That's the finding of a group of Livermore scientists, who in collaboration with colleagues at Scripps Institution of Oceanography, had earlier established that climate models can replicate the ocean warming observed during the latter half of the 20th century, and that most of this recent warming is caused by human activities.
The observational record also shows substantial variability in ocean heat content on interannual-to-decadal time scales. The new research by Livermore scientists demonstrates that climate models represent this variability much more realistically than previously believed.
Using 13 numerical climate models, the researchers found that the apparent discrepancies between modeled and observed variability can be explained by accounting for changes in observational coverage and instrumentation and by including the effects of volcanic eruptions.
The research, which will appear in the June 18 early online edition of the journal Proceedings of the National Academy of Sciences, casts doubt on recent findings that the top 700-meters of the global ocean cooled markedly from 2003-2005.
“Our analysis shows that the 2003-2005 'cooling' is largely an artifact of a systematic change in the observing system,” said Krishna AchutaRao, previously of Livermore's Program for Climate Model Diagnosis and Intercomparison (PCMDI), now at the Indian Institute of Technology Delhi and the lead author of the paper. “The previous research was based on looking at the combined ocean temperature observations from several different instrument types, which collectively appear to have a cooling effect. But if you look at the observational instruments individually, there is no cooling.”
Observational estimates of ocean heat content change in the 2005 World Ocean Atlas are based on millions of individual temperature measurements; however, they are unevenly distributed in space and time. In fact, until recently, many portions of the global ocean were very poorly sampled. To get a complete four-dimensional picture of global ocean temperatures, most researchers use statistical methods to “infill” missing observational data.
Climate models provide spatially complete ocean temperature data, so unlike the incomplete observations, infilling is not required. By sampling the models only where there are observations, the Livermore team found that infilling had a pronounced effect on observed estimates of ocean variability, and brought model results closer in line with observations. Models agreed even more closely with observations when the cooling effects of intermittent volcanic eruptions were included.
The research team also looked at the impacts of changes in ocean observing systems. A warm bias in the older instruments was recently discovered by researchers in Germany. With the introduction of new instruments called Argo floats, more complete and more reliable ocean temperature measurements have become possible. The first Argo floats were deployed in the Atlantic in 2000 and their network has rapidly ramped up to several thousand floats with near-global coverage of the world's oceans.
“This transition from a measuring system biased warm to a more realistic one appears as a cooling. Obviously, models can't account for spurious variability caused by instrument changes,” AchutaRao said.
Anne Stark | EurekAlert!
Species may appear deceptively resilient to climate change
24.11.2017 | University of California - Davis
Scientists team up on study to save endangered African penguins
16.11.2017 | Florida Atlantic University
High-precision measurement of the g-factor eleven times more precise than before / Results indicate a strong similarity between protons and antiprotons
The magnetic moment of an individual proton is inconceivably small, but can still be quantified. The basis for undertaking this measurement was laid over ten...
Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
24.11.2017 | Physics and Astronomy
24.11.2017 | Health and Medicine
24.11.2017 | Earth Sciences