5. Global Warming
2010 was the warmest year on record, with global temperatures 1.12 degrees Fahrenheit hotter than the average for the 20th century, provoking ever more volatile weather patterns and violent climate events like floods, typhoons, tsunamis and extreme blizzards.
As temperature rises, food will become scarce, air quality will worsen and diseases will spread. And as an investigation by the International Institute for Strategic Studies revealed, up to 65 countries are likely to lose more than 15% of their agricultural output by 2100. The World Health Organization considers that at least 150,000 people are already killed by climate-change related issues each year, mostly in the poorest countries.