Statistical Graphics and more

2 years ago, I did post the data on the CO₂ and global temperature relationship. The conclusion was: at least in the last 10 years, CO₂ concentration kept rising, but the global temperature didn’t.

Now, as the last year was the warmest year ever measured, it is time to look at the data again – having two more years of data.

Let’s first look at the scatterplot of temperature vs. CO₂ concentration, with the last 10 years highlighted:

Again, there is no (linear) relationship whatsoever. Certainly CO₂ is a greenhouse gas, and we all know how a greenhouse works.

Looking at the temperature development, we can’t ignore that 2014 was the warmest year ever recorded. Nonetheless, when we use a smoother with a wider span (smoothing spline with 6 degrees of freedom), which picks up the almost linear trend nicely, the temperature rise looks like it has stalled roughly 10 years ago:

Using a far more flexible smoother (25 degrees of freedom) we get a different result, indicating a dramatic rise in temperature in the last year:

As we all know, the volatility of a trend estimate is always highest at the end, where we only have data on one side of the estimate.
Thus, I am afraid we need to wait for another 2 years of data to tell, whether 2014 was the end of the temperature stagnation or not.