Earth's 'missing' heat impacting climate change

Scientists at the National Centre for Atmospheric Research (NCAR) warn that such instruments are inadequate to track this "missing" heat, which may be building up in the deep oceans or elsewhere in the climate system. "The heat will come back to haunt us sooner or later," says NCAR scientist Kevin Trenberth, lead study author.

"The reprieve we've had from warming temperatures in the last few years will not continue. It is critical to track the build-up of energy in our climate system so we can understand what is happening and predict our future climate," Trenberth adds. The authors suggest that last year's rapid onset of El Niño, the periodic event in which upper ocean waters across much of the tropical Pacific Ocean become significantly warmer, may be one way in which the solar energy has reappeared.

Trenberth and his co-author, NCAR scientist John Fasullo, focused on a central mystery of climate change. Whereas satellite instruments indicate that greenhouse gases are continuing to trap more solar energy, or heat, scientists since 2003 have been unable to determine where much of that heat is going.

Either the satellite observations are incorrect, says Trenberth, or, more likely, large amounts of heat are penetrating to regions that are not adequately measured, such as the deepest parts of the oceans. Compounding the problem, Earth's surface temperatures have largely levelled off in recent years.

Yet melting glaciers and Arctic sea ice, along with rising sea levels, indicate that heat is continuing to have profound effects on the planet. In their Perspectives article, Trenberth and Fasullo explain that it is imperative to better measure the flow of energy through Earth's climate system.

But tracking the growing amount of heat on Earth is far more complicated than measuring temperatures at the planet's surface, said an NCAR release.  The oceans absorb about 90 percent of the solar energy that is trapped by greenhouse gases.

Additional amounts of heat go toward melting glaciers and sea ice, as well as warming the land and parts of the atmosphere. Only a tiny fraction warms the air at the planet's surface. The study was published in this week's issue of Science.