May 14, 2007

Questioning Ocean Warming?

We just did an internet search on “Ocean Warming” and found an incredible 7.2 million sites! We sampled a few and found exactly what we expected – endless stories of how the oceans of the world are heating up at an unprecedented rate; absolutely anything and everything related to the ocean is currently in peril according to these sites. Even if you live thousands of miles from the sea, ocean warming will negatively impact you given how ocean temperatures influence weather and climate any place on the planet. Our survey of “Ocean Warming” internet sites did not reveal anyone questioning whether or not the oceans are actually warming up – “Ocean Warming” is simply assumed to be a fact.

Well, in a recent issue of theJournal of Physical Oceanography, an article appears entitled “Is the World Ocean Warming? Upper-Ocean Temperature Trends: 1950–2000”. Once again, we at World Climate Report are attracted to research that dares to question any of the pillars of the greenhouse scare, and from just the title alone, we knew we would enjoy this article. We were not disappointed.

The article is written by scientists at the School of Oceanography at the University of Washington and the research was funded by the National Oceanic and Atmospheric Administration. Harrison and Carson begin their article noting that interest in ocean temperatures is at an all-time high given the buzz about climate change and the greenhouse effect. They state that below-surface ocean temperature data are sparse, and the existing data sets involve substantial “interpolation, extrapolation, and averaging” that may compromise the integrity of results from such data sets. Harrison and Carson “present results that involve very little manipulation of the data and do not depend upon an analyzed field.”

The scientists organized the temperature observations into 1° latitude by 1° longitude boxes, and over the past 50 years, huge areas of the southern oceans have no data whatsoever. Many other oceanic areas have data, but many of the 1° by 1° grid boxes have only one observation per year. They note that “Our results raise a number of questions about the uncertainty that should be assigned at present to basin-scale integral ocean thermal quantities, whether zonal averages, basin averages, or averages over the World Ocean.”

Harrison and Carson present a figure showing different characteristics of their data. Their figure is below (Figure 1) along with their own figure caption. Do you notice anything odd in the figure? Unless you are looking at this upside-down, you cannot help but notice cooling in all five graphs for the 1980-1999 time periods (note: the graphs are for different individual gridcells, not a worldwide average).


Figure 1. “Time series of some individual 1°x1° boxes at (a) 42°N, 66°W, 100 m; (b) trend lines for 42°N, 66°W, on same scale as other graphs; (c) 51°N, 131°W, 100 m; (d) 40°N, 155°W, 100 m; and (e) 23°N, 156°W, 500 m. Trend lines are fitted only by data within the periods they cover” (from Harrison and Carson, 2007).

Another figure in their article is just as interesting. As seen in Figure 2, temperature trends over the past 50 years reveal some areas of warming, but also many areas of cooling, as well. In their own words, we learn “The ocean neither cooled nor warmed systematically over the large parts of the ocean for the entire analysis period.” Also evident in the figure is the oceanic expanse without data for making such any such assessment; note in their figure caption that five observations in a decade for at least four decades is all that is required to stay in the analysis! They conclude “Evidently, oceanic regional trend estimates pose substantial sampling challenges and very long records are needed.”

Figure 2. “The 51-yr temperature trends [°C (51 yr)-1], based on the linear trend line over 1950–2000 in 1°x1° regions meeting the sampling criterion (at least five observations per decade in at least four of the five decades of the analysis period). Trends shown in the left panels are 90% significant [warm colors indicate rising trends, cool colors indicate declining trends]; trends over all regions are shown in the right panels at (a), (d) 100, (b), (e) 300, and (c), (f) 500 m.” (from Harrison and Carson, 2007).

There are 1,000 ways to interpret their results, but several themes from the research are inescapable. First and foremost, the authors asked the question “Is the World Ocean Warming” and the answer is definitely not “yes.” At no point in the article do we find any global assessment of “World Ocean Warming” and no statement is made about any global trend over the past 50 years. Second, the ocean could be warming or cooling, and we may not have the data needed to detect such a change in heat content. The research pair tells us “There are no results to offer for most of the ocean south of 20°S.” Go look at a globe, look down at it with the South Pole pointing upward. Literally everything you see is south of 20°S, and with little exception, everything you see is water. Oops, there are no data available to assess whether the water you are looking at is either warming or cooling.

Seven million sites declaring that the ocean is warming cannot possibly be wrong? Well, for the record, there are over a million sites for “Ocean Cooling” and 750,000 sites for “Ocean Temperature Unchanged”. You be the judge, but don’t look for Harrison and Carson to be featured in the 7,000,000 sites claiming that our oceans are warming.

Reference:

Harrison, D.E., and M. Carson. 2007. Is the World Ocean Warming? Upper-Ocean Temperature Trends: 1950–2000. Journal of Physical Oceanography, 37, 174-187.




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