In my previous post I calculated the temperature trends for most of the countries in South-East Asia. This region comprises the countries of modern Indochina (Burma, Thailand, Malaysia, Laos, Cambodia and Vietnam) as well as Singapore and the Philippines. Unlike Berkeley Earth, I have not included Indonesia in this regional analysis, primarily because it is located mainly in the Southern Hemisphere. Instead I discussed the temperature trends of Indonesia separately in Post 31. There was no warming there except in the capital, Jakarta.
In Post 69 I showed that there has been almost no warming in Thailand, Malaysia, Vietnam or the Philippines either since 1900, with none is Burma (Myanmar) before 1980 (in fact the climate cooled by about 0.2°C) and perhaps about 1°C of warming since. Both Cambodia and Laos were excluded from the analysis in Post 69 because of their lack of data. In this post I will present calculations for the overall temperature trend of the entire region of South-East Asia. These will involve averaging all the long and medium individual temperature records from the region, but there are many ways to do this. I shall discuss the two most obvious methods.
Fig. 70.1: The (approximate) locations of the long and medium temperature records in South-East Asia. Those stations with a high warming trend are marked in red while those with cooling or stable trends are marked in blue. Those denoted with squares are long stations with over 1200 months of data.
The first method is a simple average of all the individual temperature time series from the various stations across the region. This will give a good approximation to the true regional trend if the stations are evenly distributed and if they have the same reference period for the monthly reference temperatures (MRTs). The map in Fig. 70.1 above suggests that the geographical spread of stations is fairly even, but with significantly fewer stations in Burma and Vietnam than in Malaysia, Thailand and the Philippines. It can also be seen from Fig. 70.1 that most of the stations in Malaysia and Vietnam are near the coast.
Fig. 70.2: The temperature trend for South-East Asia based on an average of anomalies from all long and medium stations. The best fit is applied to the monthly mean data from 1888 to 2007 and has a positive gradient of +0.09 ± 0.03 °C per century. The monthly temperature changes are defined relative to the 1961-1990 monthly averages.
The result of the employing the simple average method is shown in Fig. 70.2 above. The overall trend exhibits a gentle cooling of about 0.3°C for the 100 years before 1980, and a slight warming of 0.4°C since. Overall, the trend appears fairly stable with current temperatures not noticeably higher than in 1900.
Fig. 70.3: The temperature trend for South-East Asia based on an area weighted average of trends from all countries. The best fit is applied to the monthly mean data from 1888 to 2007 and has a positive gradient of +0.17 ± 0.03 °C per century. The monthly temperature changes are defined relative to the 1961-1990 monthly averages.
The second method for combining the data is to average the trends for the different countries, but to also weight each country's contribution in proportion to its area. These individual country trends are shown in the previous post. The advantage of this method is that it corrects for any bias due to differences in station density between countries. The disadvantage is that large countries with low station densities can introduce large errors due to their bigger area and less reliable national trend.
The result obtained using this method is shown in Fig. 70.3 above. It can be seen that the main difference from Fig. 70.2 occurs after 1980 where the recent warming is larger and close to 0.6°C. This difference is primarily due to the larger contribution from the trend for Burma. The overall trend is, though, still much less than that claimed by mainstream climate science.
Fig. 70.4: Temperature trends for South-East Asia based on an average of Berkeley Earth adjusted data from all long and medium stations. The best fit linear trend line (in red) is for the period 1891-2010 and has a gradient of +0.83 ± 0.02°C/century.
If we compare these results with those derived using Berkeley Earth (BE) adjusted data, the difference is profound. A simple average of BE adjusted data yields the curve in Fig. 70.4 above. It is unrecognizable from the curve in Fig. 70.2, but perhaps not unsurprisingly, follows the official IPCC global trend very closely. The warming is over 1°C, and it is continuous except for a hiatus in the 1940s and 1950s.
Fig. 70.5: Temperature trends for South-East Asia based on an area weighted average of Berkeley Earth adjusted data. The best fit linear trend line (in red) is for the period 1891-2010 and has a gradient of +0.80 ± 0.02°C/century.
Nor does the weighted area average method fare any better for BE adjusted data, as Fig. 70.5 above shows. In fact the curves are almost indistinguishable from their equivalents in Fig. 70.4. This is probably because the station density remains fairly constant across the region as Fig. 70.1 shows. So, irrespective of the method, the BE adjusted data claims a warming of over 1°C for the region, while the raw data in Fig. 70.2 and Fig. 70.3 tells a completely different tale.
Fig. 70.6: The temperature trend for South-East Asia since 1840 according to Berkeley Earth.
Finally, we can compare these results with the trends published by Berkeley Earth. These are shown in Fig. 70.6 above. It is pretty clear that both the 12-month and 10-year moving averages shown in Fig. 70.6 are in close agreement with their counterparts in both Fig. 70.4 and Fig. 70.5. This is despite the Berkeley Earth trends in Fig. 70.6 also incorporating data from Indonesia. Overall, the Fig. 70.6 curves are probably marginally closer to those in Fig. 70.5 than those in Fig. 70.4. This is not surprising as the area weighting method employed for Fig. 70.5 is closer in methodology to the homogenization methods used by Berkeley Earth and other climate groups than is the simple average method.
Conclusions
The regional temperature trends based on the raw data show little or no warming in the region over the last 100 years.
In contrast the adjusted data adds almost 1°C of warming over the last 100 years, primarily due to those adjustments. Without the adjustment there is no significant warming.
