Deke Arndt

First - what is this. The height of each bar is the global temperature, by month, since Jan 1980. The temperature is expressed as an “anomaly” or the difference versus the 20th century avg for that month. As reported, monthly, here: https://www.ncdc.noaa.gov/sotc/global/ 

The color of each bar represents the month’s ENSO status as defined by CPCs ONI metric. Red months are El Niño months, blue are La Niña months, grey are neutral (“La Nada”) months. ENSO is important for many reasons but lets focus on its impact on global temperature 3/n

Looking only at El Niño periods (red), they tend to stand taller (warmer) than neighboring months. El Niño’s temporary warming bump arises from (to oversimplify) lots of heat transfer from resulting large warm patch in tropical east pacific. 4/n

In this sense, El Niño is not entirely unlike a big temporary equatorial pacific heating pad at the bottom of the atmosphere. (it’s also dynamic and complex and I’m flattening out a lot of rich detail studied by some amazing people) 5/n

Still looking at just the red El Niño (EN) periods, notice that during the more substantial EN events, the global temperature tends to warm through the event, attesting to the cumulative influence of longer, stronger ENs (exception: the volcano-stunted 91-92 event) 6/n

Again considering only the EN episodes, notice that the global temperature is increasing over time for the red months. 7/n

Switching to La Niña (LN, blue). Pretty much opposite: these periods are cooler than neighboring months, owing to the influence of an associated resultant large patch of cool water in EPac. Also they tend to cumulatively drive temp down over the course of a single event. 8/n

What’s NOT different: the global temperature during La Niña is also warming (look only at the blue bars), at roughly the same rate as the global temperature is warming across the EN-only timeline. 9/n

Likewise, neutral months are warming, too. In fact, the rate of general warming is such that the recent LN and neutral months exceed most of the global temps from the strong 1997-98 EN, which were monumental at the time. 10/n

Also notice how EN and LN worked to create (in part) the illusion of false “hiatus” from late 1990s to 2013ish. Much red on the left side of that span, more blue and grey on the right. The false hiatus also more complex than simply ENSO, but ENSO contributed to the illusion 11/n

Long story short: our world is warming. ENSO phases provide much of the year to year “wiggle” in the upward temperature trajectory. All three phases are warming in their own right. 12/n