The latest analysis of global temperature from GISs looks at the 12-month running average global temperature. Using the twelve month average smoothes out the chaos of monthly weather changes. The running average averages successive twelve month periods: March through February, April through March, May through April, etc. It’s a little different way of looking at the numbers that acts like a fine tuning knob. It makes the "picture" more clear. It allows the "music" to be heard without static. That static is the chaos of the weather.
Look at the top line that shows average monthly temperature. That extreme jaggedness is the chaos. The running average smoothes out the chaos. Now look at the El Nino line. Red is the warm El Nino phase of the South Pacific, blue is the cool La Nina phase. See how the averaging is more easily seen in relationship to the El Nino / La Nina phases? El Nino and La Nina are the largest form of short-term global temperature fluctuations. Next are major volcanoes. Except for the 1984 eruption where we had the second largest El Nino warm phase, volcanoes serve to significantly cool the planet for a couple of years. What does it is all that smoke – those aerosols that come out of the volcano when it erupts. They block sunlight and keep the planet from warming.
Paper abstract: We update the Goddard Institute for Space Studies (GISS) analysis of global surface temperature change, compare alternative analyses, and address questions about perception and reality of global warming. Satellite-observed nightlights are used to identify measurement stations located in extreme darkness and adjust temperature trends of urban and peri-urban stations for non-climatic factors, verifying that urban effects on analyzed global change are small. Because the GISS analysis combines available sea surface temperature records with meteorological station measurements, we test alternative choices for the ocean data, showing that global temperature change is sensitive to estimated temperature change in polar regions where observations are limited. We suggest use of 12-month (and n×12) running mean temperature to fully remove the annual cycle and improve information content in temperature graphs. We conclude that global temperature continued to rise rapidly in the past decade, despite large year-to-year fluctuations associated with the El Niño-La Niña cycle of tropical ocean temperature. Record high global temperature during the period with instrumental data was reached in 2010.
Hansen et. al., Global Surface Temperature Change, Geophysical Research Letters, December 14, 2010.