In this post I show how to map NASA GISS’s 2×2 degree temperature anomaly data using R mapping tools. Rather than rely on a single value to reflect monthly global temperature anomaly, this map shows the anomalies in each of the 16,200 cells in a 2 degree lon/lat grid. This lets us see the details that make up the global mean, we can see which areas are warmer and which are cooler. I provide a link to my RClimate script and data file so that interested R users can make their own maps.
Here’s my R Climate map of NASA’s July 2010 2×2 degree data set. (Click map to check out the enlargement )
Users can use NASA’s interactive tool to make a comparable map at this link. Here’s what NASA’s map version looks like.
NASA’s map is very good, so why bother making my version in R? I had several reasons:
- I am not happy with NASA’s color scheme, I wanted to see if I could improve it
- Northern Hemisphere polar amplification is an important issue that I think gets masked with NASA’s color scheme because so a large area shows up “reddish”, Does better color separation help to show NH polar amplification?
- I don’t like NASA’s color bar scale, notice how the intervals vary by location along the scale axis. Interval span range from a low of 0.1 to a high of 1.8 . I’m sure there’s a good reason, but I wanted to see how other scales look.
- Size, I wanted to make a larger image so that I could magnify the zoom farther to see specific areas in more detail.
- I wanted to learn how to map climate data myself.
RClimate Map Features
Here are the features I was trying to incorporate into my map:
- Larger size (1200 * 1000) – feel free to zoom in
- Increased color separation to distinguish really cool/warm areas
- Uniform 1 degree C scale bar intervals
- Missing data shown in white
- Can show entire globe or map only a portion of the globe by adjusting the “bounding box”
RClimate Script Details
Here are the data and RClimate Script links: