Thursday, February 19, 2009

Encyclopedia Brown

Yesterday my son said, "I solved my first case today."


"So-and-so said that he went to the moon with his dad, but I knew he was lying because the space suits are too big for a kid to wear."

Perhaps we need to slow down on reading Sobol's books to him...

Tuesday, February 10, 2009

Sunday, February 8, 2009

Why do soap bubbles float in the air? A follow-up

My dear mother-in-law (the good kind) asked in a comment why soap bubbles seem to float in the air, all the while maintaining their (approximate) original shapes.

She also asked if my son actually understands what I post. I (usually) go into more detail here than I do with him. He is, after all, only six years old. I haven't quizzed him. This is more to get him excited about asking "why?" in a more permanent way than the "why? phase" all 3-5 year-olds go through.

So, the soap bubble maintains its shape because there's not enough force on it from outside (or inside) influences to overcome the cohesive forces that keep the water together. Once any one spot is broken, the entire bubble will collapse because surface tension is no longer competing with itself.

The bubble floats as long as there is some force (usually a breeze, a child's breath, etc.) pushing it up even slightly. Whenever gravity times the bubble's mass is the dominant force, the bubble falls because the buoyancy force being applied by the atmosphere is too weak compared with that downward force.

Thursday, February 5, 2009

Climate change is irreversible...but not (completely) unavoidable

Some of you may have seen this in the press. If you watch TV, I'm sure you've seen it being refuted by quacks who don't understand basic heat flow, much less the most simple of GCMs.

Climate scientists with the NOAA have modeled the expected globally averaged warming (I'll come back to that global average in a bit) for the next 1000 years given a range of CO2 (and only CO2) emission profiles. For each run of the model, the CO2 is emitted for some period of time and then ALL emissions are shut off completely. The model continues to run until the year 3000.

A few things to note from this paper and from other works:

  1. Atmospheric CO2 obviously increases the global average temperature.
  2. No matter which emission profile they use, the CO2 does not go back to pre-emission levels for a long, long time. Let me repeat that. CO2 has a 1/2 life in the atmosphere; the time it takes to remove the CO2 is much greater than the time it takes to add the CO2.
  3. As the oceans warm up, removal of CO2 takes longer.
  4. Global average temperatures follow a similar profile: quick increase to the peak, very slow decrease once CO2 emissions are stopped.
Right now we are somewhere above 385 parts per million by volume (ppmv) CO2 concentration in the atmosphere, as measured at Mauna Loa. The IPCC estimates that we'll hit more than 600 ppmv CO2 by 2100.

According to this new paper, if we hit 650 ppmv sometime this century, we'll have ~2.5 degrees C of surface warming (globally averaged), and the sea level rise JUST due to thermal expansion will be around 0.5 meters. By 3000 AD, the globally averaged temperature will still be ~2 degrees warmer than the beginning of the industrial age, and the seas will NOT go down; by 3000, they'll have increased by another 0.1 or so meters.

That may sound like nothing or it may be frightening, depending on your familiarity with global averages. claim that this is one of the coldest winters on recent record for much of the eastern US and therefore all the scientists in the world are wrong about global climate change. Of course right now, Australia is experiencing the hottest summer on record, but that doesn't seem to factor into the deniers' moronic ramblings. In case you hadn't noticed, I'm raving and ranting.

The important thing to understand is that over the last 150 years or so, our global average temperature has already increased by 1 degree C, the globally averaged sea level has already increased by ~200 mm, and the northern hemisphere snow cover has decreased by a few million square km since about 1920. Since 1970, there have been no more than a few small places in the antarctic circle that have escaped an increase in temperature. No land mass with monitoring equipment has avoided an increase in temperature.

Some arguments people use against human-caused increases in temperature:
  1. "We are also in the midst of a natural warming trend that began about 1850, as we emerged from a 400 year cold spell known as the Little Ice Age." This myth was started by the idiot author Crichton.
  2. "the well-known phenomena of the Medieval Warming Period–when, by the way, it was warmer than it is today"
  3. "there is a total absence of any recent acceleration in sea level rise".
  4. "current Arctic temperature is no higher than temperatures in 1930s and 1940s"
  5. The sun is going through a natural lull in sunspots, which increases its output, increasing Earth's temperatures.
  6. The "elite", "establishment" scientists are just afraid of being shown to be wrong about global warming.
  7. There is no consensus that there is global warming.
Let's take these on one at a time.
  1. There are no peer-reviewed, scientific articles that do not acknowledge that anthropogenic CO2 is required to help explain the warming.
  2. In fact, pretty much published articles about historical and geologically recorded temperatures come to the opposite conclusion; it's warmer now than it has been since the pliocene.
  3. All published studies of the sea levels in recent history come to the same conclusion; sea levels are higher now than they have been in recorded history.
  4. Current arctic temperatures may be warmer now than in recent history, but all reliable climate models show that the higher latitudes have larger swings in temperatures; variability is higher at higher latitudes.
  5. If this were the case, then the entire atmosphere would be warmer. In fact, it's just the lower atmosphere that's warmer. CO2 stays in the lower atmosphere, right where we've recorded warming.
  6. Global climate change proponents had to fight the establishment to get published in the first place. There is consensus precisely because the data and models are quite convincing.
  7. There is complete consensus that the globe is warming, that anthropogenic causes are forcing it to warm, and that we're on the verge of (if not past) the point where we have no chance to stop a positive feedback loop causing dramatic and irreversible climate changes.
Now, just because climate change is irreversible does not mean it's unavoidable. Yes, we've already hit the point where something like 2 degrees C of warming over pre-industrial age is unavoidable, but if we can limit the CO2 concentrations to pre-1990 levels, we should be able to handle this warming. If we get much higher than 450 ppmv, we're subjecting our children, their children, and at least 1000 years worth of children to having to deal with drought, extreme weather, higher ocean levels, drought-caused starvation throughout much of Africa and parts of South America, permanent drought in much of the southwest US, droughts in Europe and Asia, etc. Diseases are going to get worse and last longer; for example, cases of plague have been shown to increase as temperatures increase.

We CAN stop this, but we need people who think further into the future than the next quarterly report to act and have influence on our governments.