I had thought about combining the temperature data for Papua New Guinea (PNG) with that of Indonesia, just as I did with East Timor (Timor Leste) in the previous post. Like East Timor, PNG shares an island (in this case Papua) with Indonesia, so from that point of view it would be logical. However, in the end I decided there was enough data in Indonesia, and extending the analysis to PNG would not only increase the data analysis complexity, but also the geographical area of coverage, and that would be too much.
Like Indonesia, PNG has only one long station with a temperature record longer than 1200 month (Port Moresby AP - Berkeley Earth ID: 157418). It also has seven medium stations with records of more than 480 months of temperature data, and there are approximately 30 other shorter records that are too small to be useful. One of the medium stations (Port Moresby - Berkeley Earth ID: 19383) is excluded from the following analysis even though it contains data that suggests temperatures in the late 1800s were up to 1.0 °C higher than in the early 20th century. This is because: a) it is close to another long station (Port Moresby AP - Berkeley Earth ID: 157418) which has longer and more complete data in the 20th century; and b) because it has no data after 1941, and so its monthly reference temperatures (MRTs) cannot be calculated for the same time period (1961-1990) as the other stations. For an explanation of MRTs, and how they are used to calculate the monthly temperature anomaly, see Post 4.
Fig. 32.1: Temperature trend for all long and medium stations in Papua New Guineasince 1900 derived using the Berkeley Earth adjusted data. The best fit linear trend line (in red) is for the period 1912-1999 and has a gradient of +0.83 ± 0.03 °C/century.
Averaging the Berkeley Earth adjusted anomaly data from the eight long and medium stations yields the temperature trends shown in Fig. 32.1 above. These are very similar to the versions published by Berkeley Earth and shown below in Fig. 32.2, which suggests that the weightings for each station used by Berkeley Earth in their averaging process were fairly equal.
Fig. 32.2: Temperature trend for Papua New Guinea since 1880 according to Berkeley Earth.
The high level of agreement between the data in Fig. 32.1 and Fig. 32.2 allows us to repeat the process for the raw anomaly data without the need for different station weighting coefficients. The result is shown below in Fig. 32.3.
Fig. 32.3: The temperature trend for Papua New Guinea since 1900. The best fit is applied to the interval 1912-1999 and has a gradient of 0.44 ± 0.07 °C per century. The temperature changes are relative to the 1961-1990 average.
It can be seen that once again, the temperature trend derived from the raw anomaly data in Fig. 32.3 is significantly different in its degree of warming compared to that derived using the Berkeley Earth adjusted data in Fig. 32.1 and Fig. 32.2. While there are qualitative similarities (the peaks at 1910 and 2000, and the local minimum around 1965), the overall temperature rise seen in the raw data is much less. At worst, the temperature rise seen in the raw data in Fig. 32.3 is less than 0.4 °C, while the 5-year average in 2010 is barely higher than the peaks in the same curve before 1940.
The 5-year average in 2010 is also only 0.3 °C higher than the 80-year average for 1903-1982. This is hardly conclusive evidence of cataclysmic global warming. In fact the 5-year mean in 2010 is less than two standard deviations above the pre-1982 mean. It is, therefore, within the expected range for natural fluctuations for the given timescale of 110 years.
The data in Fig. 32.3 is also noticeably noisier before 1950 than it is after 1950. This is because there are only two temperature records with data before 1950, and only one of those, Port Moresby AP (Berkeley Earth ID: 157418), is reasonably continuous.
A final point of interest is the qualitative similarity between the data for PNG in Fig. 32.3 above, and that for Queensland shown in Fig. 24.4 previously. The biggest difference appears to be the overall temperature rise which is significantly higher in the case of Queensland (0.74 °C per century compared to 0.44 °C per century for PNG).
Fig. 32.4: The contribution of Berkeley Earth (BE) adjustments to the anomaly data after smoothing with a 12-month moving average. The linear best fit to the data is for the period 1904-2012 (red line) and the gradient is +0.34 ± 0.03 °C per century. The orange curve represents the contribution made to the BE adjustment curve by breakpoint adjustments only.
It is clear that the Berkeley Earth adjusted data for PNG results in almost double the temperature rise since 1900 compared to that found using the raw data. The actual difference is shown in Fig. 32.4 above and amounts to about 0.34 °C per century, most of which is due to breakpoint adjustments.
Conclusions
1) Papua New Guinea has experienced a modest temperature rise since 1960 (perhaps 0.5°C), but overall, temperatures have barely risen by more than 0.3 °C since 1900 (see Fig. 32.3).
2) The temperature trend for Papua New Guinea from 1900 to 2013 is broadly similar to that seen in neighbouring countries and regions (e.g. Indonesia, Australia and New Zealand).
3) The fluctuations in temperature for Papua New Guinea appear broadly consistent with natural variability. The magnitude of these temperature changes clearly challenge the current prevailing paradigm regarding anthropogenic global warming of more than 1.0 °C.
4) The adjustments made to the temperature data by Berkeley Earth have once again had a material and significant impact on the overall temperature trend. It is only with the inclusion of these adjustments that the temperature trend for Papua New Guinea resembles that of the IPCC HadCRUT4 temperature record.
5) The lack of data means that the temperature record of Papua New Guinea before 1950 is extremely uncertain. It can only be speculated upon based on similarities with neighbouring countries.
Addendum
The maximum number of temperature records used to derive the mean temperature trend in Fig. 32.3 is seven but before 1940 this reduces to two or less (see Fig. 32.5 below). See here for a complete list of all stations in Papua New Guinea.
Fig. 32.5: The number of station records included each month in the mean temperature anomaly (MTA) trend for Papua New Guinea in Fig. 32.3.
No comments:
Post a Comment