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ESA Launches GOCE To Map Earth's Gravity
DSG2 sends in an ESA press release which reads in part: "This afternoon, the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite developed by the European Space Agency was lofted into a near-Sun-synchronous, low Earth orbit by a Rockot launcher lifting off from the Plesetsk cosmodrome in northern Russia. GOCE is the first of a new family of ESA satellites designed to study our planet and its environment in order to enhance our knowledge and understanding of Earth-system processes and their evolution, to enable us to address the challenges of global climate change. In particular, GOCE will measure the minute differences in the Earth's gravity field around the globe." One consequence of mapping the planet's geoid in finer detail is that ocean currents can be limned more accurately. This BBC article from 2007 goes into some detail about this application.
GOCE is a gravity measuring satellite -- the spiritual successor to the amazing GRACE pair of satellites from a few years ago.
GRACE works by flying two satellites in the same orbit, one a few dozen miles ahead of the other. By monitoring the distance between the satellites with laser rangefinders, one can measure how strong gravity is -- the more gravity, the faster the satellite goes, so the distance between the satellites grows until the second one reaches the same area. This was the state-of-the-art, and GRACE made some amazing measurements. It was able, for instance, to measure the amount of extra groundwater during flooding along the Mississippi.
But GOCE does it all with one satellite. Where the baseline for GRACE was many miles, for GOCE it is just 50 cm.
Now, if you think about it, in any satellite, the amount of gravity you would feel is zero...or at least, very very close to zero, as you are orbiting inertially. But, really, gravity is only zero right at the center of mass of the satellite. You'd feel a tiny amount of acceleration the further you go. As you go toward the center of the earth, you would be in a lower orbit, and you would be pulled down with respect to the satellite.
GOCE measures this microgravity to rediculous precision. By measuring the difference in gravity affecting two test masses 50 cm apart, it can measure how strong gravity is at that point. It should have much better accuracy, and far better resolution, than GRACE.
GOCE is amazing in other ways, too. It flies very low, to get better resolution. So, it has fins! A satellite with fins, to keep it pointing along the direction of travel. Because there is some tiny amount of air drag at the altitude it is flying, GOCE has a tiny xenon ion engine pushing it along to keep it at the same altitude, and to keep the air drag on the satellite from overwhelming the gravity measurement.
Hats off to ESA, this is an amazing machine!
I love Mondays. On a Monday, anything is possible.
For 24 months, GOCE will collect three-dimensional gravity data all over the globe. The raw data will be processed on the ground to produce the most accurate map of the Earth's gravitational field to date and to refine the geoid: the actual reference shape of our planet. Precise knowledge of the geoid, which can be considered as the surface of an ideal global ocean at rest, will play a very important role in further study of our planet and, with any luck, by detecting subtle changes in gravitational potential, it will be able to provide mankind with its first indirect measurement of your girlfriend's mass.
It actually flies "sideways" though. The upper side of the two big wings always face the sun. The two smaller wings at the back are for aerodynamic stability.
While I'm here, there is more information at the ESA GOCE sites.
You can have both global warming and local cooling.
For instance, one possible effect is that while the average temperature over the whole planet does rise (global warming), the melting of the ice will shutdown the gulf stream and make some countries like Britain colder.
http://en.wikipedia.org/wiki/Rockot
It's a rather small Russian rocket.
I think the term global dimming more accurately describes a separate problem that is sometimes referred to as global cooling. Aerosols decrease the size of cloud droplets, thus increasing the albedo (whiteness) of the clouds. This reflects more sunlight back into space. Its effects have been seen in long-term sunlight brightness studies (in Israel) and in long term evaporation rate measurements (amazingly, evaporation depends on the number of photons hitting the surface rather than just the temperature, so it serves as an independent check of the phenomenon).
It's not such a big deal anymore because regulations were effective at curbing emissions of these aerosols. Unfortunately, it used to act to counter greenhouse gases like CO2...
I think we're talking about different things. You're talking about natural variability, and I'm talking about human-caused climate change. Scientists are aware that both phenomena exist, and based on the research I saw at the December 2008 American Geophysical Union conference, I'm fairly confident that we can tell how much climate variability is due to humans.
Vostok ice core data confirms that for nearly half a million years, the climate has changed cyclically. But in all that time, the maximum CO2 concentration never went above 300 ppm. (It's hit higher levels millions of years ago, but that was a slow and gradual change. Plus the Earth was essentially a different planet back then, with a different solar luminousity and biosphere so comparisons across that much time are tricky.)
I presume you're referring to the Vostok ice core data I just linked. You're right to say that natural variations are cyclic- that graph displays variations that are governed by (among other effects) Milankovitch cycles which are caused by periodic variations in the earth's orbit.
But I'll reiterate the point I made in my original post: CO2 concentrations are at 380 ppm today. That's a level it hasn't hit in the last half million years. If we're seeing natural variability alone, it's quite a coincidence that it occurs right when we started excavating fossil fuels to fuel a billion cars.
Plus, the Vostok data is a little difficult to analyze in this manner, but it seems like at Vostok the CO2 always increased 600 years AFTER the temperature started to increase. At least, that's the way it used to work. Right now, the CO2 concentration is at an unprecedented level but the temperature is barely above normal. Again, that suggests that we're not facing natural climate change, we're dealing with anthropogenic abrupt climate change.
I've read through their reports and rebuttals, and I've not seen any difference between the science they're reviewing and my own work (or the work of my colleagues or my advisor). In fact, some of my personal research results support their conclusions. I guess that means that my dissertation research is just politically motivated claptrap?
Wow. If you politely asked a climate scientist for details of their model, and got that reaction then you were talking to a pretty bad scientist. Alas, PhDs cannot be revoked...
The science isn't obscured from where I'm sitting, and it isn't for anyone within driving distance of a university library. Those biases you're talking about don't make it into the peer reviewed journals like Geophysical Research Letters. I'd recommend those sources over the secondhand sources that you're reading. They sound like horrible sources of information.
Umm... I'm not writing a scientific journal article right now. It's just an online forum. I definitely wouldn't include statements like that in my article submissions.
What a coincidence! I, too, work with climate scientists. And my experience with scientists in general is that they're much less likely to overstate their case than other people. Scientists are more likely to add caveats to their statements, and less likely to make statements of certainty when all that the evidence supports is "strong probability". What you're describing is just the normal way scientists act.
Show me an experiment from a peer reviewed journal article that you think is politicized. I'll review it and get back to you. On the other hand, if you were talking about Rush Limbaugh's editorial about climate science, then I think we mean different things when we use the word "science".