The planet’s overall temperature has been climbing upward, but that trend stalled during the early 2000s — and now scientists think they can explain why. Several studies suggest that tiny sulfur-rich particles called aerosols, which shield the Earth from the sun’s incoming rays, are to blame.
Some of those particles come from volcanic eruptions, such as the Soufrière Hills volcano in Montserrat that has been puttering along since 1995. Although such eruptions aren’t as dramatic as the 1991 eruption of Mount Pinatubo in the Philippines, which cooled the whole planet for several years, the aerosols from several small volcanoes are enough to add up to a cooling influence (SN: 8/13/11, p. 5). Also playing a role are coal-burning power plants, particularly in Asia. Sulfur particles coming from the plants mostly counterbalanced the warming produced by their carbon dioxide emissions (SN: 7/30/11, p. 17).
Overall, the buildup of carbon dioxide is expected to keep sending temperatures upward — a trend observed by three independent research teams and confirmed this year by yet another analysis performed by the Berkeley Earth Surface Temperature group. —Alexandra Witze
Riches from on high Many of the precious metals mined today were delivered via a bombardment of stony meteorites that pummeled the Earth and left craters on the moon billions of years ago (SN: 10/8/11, p. 11).
Chiseled from below Molten material rising from beneath is chiseling chunks of rock off the bottom of the Colorado Plateau, possibly explaining why this area has lifted upward over millions of years (SN: 5/21/11, p. 12).
Record high tie Analyses from NASA and the National Oceanic and Atmospheric Administration rate 2010 as tied with 2005 for the hottest year on record, followed closely by 1998. Others rank 2010 as the second hottest (SN: 2/12/11, p. 17).
Waistline growth Ice melting off Greenland and Antarctica has changed the shape of the Earth, making it more bulgy at the equator, scientists find (SN: 7/16/11, p. 13).
Tipping point An analysis reveals that a small change in rainfall or other factors can cause an ecosystem to switch abruptly between forest and savanna (SN: 11/5/11, p. 5).
Climate meddlers Humans removing trees to work the land put nearly 350 billion metric tons of carbon into the atmosphere by 1850, researchers suggest (SN: 4/23/11, p. 17). Another team argues that Christopher Columbus and other New World explorers may have set off a series of events contributing to Europe’s Little Ice Age (SN: 11/5/11, p. 12).
Polar flip The occasional swapping of the north and south magnetic poles may be tied to plate tectonics; when landmasses have bunched together, Earth’s magnetic field has begun flipping soon after (SN: 11/19/11, p. 9).
Quick colonizers Fossils dating to 530 million years ago suggest that Earth’s first animals colonized freshwater earlier than thought, soon after diverse forms appeared in marine habitats (SN: 6/4/11, p. 9).
In clusters Researchers argue that Japan’s catastrophic March earthquake was part of a spasm of quakes, the second spasm since 1900 (SN: 5/7/11, p. 5).
Early meat-eater Researchers uncover a fossil of a pint-sized meat-eater named Eodromaeus, or “dawn runner”, that dates to 230 million years ago, the dinosaurs’ earliest days (SN: 2/12/11, p. 10).
Extinction causes New studies suggest that gassy volcanic eruptions (SN: 1/15/11, p. 12) and acidifying oceans (SN: 10/8/11, p. 10) could have contributed to the mass extinction at the end of the Permian period, some 250 million years ago.
Big blowup Geologists find evidence for one of the biggest volcanic eruptions ever, in southern Java 21 million years ago (SN Online: 8/6/11).