According to Bill McKibben, the first author to write a book on global warming, 350 is the most important number in the world. It represents 350 parts per million CO2 which is the atmospheric CO2 concentration to which the the earth's atmosphere must be reduced if life on earth is to avoid huge climate changes. At the present time, the earth's atmosphere is well past this with 394 ppm CO2.
To scientists' surprise, this 387 ppm CO2 is causing major changes in the earth's climate including rising sea levels, increasing acid in sea water, melting glaciers in the Himalayas, the Andes, and the Sierras, drought, floods and violent weather, and the spread of malaria and dengue fever. As glaciers melt and disappear, the rivers they feed will dry up too, and millions of people will be without water. According to a report by the Global Humanitarian Forum, an annual conference led by Kofi Annan, the former United Nations Secretary General, global warming is causing more than 300,000 deaths and about $125 billion in economic losses each year. Read the key findings of the U. S. Global Change Research Program.