Tag Archives: Tamino

Data Watch: UAH Global Mean Temperature, June 2015 Release

On July 6th, Dr Roy Spencer released the University of Alabama-Huntsville (UAH) global average lower tropospheric temperature anomaly as measured by satellite for June 2015 (here). The anomaly refers to the difference between the current temperature reading and the average reading for the period 1981 to 2010 as per satellite measurements.

June 2015: Anomaly +0.33 degrees Celsius This is the 3rd warmest June temperature recorded since the satellite record was started in December 1978 (36 June observations). The warmest June to date over this period was in 1998, with an anomaly of +0.56 degrees Celsius. Full data set available here (click for larger image).

UAH Global Temp July 2015 jpeg

The El Nino Southern Oscillation (ENSO) cycle is the main determinant of new temperature records over the medium term (up to 30 years) . The U.S. government’s Climate Prediction Centre currently has an El Nino advisory in effect and is forecasting that the current El Nino event is set to continue through into 2016 (update 9 July 2015 here):

Overall, there is a greater than 90% chance that El Niño will continue through Northern Hemisphere winter 2015-16, and around an 80% chance it will last into early spring 2016.

Given this background, I would expect the UAH anomalies to remain elevated for some time.

As background, five major global temperature time series are collated by different international agencies: three land-based and two satellite-based. The terrestrial readings are from NASA GISS (Goddard Institute for Space Studies), HadCRU (Hadley Centre/Climate Research Unit in the U.K.), and NCDC (National Climate Data Center). The lower-troposphere temperature satellite readings are from RSS (Remote Sensing Systems, data not released to the general public) and UAH (Univ. of Alabama at Huntsville).

The most high profile satellite-based series is put together by UAH and covers the period from December 1978 to the present. Like all these time series, the data is presented as an anomaly (difference) from the average, with the average in this case being the 30-year period from 1981 to 2010. UAH data is the earliest to be released each month.

One of the initial reasons for publicising this satellite-based data series was due to concerns over the accuracy of terrestrial-based measurements (worries over the urban heat island effect and other factors). The satellite data series have now been going long enough to compare the output directly with the surface-based measurements. All the time series are now accepted as telling the same story (for a fuller mathematical treatment of this, see Tamino’s post at the Open Mind blog here). Note that the anomalies produced by different organisations are not directly comparable since they have different base periods. Accordingly, to compare them directly, you need to normalise each one by adjustment to a common base period.

Preparing for the Arctic Melt Season

In 2012, the maximum Arctic sea ice extent was reached on 18 March at 15.24 million square kilometres according to National Snow and Ice Data Center (NSIDC). Nonetheless, this was far from a record low—indeed, only number eight historically. The year 2011 held (and still holds) pole position for the freeze season maximum low, at 14.64 million square kilometres.

However, for the 2012 melt season, we all know what happened next (or at least the sentient part of mankind knows what happened next). The NSIDC announced the crash in sea ice extent to 3.41 million square kilometres at its September 16 low (smashing the previous 2007 record of 4.17 million square kilometres) with all the gory detail here.

The upshot of all this? Basically, current sea ice extent won’t tell us if we will hit a new record low this coming September. So we need to be patient if we want to answer the big question of whether we will continue to see a jagged descent this year (with even a possible year-on-year marginal gain) or a further phase change (setting us up for an ice free summer Arctic within a decade). In other words, will the patient cling on for a while longer or opt for a quick death.

With two kids aged 11 and 16, this must be one of the most depressing data tracking exercises I have ever done. In short, my children will surely now inherit an ice free summer Arctic (and possibly spring and autumn too by their middle age), with all the consequences that this implies. But how quickly?

So what will I be looking at? First stop is always the NSIDC’s daily image update, which gives you this chart:

Arctic Sea Ice Extent jpeg

And while I am at the NSIDC site, I will be checking their new Greenland Ice Sheet Today page, which shows the latest domino to fall: Greenland ice sheet melt.

The only problem with the NSIDC image is that it does not contain a daily ice extent number. For that, I like the Japan-hosted IARC-JAXA Information System (IJIS) sea ice extent data series that can be found here. If you look at this series, then it is possible that we have already peaked for the year (but watch out for the last reported day to be always revised substantially).

Next, I go over to Neven’s incomparable blog for all things sea ice. Currently, Neven is reporting good news, bad news. The good news (well let’s say goodish news) is that sea ice volume (as opposed to extent) is above last year’s level. The bad news is that many parts of the Arctic sea ice are showing large unseasonal cracks that could herald further record sea ice lows in the months to come.

Neven’s site is also a chart fest and live-cam orgy. It is like having a ring-side seat of the sea ice collapse. Comments area also generally very interesting.

After that, I will periodically check on the Open Mind blog, in which Tamino will be statistically slaying the latest nonsense from Anthony Watts and his ilk (good example here). If you want to dust off your stats, read Tamino’s series of posts on ice sheet loss in preparation for the new melt season. They start here.

Finally, I will try to bring the dire state of the Arctic sea ice into conversations with those I meet. Most will, in turn, change the subject. Planeticide is such an unseemly topic—best not to talk about it and pretend it isn’t there.

First Release on 2012 Global Average Temperature

There are five major global temperature time series: three land-based and two satellite-based. The most high profile satellite-based series is put together by the University of Alabama-Huntsville (UAH) and covers the period 1979 to the present. Like all these time series, the data is presented as an anomaly from the average, with the average in this case being the 30-year period from 1981 to 2010.

The official link to the data at UAH can be found here, but most months we get a sneak preview of the release via the climatologist Dr Roy Spencer at his blog here. Continue reading