-carbon dioxide levels are increasing in the atmosphere
Carbon dioxide is known to be a greenhouse gas, which means that increased levels of carbon dioxide in the atmosphere could lead to global warming. This could have serious environmental consequences for the entire world. Scientists also think that humans may be responsible for the increases, from such things as cars, industry, and the burning of the rainforests. , leading to higher amounts of carbon dioxide in the air.
Credit:http://earth.rice.edu/mtpe/atmo/atmosphere/hot/anom_99/co2_in2.html
-The planet's temperature is rising
Over the past 130 years, the global average temperature has increased 1.5 degrees Fahrenheit, with more than half of that increase occurring over only the past 35 years. The pattern is unmistakable: The 12 warmest years on record have all occurred since 1998 and every one of the past 38 years has been warmer than the 20th century average.
Credit: http://www.ucsusa.org/our-work/global-warming/science-and-impacts/global-warming-science#.V8xZS1uLTcc