Statistical analysis of the raw data on Global Warming suffers from two major pitfalls :-
1. You are looking at the combined effects from several causative sources. Unless you have the means to distinguish the various factors, you cannot apply statistical techniques to the data and expect to get anything truly meaningful out. All that can be said, at best, is, “The Globe. Still Warming.”, as the warming trend over a long enough period of time has managed to stand out over the short-term variations.
2. Looking at the data purely by eye, some of the warming or cooling effects are clearly short-term, others longer-term; so picking a range of years/months/seasons at random, or according to some bias, is likely to distort the analysis. This is known as “cherry-picking”. The results of cherry-picking include the fallacious and discredited claim that, “Global Warming stopped in 1998”, or the much more crafty and misleading, “There has been no statistically significant Global Warming since 1998”.
Some researchers are content just to point to the overall effect of the raw data – global temperatures on land and at sea are rising sharply and the charts should be sufficient to understand the basic problem.
However, some people still contest that Global Warming is taking place, or that if it is, it isn’t serious. This then, is the cue to do an in-depth analysis into the known factors in global temperatures, and to attempt to “deduct” obvious short-term warming and cooling features in order to eyeball the underlying trends :-