Fiction atmospheres and “flood” climates

So it appears that Florida has now decided to actually teach science in their science classrooms. After a February 19th vote, the United States science curriculum made the improvement from worse to bad, now allowing the young padawans to learn evolution in class. The infamous motto of “Teach the controversy” (like gravity and cell theory) won 4-3, but of course with the scientific caveat that “it’s just a theory.”; my guess is that lecture begins right after discussing “hypothesis,” “theory,” “law” definitions in chapter 1. Now, reading this new Nature article, it looks like the Institute for Creation Research wants to grant online master’s degrees in science education in Texas. But I loved the next line, which reads, “The ICR accepts the Bible as literal truth on all topics. According to its website, the palaeoclimatology class covers “climates before and after the Genesis Flood””. Maybe someone like Paul Reiter can moan about the IPCC not covering creation paleoclimates in the report…too bias I suppose.

Chris Colose even finds a book here. There you go, now we don’t need to hear about “CO2 lagging temperature” anymore. From our interpretation of the “young ice cores” the CO2 levels and temperatures fluctuated significantly over just a few thousand years…we’ve even gone through several ice ages since the global flood. Aside from the obvious climate pitfalls of a young ice sheet hypothesis, the other argument reads like “there were WW2 planes found deep in the ice sheet” so it must be a young ice sheet, but this discounts the fundamental fact that glaciers flow and so ice at the bottom is much more compacted than ice at the top. This means one meter of ice core at the bottom represents a much longer amount of time than one meter of core near the top.

So what about that global flood?

As far as I know, the leading creation hypothesis for a global flood (or the source of water for that flood) is a canopy of water in the atmosphere. What kind of climate implications would this vapor canopy have?

First of all, the atmospheric pressure caused by the amount of vapor in the atmosphere needed to flood the Earth would by far and away overwhelm that of even Venus, and would be similar to that of the deep ocean. This would have made a pancake out of Noah and company. Modern day air pressure is roughly 1 bar. It only takes a few centimeters of precipitable water to saturate a column of air at Earthlike temperatures, and much less to saturate air aloft, because of the adiabatic lapse rate cooling with altitude. It would take kilometers to create the waterworld of Noah.

There would be many effects on temperature. For the greenhouse effect, water vapor in the mid to upper troposphere is more important than water vapor near the ground. Low clouds or vapor have a modest longwave effect because the temperature is similar to the surface. In contrast, high clouds and upper level water vapor has a considerable longwave effect. If you’re to add a cloud in the boundary layer, from the perspective of the top of the atmosphere (TOA) there is very little change on the planet because the temperature of the lower clouds is basically that of the surface, and since from the TOA perspective, the planet is in energy balance you don’t need to get warming. The low level stuff “looks” just like the surface, and only wavelengths through the “atmospheric window” get by the lower levels. Because they look radiatively like the surface, the energy out changes little (in fact the large influence from a low cloud is on the incoming side, from the albedo effect).  High stuff has much more of a longwave effect because the temperature is considerably colder, and you start to introduce water vapor where there was none.  In the case of clouds, they will block some IR that comes from all lower layers of the atmosphere.  The water vapor canopy would need to extend to the upper atmosphere, and in doing so would create an extremely large greenhouse effect.  However, it would also have a cooling component by increasing the planetary albedo from sunlight reflection. The net effect would surely be to warm, but no large climate jumps are apparent in the proxy records, and no evidence for any global flood. At sufficiently high pressures, the diatomic gases will also act as greenhouse agents from collision-induced absorption.

If there are no other greenhouse gases, then the OLR for a dry case (zero relative humidity) is just σTg^4. But, at larger RH, the curve of the OLR (T) begins to flatten at high temperatures, making the climate much more sensitive to radiative perturbations (reminder of the Kombayashi-Ingersoll limit in Greenhouse effect part 2. Not exactly a runaway effect, but much hotter. Further, when vapor condenses into water, it releases the same amount of heat which originally turned it into vapor. The water vapor canopy would release enough latent heat to burn up the guys on the ark, and the millions of animals with them. The temperature changes at the surface would be a competition between latent heat of vaporization and increased longwave absorption, and reduced sunlight at the surface.

A further question for the vapor canopy assuming a habitable Earth is how enough water got there? Because of the Clausius-Clapeyron relationship, with relationship between vapor pressure and temperature being

ln P1/P2 = dHvap/R [ (T1 – T2)/T1T2]

where P is the vapor pressure. Essentially, for the amount of vapor needed to flood the world, the temperature would need to be much, much hotter (not habitable) to prevent condensation, since the saturation vapor pressure increases nearly exponentially with T. At Earth temperatures and pressures, water diminishes rapidly with height because of temperature drop, and saturation in the atmosphere quickly leads to a cloud, and precipitation.

There are some other theories for the source of water, like runaway subduction and bursting from the crust. None stand up well, but it is also neat to see the “what ifs” in climate and other geological thought experiments.

FICTION ATMOSPHERES IN THE MOVIES

Just as ridiculous as the overhanging vapor canopy, are some other neat climates presented on television. Of course, at the top of the list is The Day After Tomorrow. In this movie, there is a “shutdown” of the North Atlantic circulation (to their credit, they didn’t say Gulf Stream). This is not unreasonable, but what follows is an overnight freeze down to at least the middle of the United States. What can we say about the THC shutdown often discussed on the internet? A rapid, large reduction in north Atlantic circulation appears very unlikely (10% chance, according to IPCC) but surely not impossible (it happened before). Unfortunately, putting an exact number on the freshwater flux required for a shutdown is not possible right now; although the broad picture of deepwater formation is known and modeled, the details are not, and such details are required to get quantitatively accurate numbers. There is a decline though over time in models (maybe next century for a shutdown); what happens with a shutdown depends on when the shutdown is, because if you got one tomorrow, then there would be cooling in certain places of the North Atlantic (not global), but if you get one next century, then that is likely to be overwhelmed by the increased CO2. In any event, it would most certainly not cause an ice age. Because ocean circulation transports heat from the warm tropics to the cooler high latitudes, a reduction of that transport would cause anomalous cooling in certain areas (more snowblowers in Europe from harsher winters), but not glacial conditions. Moreover, because of the immense volume of the water and the time it takes to gain/lose heat, as well as the response time of ice, it would take a minimum of decades to get abrupt climate changes. Even if the sun shut off, you don’t get “The Day After Tomorrow” tomorrow. “Abrupt” is a word compared to geologic changes. If I recall right, there were also hurricanes forming in the arctic…that just doesn’t happen because of the low SST’s.

One interesting planet is in Star Wars Episode 2, where our cloner friends, Jango Fett, and Obi Wan enjoy a planet which I get the impression is covered in water, and is characterized by constant rainfall. There is no silicate weathering, no volcanoes, so depending on the solar conditions, the planet will swing into a runaway greenhouse or a snowball planet in a geologically short period of time. As I mentioned with the water vapor canopy, there is not that much water in a column of air, and at a habitable range of temperatures you cannot get never-ending rainfall. To sustain evaporation would require solar input of thousands of W/m2 which would bring the planet into a runaway greenhouse state.

The very dry but habitable planets such as Tatooine (Luke’s home) or in the movie Dune are also good for a short time. Because of the very high albedo of sand, the planet must be greenhouse-enriched or close to the sun (or two suns in Tatooine’s case). Unfortunately, with no water on the surface, the silicate weathering processes that remove CO2 from the atmosphere will not occur. When CO2 dissolves in water it forms a weak acid which reacts with silicate minerals to form carbonate minerals (e.g. limestone), but with no water, CO2 will just accumulate in the atmosphere until it is all lost from the interior…this will soon make the planet too hot for life. It might seem like a good idea then that Muad’Dib comes along and fulfills the prophecy of bringing water to Arrakis, but introducing an ocean to an already habitable planet is likely to be even more catastrophic. On Earth, if it were not for the greenhouse effect from water vapor, we would surely be locked in a snowball world; creating a much more sensitive planet by bringing in a water vapor effect to the Dune-situation would likely bring the planet into a runaway state.

Luckily, only one of these states of affairs claims not to be fiction.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s