Recently Walt Meier posted about artic sea ice 2010 on WUWT. Good for Anthony for giving Dr. Meier the podium. Meier emphasized that the state of arctic sea ice has changed dramatically. Referring to predictions of this year’s summer minimum in arctic sea ice extent:



The first thing to point out is that none of the estimates approached the 1979-2000 monthly September average of 7.0 million square kilometers. Even the highest estimates were nearly 20% lower. This is a recognition that conditions have clearly changed since the 1980s and 1990s. It is no longer plausible to prognosticate anything near average levels.



So: things have changed.



Meier mentions that several factors affect the extent of sea ice (and its summer minimum), including winds and currents and generally “weather,” but makes it clear that these factors are not responsible for the long-term decline we’ve witnessed. That’s due to warming:



The bottom line is that while winds can make a difference at times, the overriding factor in seasonal and long-term Arctic sea ice decline is that warmer temperatures lead to less ice.



So: things have changed. Warming is the reason.

Another of the notable changes, in addition to simply having less ice, is that the arctic has thinner and younger ice. As Dr. Meier says:



… what we’re seeing is that the MYI [multi-year ice] just is not surviving like it used to. There is now almost no ice older than 4 years old remaining in the Arctic. This is a stark and fundamental change in the character of the Arctic sea ice.



So: things have changed. Warming is the reason. The change is “stark” and “fundamental.”

Is this truly something new, or does it happen all the time? Dr. Meier addresses the common (but faulty) claims that things were pretty much the same in the early or mid 20th century, concluding:



However, this doesn’t mean conditions in the past were anything like today. They were not.



Not only were things in the past not like they are today, they weren’t anything like today. Not.

So: things have changed. Warming is the reason. The change is “stark” and “fundamental.” Over the past century or so things were not anything like they are today.

What about even longer before now? Dr. Meier points out:



the most recent and comprehensive analysis of all available proxy sea ice records, published earlier this year (Polyak et al., 2010 – note that Polyak is a co-author on the 2006 paper), indicates that current total Arctic-wide sea ice extents are likely lower than any time in the last several thousand years and are “not explainable by known natural variabilities”. The data are still sparse, but this is the best information we have at the moment.



Let’s summarize.

Things have changed. Warming is the reason. Stark and fundamental. Last century or so at least, nothing like today. Extent probably lowest in the last several thousand years. Not explainable by known natural variabilities.

It’s glaringly obvious that conditions in the arctic, and especially of arctic sea ice, are some of the strongest evidences of global warming. This isn’t some “urban heat island” effect and it really was not like this back in the 50s or the 40s or any other decade you care to mention, and probably not like this since at least sometime B.C. Things have changed in a fundamental way, unexplainable except by the fundamental change in our atmosphere we brought about via the industrial revolution.

The arctic is only one region of the globe, and its dramatic changes are not complete proof of anthropogenic global warming. But it is strong evidence. Very strong. Damn strong.

So if we’re to talk, seriously, please stop denying that.

You may disagree that global warming is really happening as fast as I think. Or that humankind is the principal cause. Or that the polar bears are endangered. You might think I overestimate the seriousness of the consequences. You may doubt forecasts of sea level rise, you may pooh-pooh any connection with hurricane frequency or intensity. Etc. etc. till the cows come home.

But if you try to tell me that what’s happening to the arctic, and especially to its sea ice, is not damn strong evidence of global warming … then I have to wonder whether it’s possible for us to have a productive dialogue. Because I don’t think you’re a “skeptic.”