On 9th May 2013, atmosphericCO2 concentration hit 400 ppm. The number means there are 400 molecules of carbon dioxide in the air per every million air molecules. This happens first time in human history.The National Oceanic and Atmospheric Administration (NOAA) on 10th May, 2013. Carbondioxide and other greenhouse gases warm the planet by absorbing the sun’s energy and preventing heat from escaping back into space. Once emitted, CO2 added to the atmosphere and oceans remainsfor thousands of years.
Thus, climate changes forced by CO2 dependprimarily on cumulative emissions, making it progressively more and more difficult to avoid further substantial climate change. Dr James "Jim" Hansen calculated global warming traps heat equal to energy by 400,000 Hiroshima atomic bombs explosion/ day. Al Gore urged on 10th May "Take this day and the milestone it represents to reflect on the fragility of our civilization and and the planetary ecosystem on which it depends……….We must take immediate action to solve this crisis. Not tomorrow, not next week, not next year. Now."