Half of the energy expected to have fueled global warming since 2003 has gone missing, researchers report.
Scientists can't tell whether the climate system has changed in the last few years -- in the oceans, for instance -- or if there is something wrong in the way they keep track of energy as it moves down through the atmosphere from the sun and then escapes back into space.
Researchers thought they could account for the energy in Earth's climate system like a family keeping a budget. They measured solar income and out-go and saw the excess in incoming heat generated by greenhouse gases as rising temperatures -- global warming.
Around 2003, however, this energy budget model evidently sprang a leak.
The imbalance between income and out-go continued to widen as more carbon dioxide and other greenhouse gases continued to flow into the atmosphere, but rising global temperatures were no longer keeping pace. At the same time, mysteriously, the measurements of a new monitoring system indicated that the oceans were absorbing a smaller proportion of the incoming solar heat.[This simplified depiction of the global energy budget, measured in watts per square meter, shows the diverging trends between changes in energy observed in the climate system and changes in net radiation observed by satellites at the top of the atmosphere.]
"It is possible to track how much extra energy has gone back to space as the planet warms and where the rest of the energy has accumulated. Over the past 50 years, the oceans have absorbed ~90% of the energy added to the climate system; the rest has gone into melting sea and land ice and heating the land surface and atmosphere. CO2 concentrations have further increased since 2003, and even more heat should have accumulated at a faster rate since then. Where has this energy gone?"
The scientists' suspicions naturally turn to the world's oceans, the dominant factor in the energy budget. Has the missing heat moved into the deeper ocean, beyond the detection of the current system of marine floats? Without better ways of tracking energy through the climate system, they can't say. Is there something awry in the way data is processed from the new ocean monitoring system? They don't know.
"Our goal was to explain recent variations in global surface temperature and we wished to provide an energy perspective on this," Fasullo told me in an email. "Our inability to come up with a coherent narrative undermined these efforts, but was a story in and of itself."
The study "reveals a glaring hole in our ability to observe the build-up of heat in our climate system," he said.
Climate scientists may not have the answers to these short-term variations, but physics doesn't really take days off, and there seems to be little doubt that the growing gap between incoming energy and outgoing energy at the top of the atmosphere is accurately measured by satellites.
"The heat will come back to haunt us sooner or later," Trenberth said. "The reprieve we've had from warming temperatures in the last few years will not continue."
IMAGE: AAAS/Science Magazine
Tags: Carbon Emissions, Carbon Footprint, Climate Change, Geophysics, Global Warming
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