Pro: El Niño’s and The Warming They Bring Are Intensified By Climate Change
How the magnitude of El Niño will change is of great societal concern, yet it remains largely unknown. Here we show analysis of how changing El Niño properties, due to 20th century climate change, can shed light on changes to the intensity of El Niño in the future. Since the 1970s, El Niño has changed its origination from the eastern Pacific to the western Pacific, along with increased strong El Niño events due to a background warming in the western Pacific warm pool. This suggests the controlling factors that may lead to increased extreme El Niño events in the future. If the observed background changes continue under future anthropogenic forcing, more frequent extreme El Niño events will induce profound socioeconomic consequences.
The aforementioned observational analysis reveals the controlling factors that would lead to increased large-amplitude El Niño events in the future. We hypothesized that more frequent occurrences of SBW and MCP events require an enhanced zonal SST gradient in the CP. We have tested this hypothesis using 8 CMIP5 (Coupled Model Intercomparison Project phase 5) models’ historical runs and future projection results (Methods). We find that the model results are consistent with the hypothesis derived from the observations. Under anthropogenic forcing-induced warming, the 8 CMIP5 models project different changes in the mean-state zonal equatorial SST gradients measured by the western Pacific (WP) SST (5°S–5°N, 150°–180°E) minus EP SST (5°S–5°N, 120°–150°W) (Fig. 6). As shown in Fig. 6, when the zonal mean SST gradient increases under the anthropogenic forcing, both the frequency of occurrence and the intensity of the SBW El Niño events increase significantly. This implies that if anthropogenic forcing enhances the SST gradients in the CP as we have observed over the past century, the extreme El Niño events will occur more frequently.
While climate change appears to make big El Niños more frequent, it is also true that El Niños return the favor by giving a short-term stimulus to atmospheric global warming. This is because the spread of warm waters across the tropical Pacific results in a release of heat energy from the oceans into the atmosphere.
The last big El Niño, in 1998, set global temperature records that lasted for several years. In fact its impact was so marked that in the aftermath of that spike in temperatures, many concluded that global warming had somehow “stalled” because temperatures fell briefly from those heights.
Con: El Niño events in the Pacific Ocean are Natural
El Niño is a naturally occurring climate pattern associated with warming of the ocean surface temperatures in the central and eastern tropical Pacific Ocean, which can significantly influence weather patterns, ocean conditions, and marine fisheries worldwide.
El Niño events in the Pacific Ocean are natural patterns that have been going on for millions of years. It’s true that El Niño events in the 21st century have had some very strong warming spikes. However, if you remove the effect warming El Niño events in the climate record, the amount of warming since 2000, you find almost half of the global warming in the 21st century is due to El Niño events.
A major uncertainty in figuring out how much of recent warming has been human-caused is knowing how much nature has caused. The IPCC is quite sure that nature is responsible for less than half of the warming since the mid-1900s, but some climate scientists, politicians, activists, and various green energy pundits go even further, behaving as if warming is 100% human-caused. But real-world data shows that natural El Niño events add to global warming, and it strongly effects climate over time.
If we look at the warming over the 19-year period 2000-2018, we see the record El Nino event during 2014-16 which caused increased sea surface temperature in the Pacific Ocean, which in turn increased air temperature globally as seen in Figure 1:
That event created a “warm spike” in the global temperature record in 2015 and 2016, and caused increased global warming trends.
Climate Scientist Dr. Roy Spencer of the University of Alabama, Hunstville, performed a calculation to remove the effect of the 2015/2016 El Niño event as seen in Figure 2 below.
The observed trend in HadCRUT4 surface temperatures is nearly cut in half compared to the CMIP5 climate model average warming over the same period, and the UAH tropospheric temperature trend is almost zero.
The observed rate of warming — when we ignore the natural fluctuations in the climate system is only about one-half of that projected by climate models at this point in the 21st Century.
Dr. Roy Spencer, online publication, 2019. http://www.drroyspencer.com/2019/05/half-of-21st-century-warming-due-to-el-nino/
IPCC AR5 report on climate, 2015, IPCC Website: https://www.ipcc.ch/assessment-report/ar5/
NOAA NESDIS sea surface temperature satellite imagery: https://www.ospo.noaa.gov/Products/ocean/sst/anomaly/2015.html
Understanding El Nino, NOAA Website, 2016: https://www.noaa.gov/understanding-el-nino
El Nino’s Grip on Climate, Nature, 2012 https://www.nature.com/scitable/knowledge/library/el-nino-s-grip-on-climate-25816069/