I have not analyzed any data yet and the purpose of plotting the time series was to show an example of the data as a function of time. As others have already mentioned, the swing in Durban temperatures over the seasonal cycle is ~25°C while global temperature increases due to climate change so far are on the order of 1°C.

Plus weather data tends to be quite noisy, just think how variable the weather can be day-to-day and we're squishing 80 years of that into one plot. Also worth noting that different places may experience climate change differently. Some places may be the average temperature go up, some maybe only in the summer, so you'll have to look at averages. Some places may see more extreme summer highs, so then you can't just look at averages but the average extremes or the tail end of the temperature distribution.

So it'll be hard to discern any climate change from just a cursory glance. I'm not saying it's there, just that it requires more analysis.

Have you read any climate science? These are not the (only) numbers that the knowledge is based on.

Huh, I wonder if climatologists might have based their analyses on more than just this single time series. No way of knowing.