This post updates a similar post that was based on data available in July 2011. I now have data from three more years.
World surface air temperature
The blue line shows how the air has warmed and cooled during the 21st century. It is based on GISS, which is one of three century-long records that estimate the surface air temperature of the whole earth. The other two are HadCRUT and NCDC.
Monthly values of GISS vary wildly, and I have smoothed them with a 37-month moving average. Ole Humlum uses 37-month smoothing in many graphs on his website.
The 37-month smoothing allows plotting only up to 18 months ago, in December 2012. As you see, the GISS air temperature anomaly (See Note 1.), when smoothed in this way, moves rather steadily in one direction for years at a time.
The world’s surface air warmed rapidly from early 2000 to late 2002, then warmed slowly to a peak in early 2006. This is the warmest the world surface air has been in hundreds of years. After that peak, the air cooled rapidly by two-thirtieths of a degree to a trough in late 2007. It warmed again slowly to a lower peak in early 2010, steadied for a year, then fell to a trough in January 2012 that was like the previous trough. The air warmed rapidly through 2012.
I have checked that, as Ole Humlum has shown on a graph, the 30-year linear trend of GISS temperature to date is 0.170° per decade. (Trends to date taken over shorter or longer intervals are not so steep. (See Note 2.))
I have overlaid the trend line on the graph of smoothed data. The warming from 2002 to 2006 is almost parallel to the trend, and so is the warming from 2007 to 2010. From 2010 to 2012 (or, at a broader level, from 2006 to 2012) there has been no warming. This has been called a “pause” or a “hiatus”. There were similar pauses, each lasting for three decades, when global surface air temperature did not increase from 1880 to 1910 and from 1945 to 1975.
Manilla NSW surface air temperature
I have plotted in red the changes in Manilla’s average temperature during this time, using the same 37-month smoothing. To make the best match, I have used a temperature scale eight times wider, and moved the zero line.
The shape of the trace of the Manilla record is very similar to that of the global record. As I noted in the earlier post, the two traces warm together from 2002 to the high peak in early 2006, and cool together to a deep trough in late 2007. The next deep trough, which comes in January 2012 in the global trace, comes slightly earlier (November 2011) in the Manilla trace. Through 2012 the rising traces coincide.
In the interval between the two troughs, the match is poor. However, the highest local peak in the global trace, in early 2010, matches an even higher plateau in the Manilla trace.
Manilla’s record of rises and falls of average monthly surface air temperature in the 21st century has closely matched those in the global record. That said, the temperature changes at Manilla have been eight times larger. There may be at least two reasons for this:
1. Manilla is a place particularly responsive to the drivers of climate change;
2. Less variable surface air temperature over the oceans reduces the mean global variation.
I have plotted Manilla temperature changes at a six-month resolution in the series of posts: “3-year trends to…“. In the post “…to March 2013“, it is clear from all six graphs that January 2012, which the graph above shows to be cold locally and globally, had extremely low daily maximum temperature. But October 2010, which had equally cold days, does not appear as a cold time in the above graph. One reason appears in the lower left graph in the linked post: daily minimum temperature, which was very low in January 2012, was not low in October 2010, but high. As a result, the mean temperature was not low at that time.
The GISS smoothed trace on this graph does not agree with that on the earlier post. Values are now about 0.4 degrees warmer (in this time interval) than they were before. I took the values from the same NASA URL link as before, but I found that I had been re-directed from “/tabledata/” to “/tabledata_v3/”. This is the third revision of GISS. There is a “lack of temporal stability” in global temperature records. The warming effect that can result has been called “administrative warming”.
In Ole Humlum’s website climate4you, choose “Global Temperature” from the index, then choose “Global temperature trends” from the List of Contents. Graphs show the latest 5, 10, 20, 30, 50, 70 and 100 year linear annual global temperature trends. GISS surface air temperature data (with NCDC and HadCRUT4) are shown in the second graph.