Saturday, 7 January 2017

"Assessing recent warming" (2017) put in perspective

ScienceMag (AAAS) published a "rebuttal" of the whole idea of any 21st century pause in global temperature increase a few days ago. The Sceptical blogosphere is awash with indignant posts (and comments) claiming data tampering, or "torturing the data until it confesses". I'm reserving my judgement, except to say that the "pause" has been widely acknowledged by climate scientists, referred to in the last IPCC report (AR5), and concerns surface temperature. The Hausfather et. al. article (not AFAIK peer-reviewed, not that that means much these days) concerns sea surface temperature, a wholly different kettle of fish (I really didn't think of that as a pun, honest!).
Sea surface temperature (SST) records are subject to potential biases due to changing instrumentation and measurement practices. Significant differences exist between commonly used composite SST reconstructions from the National Oceanic and Atmospheric Administration’s Extended Reconstruction Sea Surface Temperature (ERSST), the Hadley Centre SST data set (HadSST3), and the Japanese Meteorological Agency’s Centennial Observation-Based Estimates of SSTs (COBE-SST) from 2003 to the present. The update from ERSST version 3b to version 4 resulted in an increase in the operational SST trend estimate during the last 19 years from 0.07° to 0.12°C per decade, indicating a higher rate of warming in recent years. We show that ERSST version 4 trends generally agree with largely independent, near-global, and instrumentally homogeneous SST measurements from floating buoys, Argo floats, and radiometer-based satellite measurements that have been developed and deployed during the past two decades. We find a large cooling bias in ERSST version 3b and smaller but significant cooling biases in HadSST3 and COBE-SST from 2003 to the present, with respect to most series examined. These results suggest that reported rates of SST warming in recent years have been underestimated in these three data sets.
Here's Figure 1 from the article:

Fig. 1 Comparison of the different ERSSTv3b, ERSSTv4, buoy-only, and CCI SST monthly anomalies from January 1997 to December 2015, restricting all series to common coverage. ERSSTv4 is shown as a broad band for visualization purposes; this band does not represent an uncertainty range. The series are aligned on the 1997–2001 period for comparison purposes. Spatial trend maps are also available in fig. S1, and a similar comparison with Argo data is shown in fig. S2.

What it amounts to, is that the authors have found data series which match their agenda, and found reasons to ignore the other data series which don't. Par for the course these days. As it happens, I've been compiling a set of regional temperature records using GISS data (unadjusted of course), since before Christmas. Just to be different, I'm not ignoring data which doesn't match my agenda, I'm concentrating on large areas of the globe which show interesting results on analysis. More in later posts. For the moment, I thought it might be interesting and amusing to look in detail at the temperature record nearest to President Obama's residence (soon to be vacant for a very short period) and NOAA  headquarters at 1401 Constitution Avenue, Washington DC. The thermometer is at Washington National Airport, just 5km across the Potomac river from NOAA, just inside Virginia.


The 11-year Loess filter shows an uptick around the middle 2000s, after a bumpy "plateau" from 1973. No late 20th C warming evident at all. However, the Loess filter works in a way which includes future change (weighted). If the filter range is constrained to 1880-2009, we get:

1960-2016, Loess range to 2009

Warming began in 2010, after a 27-year "pause". Washington itself would undoubtedly show warming, mostly due to the "Urban Heat Island" effect, but the airport is on the west bank of the Potomac, effectively rural and uncontaminated. A little ironic, that a thermometer just across the river from the nation's capital, seat of a president pledged to "halt global warming" shows no 21st C warming until 2010. The plateau runs from 1974, when he was 12yo - he can't claim responsiblity!

More soon, beginning with Pacific islands. Watch this space.

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