August 2008 Update on Global Temperature – HadCrut
Posted by The Diatribe Guy on August 18, 2008
So far, all the major temperature measures are in general agreement with regard to July 2008 versus June 2008 anomalies. HadCrut is in agreement with GISS in the relative anomaly comparison between July 2008 to July 2007. HadCrut and GISS derive their estimates from surface station (SST) readings (though HadCrut doesn’t publish their methodology and GISS does, as convoluted as it may be). The SST measures differ from the satellite data in the year over year comparison, with the satellites showing more dramatic cooling from last year.
The current HadCrut reading is 40.30, compared to 31.20 in June. This jump is not as large as GISS – it’s not quite a full tenth of a degree Celsius, whereas GISS was a quarter of a degree. However, both of the measures were nearly identical to previous year, with only the smallest of decreases (July 2007 was 40.6 for HadCrut).
As for where July ranks in the HadCrut data, the 40.3 reading is the coolest reading since 2004, and second coolest since 2000. So, for those looking at the short-term trends, anticipating that we are on the trip back down from the recent peak, the data can support that assertion. The data can also support the longer-term perspective of warming, since the current July reading is the eight warmest anomaly in the HadCrut record. I’m sure both sides will use the data as they desire.
In my opinion – as strictly a data guy – I have to subscribe to the shorter-term trend as the current dominant trend, riding a curve of an overall long-term warming trend. The difference in my perspective from traditional AGW warmers is that I believe the real trend is the overall trend that shows minor warming over the long-term that is in no way a concern. There are accelerated warming and cooling cycles around this long-term trend line, and we’ve experience accelerated warming over the last few decades. It makes sense to imagine that there will now be a cooling trend that pulls us back to – and perhaps even under for a time – the overall trend line. That overall trend is presented here:
The consecutive months trend of year-over-year cooling is only at three months, thanks to April’s reading being higher than April 2007. But 12 of the last 13 anomalies have had a cooler reading than the prior year.
The new reading maintained the cooling period from the prior month. It actually removed a month from the beginnning of the trend, while adding a month at the end. Here is that chart:
The last 12-month average anomaly is 29.9, which is the coolest 12-month reading since the period ending October 2001.
The predicted anomaly for the month of July was around 33, so the new anomaly came in a bit higher than predicted, though less than a tenth of a degree off. The projected anomaly for August is about 37 based on my predictive model. Depending on the individual models, the potential range of anomalies is from 19.3 to 48.3. Best estimate is in the 35.9 to 37.0 range.
The long-term predictive ability of the model is still questionable, and I will monitor that. It was built more with the specific error term minimized against the next month’s accuracy only. Still, logic dictates that the next month’s best prediction should present the subsequent month’s best prediction, and so on. Carrying this out a few years shows fairly steady temperature anomalies through the end of 2009, though slightly cooler. We will start to see cooler anomalies in 2010, with some becoming negative. I have only gone through 2012, but the model shows relentlessly negative anomalies from mid-2011 to the end of 2012. Here’s hoping my model’s a bust.
I present the next series of short-term charts for the interested reader. I’m not trying to ignore the longer term trendlines, which show positive slopes on the raw data, while declining slope trends. I am not presenting all of those because they are ultimately pretty similar to the GISS charts (though GISS has higher slope values, indicating more severe warming than HadCrut). In my previous post you can enjoy all the charts for various trend periods.