Scientists know that certain gases trap heat and act like a blanket to warm the planet. One of the most important is carbon dioxide (CO2), which we release into the atmosphere when we burn fossil fuels oil, coal, and natural gas to generate electricity, power our vehicles, and heats our homes. As we overload our atmosphere with carbon dioxide, more and more heat is trapped and Earth steadily warms up in response. How do we know? The scientific evidence is overwhelming. Trends in temperature readings from around the world show that global warming is taking place. Every one of the past 40 years has been warmer than the 20th century average. 2016 was the hottest year on record. The 12 warmest years on record have all occurred since 1998.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: Every one of the past 40 years has been warmer than the 20th century average. 2016 was the hottest year on record. The 12 warmest years on record have all occurred since 1998.