Washington: The existing observational tools are not adequate to measure a significant portion of heat that is believed to have built up on Earth in recent years and this ``missing`` heat may affect future climate change, scientists have warned.
The study has appeared in a "Perspectives" article in this week``s issue of the journal Science.
According to scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., satellite sensors, ocean floats, and other instruments cannot track this "missing" heat, which may be building up in the deep oceans or elsewhere in the climate system.
Lead author and NCAR scientist Kevin Trenberth said: "The heat will come back to haunt us sooner or later.
"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."
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, pointed out 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. Trenberth and Fasullo believe it is imperative to better measure the flow of energy through Earth`s climate system.
For instance, any geoengineering plan to artificially alter the world``s climate to counter global warming could have inadvertent consequences, which may be difficult to analyse unless scientists can track heat around the globe.
Improved analysis of energy in the atmosphere and oceans can also help researchers better understand and possibly even anticipate unusual weather patterns, such as the cold outbreaks across much of the US, Europe, and Asia over the past winter.
As greenhouse gases accumulate in the atmosphere, satellite instruments show a growing imbalance between energy entering the atmosphere from the sun and energy leaving from Earth``s surface.
This imbalance is the source of long-term global warming.
But tracking the growing amount of heat on Earth is far more complicated than measuring temperatures at the planet``s surface.
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.
Satellite measurements indicate that the amount of greenhouse-trapped solar energy has risen over recent years while the increase in heat measured in the top 3,000 feet of the ocean has stalled.
Although it is difficult to quantify the amount of solar energy with precision, Trenberth and Fasullo estimate that, based on satellite data, the amount of energy build-up appears to be about 1.0 watts per square meter or higher, while ocean instruments indicate a build-up of about 0.5 watts per square meter.
That means about half the total amount of heat is unaccounted for.
A percentage of the missing heat could be illusory, the result of imprecise measurements by satellites and surface sensors or incorrect processing of data from those sensors, the authors explained.
Until 2003, the measured heat increase was consistent with computer model expectations.
But a new set of ocean monitors since then has shown a steady decrease in the rate of oceanic heating, even as the satellite-measured imbalance between incoming and outgoing energy continues to grow.
ANI
