The Blob (Pacific Ocean) the surface waters of the mid-latitude Pacific Ocean flipping from a cold phase to a warm phase in a cycle known as the Pacific decadal oscillation (PDO). This poorly-understood change happens at irregular intervals of years or decades. During a warm phase, the west Pacific becomes cooler and part of the eastern ocean warms; during the cool phase, these changes reverse. Scientists believe a cold phase started in the late 1990s and the arrival of the Blob may be the start of the next warm phase. The PDO phases may also be related to the likelihood of El Nino events.
Environmental threats to the Great Barrier Reef consequential rise of sea temperatures, gradual ocean acidification and an increase in the number of "intense weather events". Hughes writes of "the demonstrable failure of the state and Commonwealth" to address the issue of climate change in his August 2014 article. Furthermore, a temperature rise of between two and three degrees Celsius would result in 97% of the Great Barrier Reef being bleached every year. Reef scientist Terry Done has predicted that a one-degree rise in global temperature would result in 82% of the reef bleached—two degrees would result in 97%, while three degrees would result in "total devastation". A