It is well known now that 2017 was the second-warmest year ever recorded, after 2016. In fact, the five hottest years ever recorded have occurred since just 2010, according to NASA.
What hasn't received as much attention is the fact that 2017 was the warmest year ever recorded for the planet's oceans. The previous warmest year for the oceans was 2015.
In fact, when it comes to the overall impacts of human-caused global warming, the oceans have taken most of the hit: They have absorbed 93 percent of the warmth humans have generated since the 1970s.
Oceanic Warming Intensifying
If you took all of the heat humans generated between the years 1955 and 2010 and placed it in the atmosphere instead of the oceans, global temperatures would have risen by a staggering 97 degrees Fahrenheit.
The study that found 2017 to be a record year of oceanic warming was conducted by the Institute of Atmospheric Physics with the Chinese Academy of Sciences, and published online by Advances in Atmospheric Sciences on January 18.
The study found that the top 2,000-meter layer of Earth's ocean waters was at its warmest levels ever, and that this warming, according to the study, "represents the signature of global warming." This is due to the fact that, according to the Intergovernmental Panel on Climate Change's 5th Assessment Report, oceans absorb the vast majority of human-generated heat primarily because water has a high heat capacity, given that it takes much more heat to warm water than it does air.
Oceanic warming is clearly dramatically escalating. The study found that the last five years have been the five warmest years for the oceans, and added, "Therefore, the long-term warming trend driven by human activities continued unabated."
Warm water expands in volume. Thus, the warming is causing increases in sea level rise, in addition to causing more coral bleaching events, declines in oceanic oxygen levels, and increasing melting of sea ice and ice shelves. Studies show that warming ocean waters are causing major species relocations, along with extinctions of some species of fish and marine life.
"The impacts of anthropogenic climate change so far include decreased ocean productivity, altered food web dynamics, reduced abundance of habitat-forming species, shifting species distributions, and a greater incidence of disease," reads the summary of a study published in the journal Science. "Although there is considerable uncertainty about the spatial and temporal details, climate change is clearly and fundamentally altering ocean ecosystems."
Sans El Niño
The fact that 2017 was the second-warmest year on record for the atmosphere, and the warmest on record for the oceans, is particularly troublesome given that 2017 was a non-El Niño year.
El Niño is a shift in Pacific Ocean weather patterns in the tropics that is generally linked to record-setting heat in the atmosphere and oceans alike. Last year was predicted to be a cooler year since it was not an El Niño year. The fact that it was as warm as it was underscores how rapidly the planet is continuing to heat up.
According to both NASA and the National Oceanic and Atmospheric Administration, 17 of the 18 warmest years on record for the planet have occurred since 2001.
"This is the new normal," NASA's Gavin Schmidt who directs that agency's Goddard Institute for Space Studies, told the New York Times. But, he said, "It's also changing. It's not that we've gotten to a new plateau -- this isn't where we'll stay. In ten years we're going to say 'oh look, another record decade of warming temperatures.'"