Sea Ice Hyperbole

There have been a number of reports recently, in the blogosphere and elsewhere, about arctic sea ice. From the septic side come statements that arctic sea ice is on the increase, pointing to a cooling planet and contradicting the reality of global warming. From the supporting side there are statements that arctic sea ice loss has so accelerated due to storms in the frozen north that we’re sure (or nearly so) to break the record for lowest arctic sea ice extent again this year.

Open Thread #5

For discussion of things global-warming related, but not pertinent to existing threads.

Yet More CO2

This has turned out to be “CO2 week,” with numerous posts on the topic already. I figured I was done with it for a while, but in comments to the last post, some questions were asked which deserved a detailed look at CO2 measurements. One reader asked why the increase is so linear in spite of the fact that human emissions have increased so much — shouldn’t CO2 levels be accelerating? I responded that the increase wasn’t nearly as linear as the graph might suggest, that in fact CO2 growth had accelerated. Another reader asked whether or not the amplitude of the annual cycle had changed, as one of the graphs suggested. I replied that yes, it had.

A (brief) Tale of Three Sites

There’s been quite a bit of discussion about CO2 data lately. Most of it has centered around Anthony Watts’ nonsense and the recent revision to the Mauna Loa monthly averages. What’s been lacking is a look at what the data are telling us about the changing CO2 concentration of the atmosphere. So let’s take a “quickie” look at monthly average CO2 data from three different locations: Mauna Loa, Barrow (Alaska), and South Pole station.

Revising Mauna Loa CO2 Monthly Data

The first report of the monthly average Mauna Loa CO2 estimate for July 2008 was lower than expected; the reported value was 384.93 ppmv, with a “seasonally adjusted” value 384.54. In less than a day the figures were revised so that the new reported value is much more in line with the prevailing trend. Anthony Watts noted the change, which caused quite a stir in reader comments. Many (if not most) spouted conspiracy/fraud theories of the first magnitude, even after the reason for the change was explained by the scientist in charge of the data.

To AR1 or not to AR1?

I’ve been keeping my eye on daily data for arctic sea ice extent (but not obsessing about it). These daily data begin June 21, 2002, so they cover only a brief part of the era of satellite observations. Nonetheless, the other day I decided, just for kicks, to estimate the trend rate of northern hemisphere sea ice extent anomaly, using only the daily data from June 21, 2002 to the present. The slope of the linear regression line was about what I expected it to be (arctic sea ice extent anomaly is declining at around 128,500 km^2 per year), but to my surprise my little trend analysis program indicated that the result was not statistically significant!

New Kid in Town

I found another climate-science website which shows great promise: More Grumbine Science. I saw a link to it on RealClimate, and took a look. I was struck by two things. First, the post I read was clear, comprehensible, and to the point without being at all hostile. Second, the blogger’s goal is:

I’ll be trying what seems to be an unusual approach in blogs — writing to be inclusive of students in middle school and jr. high, as well as teachers and parents (whether for their own information or to help their children). To that end, comments will have to pass a stricter standard than I’d apply for an all-comers site.

I haven’t seen much of it yet, but what I have seen fulfills the stated purpose, admirably.

There’s only one drawback: a dearth of comments. I hope it’s not because he hasn’t got much readership! This effort deserves encouragement and even popularity. So I recommend that you take a look, and if you like what you see, leave a note to that effect.

Jump!

A while ago I posted about the fact that the dip in Mauna Loa CO2 data for March of 2008, as noted in a post by Anthony Watts, was really nothing out of the ordinary. The “event” was a drop in the seasonally adjusted CO2 level, a circumstance which is not very common but by no means extraordinary.

Spencer’s Folly 3

Part 3: Fast and Slow

We’ve had a look at a simple model of the influence of climate forcing on global temperature (the zero-dimensional one-component model), and we’ve noted that when it comes to feedback (in the usual sense) in the climate system, some are reasonably fast (water vapor takes a few weeks or so to equilibrate) while others are slower (ice takes years to decades or longer to melt), as well as a method to use observed data for surface temperature and net radiation imbalance to try to estimate climate sensitivity.

Spencer’s Folly 2

Part 2: Climate Forcings and Climate Sensitivities

Solar energy enters earth’s climate system in the form of radiation from the sun; the vast majority of it is short-wave (SW) radiation. Some of that solar energy is simply reflected back to space (the fraction reflected back is called earth’s albedo). Energy is also radiated away as infrared, or long-wave (LW) radiation. If we imagine an envelope surrounding the earth, at the top of the atmosphere, we can also imagine measuring the amount of energy coming in through the envelope and the amount of energy going out. If these quantities are equal, then the earth is in energy balance. If not, the difference between the amount coming in and the amount going out is the net radiation imbalance at the top-of-the-atmosphere (TOA).