Since 1958 Cuba has been subject to an almost total trade embargo by its nearest neighbour, the USA. The result is that much of Cuba looks like it is stuck in a time warp from the 1950s, and the same can be said for its climate. There has been no permanent rise in temperatures in over 130 years. Are these two facts related? How much do industrialization and consumerism lead to warming of the local climate, and how much is due to carbon dioxide? Cuba could be an interesting case study.
Fig. 107.1: The mean temperature change for Cuba relative to the 1971-2000 monthly averages. The best fit is applied to the monthly mean data from 1888 to 2007 and has a slight negative gradient of -0.05 ± 0.05 °C per century.
Like all the US states that border the Gulf of Mexico, Cuba has not experienced any global warming. In fact over the last 120 years the climate of Cuba has remained fairly stable as shown by the mean temperature anomaly (MTA) data for the state illustrated in Fig. 107.1 above.
The MTA in Fig. 107.1 was calculated by averaging the temperature anomalies from the eleven longest temperature records for the state. All these records had over 400 months of temperature data before the end of 2013 but there is only long stations with more than 1200 months of data, and eight medium stations with over 480 months of data. For a full list of stations see here.
The anomalies for each station were determined using the usual method as outlined in Post 47. This involved first calculating the monthly reference temperatures (MRTs) for each station using a set reference period, in this case from 1971 to 2000, and then subtracting the MRTs from the raw temperature data to deliver the anomalies. If a station had at least twelve valid temperatures per month within the MRT interval then its anomalies were included in the MTA calculation. In total ten stations were included with only one (Havana) being excluded for lack of data between 1971 and 2000. The total number of stations included in the MTA in Fig. 107.1 each month is indicated in Fig. 107.2 below. The peak just around 1980 suggests that the 1971-2000 interval was indeed the most appropriate. It also shows, though, that the trend before 1940 is dependent on data from only one station: Habana Casa Blanca.
Fig. 107.2: The number of station records included each month in the mean temperature anomaly (MTA) trend for Cuba in Fig. 107.1.
The locations of the eleven main stations are shown in the map in Fig. 107.3 below. This appears to show that the geographical spread is fairly uniform, although there does appear to be a greater concentration of stations in the capital, Havana. This variation in station density is probably not sufficient to significantly distort the average in Fig. 107.1 from its true value though. In which case the simple average of the anomalies from all stations used to construct the MTA in Fig. 107.1 should still yield a fairly accurate temperature trend for the country as a whole. Only four stations in Cuba appear to have warming trends, where a warming trend is defined as one where the temperature gradient for 1911-2010 is positive and exceeds twice the error in that trend.
Fig. 107.3: The (approximate) locations of the eleven longest weather station records in Cuba. Those stations with a high warming trend between 1911 and 2010 are marked in red while those with a cooling or stable trend are marked in blue. Those denoted with squares are long stations with over 1200 months of data, while diamonds denote stations with more than 400 months of data.
Next I calculate the corresponding MTA result based on data that has been adjusted by Berkeley Earth (BE). The result is shown in Fig. 107.4 below and, unlike the raw data in Fig. 107.1, it exhibits a strong warming trend with temperatures rising by over 1°C since 1890.
Fig. 107.4: Temperature trends for Cuba based on Berkeley Earth adjusted data. The best fit linear trend line (in red) is for the period 1891-2010 and has a gradient of +0.79 ± 0.02°C/century.
Comparing the curves in Fig. 107.4 with the published Berkeley Earth (BE) version in Fig. 107.5 below indicates remarkably good agreement at least as far back as 1920. This indicates that the simple averaging of anomalies to generate the MTA in Fig. 107.1 is as effective and accurate as the more complex gridding method used by Berkeley Earth. It also means that the averaging process cannot be responsible for the large difference in trends between that using unadjusted data in Fig. 107.1 and that using adjusted data in Fig. 107.4.
Fig. 107.5: The temperature trend for Cuba since 1820 according to Berkeley Earth.
The differences between the MTA in Fig. 107.1 and the BE versions using adjusted data in Fig. 107.4 and Fig. 107.5 are instead mainly due to the data processing procedures used by Berkeley Earth. These include homogenization, gridding, Kriging and most significantly breakpoint adjustments. These lead to changes to the original temperature data, the magnitude of these adjustments being the difference in the MTA values seen in Fig. 107.1 and Fig. 107.4. The magnitudes of these adjustments are shown graphically in Fig. 107.6 below. The blue curve is the difference in MTA values between adjusted (Fig. 107.4) and unadjusted data (Fig. 107.1), while the orange curve is the contribution to those adjustments arising solely from breakpoint adjustments. Both are considerable with the former leading to an additional warming since 1880 of up to 1.8°C.
Fig. 107.6: The contribution of Berkeley Earth (BE) adjustments to the anomaly data in Fig. 107.4 after smoothing with a 12-month moving average. The blue curve represents the total BE adjustments including those from homogenization. The linear best fit (red line) to these adjustments for the period 1891-2010 has a positive gradient of +0.823 ± 0.019 °C per century. The orange curve shows the contribution just from breakpoint adjustments.
Summary
According to the raw unadjusted temperature data, over the past century the climate of Cuba has remained stable (see Fig. 107.1).
Over the same period adjusted temperature data from Berkeley Earth claims to show that the climate of Cuba has warmed by as much as 1.0°C (see Fig. 107.4 and Fig. 107.5).
Acronyms
BE = Berkeley Earth.
MRT = monthly reference temperature (see Post 47).
MTA = mean temperature anomaly.
List of all stations and their raw data files.
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