EMBARGOED BY NATURE CLIMATE CHANGE

FOR RELEASE ON Sunday, April 1, 2012 10:00 AM PDT

Sunday, April 1, 2012

New Comparison of Ocean Temperatures Reveals Rise over the Last Century

Ocean robots used in Scripps-led study that traces ocean warming to late 19th century

Scripps Institution of Oceanography / University of California, San Diego

A new study contrasting ocean temperature readings of the 1870s with temperatures of the modern seas reveals an upward trend of global ocean warming spanning at least 100 years.

The research led by Scripps Institution of Oceanography at UC San Diego physical oceanographer Dean Roemmich shows a .33-degree Celsius (.59-degree Fahrenheit) average increase in the upper portions of the ocean to 700 meters (2,300 feet) depth. The increase was largest at the ocean surface, .59-degree Celsius (1.1-degree Fahrenheit), decreasing to .12-degree Celsius (.22-degree Fahrenheit) at 900 meters (2,950 feet) depth.

The report is the first global comparison of temperature between the historic voyage of HMS Challenger (1872-1876) and modern data obtained by ocean-probing robots now continuously reporting temperatures via the global Argo program. Scientists have previously determined that nearly 90 percent of the excess heat added to Earth's climate system since the 1960s has been stored in the oceans. The new study, published in the April 1 advance online edition of Nature Climate Change and coauthored by John Gould of the United Kingdom-based National Oceanography Centre and John Gilson of Scripps Oceanography, pushes the ocean warming trend back much earlier.

"The significance of the study is not only that we see a temperature difference that indicates warming on a global scale, but that the magnitude of the temperature change since the 1870s is twice that observed over the past 50 years," said Roemmich, co-chairman of the International Argo Steering Team. "This implies that the time scale for the warming of the ocean is not just the last 50 years but at least the last 100 years."

Although the Challenger data set covers only some 300 temperature soundings (measurements from the sea surface down to the deep ocean) around the world, the information sets a baseline for temperature change in the world's oceans, which are now sampled continuously through Argo's unprecedented global coverage. Nearly 3,500 free-drifting profiling Argo floats each collect a temperature profile every 10 days.

Roemmich believes the new findings, a piece of a larger puzzle of understanding the earth's climate, help scientists to understand the longer record of sea-level rise, because the expansion of seawater due to warming is a significant contributor to rising sea level. Moreover, the 100-year timescale of ocean warming implies that the Earth's climate system as a whole has been gaining heat for at least that long.

Launched in 2000, the Argo program collects more than 100,000 temperature-salinity profiles per year across the world's oceans. To date, more than 1,000 research papers have been published using Argo's data set.

The Nature Climate Change study was supported by U.S. Argo through NOAA.

# # #

Note to broadcast and cable producers: University of California, San Diego provides an on-campus satellite uplink facility for live or pre-recorded television interviews. Please phone or e-mail the media contact listed above to arrange an interview.

About Scripps Institution of Oceanography
Scripps Institution of Oceanography at University of California, San Diego, is one of the oldest, largest and most important centers for global science research and education in the world. Now in its second century of discovery, the scientific scope of the institution has grown to include biological, physical, chemical, geological, geophysical and atmospheric studies of the earth as a system. Hundreds of research programs covering a wide range of scientific areas are under way today in 65 countries. The institution has a staff of about 1,400, and annual expenditures of approximately $170 million from federal, state and private sources. Scripps operates robotic networks, and one of the largest U.S. academic fleets with four oceanographic research ships and one research platform for worldwide exploration. Birch Aquarium at Scripps serves as the interpretive center of the institution and showcases Scripps research and a diverse array of marine life through exhibits and programming for more than 415,000 visitors each year. Learn more at scripps.ucsd.edu.

Argo: Observing the Oceans in Real Time

• Robert Monroe or Mario Aguilera
• Phone: 858.534.3624
  scrippsnews@ucsd.edu

• Argo-UCSD/SIO
• Scripps Home
• ScrippsNews Home

© Scripps Institution of Oceanography, University of California, San Diego 2013. All Rights Reserved