Dan’s Wild Wild Science Journal

I saw an interesting press release about a paper this past week.  The headline was along the lines of “Climate Change Increasing Space Junk”.

Say what? I can predict the comments now that this will get. “You blame everything on global warming!”

Well, let’s look at what the paper really says and why they reached the conclusions they did.

I know one of the authors of this paper. Judith Lean is a solar physicist at the U.S. Naval Observatory. Dr. Lean is one of the scientists who has shown very conclusively that the sun is NOT responsible for more than a small part of the warming temps. over the last 50 years (in spite of numerous political web sites online that claim otherwise).

She quickly responded and the story behind this is really fascinating.

The Atmospheres layers- NASA/U. Cal. (Living With a Star)

First some basics.

The atmosphere has 5 main layers.

Most weather happens in the bottom 10km called the troposphere. From around 10km to 50km is the Stratosphere, and above that is the mesosphere and thermosphere.

The thermosphere extends several hundred miles above the surface into what most people think of as “space”.Temperatures in this layer of the atmosphere are several thousand degrees, but there is so little air that if you were to stick a hand out of a spacecraft, it would feel very cold. (Just before the blood in your hand boiled).

The Stratosphere is getting colder.

It’s common knowledge that the planet’s temperature is rising. The troposphere is warming. What is not commonly known is that the stratosphere is cooling for the same reason. Greenhouse gases warm the troposphere and cool the stratosphere.

Image courtesy Dr. Ben Santer LLNL. (personal comm.) Santer has done research into the fingerprints of climate change. Santer is an expert on climate fingerpints. His research is actually quite famous if you follow climate science. Click to get a larger size.

The reasons for cooling aloft are rather complex but John Cook of Skeptical Science has an understandable explanation of it here. Gavin Schmidt of NASA GISS has a more detailed and more complicated explanation here.

The sun is responsible for very little of the observed warming over the past century.

The Solar Cycle.

The big player here is the sun. It goes through an 11 year cycle of sunspots. When the sun is producing a lot of spots it puts our quite a bit more energy in the extreme ultraviolet portion of the electromagnetic spectrum. This causes the thermosphere to heat up and increases the density at any given altitude. When the sun is at the quiet end of the cycle, just the opposite occurs and satellites in orbit run into fewer molecules (mainly oxygen).

Since we just had a very long lasting solar minimum, you would expect the thermosphere to have cooled and so it did!

So what you ask?

Satellites and space junk are running into fewer molecules, so they will stay in orbit longer. In most cases this is bad, since there is a HUGE amount of junk up there. If you are on the ISS, it is good news. You do not need a boost back to your preferred orbital altitude by the space shuttle as often.

What the authors of the paper ”Record‐low thermospheric density during the 2008 solar minimum

J. T. Emmert,1 J. L. Lean,1 and J. M. Picone2

(Geophysical Research Letters- published 19 June 2010)

discovered was this. The thermosphere density hit a record low during the recent solar minimum. Besides that, the drop in extreme ultraviolet radiation (EUV) does not seem to be enough to account for all of the drop.

Density of the Thermosphere at 400 km over the last 4 solar cycles. from the paper referenced in the text and ctsy Judith Lean. F10.7 is the solar flux at a wavelength of 10.7cm. this is a good proxy for Extreme Ultraviolet Radiation (EUV) from the sun.

The big discrepancy.

This last solar cycle saw a 29% drop in thermosphere density. Only about 10% of this drop can be blamed on less EUV radiation from a quiet sun. It’s estimated that about 3-6% can be added for extra co2 from humans in the atmosphere. (remember that co2 causes warming near the surface but cooling in the upper atmosphere.)

So what about the 13-16% of the density drop that is not accounted for.

Here is what the authors say about it:

Internal MLT(mesosphere and lower thermosphere) processes

possibly in combination with longer‐term anthropogenic

changes are therefore appealing candidates for explaining

the density changes. In addition to enhanced radiative

cooling by CO2 and CH4 (CH4 is Methane, another greenhouse gas, that is increasing), changes in two other MLT minor

species, O3 (O3 is Ozone) and H2O, also influence thermospheric densities, but trends in these latter species were

small during cycle 23 . Prior work has established that greenhouse‐gas

cooling of the thermosphere is enhanced during solar

minima, a relationship that the prolonged (by more than a

year) 2008 minimum may have amplified. If changes in the

radiative properties of the MLT are responsible for the

temperature and composition changes of the upper thermosphere,

then the density anomalies may signify that an as yet

unidentified climatological tipping point, involving energy

balance and chemistry feedbacks, has been reached.

There is a LOT of space junk up there. ctsy. ESA.

So the short of it all is this- Climate change AND a quiet sun are causing space junk to stay in orbit longer. The data also indicates that some fundamental changes might be underway in the atmosphere.

You might wonder how the density of the thermosphere is estimated. Simply by how quickly satellite orbits decay. How is the sun’s EUV radiation measured? Directly since 2002 but before that the noise of the sun at a frequency of 10.7 cm is used. The data indicates that this proxy itself may be starting to change for unknown reasons.

I wanted to tell this story because it’s a nice example of how scientist use data to discover new things. You would not think at first that there would be any connection to how fast satellites fall out of orbit to climate change, but now you know there very likely is.

Remember in your junior high science book where it says that scientists make observations and then formulate a hypothesis. This is true, but it rarely works in the exact order or as neatly as your book implied!

Active region on the sun from NASA's Solar Dynamics Observatory. (Upper left corner of the sun)

CME today from strong sunspot. Courtesy NASA Solar Dynamics Observ.

Space weather experts at NOAA and NASA have been monitoring a very active sunspot over the last few days.

This area has produced several Coronal Mass Ejections (CME). These flares can cause trouble with radio communication and even cause power outages if they hit Earth. Satellites can be especially hard hit. Past solar flares have crippled communication satellites.

A really big flare could cause billions of dollars in damage to the electrical grids and stop HF radio communications for hours.  Commercial passenger flights over the North Pole use HF radio to keep in contact with air traffic control. When there is a large flare the HF frequencies are not usable and these flights must take a longer route.

This sunspot is not facing Earth so these flares have not affected us. The flare is, however,  turning in our direction. If it stays active, then we could see a geomagnetic storm. More than likely the only major effect will be a display of the Aurora in high latitudes.

The folks at NOAA’s Space Weather Prediction Center are only forecasting a 1% chance of a big class M or class X flare, but if you live in the high latitudes, be on the look out for a display of the Aurora Borealis.

Tropical Storm Alex is looking quite healthy this afternoon and has finally started moving. There seems to be a growing consensus among the models that Alex will come ashore in Mexico, well south of Brownsville, Texas. The latest movement, along with the new guidance, is a bit left of the last NHC track.  Look for a shift the forecast a little southward in the next advisory.

Click for full resolution- Courtesy USNRL.

It is not out of the question that Alex could reach Category two strength before landfall, and the swells from the storm will likely impact the oil slick operations well across the Gulf.

Update: The NOAA 18 Polar orbiter has a a sensor called the Advanced Microwave Sounding Unit. This allows a radar type image of the storm and can be very helpful in determining storm structure. Looking at the latest pass, it does not show an eye yet.

The rest of the tropics seem quiet right now.

Meteorologist Alan Raymond from our office will be on board the Air Force recon. aircraft for the overnight fixes. He may very well be flying into a hurricane. Alex is very close now…

Click the image below to see in high res.

Image taken Saturday afternoon June 19 2010. NASA Aqua satellite at 500 meter resolution.

It sure seems to be getting bigger…

Dan

Update: The pic below was Orange Beach last weekend. Image from Karen Parden.

Click the image above for full resolution.

The images from the NASA Terra and Aqua satellites have at times shown the oil slick in the Gulf very dramatically. Today’s is one of the best I have seen. The sun angle was just right. You can also see a smoke plume at the very bottom. This is where they are burning the oil off the top of the ocean. (That seems very strange to have to write.)

How much is leaking? See my previous post.

June 9, 2010 from NASA Terra satellite. True colour image. Click for higher resolution.

The newsroom tells me quite a lot of oil washed up on Orange Beach, Alabama today…