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Thursday, September 26, 2013

John Cook's Climate Change Mythbusters 9

This is part of a series reposting material from John Cook's Skeptical Science website. Although he is a physicist rather than a specialist in climate science, he is a convinced "global warmist" and tries to rebut frequently-raised objections to the theory. However, it is always possible to question the data (e.g. this valuable note about measuring temperature) and the line of argument. Please help advance the debate - with facts and logic.
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What has global warming done since 1998?

What The Science Says:
For global records, 2010 is the hottest year on record, tied with 2005.
Climate Myth: It hasn't warmed since 1998
For the years 1998-2005, temperature did not increase. This period coincides with society's continued pumping of more CO2 into the atmosphere. (Bob Carter)
No, it hasn't been cooling since 1998. Even if we ignore long term trends and just look at the record-breakers, that wasn't the hottest year ever. Different reports show that, overall, 2005 was hotter than 1998. What's more, globally, the hottest 12-month period ever recorded was from June 2009 to May 2010.
 
Though humans love record-breakers, they don't, on their own, tell us a much about trends -- and it's trends that matter when monitoring Climate Change. Trends only appear by looking at all the data, globally, and taking into account other variables -- like the effects of the El Nino ocean current or sunspot activity -- not by cherry-picking single points.
 
There's also a tendency for some people just to concentrate on air temperatures when there are other, more useful, indicators that can perhaps give us a better idea how rapidly the world is warming. Oceans for instance -- due to their immense size and heat storing capability (called 'thermal mass') -- tend to give a much more 'steady' indication of the warming that is happening. Here records show that the Earth has been warming at a steady rate before and since 1998 and there's no signs of it slowing any time soon.
 
Fig 1

Land, atmosphere, and ice heating (red), 0-700 meter ocean heat content (OHC) increase (light blue), 700-2,000 meter OHC increase (dark blue). From Nuccitelli et al. (2012).

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