The latest evidence that average temperatures are increasing around the globe comes from the deepest parts of the ocean, Dr. James McCarthy of Harvard University told a Senate committee hearing on climate change on Wednesday. (His ten-minute testimony begins just after the 126 minute mark and is well worth a listen.) As it happens, what to do about climate change is the second of 14 questions that ScienceDebate.org is asking President Barack Obama and likely Republican presidential nominee Mitt Romney to answer as part of a quest to get more discussion about science and scientific issues in the run-up to this year’s U.S. elections.

Scientific American is a partner in this quest because we believe that most of the current challenges, threats and opportunities that the U.S. faces require a better grasp of some key scientific question or research field. I posted the full set of question here and will be looking more closely at the questions one by one each week from now through mid-October. Then my colleagues and I will grade the presidential candidates on all 14 science-related questions and rank the positions of various key Congressional leaders on a sub-set of eight of those questions.

As a newcomer to reporting on climate change (I usually cover health and medicine), I was particularly struck by McCarthy's presentation on deep-ocean temperatures. There is so much water in the oceans, which cover so much of the word at an average depth of 12,000 feet, he told the committee, that the deepest parts are extremely well insulated from any transient temperature changes at the surface. As decades and even in some cases more than 100 years of data show, water temperature does not usually vary much in the deepest parts of the ocean.

Over the past ten years, however, the average temperature of even this deepest water has started to rise. Given that the deep ocean is so well protected from the kinds of measuring problems that can confound temperature results on land, the deep water trend provides some of the best evidence to date that average temperatures on the Earth are climbing.

"There is no debate that the earth's temperature is increasing," McCarthy concluded. "Over the last half century the atmosphere, land surface, ocean surface and deep ocean and ice loss in polar regions have all confirmed this. And they can only be explained by the increase in greenhouse gases. There is no scientific evidence that refutes this conclusion." (Download McCarthy's prepared remarks here.)

Unfortunately the Senators engaged in pointless political debate rather than grappling with the bitter reality of global warming, how we might mitigate its impact and how we can do it in a way that is fair to the many citizens of the poorest parts of the world who haven't yet had the opportunity to grow their economies without counting the cost to the planet or our collective future.

Below is the question on climate change that we are asking our political leaders and those who would govern us. I look forward to reading and responding to your comments.

Question #2 Climate Change. The Earth’s climate is changing and there is concern about the potentially adverse effects of these changes on life on the planet. What is your position on cap-and-trade, carbon taxes, and other policies proposed to address global climate change—and what steps can we take to improve our ability to tackle challenges like climate change that cross national boundaries?

Update (Sept. 5, 2012): Click to see the answers to the top 14 science questions from Gov. Mitt Romney and President Barack Obama.

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