http://nai.arc.nasa.gov/astrobio/index.cfm NAI Ask an Astrobiologist The current global warming on Earth is extremely unlikely to lead to a runaway greenhouse effect, although to be honest scientists are not sure exactly what triggered the runaway greenhouse on Venus. But that does not mean that we can ignore the more modest warming that is happening now. What is a very small increase in global temperature of a few degrees could profoundly change our environment, for example by raising sea levels and flooding most the the largest cities on Earth. These changes do not threaten life on Earth, but they do threaten our economy and way of life. Climate changes are defined as those that take place over decades, not the shorter-term atmospheric effects that we call weather. The current global warming has been taking place for more than a century. Superimposed on the general warming are shorter-term changes, such as cooling after the injection of aerosols into the atmosphere by the eruption of Mt Pinatubo in 1991, and higher temperatures in the late 1990s associated with El Nino effects. The El Nino probably plays a part in the leveling of global temperatures in the past few years. The two hottest years on record are 1998 and 2005. While the directly measured temperatures have leveled, the large-scale effects of global warming are continuing, including melting of mountain glaciers and of the icecaps in Greenland and the Antarctic, and the dramatic shrinkage of the Arctic Sea ice cover. <br /><br /> The is a lot of misinformation and disinformation about global warming on the Internet, driven in part by political and economic issues. Following in italic are some “red flag” arguments from global warming deniers that can help you spot disinformation. (1) <i>We should not worry about carbon dioxide, since the main greenhouse gas is water vapor.</i> This is partly true, but it is the carbon dioxide (and methane) that control the structure of the atmosphere. Water vapor content is highly variable and essentially follows the carbon dioxide. (2) <i>What we are seeing is “natural variations”, caused primarily variations in solar output.</i> This is false; we have been monitoring solar energy for a quarter century, and the small variations are taken into account in all the climate models. (3) <i>The apparent increase in temperature is an artifact, caused by the fact that much of the data is from cities, which are warmer than the surroundings.</i> This is also wrong; the “heat island” effect has been corrected in plots of global temperatures. (4) <i>While temperatures seem to have been rising in the lower atmosphere (the troposphere), they are dropping in the stratosphere.</i> People who say this don’t realize this is the expected signature of greenhouse warming. If there were an external cause, such as increased energy from the Sun, both troposphere and stratosphere would be heating. (5) <i>This is no big deal; temperatures are actually lower than they were in the Medieval warm period.</i> This is wrong; over at least the past few thousand years, temperatures have never been as high as they are today. (6) <i>More carbon dioxide is good, since it makes plants grow better.</i> Yes, if we could increase carbon dioxide without greenhouse heating, this might be true, but high temperatures are not good for most plants, and the increase in carbon dioxide is also acidifying the oceans, which can be very bad, for example by destroying coral reefs. (7) <i>There is no consensus; many scientists disagree about global warming.</i> Hardly any peer-reviewed scientific papers have been published by dissenters in the past decade; the dissenter are mostly not climate scientists, and they have offered no alternative models to explain the data. The national academies of science in all of the industrialized countries have endorsed the findings of the Intergovernmental Panel on Climate Change, which represents a strong scientific consensus on both the reality of global warming and the challenges it implies. <br /><br /> <i>David Morrison<br /> NAI Senior Scientist</i> http://nai.arc.nasa.gov/astrobio/astrobio_detail.cfm?ID=7789 Charged particles trapped in the magnetosphere of Jupiter create a high radiation environment when they strike the surfaces of the two inner Galilean satellites, Europa and Io, or when they hit a spacecraft operating in these parts of the jovian system. The most extensive study of Europa was carried out by the NASA Galileo spacecraft, which repeatedly approached this moon. However, the spacecraft spent most of its time farther from Jupiter, just plunging briefly into the heavy radiation areas for each flyby of Europa. Near the surface of Europa, the radiation doses are several times higher than in the Van Allen Belts of the Earth’s magnetosphere. Studies carried out a decade ago of a possible Europa orbiter indicated that the spacecraft would survive only about a month once it went into orbit 200 km above the surface. More recent studies, however, suggest that it is possible to use radiation-hardened and shielded electronics to extend the lifetime of an orbiter substantially. For a Europa lander, a few meters of ice provide effective shielding, so if we could get below the surface, the high radiation levels would not be a problem. <br /><br /> <i>David Morrison<br /> NAI Senior Scientist</i> http://nai.arc.nasa.gov/astrobio/astrobio_detail.cfm?ID=7798 I thought that by now I had heard every weird idea about 2012, but these are new. First, there is no planet alignment now or in the next few decades. Even if there were, it would have no measurable effect. The public interest in alignments comes from astrology; this is not a scientific concept at all. Second, we are not about the cross the galactic plane (or galactic equator), but even if we did it would not change gravity on Earth. Earth gravity is entirely related to the mass of our planet, not to its location in the Milky Way. It interests me that as it becomes obvious that Nibiru is a no-show, people come up with so many alternate explanations for a coming doomsday. However, I still receive at least one question a day about Nibiru, most of them with supposed (but completely undocumented) photos. For example, several people sent me photos of the Sun taken through the thick dust clouds in eastern Australia a few weeks ago and said they were of Nibiru. I suppose that once one buys into the end of the world, rational thinking becomes more difficult. <br /><br /> <i>David Morrison<br /> NAI Senior Scientist</i> http://nai.arc.nasa.gov/astrobio/astrobio_detail.cfm?ID=7758 On September 19 there was a research rocket launch from Wallops Island (on the Eastern Shore of Chesapeake Bay) that released a luminous cloud into the upper atmosphere. This was widely reported in the press. For instance, Newsday wrote "Staff at several National Weather Service offices in the Northeast received calls of strange lights after NASA launched a rocket from Virginia, a meteorologist with the weather service in Upton said. And along the East Coast, reports of the bright, cone-shaped light poured into weather stations and news organizations, a Boston TV station said on its Web site." Associated Press wrote "The space agency said it launched the Black Brant XII on Saturday evening to gather data on the highest clouds in the Earth's atmosphere. About the time of the launch, dozens of people in the Northeast started calling local television stations to report seeing strange lights. The calls came from as far away as Boston, which is about 380 miles northeast of the launch site." From CNN "A series of spooky lights above parts of the northeastern United States Saturday sparked a flurry of phone calls to authorities and television news stations. NASA said strange lights seen in the Northeast on Saturday were caused by an experimental rocket. CNN affiliate stations from New Jersey to Massachusetts heard from dozens of callers who reported seeing it.” <br /><br /> <i>David Morrison<br /> NAI Senior Scientist</i> http://nai.arc.nasa.gov/astrobio/astrobio_detail.cfm?ID=7671 The simple basic fact is that nothing astronomical is happening in 2012. All the talk about 2012 doomsday is a hoax. The more detailed “straight answers” are in the 20 questions and answers at the top of this webpage. If you haven’t done so yet, please click on the “summary” and read them. <br /><br /> <i>David Morrison<br /> NAI Senior Scientist</i> http://nai.arc.nasa.gov/astrobio/astrobio_detail.cfm?ID=7646