Tuesday, January 9, 2018

December global surface temperature unchanged; 2017 was second warmest year.

TempLS mesh anomaly (1961-90 base) was virtually unchanged, from 0.716°C in November to 0.721°C in December. This compares with the rise of 0.075°C in the NCEP/NCAR index, and a similar rise (0.05) in the UAH LT satellite index.

The TempLS average for 2017 was thus 0.757°C, which puts it behind 2016 (0.836°C), and ahead of 2015 (0.729°C), and so was the second warmest year in the record. I expect this will be a common finding, although 2015 is close. I'll post a graph showing the history of records.

The breakdown is interesting. The main cooling effect came from SST, well down on November. The balancing rises came from the Arctic and Siberia. Since TempLS, like GISS, is sensitive to Arctic temperature, indices like NOAA/HADCRUT may well show a fall. Otherwise the map shows those effects, along with much-discussed cold around the Great Lakes region and also W Sahara.

Here is the temperature map:

This post is part of a series that has now run for six years. The TempLS mesh data is reported here, and the recent history of monthly readings is here. Unadjusted GHCN is normally used, but if you click the TempLS button there, it will show data with adjusted, and also with different integration methods. There is an interactive graph using 1981-2010 base period here which you can use to show different periods, or compare with other indices. There is a general guide to TempLS here.

The reporting cycle starts with a report of the daily reanalysis index on about the 4th of the month. The next post is this, the TempLS report, usually about the 8th. Then when the GISS result comes out, usually about the 15th, I discuss it and compare with TempLS. The TempLS graph uses a spherical harmonics to the TempLS mesh residuals; the residuals are displayed more directly using a triangular grid in a better resolved WebGL plot here.


  1. Thanks for the timely update Nick. I like your TempLS Mesh analyses. I find it interesting that the Arctic is once again not near as cold as normal this NH winter, as has been the case for the two previous NH winters. More and more I am convinced that the Arctic Ocean water temperature is the main driving factor, probably from currents bringing in surface water that is not as cold as normal mainly from the North Atlantic, but also to some extent in the Bering Sea area. I suspect this is yet another somewhat random feedback driven and limited oscillation that may be occurring over time spans of decades (perhaps related to NAO?). I wish we had several thousand years of actual measurements similar to what we have today. Oh well, I guess our descendants will have that benefit some day many generations down the road and will look back to this time period as being poorly informed.

    I have been watching Arctic Ocean buoy observations for a couple of years now and noticed that oddly this NH winter, there are only three buoys reporting to the global synoptic weather network that are not grounded at the coast, unlike past years where there are typically about a dozen or more. There are more than three reporting at the International Arctic Buoy Programme, but most of these are not reported to the synoptic weather network, so I doubt if those data are being ingested into the global weather models. You'd think with all the interest in the Arctic weather these days there would be more buoys and not less now.

    Another problem I've noticed is that some of the buoys are only reporting "surface" temperature at IABP, which is the temperature below the buoy hull and is either the temperature of the sea ice or surface water, as opposed to the "air" temperature. I noticed that two of the buoys reporting supposed air temperatures in the synoptic weather network were actually reporting what is shown as the "surface" ice temperature at IABP and these buoys did not have a reported "air" temperature at IABP. For buoys that report both the ice and the air temperature at IABP, the air temperature is almost always substantially lower than the ice temperature in the NH winter extended night. Thus, if I am not mistaken, this problem could be biasing the weather models a bit high over the Arctic Ocean in recent months, especially with the sparse data in the synoptic network. Perhaps the reanalyses pick up the additional IABP data, but I don't know if they do.

    Yet another potential serious problem with Arctic winter measurements is possible rime icing on the air temperature sensors, especially at unattended automated weather stations which are becoming more common these days. Ice encased sensors are like little igloos and will cause the readings to be substantially higher during times of extreme cold which would include most of the winter, although they may also read too low when air that is not as cold is advected into the area, mainly in the spring before the ice melts. I don't know how often this problem might occur nor have I been able to find any studies of the situation. I do know that weather stations on high peaks at high latitudes have to deal with severe rime icing, like Mt Washington in the US and Cairngorn in Scotland. I'm not sure how they deal with the icing for temperature measurements at Mt Washington, but I have seen photos of a retractable measurement platform at Cairngorn that is only raised to make spot measurements, rather than continuous measurements. My guess is this type of solution is not likely being used for Arctic buoys or most automated weather stations.

    I'm hoping some readers here may have more knowledge of these issues and might be willing to share so the rest of us can learn.

    1. Thanks Bryan,
      On the question of ocean heat transfer into the Arctic, you might find the SST movies helpful. I mainly look at them for the ice, but they do show something about the convection of warm water.

      I don't know much about the workings of the ice buoys. I wish I did, since they would make a valuable addition to the data I use. So yes, I do hope that someone can help.

    2. Bryan,

      With ice present, arctic ocean water is held near the freezing point of sea water. Shrinking sea ice is a bigger factor in arctic winter warming. Reanalysis has a significant cold bias when sea ice data is not incorporated.