Phil Plait, he of the Bad Astronomy blog (it’s on Slate these days, so you know he’s for real), is a fun read.  He reports all kinds of interesting astronomical stuff, and I enjoy reading his work.  On some days, however, he insists upon breaking wind about non-astronomical matters, and in many of these blog entries he gets to be quite annoying.  Can you say: specialist trying to comment outside his area of specialization?  That’s Phil Plait from time to time.

Global Warming Deniers

Phil gets really exercised about people who won’t take global climate change seriously.  He seems to regard them as the moral equivalent of Holocaust Deniers.  A recent post of his concerning old arctic Ice melting is a case in point.

Phil has posted about his Denier fixation before, and while I definitely apprecaite his frustration (I have to deal with people who can believe the craziest things, too), what does he expect to accomplish?  He writes:

We don’t know how long it will be before we see our first ice-free Arctic summer, but it may be as soon as 30 years. Most likely it will be somewhat longer; I hope so. But the bottom line is that the ice is going away due to global warming, and as it does we’ll see worse and worse effects from it. The time to stick our heads in the sand about this is long, long gone.

OK, let’s assume that climate change is real, and that we’re warming up.  Further, let’s assume that the warming is caused by human activities (something that I am still not convinced of).  What about it?  More to the point, what do we do about it?

Enact the Kyoto Accords?  Everyone stop breathing? Kill all the cows?

Well, cattle are responsible for enormous amounts of methane, an even better greenhouse gas than carbon dioxide, so they have it coming.  Clearly.  And lest PETA put out a contract on me, I’m joking.

When was the last time something like this happened?  It might have happened during the so-called Medieval Warm Period (MWP), a period lasting three hundred years from 950-1250 AD.  I have been unable to determine if the warming effects included an ice-free Arctic Ocean or not, and what I’ve read suggests that the warming was not global.  I guess some scientists prefer to call this period the Medieval Climatic Anomaly. And apparently during this time the southern hemisphere was experiencing other effects than increased warmth – Antarctica was colder than today, for example, and the tropical Pacific was cooler and drier.

And then there’s the Roman Warm Period!  This proposed period, RWP, is less well attested than the MWP.  But the point is, this period from 250 BC to 400 AD was another time in which global climate got frisky, it seems, much the same way during the MWP.  And in neither one of these periods were the Vikings or the Romans driving SUVs or selling carbon credits to the Huns.

So, Who’s to Blame?

Phil Plait is one of many would-be Cassandras who is desparately trying to get our attention about how Global Climate Change is going to Kill Us All.  And ironically enough, from the viewpoint of the Cassandra Chorus, we have met the enemy and He is Us (with apologies to Walt Kelly).  I’m not convinced, of course.  In this game of correlation and causation, who would I prefer to blame?  The cows, of course.  There are now more cows upon the face of the earth than there have ever been before upon the face of the earth.  If you can’t see the obvious correlation there isn’t much I can do for you.

But joking aside, and quite frankly I don’t give a darn if we humans are driving the climate change or not, look at this chart of global temperatures over the last 12,000 years (the chart from the Wikipedia article on the Holocene Climatic Optimum) :

What do you see there?  Notice that modern times is on the right side of the chart (the right edge is 2000 AD).  You see the humps of the MWP and RWP, ocurring at around 1,000 and 2,000 years ago respectively?  You see the right edge of the chart show temps about in the same neighborhood as the MWP and RWP?  And further, that as we move off the chart to the right, the temperature line goes up to near 0.5 degrees.  Now, that’s hot, but notice that it’s only just a little hotter than it was 8,000 years ago!  In short, we’ve been here before.  Is it perhaps too early to panic?  Well, perhaps not, since temperatures now are hotter still — off the chart to the right, in fact, they’ve popped up dramatically to over 0.5 degrees (see the note there for year 2004?).

But I do wish to have you consider the entire chart.

See how the temperatures fall very dramatically off as we go backwards pass 10,000 years?  That, my friends, is the last glaciation period.  It’s warmed up since then, yes?  But I want you to lay a ruler, figuratively, along the middle of that squiggly line starting at around 8,000 years ago where the temperature line crosses 0 degrees, and end up at about the midpoint of the upward trending squiggle, at about -0.25 degrees.  What slope do you see on your ruler?  That’s right!  Downwards!

In other words, up until just very recently, since the end of the last glacial period, 8,000 years ago when we were at a peak in temperatures, we’ve been trending colder, not hotter

And here’s something you may not be aware of: we are not yet out of the last Ice Age.  I can hear your eyelids snap open in surprise at this, so I will repeat myself: we are not yet out of the last Ice Age!  We are presently in a period known as the Quaternary Glaciation, which started 2.6 million years ago and hasn’t ended yet.  The only reason why you’re not sitting on a huge pile of ice reading this is because we happen to be in what is called an Interglacial Period.  This one even has a name: the Holocene Interglacial, “Holocene” being a fancy scientific name for “modern times”, in case you’re wondering.  And do you know what the paleoclimatologists were doing in 1972?  They were worried that we were heading out of the current interglacial and into the next stage of glaciation.  Or, in other words, they were worried about global cooling.  There were at the time several articles in popular magazines reporting on this worry; can you remember back that far?  The climatologists felt that since interglacial periods tended to last about 10,000 years, and we were 10,000 years into the current interglacial, things were about to start getting seriously colder — and the data on the chart above tended to bear them out.  Since then they have changed their minds, however.  The increase in atmospheric CO₂ has given good cause to believe that the trend is reversing (and recent temperature trending confirms this).  In short, while we could have been heading out of the current interglacial period and into some serious ice, this won’t happen after all because — wait for it — we’ve been dumping enough CO₂ and other greenhouse gases into the atmosphere to hold off the next glaciation period another 15,000 years!  And if we can just get the greenhouse gas level up to twice what it is now, we will delay the next glacial period up to 60,000 years!  Yay!  Does this mean that I have now changed my mind about the climate change being human-caused?  No, I’m still not convinced, but I will allow the possibility.  We aren’t the only thing blowing out greenhouse gas — I am convinced the situation is very complicated.

Now, what would you prefer: being dumped into the deep freeze, or being warm and toasty?  I don’t know what course others might prefer, but give me warm summers and a mild winter.

You see what this means, of course.  We need more cows.

For a follow-up post see: Global Climate Change One More Time.