"Will pluto and neptune ever collide since thier orbits seems to cross, if so when? and if so what would that collision be like? "
I've noticed in many of the answers you state that the far more pressing threat to our planet is global warming. However, I'm wondering what specific threats humans will face if the carbon dioxide levels continue to increase, in the worst-case scenario. What can ordinary people be doing to address the problem of climate change?
We are already seeing the impacts of global warming. The rapid shrinking of the arctic icecap has opened the northeast passage to shipping, and within a decade it will also open the northwest passage. The melting arctic ice and permafrost are exposing oil and mineral deposits for exploitation, but also endangering arctic wildlife. Most important, the melting of arctic snow and ice darkens the surface, leading to rapid warming during the summer and a shift in weather patterns over North America. Loss of ice from Greenland and Antarctica is also contributing to sea level rise, making destructive storms like Sandy much more likely. The recent severe droughts in the U.S., Russia, and Australia can also be traced to global warming. Within a few years, the accelerating loss of ice from the Himalayas will lead to the summer drying up of several great Asian rivers, which are the source of water for more than a billion people in China, India, Pakistan, and Bangladesh. By the middle of the century, the loss of water from the Colorado River basin and the aquifers in northern Arizona may make Phoenix and Las Vegas uninhabitable, while rising sea levels and stronger storms are likely to lead to the permanent evacuation of much of New Orleans, New York, Miami, Amsterdam, and Venice. By late in the century we can expect to lose Los Angeles, Seattle, Houston, London, Rotterdam, Mumbai, Shanghai, Tokyo-Yokohama, Dhaka, and many other large cities, as well as several small island nations. We don’t know how fast the warming and sea level rise will take place, so I can’t predict the dates for these events, but the direction is inescapable unless we stop polluting the atmosphere with carbon dioxide and methane. In the next century we might entirely lose the great icecaps of Greenland and Antarctica, which would make the situation much worse than I have described above.
Astrobiology Senior Scientist
December 27, 2012
- After ten years and more than two thousand posted answers, David Morrison retires from answering Ask an Astrobiologist. Read his departing letter here
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