Examining A Climate Conundrum
MICHELE NORRIS, host:
Global warming skeptics have made quite a fuss over the fact the planet hasnt actually warmed that much over the past decade, and there lies a genuine scientific mystery. The planet has been receiving more solar energy than it's been releasing back into space. Heat ought to be building up somewhere but scientists can't find it.
NPR's Richard Harris has the story.
RICHARD HARRIS: Carbon dioxide has been building up in the atmosphere where it traps energy. Since carbon dioxide is sharply on the rise, the world's temperature should be as well. But it turns out that the story isnt so simple. So, Kenneth Trenberth and John Fasullo, at the National Center for Atmospheric Research in Colorado, set out to take on a basic and contentious question about the Earth's climate.
Dr. JOHN FASULLO (Project Scientist, Climate Analysis Section, National Center for Atmospheric Research): Our initial goal was to explain why the past few years have seen somewhat of a reprieve from warming, globally, and to explore what the causes of that might be.
HARRIS: Fasullo says one possibility was simply that the Earth's atmosphere had changed in some way to counteract the effect of carbon dioxide. If that were true, more energy could be radiating back into space to balance the energy thats coming in. But satellite measurements show thats apparently not the case. In fact, Fasullo figures that the Earth is absorbing far more solar energy than its shedding and a lot of energy is building up.
Dr. FASULLO: It's the equivalent of energy as if you gave everybody on Earth 1,000 light bulbs.
HARRIS: And all 6.5 billion of us left those light bulbs on 24 hours a day. And since energy is typically stored as heat, something on Earth should be heating up. But what is it?
They started ticking off the possibilities. The air can't hold much heat at all. Melting glaciers and permafrost can soak up some energy but not nearly enough to explain the energy gap. And the ground isnt warming appreciably. That leaves the oceans. In fact, oceans are responsibility for storing more than 80 percent of the planet's near-surface heat.
Dr. FASULLO: And what we found is theyve been relatively stable for the past five or six years, across the board. And so we have a paradox here: How could the energy coming into the system be going up, at the same time as the ocean storage is essentially constant?
HARRIS: Fasullo and Trenberth described this unsolved mystery a few weeks ago in Science magazine. From Fasullo's point of view, as a scientist, it's exciting to have a mystery to chew on.
Dr. FASULLO: We wouldnt do science if there weren't a lot of open issues. This is what gets us to work every day.
HARRIS: But climate science isnt happening in a political vacuum, so describing unanswered questions like this can be fodder for climate skeptics. Fasullo has seen this firsthand with this very issue. Last November, climate skeptics found an email his boss Kevin Trenberth had written about this climate mystery and published it on the Internet.
Dr. FASULLO: This led to a fairly widespread quote of my bosses that we have a travesty here that we can't explain the lack of warming.
(Soundbite of laughter)
Dr. FASULLO: And this got misinterpreted in many ways.
HARRIS: In fact, Trenberth was not doubting global warming at all. Scientists know any uncertainty they voice is going to be seized upon by bloggers as fuel for more doubt. So was it a good idea that Science magazine published this recent paper on the mystery?
Ralph Cicerone, who heads the National Academy of Sciences, says it was.
Dr. RALPH CICERONE (President, National Academy of Sciences): I love papers like this because they show how far we've come and also how far we have to go. Thats exactly how science proceeds.
HARRIS: Cicerone says it would be great to understand not just the long-term climate trend, but to understand why global warming sometimes speeds up and why it sometimes slows down. Thats the mystery the paper is probing.
Dr. CICERONE: But from the point of view, for example, of estimating how climate is going to change in the future, I think the discrepancy shown in this paper are overblown because they're short-term fluctuations.
HARRIS: And it fact there are already strong hints about how this mystery will be solved. Sidney Levitus, at the National Oceanic and Atmospheric Administration, monitors the temperatures of the world's oceans using thousands of buoys that dive down to take readings. Most of the measurements have concentrated on the top 2,000 feet of the ocean and those temperature readings have not gone up in recent years.
But Levitus says the story changes appreciably when you look deeper.
Mr. SIDNEY LEVITUS (Director, Climate Laboratory, National Oceanic and Atmospheric Administration): The ocean heat content is increasing. You just have to look deep enough to find that increase.
HARRIS: He's finding evidence of warming deep in the ocean. He's still analyzing that data, so he can't yet say whether it will explain the entire paradox. But he says it will explain at least a chunk of it, and thats how science proceeds: mysteries, explanations, more questions and gradually deeper understanding.
Richard Harris, NPR News.
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