Historical Temperature Change in Penang

 Key points of post

• Air temperature has risen in Penang since the mid 1970's

• Between 1935 and mid 1970's, temperatures did not change substantially

Ever wondered how air temperature has changed in Penang over the last few decades?

Worldwide climate databases are becoming increasingly sophisticated and it is now straightforward to obtain time-series data for many climatic variables (e.g. rainfall, windspeed) for most regions. We at Worldfish are using these data increasingly to provide background for our climate change research for CCAFs (Climate Change Agriculture and Food Security).

Here we have plotted monthly average temperatures for a meteorological station on Penang Island (The Airport) off the northwest coast of Peninsular Malaysia since 1935.

Location of Penang/Bayan GHCN Weather Station

The data are compiled, maintained, and distributed freely by the Global Historical Climatology Network http://www.ncdc.noaa.gov/oa/climate/ghcn-daily/. The blue line is a moving average function that summarizes long-term change over time. The plot shows that temperatures were quite stable between the mid 1930s and early 1960s (around 27°C), after when average temperatures fell slightly to bottom out in the mid-1970s. Note that the outbreak of World War II caused a break in the time-series. Since then average temperatures have risen steadily to around 28°C, although they do seem to have fallen in the most recent years (see the raw data for between 2007 and 2013). There is also some suggestion that variability (the range of average temperatures) may have increased with particularly sultry months being observed in 1984 and 1998 (incidentally 1998 is the year of highest global average temperatures since records began).

Note: All the plots were done using the free package R http://cran.r-project.org/ and the instructions, data source and code for producing this graph are provided below. This enables the interested reader to update the graph at any time in the future.

The data was sourced from the NCDC Global Historical Climatology Network Monthly Version 3 (GHCMNV3) via the CISL Research Data Archive managed by the Data Support Section of the Computational and Information Systems Laboratory (CISL) at the National Center for Atmospheric Research.

The CISL is hosting a copy of the monthly-average surface temperatures in support of UCAR's Global Learning and Observation to Benefit the Environment (GLOBE) program.

More information can be found at the following link - http://rda.ucar.edu/datasets/ds564.1/#!description

The raw temperature data was downloaded in csv format via a Google Earth kml file which can be downloaded at following link - http://rda.ucar.edu/datasets/ds564.1/docs/CISLdata.kmz

The csv file is the read into R and reformatted accordingly to produce the graph. The code below was used to produce the monthly average temperature graph.