists were actually somewhat cautious in what they said about the big 2007 melt. At Real Climate, for example, they said:

The disappearance of the ice was set up by warming surface waters and loss of the thicker multi-year ice in favor of thinner single-year ice. But the collapse of ice coverage this year was also something of a random event. This change was much more abrupt than the averaged results of the multiple IPCC AR4 models, but if you look at individual model runs, you can find sudden decreases in ice cover such as this. In the particular model run which looks most like 2007, the ice subsequently recovered somewhat, although never regaining the coverage before the meltback event.

* even if the current round of substantially lower than average summer ice is caused by completely different cyclic factors from CO2 increase, it may be a worry if the cycle continues because of its potential to have an enhancing effect on any warming that is caused by CO2 in coming decades.

Methane coming out of the Arctic ocean may well end up being a major concern too. We will hear more about that soon, it seems.

* Above all, remember my official line is that ocean acidification is a big enough issue alone to limit CO2 anyway. Doesn't matter if temperatures go up or down: a huge gamble with what will happen to ocean ecology is in play if CO2 is allowed to soar to levels not seen for millions of years.