Earth’s hottest periods occurred before humans existed. Those ancient climates would have been like nothing our species has ever seen.

The annual average concentration of carbon dioxide (CO2) in the atmosphere stood at 395.3 parts per million (ppm) in 2013—a 27 percent increase compared to conditions before the Industrial Revolution. On May 9, 2013, the daily average concentration of CO2 surpassed 400 ppm for the first time at the Mauna Loa Observatory in Hawaii.

Decision Maker's Toolbox Annual Greenhouse Gas Index

Since 2004, researchers in NOAA’s Global Monitoring Division have released the Annual Greenhouse Gas Index: a single value that compares the total warming effect of each year's concentrations of heat-trapping gases to 1990 levels.

CarbonTracker is a tool for modelling sources and sinks of carbon dioxide. Users can download the code, carbon dioxide data, and the tool's carbon flux estimates to conduct their own analyses or to help improve the system.

Like a prehistoric fly trapped in amber during dinosaurs' days, airborne relics of Earth's earlier climate can end up trapped in glacial ice for eons. How do climate scientists turn those tiny relics into a story about Earth's ancient climate?

The Amazon Rainforest is a living warehouse for carbon dioxide. As climate changes, the lush tropical ecosystems of the Amazon Basin may release more carbon dioxide into the atmosphere than they absorb. NOAA scientist John Miller talks about how climate conditions in 2010 and 2011 created a natural experiment on how drought affects the Amazon's carbon balance.

From Sept. 8-11, the National Association of State Energy Officials will hold its Annual Meeting at the Hilton DeSoto in Savannah, Georgia.

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