To what extent does global warming influence El Niño Southern Oscillation (ENSO) SOI index?

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To what extent does global warming influence El Niño Southern Oscillation (ENSO) SOI index?

 

Environmental Issue 

The decreasing of the Pacific Ocean´s salinity and temperature due to the increment of ENSO´s intensity and frequency

 

Living in Peru, a biodiverse country, that is also rich in different climate zones, I was interested in investigating the different types of ocean environmental issues around our continent and their effect on our environment. This fact inspired me to research to what extent the South American Pacific Ocean´s salinity and temperature are affected by El Niño Southern Oscillation (ENSO) due to the increase of global warming.

 

As the earth observatory said, “El Niño Southern Oscillation reduces the upwelling of cooler, nutrient-rich waters from the deep shutting down or reversing ocean currents along the west coast of central and south America” (E.O, 2017). It´s important to point out that ENSO´s effects on the environment have been increasing hugely since the 20th century, which mainly occurs on the South American Pacific Coast. Considering that ENSO is a naturally recurring phenomenon it´s important to point out that, “ENSO´s impact is modulated by a multitude of factors, including event diversity within ENSO itself, other modes of climate variability within and outside the Pacific, inter-basin climate interactions and greenhouse warming, making it seasonal prediction challenging” (McPhaden, Grimm et al, 2020). Knowing this is important to state that The Southern Osicalization Index (SOI) indicates the development and intensity of El Niño events in the Pacific Ocean, and negative values of the SOI lower than -7 indicate El Niño episodes.

Connection of Environmental Issue to Research Question

 

The environmental issue is connected to the research question as ENSO´s intensity and frequency increased over the years, thus altering the Pacific Ocean´s temperature and salinity due to the possible influence of global warming. It's important to know the context of the Salinity decreased by ENSO, as the scientist's Zhu, Huang, Zhang, and Zhen Hu, among others (2014), affirm that “during el Niño, sea surface salinity decreases in the western and central equatorial Pacific Ocean, as a result of zonal advection of low salinity water by anomalous eastward surface currents and to a lesser extent as a result of a rainfall excess”.

 

In this study, I´m going to analyze to what extent global warming influences ENSO´s SOI index causing an effect on the Pacific Ocean´s salinity and temperature in order to propose a viable solution to it. To investigate this external environmental issue, I observed the correlations between ENSO´s SOI index with global warming, the Pacific Ocean´s salinity, and temperature, in order to state a cause-effect relationship.

Hypothesis with justification

I expect to see a high correlation between ENSO´s SOI index and global warming, consequently obtaining a high correlation between ENSO and the Pacific Ocean´s salinity and temperature. This is because if global warming is related to the increase of ENSO´s SOI index this would explain the increment in salinity and temperature.

 

Justify Sample Strategy

To collect data for this experiment, I used public databases of the National Center for Environmental Information (NOAA), the world resources institute, and the Bureau of Meteorology. These information sources enabled data to be quickly and efficiently obtained and assured that I observed a representative and accurate sample of the salinity and ENSO events, over the years, due to their reliability and reliance.

 

Variables and explanation

Independent -  Appearance of ENSO

 

Dependent - Change in Salinity concentration and temperature in the Pacific Ocean (percentage)

 

Controlled -  Approximately similar total area investigated, same species identification key, the same world maps investigative tools, same secondary resources information and time.

 

Equipment List

• Raw data of ENSO´s SOI index, global warming, and Pacific Ocean´s salinity and temperature between 1950 - 2022 -
• Map of carbon dioxide emissions and temperature variance between 1950 - 2022

 

Risk Assessment and Ethical and Environmental considerations

When calculating and identifying the main data, be sure to be situated in the correct period, to avoid any struggle with committing errors in transferring the information. If the data is not specified, the study wouldn´t be reliable due to poor exactitude in time. Avoid using unreliable resources, it's necessary to have reliable information in order to see an accurate representation of the global issue, and to have a more representative and validated analysis. Also, citing the information to have an ethical study and not steal data from external people is important.

 

Methodology

First, enter this link Australian Climate Influences (bom.gov.au) regarding the diverse world maps of ENSO outlook history by the Bureau of Meteorology. Focusing on analyzing the first two graphs about ENSO´s intensity, and SOI index, then extracting that information from 1950-2022.

Then download the Pacific Ocean´s salinity index between 1950 - 2022 at WOD Geographically Sorted Data (noaa.gov) (MBT, DBT, and micro BT data)

 

At Climate at a Glance | National Centers for Environmental Information (NCEI) (noaa.gov) extract the Pacific Ocean´s Temperature between 1950-2022

Go on in The History of Carbon Dioxide Emissions | World Resources Institute (wri.org) and extract the carbon emissions from 1950 - 2022

With all the data collected, organize it in a graph and then calculate Pearson´s correlation coefficient in order to establish the relationship between them

Overall the graph illustrates a rise of greenhouse gasses emissions from 1950 to 2022, showing substantial growth throughout the whole period with some slow down between 1978 to 2002, then in 2008 there was a brief slow down due to the economic crisis and finally we can observe another slow down from 2012 nevertheless during the observed, the greenhouse gasses emissions has gone with 15% approximately, in comparison to 2022. In general, it is presented a constant growth with some decreases between the years, the ones that highlight the most, due to high levels of GT are from 1972 to 1966 when it started the constant growth until 2020.

The SOI index shows the historical events that ENSO had taken place, its occurrence can be determined when the value of SOI drops below -7. According to the graph, ENSO´s frequency had a significant increase between 1988 and 1998 which indicates an SOI level that falls at -13, a level that stands for high intensity. It's important to point out that over the years ENSO´s SOI index has been reaching considerably lower quantities in comparison to the starting years, such as 1950-1960 that only reached between -3 and -7. ENSO´s SOI index started to dip in 1964 and it reached its maximum lower point in 1982 and 1987. Overall, in the graph can be seen a change of ENSO intensity over the years, it starts low, then increases, and finally declines again. This is clearly illustrated between 1966 to 2006.

As is shown in graph #4 The increase in temperature has occurred since 1976 at a rate of 0,15 to 0,20 per decade, which has been constantly growing over the years. In the starting years, it can be seen that the average temperatures were below zero, moreover, since 1976 it has been constantly rising with some fluctuations.

As it is presented on the graph we can observe an apparent decrease in salinity over the years, illustrated as a curve that starts approximately in 1970 and ends in 2000. It's important to mention that it is very worrisome when salinity decreases below 33ppm because it alters the ocean´s environment, while it increases over 37ppm it affects the environment as well. In Figure # 5 We can observe that between 1970 and 2000 the salinity decreased at its maximum level reaching 32,4ppm, a significant decrease that affected the Pacific Ocean then.

 

Conclusion

From the graphs shown before, it's revealed that there´s a possible correlation between the aspects studied, to demonstrate this mathematically, it´s going to be used the Pearson correlation coefficient to state the significance of the correlation. For applying this statistical test, it´s needed to use the following hypothesis -

 

H1 - There is a significant correlation between the variables used

 

H0 - There isn´t a significant correlation between the variables used.

 

For this test it was used an online calculator of correlation tests (Appendix 1), these are the following results -

Observing the results given before, it's important to point out that there are measured with the table of Pearson correlation coefficient (Appendix 2), indicating that the three conditions shown in Table #3 have a very strong correlation. Meaning that when ENSO´s SOI index increases, all the variables increase as well, and the same happens if it decreases, in other words, the three conditions follow the trend similarly to ENSO´s one, depending on its recurrence and intensity.

The conclusion shows that global warming has a very strong correlation with ENSO´s SOI index between 1950 and 2022. In this period, the world experienced a constant growth of emissions due largely to industrialization and population growth. According to NOAA (2020), “increases in atmospheric carbon dioxide are responsible for about two-thirds of the total energy imbalance that is causing Earth's temperature to rise”. According to this, global warming has been constantly increasing over the years, causing an effect on different environmental issues such as ENSO. Parting from this point, considering that ENSO has a very strong correlation with the Pacific Ocean´s salinity and temperature, the fact ENSO´s SOI index has been increasing due to global warming means that the increase of temperature and salinity has the same cause, which is the increment of global warming worldwide. Mentioned this, the final result of the study indicates that the greenhouse gasses intensify the effect of ENSO´s events, consequently altering the salinity and temperature of the Pacific Ocean. So, it´s concluded that the current trend of the greenhouse gasses generates more severe ENSO events, which is supported not only by the statistical test, but also by the Proceedings of the National Academy of sciences (2019), “climate change is increasing the frequency of extreme el Niño events, leading to intensifying droughts, worsening floods, and shifting hurricane patterns”. Having clearly this, it would be possible to reduce the intensity of ENSO´s events and minimize the effect on Pacific Ocean´s salinity and temperature if we are able to reduce the greenhouse gasses emissions.

 

strength, weaknesses, and modifications

 

Some weaknesses of the study are the limitation of variables, the period of time and the external forcing agents that couldn´t be evaluated, due to this, is suggested to use more variables since it's a complicated system and requires a complex view. As well as, including a larger period of years studied, it would be a more trustworthy result due to the major number of events that are going to be considered, and analyzing the significant forcing agents that may influence ENSO activity. Some strengths of the study are the main variables considered and the correlation between them, as well as the statistical tests used to prove mathematically its relationship obtaining an unquestionable result. In the same way, some modifications in the study where the type of data analysis, it was highly recommended using maps to schematize temperature and salinity, moreover, it needed to be modified because the world map simulator didn't have the data specified

There is no doubt that ENSO´s frequency and intensity will change in the coming century if greenhouse gasses continue rising unchecked. According to the results, there is a possibility that ENSO change significantly if we limit our greenhouse gas emissions. The global energy demand is growing steadily to meet the requirements of an expanding population which 80% is currently met by fossil fuels energy. There is no immediate and massive substitution solution for fossil fuels. Moreover, the CO2 emissions can be captured and stored, this consists in capturing CO2 emitted by large industrial facilities and storing it underground, which no longer contributes to global warming. By letting immediate reductions of emissions it would allow a progressive transition to new forms of energy, meanwhile fossil fuels are contained during the time interval required for their development.

 

The solution of limiting emissions has a significant potential to reduce the intensity of ENSO, however, there is still a probability that there could be a highly active phase of ENSO even after decreasing greenhouse gas emissions Considering that storing CO2 emissions could cause soil degradation and other effects in land, not leaving the fact that unpredictable natural forcing agents could potentially intensify ENSO events. It would be a difficult environmental analysis, moreover, the solution would help to reduce ENSO´s impact on the salinity and temperature of the Pacific Ocean, but its frequency would maintain because is a naturally caused phenomenon.