New report: Ocean warming passes tipping point

July 25, 2015

Tropical storms are increasing in frequency and strength. City of Tacloban, Leyte, Philippines, after Super Typhoon Yolanda, the strongest tropical storm to make landfall in history, struck in November 2013. Photo: Partido Lakas ng Masa.

The annual State of the Climate report produced by the US National Oceanic and Atmospheric Administration (NOAA) has revealed that warming of the oceans due to climate change is now unstoppable after record temperatures last year.

Even if greenhouse gas levels were cut to zero immediately, the researchers say, the warming of the oceans is predicted to continue. Ocean warming has passed the tipping point.

The report revealed that sea levels, greenhouse gases, glacier melt, tropical storms and land temperatures all hit record highs last year, while sea ice loss continued. The results are based on the work of 413 independent scientists from 58 countries.

Greg Johnson, an oceanographer at NOAA’s Pacific Marine Environmental Laboratory, said: “Even if we were to freeze greenhouse gases at current levels, the sea would actually continue to warm for centuries and millennia, and as they continue to warm and expand the sea levels will continue to rise.”

Four independent data sets confirmed last year as the hottest year on record, with much of that heat driven by the warming of the oceans. Globally, the oceans absorb 90% of the excess heat caused by the rise in greenhouse gas emissions.

The global sea level also reached a record high, with the expansion of those warming waters keeping pace with the 3.2 ± 0.4mm a year trend in sea level rise over the past two decades.

Highlights of the report include:

Greenhouse gases continued to climb Major greenhouse gas concentrations — carbon dioxide, methane and nitrous oxide — reached historic high levels. Atmospheric carbon dioxide concentrations rose by 1.9 ppm last year to a global average of 397.2 ppm, up from 354 ppm in 1990.

Record temperatures observed on the Earth’s surface The global average temperature over land was the warmest since records began in the 1880s. The average annual temperature last year was 0.37–0.44°C higher than the 1981-2010 average, and 0.88°C higher than the 1880s.

More than 20 countries in Europe set new high-temperature records. A new record was set for Africa as a continent. Australia had its third warmest year on record, Mexico had its warmest year on record, and Argentina and Uruguay each had their second warmest year on record. Eastern North America was the only major region to experience below-average annual temperatures.

Sea surface temperatures reached record highs The globally averaged sea surface temperature was the highest on record. The warmth was particularly notable in the North Pacific Ocean.

Global upper ocean heat content was record high Globally, upper ocean heat content reached a record high for the year, reflecting the continuing accumulation of thermal energy in the upper layer of the oceans.

Global sea level was record high Global average sea level rose to a record high in 2014.

The Arctic continued to warm; sea ice extent remained low The Arctic experienced its fourth-warmest year since records began in the early 20th century. Arctic snow melt occurred 20–30 days earlier than the 1998–2010 average. On the North Slope of Alaska, record high temperatures at 20-metre depth were measured at four of five permafrost observatories. The Arctic minimum sea ice extent reached 5.02 million square kilometres on September 17, the sixth lowest since satellite observations began in 1979. The eight lowest minimum sea ice extents during this period have occurred in the last eight years.

The Antarctic showed highly variable temperature patterns; sea ice extent reached record high Temperature patterns across the Antarctic showed strong seasonal and regional patterns of warmer-than-normal and cooler-than-normal conditions, resulting in near-average conditions for the year for the continent as a whole.

Tropical cyclones above average overall There were 91 tropical cyclones last year, well above the 1981–2010 average of 82 storms.

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