Monday, 5 April 2010

The warmest year?

Since the whole brouhaha over stolen climate scientists’ emails broke last year, a clear emphasis of the science obfuscation lobby has been trying to con the public into believing the data is all flawed, and there’s nothing to worry about. One of the fall-backs in the attack on the mainstream has been the claim that satellite data hasn’t been showing as strong an increase as the data sets based on surface measurements. While NASA does their measurement independently from the UK Hadley Climactic Research Centre (CRU), the conspiracy-theoretic view is that they are all in it together.

Well, how is the satellite record looking lately? I moseyed over to the AMSU-A temperatures site maintained by Roy Spencer of the University of Alabama at Huntsville (a favourite of the denialosphere for his consistently lower warming trend) and Danny Braswell of NASA and did the following, which you can repeat to update the results:
  1. click Draw graph
  2. click all the checkboxes and click Redraw
This is my result:
 The orange line that stops in April is the daily temperatures for this year. Observe that since 10 January, every day has had the highest temperature for that date in the satellite record going back to 1998. This particular data only starts partway through 1998 so we don’t have the complete picture back to the last record or near-record year (depending whose data you look at; some put 2005 slightly higher than 1998) but if this trend continues, 2010 will easily set a new record for satellite temperatures. Is this because we’re in a super-monster El Niño? Not if you look at the SOI (most recent values at time of writing from the Australian Bureau of Meteorology):
The thing to note here is that a negative SOI value puts us in El Niño (higher than average temperatures) while a positive value indicates La Niña (lower than average temperatures). Also, there is a lag of about a year between SOI peaks and global temperature peaks. The El Niño in 2004-2005 with a peak early in 2005 resulted in 2005 being an unusually warm year. Do we see a similar pattern for the last 12 months? No. Although we have been in an El Niño phase since the second half of 2009, that effect has been nowhere near strong enough to account for a new record in temperatures, certainly not as early as January 2010.

Could the SOI be amplified by a rising solar cycle? Sunspot numbers are trending up but we are still pretty close to the solar minimum:
If you’d prefer to look at total solar irradiance (TSI) as measured by satellites, rather than sunspots, go to PMOD, where you’ll see the energy inputs from the sun are not on a steep upwards trend and should be significantly lower than in 2004-2005:
You have to line this data up with SOI to get a good idea of what is causing short term blips in global temperatures: El Niño does not in general coincide with the peak of the solar cycle. At some point this will happen, resulting a really hot year. But leave this aside, since it won’t happen soon. What we have now, early 2010, is a temperature trend tracking above all recorded temperatures since 1998 (or more properly 1999, since we don’t have 1998 temperatures in the first half of the year in the AMSU-A data set) and we can’t pin that effect on El Niño or on the sun.

What next? Is someone already planning to steal Spencer’s emails?


I’ve plotted the mean daily temperature anomaly versus 2005 (each day minus the same day in 2005) for the year to 25 April. The trend (linear regression) over this period is 6°C per century – making up for lost time from previous slower warming by satellite measurements? Oh, and the correlation coefficient of 0.79 is highly significant even with this small sample size. Enjoy (or not, if you don’t want warming to be real). For missing data (a small fraction of the total), I took the average of the two nearest days that did have data.
And here's the AMSU-A big picture for 25 April 2010:

and an update on the SOI picture:

SOI is not the whole picture for predicting the effect of ENSO on temperature; a more comprehensive model clearly shows 2010 should be a cooling phase, not a warming phase.

Still lots of time in the year …

Yet Another Update

If you go to the site now, it says Channel 4 failed in 2008. That’s what happens in science: a weird result is more likely to be a consequence of instrument failure than anything else. The major data sets do show 2010 as one of the warmer years though not by a significant margin (despite the other data indicating it should have been a cool year, including the solar cycle starting to exit an unusually deep low and a strong La Niña).

What I find particularly odd about all this is this note (dates in US format, so this is in March)
03/06/2008/1200UTC:NOAA-16 AMSU-A channel 4 has gone bad.  As a result, NOAA-16 ATOVS sounding files are no longer being produced by NESDIS, thus they are no longer in the "atovs" dumps in the GDAS and CDAS networks and they (temperature retrievals) are no longer available for assimilation by the CDAS.  The "atovs" dumps now contain only NOAA-15 ATOVS soundings and only these temperature retrievals (cloudy only) are assimilated by the CDAS.  In addition, the failed channel 4 data has resulted in no NOAA-16 AMSU-A data being assimilated by the NAM/NDAS or GFS/GDAS GSI (even though these files are still being produced by NESDIS and NOAA-16 AMSU-A data continue to be dumped in the "1bamua" files in the CDAS, GDAS, GFS, NDAS and NAM networks).
It seems someone knew nearly 2 years before the weird 2010 data went live that there was something wrong with the data. Curiously, we didn’t see wild accusations flung around the blogosphere about this one. I leave it to the reader to explain.