Oceans are warming faster

Heat trapped by greenhouse gases is raising ocean temperatures faster than previously thought, according to a new research which shows that earlier claims of a slowdown or "hiatus" in global warming over the past 15 years were unfounded.

Ocean heating is critical marker of climate change because an estimated 93 per cent of the excess solar energy trapped by greenhouse gases accumulates in the world's oceans.

Unlike surface temperatures, ocean temperatures are not affected by year-to-year variations caused by climate events like El Nino or volcanic eruptions.

"If you want to see where global warming is happening, look in our oceans," said Zeke Hausfather, a graduate student at the University of California (UC) Berkeley, in the US. "Ocean heating is a very important indicator of climate change, and we have robust evidence it is warming more rapidly than we thought," said Hausfather.

The new analysis, published in the journal Science, shows trends in ocean heat content match those predicted by leading climate change models, and overall ocean warming is accelerating.

Assuming a "business-asusual" scenario in which no effort has been made to reduce greenhouse gas emissions, the Coupled Model Intercomparison Project 5 (CMIP5) models predict the temperature of the top 2,000 metres of the world's oceans will rise 0.78 degrees Celsius by the end of the century.

The thermal expansion caused by this bump in temperature would raise sea levels 30 cms on top of the already significant sea level rise caused by melting glaciers and ice sheets. Warmer oceans also contribute to stronger storms, hurricanes and extreme precipitation.

"While 2018 will be the fourth warmest year on record on the surface, it will most certainly be the warmest year on record in the oceans, as was 2017 and 2016 before that," Hausfather said.

Unlike surface temperatures, ocean temperatures are not affected by year-to-year variations caused by climate events like El Nino or volcanic eruptions.