The Bulletin of the Atomic Scientists, which 60 years ago began keeping tabs on humanity’s temporal distance from self-annihilation with the concept of a “Doomsday Clock,� apparently found things sufficiently dire to nudge the minute hand forward two clicks, indicating that we are now “five minutes to midnight� — or Doomsday. [Source]
Is that a surprise? The reasons-
We stand at the brink of a second nuclear age. Not since the first atomic bombs were dropped on Hiroshima and Nagasaki has the world faced such perilous choices. North Korea’s recent test of a nuclear weapon, Iran’s nuclear ambitions, a renewed U.S. emphasis on the military utility of nuclear weapons, the failure to adequately secure nuclear materials, and the continued presence of some 26,000 nuclear weapons in the United States and Russia are symptomatic of a larger failure to solve the problems posed by the most destructive technology on Earth.
As in past deliberations, we have examined other human-made threats to civilization. We have concluded that the dangers posed by climate change are nearly as dire as those posed by nuclear weapons. The effects may be less dramatic in the short term than the destruction that could be wrought by nuclear explosions, but over the next three to four decades climate change could cause drastic harm to the habitats upon which human societies depend for survival. [thebulletin]
Nuclear threat is something easily perceived but when it comes to global warming, people take it lightly. Its because the effects of global warming isn’t apparent on a short time scale. Climatic change that has taken place all over the world, be it the there was a snow fall in Dubai or the draught in cheerapunji which was once the place of highest rainfall in the world or even the deadly rains here in Chennai. All these are related to global warming.
Well now the question is what is global warming and how it caused? Global warming is basically the increase in earth’s average temperature. The atmosphere has this unique property to let the lower wavelength sun rays to pass through and also the higher wavelength reflected rays back from the earth. But certain emissions, which are called greenhouse gases, like carbon dioxide and water vapour absorb this emitted shorter wavelength rays and thus raise earth’s temperature.
CFCs (Chloro fluro carbons), which were used in refrigeration before, were banned because of this very reason. CFC concentration has drastically increased lately and a ban was a must. Now refrigeration is being designed to use HCFCs (Hydro Chloro Fluro Carbons). The best thing about HCFCs is that their retention time in the atmosphere is 12 years, much lesser as compared to 100 years of that of CFCs. HCFCs are to be banned my 2020.
Carbon dioxide, whose retention time is 200-450 years!, contributes the second most to global warming. This is why the rush is towards use of cleaner technologies . Carbon trading is going to be the next big thing as far as international dealings are concerned. A limit is going to be set on the maximum amount of carbon a country can produce and if it exceeds then it has to either buy that extra amount from a country producing less or pay the money to the governing body. It has happened once that US was asked by the Canada to pay for its loss of plantation due to the carbon from US industries. Some Chinese carbon has been detected in US so we will have our fingers crossed 
Well it is going to be a big surprise to many of you that water vapour contributes the most to global warming. But the good thing is that its retention time is only for few days. So even clean technologies like Fuel Cells contribute to global warming. So next time you boil water, think about its future consequences on the coming generation 
Here is a graph showing how global temperature has changed in the last 150 years
Even this small 0.6 degrees rise in temperature can cause glaciers to melt thus flooding river banks.
This is how political events have affected the doomsday clock
Picture of the day! [Source]
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