By: CobblyWorlds

CobblyWorlds — Sat, 26 Jan 2008 05:28:11 +0000

I agree Tom,
2007 will probably be notable for some time. In particular due to the events in the Arctic.
The Potsdam Institute of Physics already consider the Arctic ice cap to have tipped. http://www.pik-potsdam.de/infodesk/tipping-points
For what it’s worth I agree, we are almost certainly in a transitional period to a seasonally ice free Arctic, with a much thinner ice cap through the winter (although the winter extent will very probably remain large). As to how fast this transition will be: Models for the IPCC showed seasonally ice free at the end of the 21st century. But this is generally agreed to be wrong. Most like Serreze point to 2030, Wadhams points to before 2020, and Maslowski between 2010 and 2015 – which can be taken as the lower bounding. So we have any time between 2015-2030 as the earliest first occurrence of summer ice free Arctic.
Given the role of the Arctic in Northern Hemisphere climate, e.g. jetstream position, this is something we need to watch. However although there is reason to expect climate impacts from a severe reduction in Arctic ice, it remains unclear what the exact impacts will be. I am happy to be on record, both here and elsewhere, that we will see IPCC regional change projections over-run by the shifts in precipitation patterns due to the Arctic changes. Some areas may benefit, some will not, overall it’s a worrying situation with >6bn mouths to feed.
I have to strongly disagree with John Howard when he says “Negative feedback is the norm. The older the system, the truer this becomes. The climate is a very old system.”
That is not correct. The Earth is not in a reducing energy state like Mars, the bisosphere has an active and ongoing role in our planet.
The amounts and potentials of feedback actually vary with time. For example leading into an ice age the build up of ice sheets is a slow process (you can only accumulate a year’s ice from snow as a result of a year’s snow fall surviving a year). However leading out of an ice age you can lose more than a year’s accumulation of glacial ice by melt processes. Hence the asymetry in the time-axis, e.g. http://www.brighton73.freeserve.co.uk/gw/paleo/400000yrfig.htm
It is clear that the direction of change impacts the nature of the feedback, and it’s strength.
Similar time asymetricality occurs in human impacts, if you move a rain band (such as the preciptation due to the Hadley cells) you can lose good farming land in a decade, but a precipitation increase in a formerly arid region will take much more than a decade to become good fertile farmland.
Furthermore John claims “The Anthropogenic Global Warming theory is a dying theory.” This is not the case in the scientific literature, which is where the meaningful consensus is to be found. All that said, I’m bored of so-called sceptics, so will merely suggest to John that we leave the ongoing physical process to answer his doubts.
I did format – apologies if lost (not formatted in preview anyway).

By: John Howard

John Howard — Wed, 16 Jan 2008 20:52:11 +0000

Sure thing Tom – you’re welcome.

By: Tom

Tom — Wed, 16 Jan 2008 15:52:31 +0000

Sure thing John – thanks for the comment.

By: John Howard

John Howard — Tue, 15 Jan 2008 13:04:44 +0000

The positive-feedback, tipping point argument is an analogy, not a fact. Positive feedbacks are quite rare in the natural sciences. Negative feedback is the norm. The older the system, the truer this becomes. The climate is a very old system. Claiming to know that positive-feedback tipping points are approaching in climate science is pure bluff and science fiction. They are counter intuitive and counter factual.
The Anthropogenic Global Warming theory is a dying theory. The tipping point scare is the latest attempt to save it. Essentially the argument says, “Maybe the facts don’t support us now, but they will suddenly tip in our direction and then we will be right. Just you wait!”
The tipping point that has come in 2007 is that AGW is no longer taken seriously by enough knowledgable people for it to survive as a viable theory.

Comments on: Climate Change 2007: Credible Science, Tipping Points, Feedback, and the Great North

By: CobblyWorlds

By: John Howard

By: Tom

By: John Howard