Ocean warming is primarily caused by greenhouse gas emissions from burning fossil fuels, which trap solar energy in the atmosphere. More than 90 percent of this trapped heat has been transferred to the oceans since the 1970s. Increasing heat in the water has been shown to stress individual organisms, alter the process of cellular respiration, and threaten the survival of coral and other organisms. Also, the ongoing absorption of excess carbon dioxide, an important greenhouse gas, by the oceans has increased the acidity of the water.