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David Whitehouse: Warm Ocean, Warm Year?

Dr David Whitehouse

Some media outlets have been reporting that the oceans are starting to get warmer, and that it signals the end to the current hiatus in annual average global surface temperatures.

Mother Nature Network says the pace of ocean warming is speeding up. “Earth’s ocean surface has been hotter in 2014 than any previous year on record, according to a new analysis by scientists at the University of Hawaii-Manoa. This suggests the recent slowdown in Earth’s long-term temperature rise — sometimes called a “hiatus” — may be coming to an ominous end.”

Responding to Climate Change includes the quote,  “Hottest ever ocean temperatures signal end to warming pause.” It also adds: But as to whether the global warming pause was over in terms of atmospheric temperatures, Met Office climate scientist Richard Betts said it was too early to say. “Even if this year ends up with a record global average surface temperatures, which is possible, that would just be one year. We’d need more than that,” he told RTCC. Betts added: “‘Has the pause ended?’ will be an important research question for some years.”

The origin of these reports was a statement made by Axel Timmermann of the University of Hawaii that temperatures in the Pacific are even greater than that during the 1998 El Nino. Timmermann suggests that this is the end of the 14-year pause in ocean surface warming. He says in April 2014 it picked up again.

A closer look at the data, Fig 1, shows that the unusual warm is confined to the North Pacific. This suggests local effects like changing wind strengths pooling warm surface water in one particular location, a quite different effect from global warming.


Fig 1. Click on image to enlarge.

Timmerman says a shift in summer trade winds played a key role, allowing nearly a decade’s worth of stored heat to escape from the tropical Western Pacific. “Record-breaking greenhouse gas concentrations and anomalously weak North Pacific summer trade winds, which usually cool the ocean surface, have contributed further to the rise in sea surface temperatures,” Timmerman says. “The warm temperatures now extend in a wide swath from just north of Papua New Guinea to the Gulf of Alaska.”

So this effect is short-term and localised, something some of the media reports missed.

Also note the overall ocean warming started in 1910 which is curiously at the same time that sea level rise changed its gradient due to unknown factors which certainly do not include any anthropogenic influence, see Fig 1a.

Fig 1a

Fig 1a. Click on image to enlarge.

The story did not get widespread coverage. Unlike the prospect of 2014 being the warmest year in the instrumental temperature record.

Is 2014 on track to be the warmest year?

It is going to be warm, but how warm, and the year’s rank depends upon which data you use.

According to the National Climatic Data Center (NCDC) the ocean surface temperature for October 2014 was globally the highest on record with a temperature anomaly of 0.62 deg C. Despite the land temperature for October being the 5th warmest the land-ocean temperature was the highest on record at 0.74 deg C.

So let’s look at year to October sea surface temperatures in their database, Fig 2. You will see that it is nothing particularly special. We are dealing with statistically insignificant variations of 0.05 deg C inside an error of at least 0.1 deg C. The trend for January-October between 2001-2014 is 0.01 deg C per decade with an error of 0.15 deg C per decade, i.e. there is no trend.

Fig 2

Fig 2. Click on image to enlarge.

The NCDC has a year-to-date graph, Fig 3, (such a representation of this data set was first used by the GWPF) showing that only in September was 2014 warmer than 2010.

Fig 3

Fig 3. Click on image to enlarge.

They also produce a prediction for the remaining two months, Fig 4, suggesting that 2014 will probably be the warmest year on record, probably by 0.01 or 0.02 deg C which is of course statistically insignificant. Why does the NCDC not put error bars on these graphs – most unscientific.

Fig 4

Fig 4. Click on image to enlarge.

The “warmest year on record” story will, by the years end, certainly sort out responsible journalists and commentators from those who just seek headlines. Expect to see a lot of headlines mentioning the warmest ever year and rather few of the surface temperature hiatus continues, which is the only conclusion that can be drawn from the data.

But will 2014 be the warmest year in other databases?

Consider Nasa Giss which essentially uses the same data as the NCDC but processes it in a different way. In Giss the year to October has an average temperature anomaly of 66 which is the same as that of 2005 and 2010. November and December 2014 must have an average of 67 to make 2014 the warmest year by just a statistically insignificant 0.01 degrees.

Since 2001 only one year, 2006, has had November and December both above 66. Of all the Novembers and Decembers since 2001 only 10 out of 26 have had temperature anomalies above 66, and the last December to achieve this was in 2006 and only twice since 2001. Because about half of Novembers since 2001 have had a temperature anomaly above 66 it is likely that the status of warmest ever year in Giss will not be decided by December not being exceptionally warm but by not being exceptionally cold. Thus at the end of the year Giss data will confirm that the global surface temperature hiatus continues.

Note that in Giss October ties for the warmest month with 2005, although this is really grubbing around in the noise for meaningless comparisons.

HadCrut4 is showing 2014 as a record year but only by 0.004 deg C which is superfluous. This will change with the inclusion of data from October, November and December. By year’s end HadCrut4 will also confirm that the temperature hiatus continues.

Satellite data tell a different story. RSS global data show that 2014 will be cooler than 2010, 2007, 2005, 2003, 2002 and 1998 (2014 will be over 0.02 deg cooler than 2010). By year’s end 2014 will probably be about the sixth warmest year.

UAH data shows that currently 2014 ranks 3rd and is likely to remain so by year’s end. There is no chance whatsoever that the satellite datasets will show 2014 to be a record year.

I suspect that if 2014 does technically become the warmest year on record (in any one of the non-satellite data sets) then we will see dramatic headlines to that effect, even if the record is broken by a hundredth or a few thousandths of a degree. The real story will be that the so-called biggest puzzle in climate science – the global surface temperature standstill – then entering its 19th year.