Thursday, March 22, 2012

Technical followup on the simplest climate model

Tuesday I took up reconsidering the simplest climate model.  This time, I'm trying to get rid of the annoying bit of having to know the planet's albedo (reflectivity) in order to find its temperature.  Instead, to have some fundamental relationship between temperature and albedo, so that everything in the model is either a fundamental constant (the Stefan-Boltzmann constant), or a fundamental principle (black body radiation, this new albedo-temperature relationship).  No great surprise that some readers have already caught on to some of the issues I wanted to talk about.

One, which I'll continue to defer for now, is the fact Arthur mentioned that what this model works with is the earth's blackbody temperature -- its temperature as seen by how much energy it releases to space -- rather than surface temperature.  Since we all live somewhere towards the surface, surface temperature is the more interesting number.  What the difference between what the model can give us and what we're truly interested in does is to suggest that an important theoretical issue is to develop an understanding of how planetary blackbody temperature relates to surface temperature.  Or (scarier) to see if it does relate in any consistent way.  But heads up that such a discussion will be coming.  Finding these issues, and seeing why they're important, is one of the purposes of the ultra simple models like this.

More issues were brought up by Nick Barnes, who also provides Python code for running your own version (see his first comment for that link).  I hope you've spent some time with either the spreadsheet or Nick's Python (use a 2.7 set-up, per Nick's comment on Tuesday) or do so now, as you read this post, and some more as you decide whether and how it makes sense.  The spreadsheet is in OpenOffice format (.ods) but I've opened that with MS Excel previously.  If you can't, please let me know.

Now, in saying 'issues', I don't mean that there's any terrible comment being made.  Rather, it is the truth that even very simple models like this one have some subtleties that you should explore before drawing your conclusions about nature.  I'll take up the more physical side of interpretation next, but first let's take a look at some of the technical issues.

Tuesday, March 20, 2012

Return of the simplest climate model

The simplest climate model balances the energy leaving the earth to space with the energy coming in from the sun.  If the climate is not changing, these two will be the equal.  As long as climate is not changing rapidly, a modifier we can make quantitative, they'll be very nearly equal.  It turns out that even for fairly rapid climate changes, by standards of geological history, the earth is very close to that balance.

I'm actually going to take a different approach this time around.  Key to deciding how much solar energy comes in to the earth (more precisely, the climate system) is knowing the albedo -- what fraction of incoming energy gets bounced right back out.  That makes the model unsatisfactory to me on a theoretical basis.  We have to know the earth's albedo to compute its blackbody temperature (the temperature which provides that balance).  The problem with that is that the albedo itself is a climate term.  The state of the climate -- how many clouds we have, how large the sea ice pack is, how large the continental ice sheets and deserts are, how green the forests are -- determines the albedo.  Knowing either the blackbody temperature or the albedo is a climate observation.  Given one, we can compute the other from that simple model.  And, which is a good point, we can compare our computed temperature with the observed.

Is it possible to remove or weaken that restriction on the albedo?  And if so, can we learn anything about the climate system?  Yes, and yes.

I'll do something that would be quite improper if I were to claim that it was exactly true, but which will turn out to be extremely educational.  Namely, I will make up a relationship between albedo and earth's blackbody temperature. 

Monday, March 19, 2012

Tempest in an ice pot

There's a bit of a tempest at WUWT and Steven Goddard's regarding satellite data on sea ice.  And there are some anxious comments about FOIA filings to be made regarding data that's been hidden.  I have to concede that it takes a bit of a historian to know what's really being said in the IPCC first report regarding sea ice.  (see page 224, figure 7.20 for the source of the tempest.)  Fortunately, I am such a historian :-)  To give away the ending: There's nothing terribly dramatic going on in the sea ice or the history. But I'll take the chance to talk history of sea ice analysis.

The tempest arises because the figure shown there has sea ice cover in the early 1970s in the Arctic being notably lower than it was through the 1980s.  (Curiously, no interest is displayed at either site regarding the Antarctic being far higher in the 1970s than the 1980s.)  If the figures were commensurate with the satellite observations such as those used in the Cryosphere Today anomaly figures, it would suggest that the Arctic coverage of the last few years wasn't as remarkable as we've generally thought.  (On the other hand, it would also say that the 'record high' Antarctic coverage of recent years was not particularly high at all, a point being neglected at both sites.)

Friday, March 16, 2012

Jupiter and Venus

If you've been looking in a generally westerly direction in the early evening, you've, no doubt noticed the two exceptionally bright 'stars'.  Those are Jupiter and Venus, also exceptionally close to each other.  On one view, they're awfully close -- about 3 degrees, or 1/30th of the distance between directly overhead and the horizon.  To a different view, however, they're very far apart -- about 6 full moons would fit between them.

Technology keeps advancing.  In the 1970s, it was about all I could do to get a photograph of a nearly full moon through my telescope.  A fair amount of patience was needed to get the focus right, avoid contaminating light, and so forth.  Below is my phone photo of Jupiter (the fainter one) and Venus.  I was in a well-lit parking lot, and it wasn't much past sunset (hence the bright lower portion of the photo), and had just aimed the phone in the general direction of the planets.


I'll invite you all to contribute your own photos of the planets. 

Thursday, March 15, 2012

25 years ago this summer

I realized today that 25 years ago was my first summer in Washington DC area.  At the time, that summer set many of the local records for hottest summer, longest streaks of hot days, and many variations on that.  I've asked a friend who is local and extremely in to weather observation* how recent summers would compare, and he said, with little hesitation, 'hotter'.  What used to be record-setting is now not very noticeable.

I made the challenge/request on my twitter feed (http://twitter.com/#!/rgrumbine), but for here: I'd be interested in seeing a widget+ of some kind that would track this year versus 1987 in DC and Chicago.  Plus, of course, any other cities you're interested in.  1987 was, at the time, an extremely hot year.  For another comparison, say summer 1981?  1982 was part of the major El NiƱo of 82-83, so perhaps would not be a good year to reference.

For keeping an eye on weather by way of twitter, I like the Capital Weather Gang for Washington DC, and Tom Skilling for Chicago.  I'm sure there are a bunch of other good sites even for those two cities.  I just have personal connections to those two.  I was secretary to the local AMS chapter some eons back when Skilling was the chapter president.

For a mailing list to discuss weather on, send an email with the phrase 'subscribe wx-talk' to LISTSERV@LISTSERV.ILLINOIS.EDU Mailing lists, I'll add, are not web pages, or web sites, or chat rooms.  Different thing, with different strengths.

Tuesday, March 6, 2012

Open Lab 2013

The Open Lab is now open again, taking nominations for posts from October 2011 through October 2012.  See Bora Zivkovic's note making the original announcement.

Also see the 'open lab 2013'  link on the right.  Feel free, of course, to nominate posts of mine.  But, more importantly, I encourage you to nominate science posts you like, regardless of where from.

Thursday, March 1, 2012

The Return of Questions

It's been a long while, but at last here's a question place post for you all to ask about what's on your mind.  Particularly if what's on your mind has something to do with thinks I know about :-)