## Tuesday, August 4, 2009

### It's Too Late, I Already Doomed the Earth

A few days ago I received an Amish Friendship bread starter. For those of you who don't know it is just a basic sourdough culture that you grow and feed for 10 days and then you make bread out of it. The catch is that the instructions instruct you to separate out 4 cups of starter material before you make the bread and put each cup in a bag and pass it along to some friends (hence how I got it). So there we have the problem and ultimately the doom of not just the US but the whole earth!

According to the instructions the starter will grow in volume by a factor of 4 every 10 days. Thus the increase in the volume of the starter can be expressed as 4^n where n is the number of 10 day periods between bread makings. Given this unchecked growth this starter which started out as l cup of material (roughly 236.6 ml) will grow and grow until it has consumed the whole earth! To give you a timescale to see what could happen, let us consider 1 year. 1 year has about 36 10 day periods which means by the end of one year we will have 4^36 cups of material. After a brief calculation we find that this equals roughly 1.12 BILLION CUBIC KILOMETERS of material!!!!!!!! This is enough to cover the whole earth with ~1.5 MILES of sourdough starter! And that is just the starter! (not counting the bread made from it) all in less than a year!

So yesterday I passed out the starters which means I have roughly 100 days before I am buried by it. I estimate that it will hit Illinois and Texas sometime by the end of this year, Colorado shortly after that and California a short time after that. Plan accordingly.

On a serious side note, something like this can be used to show the holes in the logic behind a lot of sensationalism about global warming. It seems that most (all) of the dire predictions about global warming assume unrestricted growth or extreme extrapolation with no consideration for limiting factors, negative feedback, or even other (non-negative) possible outcomes. Sort of like several of the end of the world (US) predictions mentioned on the site Nick told us about. One scenario had the Great Plains turning into a vast desert. While desertification my be a problem to some extent, this is a prime example of what happens when we take a "what if..." scenario too far. The scenario is only possible if we completely disregard how climate actually works.

1. Ryan, you are right that assumed unchecked growth predicts effects far worse than we see in reality. It is an art to come up with good ~piecwise functions that keep track of changing circumstances.

Second, have you heard of the Erdos Number: the number of collaborators between you and publishing a paper with Paul Erdos?

Well, let me define the "QuantumLeap42 Number": The number of friends between you and getting a batch of the Amish Freindship Bread Starter from QuantumLeap42.

Ryan, I'll tell you my QuantumLeap42 number once I get one.

2. Ryan,

Having talked with some people that do climate models, the extreme scenarios that some in the popular media like to wave around tend to be ones where the climate models have experienced some sort of exponential growth for a short time that jumped the solutions into another basin of attraction (one where the great plains become the Gobi desert, for example). In nature there are brief periods of exponential growth, they are simply saturated by some nonlinear feedback mechanism. Those nonlinear feedback mechanisms are the least understood parts of our climate and the hardest to model.

That being said, there are probably negative feedback mechanisms as well that may accelerate changes in ways we don't understand, so it could be worse than we think. That's why a lot of government funding for atmospheric research is being pumped into improved observations and models of the global climate.

And I've already solved the problem of the Amish Friendship Bread Starter destroying the world. All we have to do is turn Kansas into a barren desert and Colorado is saved (sorry Waco, you're toast).

3. Well, that gives a new meaning to "America's Breadbasket". Fortunately, however, UIUC campus will be saved by the correspondingly exponentially growing population of crazed psycho rabid killer squirls (which are plentiful this time of year in Urbana), which, being natives of local Amish country, are selectivly pre-disposed to eating Amish Friendship Bread Starter (they'll also eat the bread itself, but they frankly prefer rye). Therefore, Colorado need not worry about being buried under a mile of bread starter, only about being invaded by an army of crazed midwestern squirls looking for rye.

On a serious note, extrapolation is a big problem, not just in climate models, but in all sorts of areas of science. Knowing exactly how far a model or a trend can accurately be taken is one of the biggest tricks in science. It really seems to be more of an art to me.