<h2>Record warm periods</h2>

In the previous post, I cited the NOAA June temperatures report. This noted various periods of time with average temperatures that exceeded anything comparable in the record, particularly recent twelve month periods.

Sou has been tracking the average so far in this calendar year. Steve Bloom doesn't like non-physical calendar periods, and prefers the running average. I think Sou's analysis makes sense. It is the best guide to the 2015 year average, since it uses data from that year only. One could say people shouldn't focus on arbitrary year divisions, but they do.

However, if you want running twelve month averages, they are available at the maintained active plot. Just click the buttons on the side table headed Sm. twelve month running is the default (and only) smooth. Here is an example:



However, in this context, I'm a fan of polar, or radial, plots. Here curves track like a clock with time, with radial distance indicating temperature or other plot variable. I use it for ice extent here. Then there is a natural period of a year, but that isn't essential. The point is that by rolling it up, a long stretch of time can be covered with good resolution (but crowding).

So below the fold I'll show radial plots (with decade winding period) for the main surface indices, from 1950 to now. They will show clearly how warming has continued, as the curve spirals outward, even during the "hiatus". Now they are at record radius, and that is very likely to increase, at least for a little while. The reason is that the change in moving average depends on both the new readings, and the old readings that they replace. Mid-2014 was a relatively cool period, so as long as 2015 is warmer, the running mean will increase.

In these plots, there is a continuous curve in rainbow colors, violet in 1950, and ending with red now. It goes clockwise, 36°/year, crossing the y axis every decade as marked. Radial distance represents temperature anomaly (according to the source) as marked on the x axis, and shown with faint circles. The running mean is centered, so the latest at the bottom shows as Dec 2014.

So here is the NOAA Land/Ocean plot. A curiosity here is that the NOAA report says the maximum 12-month average is 0.83°C; I get 0.81, on their data. But the pattern is the same. Spiralling outward indicates warming, and it is clearly happening, with minor variations, since about the third circuit (70's). And it is now at record level (and has been for six months), and heading outward.



Here is GISS Land/Ocean, which looks much the same:



And here is HADCRUT 4. It probably shows the least adherence to uniform growth, and has more pronounced excursions in 1998, 2005, 2007 and 2010. It's still well in front now, though.



2015 will be a record year if the curve stays outside to previous levels for six more months. And as I said above, a month or two more of expansion is very likely, just on the basis of cooler mid-year 2014.

ps Arctic ice had been holding up fairly well. But it is showing signs of downturn in the last five days, dropping below 2010, and close to 2014.