Overall long term trend remains positive in lower troposphere.
Most often on this forum we have looked at either surface temperature data from surface observations or lower tropospheric temperature data derived from satellite sounders. Today I’d like to point out a short scale trend in global radiosonde data showing cooling in the last year, as well as examine the record back to 1958.
The HadAT2 dataset from the Hadley Climate Center takes in balloon radiosonde measurements taken twice daily from hundreds of points around the globe and compiles it. Here is how they describe it:
HadAT consists of temperature anomaly timeseries on 9 standard reporting pressure levels (850hPa to 30hPa). The data is also available as equivalent measures to the broad MSU satellite weighting functions. The gridded product is derived from 676 individual radiosonde stations with long-term records. Because of the criteria of data longevity the resulting dataset is limited to land areas and primarily Northern Hemisphere locations. Radiosondes are single launch instruments and there have been many changes in instruments and observing practices with time. HadAT has used a neighbour-based approach to attempt to adjust for these effects and produce a homogeneous product suitable for climate applications.
They also go on to add a cautionary note about data uncertainty:
It is important to note that significant uncertainty exists in radiosonde datasets reflecting the large number of choices available to researchers in their construction and the many heterogeneities in the data.
And they go on to suggest alternate data sets for “robustness”. For now, we’ll just stick to HadAT2, but if readers want to do comparisons against the other datasets I’ll post results here. Just visit the HadAT2 page for links.
Here is the plot of all the pressure altitude levels of temperature data since 1958:
Click for a larger image
The source data set in ASCII text is available here
In the graph above, the warmer (redder) colors represent lower tropospheric data closer to the surface (850mb for example) while the cooler blues (cyans) are the high altitude data (100, 50, and 30mb). You can see in the 850mb data, the familiar signature of the 1998 Super El Nino that raised temperatures globally.
You can also see the slow upward trend in temperature in the lower troposphere data since 1958, about 0.6°C.
To give laymen readers an idea of the vertical scope of the plot above, here is a graphic showing pressure versus atmospheric altitude.
Graphic Source: PhysicalGeography.net
Now what is interesting is when we zoom the data plotted above down to a five year level, as shown in the graph below.
Click for a larger image
Note that while preceding years have been relatively flat for trend, during the last 12-18 months, there has been a noticeable downward trend in all atmospheric levels except 50mb and 30mb, while 100mb appears to remain flat. The 50mb and 30mb levels don’t appear to have much of a positive trend in the last 12-18 months that differentiate it from the last 5 years.
For those who will immediately jump on the standard gripe of “cherry picking” let me say that I’m only using the zoomed 5 year time period above to better visually illustrate the change in the last 12-18 months. As I mentioned above, the overall long term trend since 1958 in the lower troposphere is still positive.
But whatever has happened globally in the last 12-18 months, the temperature downturn we see makes for interesting discussion.
randomengineer:
Bingo.
I’m a bit late to this, but –
There seems to me to be a confusion further up the thread between the relative weight of forcings (yes, it’s true that if GHG forcings increase they will be proportionately more significant than others) and the absolute effect of internal variation.
The ENSO effect, for example, is not an external radiative forcing. Regardless of the energy balance (and what that means in terms of rising or falling background temperatures), the extent of natural internal variation is not reduced proportionately.
Of course, there are those who speculate that a changing energy balance may increase the range of natural internal variability, but that’s a wider issue.
PDO
heck, why stop there. PDO, AMO, NAO, AO, AAO, and IPO all flipped from cool to warm from 1977 to 2001.
Then, the above all being in a warm phase already, the temperatures stopped going up.
Now the PDO has gone cool, and posibly the AO (decades ahead of schedule). The NAO and AMO are still warm but looking shaky. Temperatures are off by half a degree C,
What goes up may reasonably be expected to come down.
(The “dead sun” is a legit but separate issue.)
One has to do careful studies of the changes in the severity or frequency of extreme events or temperature records in order to draw rigorous conclusions.
Well, so far as hurricanes go, accumulated cyclone energy (ACE) and numbers of storms seem to have decreased rather steadily over the last few decades.
The Rev posted on this subject a while back.
Ah, Joel is not so bad. I’ve seen much worse.
I think I understand his main point (AGW is an underlying upward push that does not negate natural variation). I merely disagree (mostly). I think there has been some giveback from the LIA, and the recent (late 70s – 1998) increase is due to multidecadal ocean/atmospheric cycles flipping to warm.
I think the Aqua satellite data is showing us that the positive feedback from CO2 may well be negative feedback leading to more low clouds, increased albedo and homeostasis.
And now the cycles are beginning to go cool again.
Please let’s not hear any of this “we scientists know better than you laymen” talk.
Maybe they do; maybe they don’t. But it is the laymen who get to decide policy!
Evan Jones – ‘maybe they do; maybe they don’t’.
Yes. I’m prepared to accept that in relation to their sphere of expertise, indeed they do (know more than a layman). What I object to (gently) is the ‘I’m a scientist, trust me’ line – a layman with the requisite maths and science education can understand the papers and make cogent judgements. And so far as logic goes – that is for everyone, not just scientists.
Of course, one needs to see a number of papers not just those from one point of view. But given that, I see no difficulty in engaging in rational analysis of the science.
I take your point (to the effect that it is the laymen who decide). But if laymen can decide (and they do as you say), it follows that they can also agree and disagree ( or even agree to disagree.).
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