112: Venezuela - temperature trends WARMING

The climate of Venezuela is interesting because the country sits between Colombia to the west and the Lesser Antilles to the north. In this blog I have already examined the climate for both these regions and the results are not entirely consistent. The mean temperature of Colombia has remained fairly stable since 1940, increasing only slightly by about 0.1°C (see Fig. 95.2 in Post 95). The caveat to this is that there is no temperature data for the country before 1920 and only two stations of note with data before 1940. The Lesser Antilles, on the other hand, have more data but spread over a larger area, and this data shows much more warming, up to 2°C since 1890 (see Fig. 111.3 in Post 111). It turns out that the climate of Venezuela more closely resembles that of the Lesser Antilles than it does its neighbour Colombia as can be seen in Fig. 112.1 below.

Fig. 112.1: The mean temperature change for Venezuela relative to the 1976-2005 monthly averages. The best fit is applied to the monthly mean data from 1941 to 1980 and has a slight positive gradient of +0.28 ± 0.31 °C per century.

The main features of the data in Fig. 112.1 are very similar to those seen in Fig. 111.3 of Post 111. Between 1940 and 1980 the climate is stable, with the mean temperature rising by at most 0.1°C, but after 1980 there is a rapid temperature increase of over 0.5°C. This is consistent with other trends seen in the region such as for Puerto Rico (see Fig. 110.1 in Post 110) and the Dominican Republic (see Fig. 109.3 in Post 109). Yet the mean temperature anomaly (MTA) dataset in Fig. 112.1 also displays a large jump in temperatures of over 1.5°C before 1940. This is not seen in the Puerto Rico or the Dominican Republic data, nor is it seen in the data for Colombia (see Fig. 95.2 in Post 95), but it is seen in the data for the Lesser Antilles (see Fig. 111.3 in Post 111). In both cases the MTA before 1940 is based on data from only about five stations or less (see Fig. 112.2 below and Fig. 111.4 of Post 111), yet the fact that they corroborate each other suggests that the data may be more reliable than than I first thought and may be indicative of real climate change. The problem is that, if this is true, it poses a lot of difficult questions about the real nature of climate change.

Fig. 112.2: The number of station records included each month in the mean temperature anomaly (MTA) trend for Venezuela in Fig. 112.1.

If we assume that the temperature rises of 1.5°C from 1900 to 1940 that are seen in Venezuela (see Fig. 112.1 above) and the Lesser Antilles are real, then we need to ask the question, why?

Historical measurements of carbon dioxide (CO₂) levels suggest that atmospheric CO₂ levels increased from about 290 ppm in 1880 to about 310 ppm in 1940. But even with the best will in the world it is difficult to believe that a 7% rise in CO₂ would result in a 1.5°C temperature rise. In Fig. 87.3 of Post 87 I showed that the most it could lead to was a rise of 0.08°C, and even then three quarters of that rise is likely to be negated by the pre-existing presence of water vapour in the atmosphere, the absorption spectrum of which overlaps both edges of the 15 µm CO₂ absorption band. So the temperature rise seen before 1940 in Venezuela is actually nearly one hundred times greater than would be expected from CO₂ alone. So if CO₂ cannot explain the temperature rise, what does that say about our faith in climate stability? For if the climate can fluctuate by 1.5°C from time to time off its own bat, why should we care about CO₂?

Then there is the more practical issue: why did no-one even notice this temperature rise? We are constantly being told by climate scientists that a 1.5°C rise in global temperatures would be disastrous for the planet. Yet just such an increase appears to have occurred in Venezuela and the Caribbean over a century ago and nothing untoward happened. 

Fig. 112.3: The (approximate) locations of the 21 medium weather station records in Venezuela. 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 stations with over 800 months of data, while diamonds denote stations with more than 480 months of data.

The mean temperature anomalies (MTA) in Fig. 112.1 were calculated by averaging the temperature anomalies from the 38 longest temperature records for the state. The anomalies for each station were determined using the usual method as outlined in Post 47. All the records used in calculating the MTA had over 240 months of temperature data before the end of 2013 and 21 were medium stations with over 480 months of data. Of these three had over 1000 months of data and a further ten had over 800 months of data. For a full list of stations see here. 

The locations of the medium stations are illustrated in Fig. 112.3 above. This map appears to show that the geographical spread of these stations is fairly uniform but confined to the northern half of the country. The variation in station density is probably not sufficient to significantly distort the average in Fig. 112.1 from its true value though. In which case the simple average of the anomalies from all stations used to construct the MTA in Fig. 112.1 should still yield a fairly accurate temperature trend for the country as a whole. This can be verified by calculating the equivalent MTA, but using Berkeley Earth (BE) adjusted data, and comparing the results with the official BE version. If they are the same then the averaging process should be sufficiently accurate.

Fig. 112.4: Temperature trends for Venezuela based on Berkeley Earth adjusted data. The best fit linear trend line (in red) is for the period 1941-2010 and has a gradient of +1.06 ± 0.07°C/century.

The corresponding MTA result based on data that has been adjusted by Berkeley Earth (BE) is shown in Fig. 112.4 above and, unlike the raw data in Fig. 112.1, it exhibits a strong warming trend that is more uniform in its gradient. The overall temperature rise from 1900 to 2010 is about 1.5°C and so is significantly less than the 2.2°C that is seen with the raw data in Fig. 112.1.

If we then compare the curves in Fig. 112.4 with the published Berkeley Earth (BE) version in Fig. 112.5 below we see that there is remarkably good agreement between the two sets of data at least as far back as 1920. This indicates that the simple averaging of anomalies used to generate the BE MTA in Fig. 112.4 is as effective and accurate as the more complex gridding method used by Berkeley Earth in Fig. 112.5. In which case simple averaging should be just as effective and accurate in generating the MTA using raw unadjusted data in Fig. 112.1.

Fig. 112.5: The temperature trend for Venezuela since 1820 according to Berkeley Earth.

The differences between the MTA in Fig. 112.1 and the BE versions using adjusted data in Fig. 112.4 and Fig. 112.5 are therefore 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. 112.1 and Fig. 112.4. 

The magnitudes of these adjustments are shown graphically in Fig. 112.6 below. The blue curve is the difference in MTA values between adjusted (Fig. 112.4) and unadjusted data (Fig. 112.1), while the orange curve is the contribution to those adjustments arising solely from breakpoint adjustments. The vertical offset between the two curves is due to the difference in MRT intervals used by Berkeley Earth (1961-1990) and for Fig. 112.1 in this blog (1976-2005). What is clear is that after 1960 any adjustments made by Berkeley Earth to the data have little effect on the overall trend. However, before 1940 these adjustments appear to reduce the magnitude of the temperature rise by about 0.5°C. Overall the adjustments tend to make the MTA curve more linear.

Fig. 107.6: The contribution of Berkeley Earth (BE) adjustments to the anomaly data in Fig. 112.4 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 +0.19 ± 0.10 °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 Venezuela has warmed by over 2°C (see Fig. 112.1).

The climate change seen for Venezuela appears to be very similar to that of the Lesser Antilles (see Fig. 111.3 of Post 111) with 75% of the warming occurring before 1940 and very little warming between 1940 and 1980. This does not correlate with changes to atmospheric carbon dioxide concentrations over the same period. 

The origin of the 1.5°C warming before 1940 remains unexplained but its similarity to data from the Lesser Antilles suggests that the temperature change is real and not the result of measurement biases or errors.

The adjusted temperature data from Berkeley Earth appears to show that the climate of Venezuela has warmed more continuously (or linearly) and by about 1.4°C (see Fig. 112.4 and Fig. 112.5) since 1880.


Acronyms

BE = Berkeley Earth.

MRT = monthly reference temperature (see Post 47).

MTA = mean temperature anomaly.

List of all stations in Venezuela and their raw data files.

111. Lesser Antilles - temperature trends WARMING 0.5°C

Over the previous five posts I have examined the temperature records of the larger islands in the Caribbean that are found in the archipelago known as the Greater Antilles. In this post I will concentrate on the remaining islands of the Caribbean in the Lesser Antilles. 

The Lesser Antilles comprises all the islands of the Caribbean between the coast of Venezuela to the south and Puerto Rico to the north. These in turn are subdivided into three distinct smaller archipelagos: the Leeward Islands, the Windward Islands, and the Leeward Antilles (see Fig. 111.1 below).

Fig. 111.1: A map of the Caribbean Sea showing the location of the Lesser Antilles.

Most of the main islands of the Lesser Antilles have at least one weather station as illustrated in Fig. 111.2 below. However none are long stations with over 1200 months of data before 2014, although seven stations (Le Raizet, Lamentin, Codrington, Richmond Hill, Pearls Airport, St. Clair Experimental Station and St. Clair Ex) do have data from before 1900 (for a list of Caribbean stations see here). Unfortunately most of the data for these seven stations is significantly fragmented, and as a result the temperature anomalies fluctuate massively over time, particularly before 1940. The most prominent stations are shown in Fig. 111.2 and all have over 400 months of data before 2014.

Fig. 111.2: The (approximate) locations of the weather stations in the Lesser Antilles with over 400 months of data. 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.

As the stations shown in Fig. 111.2 appear well separated geographically we can as a first approximation average their individual temperature anomalies to determine the mean temperature anomaly (MTA) for each month for the region as a whole. These monthly MTAs are shown in Fig. 111.3 below. 

Fig. 111.3: The mean temperature change for the Lesser Antilles relative to the 1931-1990 monthly averages. The best fit is applied to the monthly mean data from 1941 to 1980 and has a slight positive gradient of +0.29 ± 0.14 °C per century.

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 1931 to 1990, 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. 

The MRT interval used here is twice as long as normal due to the wide distribution of data between different stations. As mentioned above, seven stations have data before 1900 but most of these have no data after 1960. In contrast most stations with data after 1970 have none before 1960. So the only way to include both sets is to widen the MRT interval. This will introduce some degree of error but that error will be limited to at most to a value equivalent to the rise in temperature across the MRT period. The data in Fig. 111.3 suggests that this is relatively small. The result is that a total of 25 stations were then included in the MTA calculation with the number each month indicated in Fig. 111.4 below. The station at St. Clair Ex was excluded due to a lack of data within the MRT interval.

The MTA in Fig. 111.3 has three distinct parts. Between 1940 and 1980 the trend is neutral as indicated by the best fit line in red. After 1980 there is significant warming of about 0.5°C. Before 1940 the picture is difficult to discern as there are fewer stations with data contributing to the MTA (see Fig. 111.4 below) and most of these stations have data that is discontinuous and highly erratic. In contrast, the MTA trend after 1940 is likely to be much more reliable as it is constructed using up to twenty different sets of station data most of which are continuous.

Fig. 111.4: The number of station records included each month in the mean temperature anomaly (MTA) trend for the Lesser Antilles in Fig. 111.3.

Next I calculate the corresponding MTA result based on data that has been adjusted by Berkeley Earth (BE). The result is shown in Fig. 111.5 below and, unlike the raw data in Fig. 111.3, it exhibits a strong continuous warming trend with temperatures rising by over 1.4°C since 1910 (see orange curve). This is about the same as is seen in the raw data. However if we just look at the period since 1930 where the data is more plentiful due to there being more active stations we see that the rise is temperature is about 1.0°C. This is 0.5°C more than is seen in the raw data in Fig. 111.3.

Fig. 111.5: Temperature trends for the Lesser Antilles based on Berkeley Earth adjusted data. The best fit linear trend line (in red) is for the period 1911-2010 and has a gradient of +1.19 ± 0.02°C/century.

The differences between the MTA in Fig. 111.3 and the BE version using adjusted data in Fig. 111.5 are 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. 111.3 and Fig. 111.5. The magnitudes of these adjustments are shown graphically in Fig. 111.6 below. The blue curve is the difference in MTA values between adjusted (Fig. 111.5) and unadjusted data (Fig. 111.3), while the orange curve is the contribution to those adjustments arising solely from breakpoint adjustments. From 1920 onwards both are similar in magnitude and lead to an additional warming since 1940 of about 0.5°C.

Fig. 111.6: The contribution of Berkeley Earth (BE) adjustments to the anomaly data in Fig. 111.5 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 1921-1980 has a positive gradient of +0.289 ± 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 forty year period up to 1980 the climate of the Lesser Antilles remained fairly stable before experiencing a rapid increase in temperature of about 0.5°C (see Fig. 111.3).

The data before 1940 is too fragmented and erratic to divulge a definitive trend.

Over the period 1901-2010 the adjusted temperature data from Berkeley Earth claims to show that the climate of the Lesser Antilles has warmed by as much as 1.5°C (see Fig. 111.5).

These adjustments appear to have added around 0.5°C of warming since 1940 (see Fig. 111.6).

 

Acronyms

BE = Berkeley Earth.

MRT = monthly reference temperature (see Post 47).

MTA = mean temperature anomaly.

 

List of all stations with data before 1900

Le Raizet (Guadeloupe)
Lamentin (Martinique)
Codrington (Barbados)
Richmond Hill (Grenada)
Pearls Airport (Grenada)
St. Clair Experimental Station (Trinidad and Tobago)
St. Clair Ex (Trinidad and Tobago)

110. Puerto Rico - temperature trends WARMING 0.8°C

The island of Puerto Rico is located just over 100 km due east of the island of Hispaniola and about 800 km north of the Venezuelan coast. It is one of the larger islands in the Caribbean but it is slightly smaller than Jamaica and much smaller than both Cuba and Hispaniola. And yet it has by far the best temperature data in the region with eight long stations and over thirty medium stations (for a full list of stations see here) and data that extends back to 1898. This is probably because it has been a US territory since 1898.

The temperature trend for Puerto Rico was determined by averaging the individual temperature anomalies from each station to generate the mean temperature anomaly (MTA) each month. These are shown in Fig. 110.1 below. Overall the temperature trend is positive with a modest warming of about 0.3°C in the 80 years before 1990 followed by a larger temperature rise of 0.5°C over the next 15 years. This fits with the pattern we have seen in many other countries of temperature stability before 1980 and a sudden rise of 0.5°C thereafter. While this is concerning and demanding of explanation, it is a long way short of the values claimed globally by climate scientists and the IPCC for land-based temperature rises.

Fig. 110.1: The mean temperature change for Puerto Rico relative to the 1951-1980 monthly averages. The best fit is applied to the monthly mean data from 1911 to 1980 and has a positive gradient of +0.39 ± 0.09 °C per century.

The temperature 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 1951 to 1980, 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 calculation of the regional mean temperature anomaly (MTA). The total number of stations included in the MTA in Fig. 110.1 each month is indicated in Fig. 110.2 below. The peak in the frequency around 1965 suggests that the 1951-1980 interval was indeed the most appropriate.

Fig. 110.2: The number of station records included each month in the mean temperature anomaly (MTA) trend for Puerto Rico in Fig. 110.1.

The map in Fig. 110.3 below illustrates the geographical distribution of the stations in Puerto Rico. There are clearly more stations in the eastern half of the island than in the west, but in both halves the distribution is fairly even except for a greater clustering around San Juan. This means that a simple average of station anomalies should be reasonably accurate as previous posts have demonstrated.

Fig. 110.3: The (approximate) locations of the 41 longest weather station records in Puerto Rico. 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 medium stations with more than 480 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. 110.4 below and, unlike the raw data in Fig. 110.1, it exhibits a continuous strong warming trend with temperatures rising by over 1.2°C since 1910 (see orange 10-year moving average curve). This is about 50% more than is seen in the raw data.

Fig. 110.4: Temperature trends for Puerto Rico based on Berkeley Earth adjusted data. The best fit linear trend line (in red) is for the period 1911-2010 and has a gradient of +1.13 ± 0.03°C/century.

 

Comparing the curves in Fig. 110.4 with the published Berkeley Earth (BE) version in Fig. 110.5 below indicates remarkably good agreement at least as far back as 1910. This indicates that the simple averaging of anomalies to generate the MTA in Fig. 110.1 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. 110.1 and that using adjusted data in Fig. 101.4.

Fig. 110.5: The temperature trend for Puerto Rico since 1820 according to Berkeley Earth.

The differences between the MTA in Fig. 110.1 and the BE versions using adjusted data in Fig. 110.4 and Fig. 110.5 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. 110.1 and Fig. 110.4. The magnitudes of these adjustments are shown graphically in Fig. 110.6 below. The blue curve is the difference in MTA values between adjusted (Fig. 110.4) and unadjusted data (Fig. 110.1), 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 1900 of up to 0.7°C.

Fig. 110.6: The contribution of Berkeley Earth (BE) adjustments to the anomaly data in Fig. 110.4 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 1911-2010 has a positive gradient of +0.471 ± 0.008 °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 Puerto Rico has warmed slowly before 1990 and then more rapidly thereafter (see Fig. 110.1). The total warming is likely to be about 0.8°C

Over the same period adjusted temperature data from Berkeley Earth claims to show that the climate of Puerto Rico has warmed by over 1.2°C (see Fig. 110.4 and Fig. 110.5).


Acronyms

BE = Berkeley Earth.

MRT = monthly reference temperature (see Post 47).

MTA = mean temperature anomaly.

List of all stations and their raw data files.

109. Hispaniola - temperature trends WARMING after 1990

To the east of Jamaica and Cuba is the island of Hispaniola. It is the second largest island in the Caribbean, and the largest by population. It is also divided between two separate countries: Haiti and the Dominican Republic. And just as the island is divided geographically and politically, so it is also divided by its temperature data.

To the west in Haiti there is only one station of note in the capital at Port-au-Prince airport, but this is also the only long station on the entire island that has over 1200 months of data before 2014 (all stations in Haiti are listed here). To the east in the Dominican Republic there are six medium stations with over 480 months of data and a further five stations with over 400 months of data (for a full list see here). The locations of all these twelve stations are indicated on the map below in Fig. 109.1. It can be seen that most 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, but five have stable or cooling trends. And nine of the twelve stations are located close to the coast. The interior of the island is therefore very under-represented.

Fig. 109.1: The (approximate) locations of the twelve longest weather station records in Haiti and the Dominican Republic. 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.

The other distinction between Haiti and The Dominican Republic is in the amount of observed warming seen in each country. The trend for Port-au-Prince airport is shown in Fig. 108.2 below and it clearly exhibits strong warming of over 3°C since 1900 with most of the warming having occurred since 1940. However the data is discontinuous and is not corroborated by any other station, mainly because there are no other stations with enough data locally. In fact it is the only temperature record of any significant length (i.e. over 400 months of data) in the whole of Haiti. It is also from a single station based in the capital city where over 10% of the Haitian population live, so that may also have a strong impact on the trend (e.g. note the difference in trends between Jakarta and the rest of Indonesia shown in Post 31).

 

Fig. 109.2: The mean temperature change for Port-au-Prince relative to the 1961-1990 monthly averages. The best fit is applied to the monthly mean data from 1916 to 1995 and has a strong positive gradient of +4.18 ± 0.09 °C per century.

 

In contrast, the Dominican Republic has eleven stations with data extending back to the 1960s or beyond, but none with data before 1940. Its mean temperature anomaly (MTA) over time is shown in Fig. 109.3 below, and while it also exhibits some warming since 1950, it is much more modest at about 1°C. However, this is not the whole story as there are issues regarding data coverage, both geographically and temporally.

 

Fig. 109.3: The mean temperature change for the Dominican Republic relative to the 1961-1990 monthly averages. The best fit is applied to the monthly mean data from 1951 to 2010 and has a positive gradient of +1.91 ± 0.13 °C per century.

 

The MTA in Fig. 109.3 was calculated by averaging the temperature anomalies from the eleven longest temperature records for the country. All these records had over 400 months of temperature data before the end of 2013. 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 1961 to 1990, and then subtracting the MRTs from the raw temperature data to generate 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. The total number of stations included in the MTA in Fig. 109.3 each month is indicated in Fig. 109.4 below.

 

Fig. 109.4: The number of station records included each month in the mean temperature anomaly (MTA) trend for the Dominican Republic in Fig. 109.3.

 

The data in Fig. 109.4 suggests that the most reliable data in Fig. 109.3 is between 1950 and 1990 as this is where the MTA is calculated using the largest number of stations. Yet the data in Fig. 109.3 suggests that the warming over this interval is negligible (i.e less than 0.2°C) with far more warming occurring in the 1990s where there is much less data. The lack of data for the interior of the Dominican Republic may also play an important factor in affecting the reliability of the warming trend.

Next I calculate the corresponding MTA result based on data that has been adjusted by Berkeley Earth (BE). The result is shown in Fig. 109.5 below and like the raw data in Fig. 109.3 it exhibits a strong warming trend. However in this case, the warming seen for adjusted data is actually less than that seen for the raw data with temperatures rising by only 0.7°C since 1950 compared to about 1°C in Fig. 109.3. This is reflected in the gradients of the best fits in each case with the best bit gradient in Fig. 109.3 being almost 50% greater than the equivalent in Fig. 109.5.

 

Fig. 109.5: Temperature trends for the Dominican Republic based on Berkeley Earth adjusted data. The best fit linear trend line (in red) is for the period 1951-2010 and has a gradient of +1.28 ± 0.06°C/century.

 

Comparing the curves in Fig. 109.5 with the published Berkeley Earth (BE) version in Fig. 109.6 below indicates remarkably good agreement at least as far back as 1950. This indicates that the simple averaging of anomalies to generate the MTA in Fig. 109.3 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 difference in trends between that using unadjusted data in Fig. 109.3 and that using adjusted data in Fig. 109.5.

 

Fig. 109.6: The temperature trend for the Dominican Republic since 1820 according to Berkeley Earth.

 

The differences between the MTA in Fig. 109.3 and the BE versions using adjusted data in Fig. 109.5 and Fig. 109.6 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. 109.3 and Fig. 109.5. The magnitudes of these adjustments are shown graphically in Fig. 109.7 below. The blue curve is the difference in MTA values between adjusted (Fig. 109.5) and unadjusted data (Fig. 109.3), while the orange curve is the contribution to those adjustments arising solely from breakpoint adjustments. Both show significant fluctuations, but there is a distinct negative trend overall.

 

Fig. 109.7: The contribution of Berkeley Earth (BE) adjustments to the anomaly data in Fig. 109.5 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 1951-2010 has a negative gradient of -0.62 ± 0.06 °C per century. The orange curve shows the contribution just from breakpoint adjustments.

 

Summary

According to the raw unadjusted temperature data, the climate of the Dominican Republic may have warmed by as much as 1°C over the past sixty years (see Fig. 109.3). But most of this warming appear to have occurred in the 1990s when there were fewer active stations (see Fig. 109.4). In contrast, there appears to be very little warming before 1990.

Over the same period adjusted temperature data from Berkeley Earth claims to show that the climate of the Dominican Republic has warmed more steadily, but by only 0.7°C since 1950 (see Fig. 109.5).

The lack of data for the Dominican Republic before 1950 and from its interior is a concern.

The data for Haiti comes from only a single station (Port-au-Prince airport) and exhibits much more warming than is seen for the Dominican Republic. It is also discontinuous at multiple times in its history and is uncorroborated by any other data.


Acronyms

BE = Berkeley Earth.

MRT = monthly reference temperature (see Post 47).

MTA = mean temperature anomaly.

List of all stations in Haiti.

List of all stations in the Dominican Republic.

108. Jamaica and Grand Cayman - temperature trends WARMING

To the south of Cuba lie the Cayman Islands and Jamaica. These islands have only five significant stations between them, one on Grand Cayman and the other four in Jamaica. Their locations are shown on the map in Fig. 108.1 below.

Fig. 108.1: The (approximate) locations of the five medium weather station records in Jamaica and Grand Cayman. Those stations with a high warming trend between 1911 and 2010 are marked in red.

All are medium stations with over 480 months of data, but only one has more than 900 months of data (Kingston-Norman Manley). Two stations have virtually no data before 1960 (Grand Cayman and Montego Bay) and two have virtually none after (Kingston and Negril Point Lighthouse). All five stations exhibit warming tends, 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. The average of the temperature anomalies from these five stations is shown in Fig. 108.2 below. The mean temperature anomaly (MTA) for the region exhibits two distinct warming trends, a moderate warming of 0.68°C per century before 1980 and a much larger jump after.

Fig. 108.2: The mean temperature change for Jamaica and Grand Cayman relative to the 1941-1980 monthly averages. The best fit is applied to the monthly mean data from 1901 to 1980 and has a positive gradient of +0.68 ± 0.07 °C per century.

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 1941 to 1980, 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. The total number of stations included in the MTA in Fig. 108.2 each month is indicated in Fig. 108.3 below.

Fig. 108.3: The number of station records included each month in the mean temperature anomaly (MTA) trend for Jamaica and Grand Cayman in Fig. 108.2.

Next I calculate the corresponding MTA result based on data that has been adjusted by Berkeley Earth (BE). The result is shown in Fig. 108.4 below and, unlike the raw data in Fig. 108.2, it exhibits a more linear warming trend with temperatures rising by about 1°C since 1910.

Fig. 108.4: Temperature trends for Jamaica and Grand Cayman based on Berkeley Earth adjusted data. The best fit linear trend line (in red) is for the period 1911-2010 and has a gradient of +0.87 ± 0.03°C/century.

Comparing the curves in Fig. 108.4 with the published Berkeley Earth (BE) version for Jamaica only in Fig. 108.5 below indicates remarkably good agreement at least as far back as 1920. This is despite the MTA in Fig. 108.4 including data from Grand Cayman. This would suggest that the simple averaging of anomalies to generate the MTA in Fig. 108.2 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 difference in trends between that using unadjusted data in Fig. 108.2 and that using adjusted data in Fig. 108.4.

Fig. 108.5: The temperature trend for Jamaica since 1820 according to Berkeley Earth.

The differences between the MTA in Fig. 108.2 and the BE versions using adjusted data in Fig. 108.4 and Fig. 108.5 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. 108.2 and Fig. 108.4. The magnitudes of these adjustments are shown graphically in Fig. 108.6 below. The blue curve is the difference in MTA values between adjusted (Fig. 108.4) and unadjusted data (Fig. 108.2), while the orange curve is the contribution to those adjustments arising solely from breakpoint adjustments. In this case, unlike most instances in previous posts for the region, the adjustments actually reduce the amount of warming.

Fig. 108.6: The contribution of Berkeley Earth (BE) adjustments to the anomaly data in Fig. 108.4 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 1911-1980 has a negative gradient of -0.252 ± 0.015 °C per century. The orange curve shows the contribution just from breakpoint adjustments.

Summary

According to the raw unadjusted temperature data, the climate of Jamaica and Grand Cayman has probably warmed by between 1°C and 2°C over the past century with only 0.5°C of warming occurring before 1980 (see Fig. 108.2). However, given that this is based on only five sets of data, and only three at most at any given time, this result contains a high degree of error.

Over the same period adjusted temperature data from Berkeley Earth claims to show that the climate of Jamaica has warmed by almost 1.0°C since 1900 (see Fig. 108.4) and 1.5°C since 1840 (see Fig. 108.5).


Acronyms

BE = Berkeley Earth.

MRT = monthly reference temperature (see Post 47).

MTA = mean temperature anomaly.

List of all stations in Jamaica.

List of all stations in the Cayman Islands.

107. Cuba - temperature trends STABLE

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.

106. Bahamas and Key West - temperature trends STABLE to 1988

The islands of The Bahamas stretch over a distance of more than 800 km on the edge of the Atlantic Ocean southeast of Florida. Yet only four weather stations in the region have sufficient temperature data to be useful (for a list see here), and two of these are in Nassau (see map in Fig. 106.1 below). In addition, however, there are two stations in Key West (Key West and Key West airport) that are so far from the Florida coast as to be possibly more representative of the climate of The Bahamas than that of Florida (see Post 103). For this reason I will include them in this analysis.

Fig. 106.1: The (approximate) locations of the six longest weather station records in The Bahamas and Key West. 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 medium stations with more than 480 months of data.

In total there are two long stations with over 1200 months of data before 2014 and four medium stations with over 480 months in this analysis. The two long stations both had more or less continuous data that stretched from before 1900 to 2013. The four medium stations were more problematic. Three had virtually no data before 1950 while the station at Nassau had no data after. Added to that, the station at Freeport airport had no data before 1970.

The temperature 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 1961 to 1990, 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 calculation of the regional mean temperature anomaly (MTA). 

As no one single time interval for the monthly reference temperatures (MRTs) would allow all six stations to be included in the final average, the MRT interval was set to be 1961-1990. The one station to be excluded from the MTA calculation in this case was the Nassau station, but this exhibits virtually zero temperature change over its data range from 1900 to 1950.

Fig. 106.2: The mean temperature change for The Bahamas and Key West relative to the 1961-1990 monthly averages. The best fit is applied to the monthly mean data from 1901 to 1980 and has a slight positive gradient of +0.11 ± 0.12 °C per century.

The resulting MTA is shown in Fig. 106.2 above. It can be seen that before 1988 there is only a very slight upward temperature trend that is less than the uncertainty in the trend. Then in 1988 the temperature jumps suddenly by about 0.5°C. This is similar to the jump of about 1°C that was identified earlier in Post 44 for the MTA of Europe which also occurred in or around 1988. Is this coincidence, or did something happen to data collection methods in 1988?

The total number of stations included in the MTA in Fig. 106.2 each month is indicated in Fig. 106.3 below. The peak in the frequency around 1980 suggests that the 1961-1990 interval was indeed the most appropriate, but it also shows how much of the MTA trend in Fig. 106.2 relies on data from just two stations: Nassau airport and Key West airport.

Fig. 106.3: The number of station records included each month in the mean temperature anomaly (MTA) trend for The Bahamas and Key West in Fig. 106.2.

Next I calculate the corresponding MTA result based on data that has been adjusted by Berkeley Earth (BE). The result is shown in Fig. 106.4 below.

Fig. 106.4: Temperature trends for The Bahamas and Key West based on Berkeley Earth adjusted data. The best fit linear trend line (in red) is for the period 1911-2010 and has a gradient of +0.79 ± 0.03°C/century.

 

Comparing the curves in Fig. 106.4 with the published Berkeley Earth (BE) version in Fig. 106.5 below indicates remarkably good agreement at least as far back as 1900 despite Fig. 103.4 also including data from Key West. This suggests that the simple averaging of anomalies I have used is effective and accurate, and adding the Key West stations was probably appropriate.

Fig. 106.5: The temperature trend for The Bahamas since 1750 according to Berkeley Earth.

The differences between the MTA in Fig. 106.2 and the BE versions using adjusted data in Fig. 106.4 and Fig. 106.5 are 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. 106.2 and Fig. 106.4. The magnitudes of these adjustments are shown graphically in Fig. 106.6 below. The blue curve is the difference in MTA values between adjusted (Fig. 106.4) and unadjusted data (Fig. 106.2), while the orange curve is the contribution to those adjustments arising solely from breakpoint adjustments. Both are considerable and produce an additional warming since 1900 of about 0.4°C.

Fig. 106.6: The contribution of Berkeley Earth (BE) adjustments to the anomaly data in Fig. 106.4 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 1901-1980 has a positive gradient of +0.682 ± 0.018 °C per century. The orange curve shows the contribution just from breakpoint adjustments.

 

Summary 

According to the raw unadjusted temperature data, over the ninety year period up to 1988 the climate of The Bahamas and Key West remained stable before experiencing a sudden jump in temperature of about 0.5°C (see Fig. 106.2).

Over the period 1901-2010 the adjusted temperature data from Berkeley Earth claims to show that the climate of The Bahamas and Key West has warmed by as much as 1.0°C (see Fig. 106.4).

Acronyms 

BE = Berkeley Earth.

MRT = monthly reference temperature (see Post 47).

MTA = mean temperature anomaly.

 

List of all stations

Nassau airport

Nassau

Abrahams Bay

Freeport airport

Key West

Key West airport

105. US southern states - summary of BE temperature adjustments

In my previous post I summarized the temperature trends since 1900 of the six US states closest to the Gulf of Mexico (Texas, Louisiana, Mississippi, Alabama, Georgia and Florida). All the trends were constructed using data from the longest available temperature records in the state, all involved averaging the temperature anomalies from over 90 different station records, and none exhibited a significant positive warming trend.

Yet in every case the official Berkeley Earth (BE) trend does exhibit warming, often lots of it. The difference of course is largely down to the adjustments that Berkeley Earth make to the data via homogenization, Kriging, gridding and of course breakpoint alignment. In the post for each state (the links are here: Texas, Louisiana, Mississippi, Alabama, Georgia and Florida) I have quantified the magnitude of these adjustments, but I thought it would also be instructive to summarize them in one post just so that their full impact can be seen and compared.

The adjustments shown in the graphs below are of two types. The orange curve is the mean adjustment each month solely from breakpoint adjustments while the blue curve is the mean adjustment relative to unadjusted data from all sources of correction. This will also include homogenization, Kriging and gridding in addition to breakpoints, but it will also be affected by any difference in the chosen period for calculating the monthly reference temperatures (MRTs). The last of these will, however, only change the offset of the blue curve in the vertical direction relative to the orange one, not its slope or total change over time.

The graphs below indicate that the BE adjustments to the temperature data add between 0.5°C and 1.2°C to the final BE temperature trends. Given that we are constantly being told by climate scientists that the total global warming experienced so far is about 1.2°C, I would suggest that this is a bit of a problem.

Fig. 105.1: The Berkeley Earth (BE) temperature adjustments for Texas since 1900. The linear best fit (red line) to these adjustments for the period 1911-2010 has a positive gradient of +0.568 ± 0.003 °C per century.

Fig. 105.2: The Berkeley Earth (BE) temperature adjustments for Louisiana since 1900. The linear best fit (red line) to these adjustments for the period 1911-2010 has a positive gradient of +0.731 ± 0.004 °C per century.

Fig. 105.3: The Berkeley Earth (BE) temperature adjustments for Mississippi since 1900. The linear best fit (red line) to these adjustments for the period 1931-2010 has a positive gradient of +1.300 ± 0.007 °C per century.

Fig. 105.4: The Berkeley Earth (BE) temperature adjustments for Alabama since 1900. The linear best fit (red line) to these adjustments for the period 1931-2010 has a positive gradient of +1.231 ± 0.012 °C per century.

Fig. 105.5: The Berkeley Earth (BE) temperature adjustments for Georgia since 1900. The linear best fit (red line) to these adjustments for the period 1911-2010 has a positive gradient of +1.087 ± 0.006 °C per century.

Fig. 105.6: The Berkeley Earth (BE) temperature adjustments for Florida since 1900. The linear best fit (red line) to these adjustments for the period 1941-2010 has a positive gradient of +0.611 ± 0.010 °C per century.