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...carbon dioxide gets most of the attention when it comes to greenhouse gases, but it's not the only one that's warming the earth. Methane - a gas that is found in everything from landfills to cow stomachs - also plays a big role. Although global methane-emissions levels are much lower than CO2 emissions, pound for pound methane is a more powerful greenhouse gas; a ton of it has 23 times the warming effect of a ton of CO2. And methane, like CO2, is on the rise thanks to us: about 60% of global methane emissions come from man-made...
...should hit before 1990. They threaded the region with seismometers and other sensors, then sat back and waited for the telltale signal that would give them notice of the coming rumble. The quake never occurred in the 1980s, nor in the 1990s. It was not until 2004 that the earth in the area at last moved again. And what did all the high-tech hardware reveal? Nothing...
...capture wonderful information about the earthquake afterwards," says Blanpied. "But the earth gave no indication with a foreshock or an electrical signal or a water signal or anything else. It demonstrates to us what we've already learned: earthquake prediction, if it can be done at all, is very difficult...
That's not to say geologists aren't making headway. Instruments that detect P waves are a good example. Earthquakes set off two kinds of seismic vibrations: body waves, which move through the interior of the earth, and surface waves, which move on top. The fastest of the body waves is the P wave, and it's thus the first to travel from the epicenter to a seismic station where it can be detected. P waves don't give you a whole lot of notice, but even a little bit can help. In California, gas lines in many homes...
After 9/11, al-Awlaki swiftly condemned the hijackers. A PBS NewsHour program in October 2001 shows him in a sermon criticizing U.S. foreign policy but arguing that it did not justify killing Americans. On the contrary, he told PBS, "Every nation on the face of the earth has a right to defend itself and to bring the perpetrators to justice...