TAMPA, Fla. (WFLA) — The Great Barrier Reef in Australia – the largest coral reef tract in the world – is enduring another mass bleaching event. This is the fourth in the last seven years.

Aerial surveys over the past few weeks found that 60 percent of the reef has severe bleaching. This is on top of the 30% of the reef that was killed during a mass bleaching event in 2016.

The Great Barrier Reef is 1,500 miles long on the Northeast Coast of Australia. Right now ocean conditions are dangerous for coral with a build up of heat, after weeks of above normal water temperatures.

The coral are being harmed by an ocean heatwave in the region. That’s because coral can only tolerate a narrow window of water temperatures. When the water gets too warm, they easily stress, turn white and sometimes die. This is called bleaching.

The warming oceans have also dramatically impacted coral reefs here in Florida. In the Florida Keys, only 2% of the coral cover is left, down from nearly 40% in the 1970s. This is due to warm water and nutrient pollution making coral more susceptible to bleaching and disease.

Globally, about 50% of the coral cover has disappeared in recent decades due mostly to stress from warm water. The upper oceans have warmed around 2 degrees Fahrenheit since 1900. This is because 90% of the excess heat from human-caused climate change is stored in the oceans.

According to this study, the energy equivalent of seven Hiroshima bombs per second was stored in the ocean last year.

Climate scientists warn that the majority of tropical coral will be lost before 2050. This loss can be minimized, though, if global warming is slowed.

However, the Earth’s oceans are going in the opposite direction. The image below shows just how quickly ocean heatwaves are increasing over the past 10 to 20 years.

Global ocean heatwave days have increased dramatically over the past couple of decades due to human-caused climate change.

Since 1925, annual global ocean heatwave days have increased by 54%. Since 1980, major ocean heatwaves have become 20 times more common due to human-caused climate change. In the coming decades, studies warn that regions of the ocean will be in a state of permanent heatwave.

In the graph below, from the study “Projected Marine Heatwaves in the 21st Century and the Potential for Ecological Impact,” the authors show just how dramatically global heatwave days are rising and will continue to rise in the coming decades. I added the approximate number of days for ease of comprehension.

The above projection is for a moderate emissions scenario. In other words, if humans continue to produce heat-trapping greenhouse gases at a moderate pace into the future. If humans ratchet up emissions even more, ocean heatwave days will only increase.

The bottom line: The health of the oceans are being jeopardized by rising temperatures. The world is rapidly losing the precious ecosystem of coral reefs, the foundation for much of the life in the ocean. Time is running out to save them.