Climate Change in Paradise

Melia Waring

9/1/2020

How does climate change in Honolulu, Hawaii affect maximum temperatures and what ecological impact does that have on ocean ecosystems? Why should we care?

Hawaii is one of the most popular vacation spots in the world. With its tropical weather, beautiful beaches, and stunning hiking trails, Honolulu, Hawaii is the perfect destination for a relaxing vacation. Tourists from all over the world travel to the islands for a tropical retreat to escape the cold in the winter. Unfortunately, not even in Hawaii can one escape the impacts of climate change.

Located along the southern coast of the island of Oahu, Honolulu is the capital and the largest city in the state of Hawaii. Honolulu experiences a semi-tropical climate with trade winds that keep the city comfortable, and the temperatures vary little throughout the months. Although some climate change skeptics may argue that Hawaii’s tropical weather makes it immune to the effects of climate change, this blog aims to call attention to the evident warming trend by working with climate data in the region of Honolulu, Hawaii.

This blog also explores the related issue of ocean acidification and its effects on coral reefs. I aim to show how the residents and indigenous people of Hawaii are very much impacted by climate change. In addition, this blog sheds a light on the environmental injustice taking place in Hawaii and exolains how climate change threatens the traditions and practices of Native Hawaiian culture. To conclude, this blog investigates the already existing yet continuous need for indigenous climate change activism taking place in the islands.

Honolulu, Hawaii

Methods

The data were gathered from the National Ocean and Atmospheric Administration (NOAA), which provides global historical weather and station history information. The Honolulu International Airport, HI US Station (station ID: USW00022521) was the source of the data in this blog. This station has been recording since June 1, 1939 to the present day and it has a 98% degree of data coverage. Located on the southern end of the island of Oahu near the ocean, this station’s climate readings are fairly representative of the larger region of Honolulu, Hawaii.

Using R, the data was plotted, analyzed, and evaluated. Daily maximum temperature for Honolulu was graphed and a line of best fit was created using linear regression. In a linear model, the dependent variable (maximum daily temperature) is equal to an intercept plus the slope multiplied by the independent variable plus an error term.

To further examine the data trend, two months (May and November) were selected and analyzed with a plot and a line of best fit. Tradiaionally, Hawaii only experiences 2 seasons: summer (Kau), which stretches from May to October, and winter (Ho`oilo), which stretches from November to April. May and November are the earliest transition points from one season to another, which is why they were chosen to further explore a relationship between temperature and time.

In order to determine the significance of the data, the p-value was analyzed in relation to the null hypothesis. The null hypothesis states that there is no relationship between the two variables, maximum daily temperature and time. A rejection of the null hypothesis indicates that there is instead some trend or relationship between temperature and time. The alternative hypothesis states that there is a relationship between the two variables of study. Statistical significance is represented as a p-value, whose value is between 0 and 1. A p-value greater than 0.05 means that the data are not statistically different from the null. If the p-value is less than 0.05, the data is statistically significant and the null hypothesis is rejected, which means that a trend exists in the data.

Maximum Temperature Data

The figure below displays a graph between maximum temperature in degrees Celsius, plotted on the y-axis, and time in years, plotted on the x-axis. The generated line of best fit had a slope that indicated an increase of 4.056e-5 °C per year, or 0.004056 °C per 100 years. The r² value was 0.025, which means 2.5% of the variance in the response variable is explained by the model. This number tells us that there is high variability in the response data. In addition, the data has a p-value of <2e-16, which means the null hypothesis is rejected and there exists an increase in maximum temperatures (a heating trend) recorded in Honolulu from 1940 to 2020.

Maximum Temperature Data for the Month of May

Hawaii has a fairly consistent tropical climate without strong seasonal change. Throughout the year, there are only small changes in the temperature. The month of May was chosen to test for a warming trend in the summer (or the dry season). The figure below displays a graph between maximum temperature in degrees Celsius in May, plotted on the y-axis, and time in years, plotted on the x-axis. A line of best fit was generated and its slope indicated an increase of 0.015 °C per year. The data has a p-value of 0.000386, which means the null hypothesis is rejected and the warming trend is evident in the month of May. The data showed the same warming trend for the other summer months, therefore the warming trend is also evident during the summer.

Maximum Temperature Data for the Month of November

The month of November was chosen to represent the winter season and to test for a warming trend. The figure below displays a graph between maximum temperature in degrees Celsius in November, which is plotted on the y-axis, and time in years, which is plotted on the x-axis. A line of best fit was generated and its slope indicated an increase of 0.00846°C per year. The data has a p-value of 0.0498, which means the null hypothesis is rejected and the warming trend exists in the month of November and during the winter.

Data analysis: What does this mean?

There is an evident warming temperature trend for the maximum temperatures of Honolulu. The lines of best fit for the yearly and monthly graphs have a positive slope, which indicates an increase in the recorded temperatures from 1940 to the present day. Based on the aggregated maximum temperature data for each month, the summer and winter seasons of Hawaii also exhibit this heating trend.

Climate change impacts in Hawaii

Climate change impacts in Hawaii include shifting rising sea levels, shifting rainfall patterns, and an increase in ocean acidity. Since Hawaii is made up of islands, the ocean is especially important when identifying climate change impacts in the state. Rising sea levels will increase coastal flooding and erosion, damaging coastal ecosystems, infrastructure, and agriculture. Also, warming oceans lead to disease outbreaks and threaten fisheries.

An article titled, “Evaluating ecosystem effects of climate change on tropical island streams using high spatial and temporal resolution sampling regimes” by Frauendorf et al., studies the effects of climate change on tropical ecosystems, precipitation, and streams. According to the article, tropical climates will see some of the earliest effects of climate change. Changes in precipitation caused by climate change can have severe effects on the function and structure of streams. They concluded that the predicted changes in stream flow would decrease stream resource and consumer quality and quantity. This affects the overall function of the stream, as well as biomass and habitat for the marine life and those dependent on the resources of the stream (Frauendorf et al., 2019).

What is ocean acidification?

In addition to the warming trend of the temperatures in Hawaii, ocean acidification is a related issue that has devastating effects on marine ecosystems. As atmospheric levels of carbon dioxide rise, thermodynamics and air-sea gas transfer processes drive some of the extra carbon dioxide into ocean surface waters, leading to substantial shifts in seawater acid-base chemistry and the chemical speciation of the large reservoir of inorganic carbon dissolved in seawater (Doney et al., 2009). This chemical process is defined as ocean acidification. Ocean acidification decreases the seawater pH, which reflects an increase in acidity.

The figure below is a graph of the carbon dioxide time series in the North Pacific. Carbon dioxide dissolved into the ocean is represented by the green data set and seawater pH is represented by the blue data set. The data was collected from Station ALOHA, located north of the island of Oahu. The data indicates a positive trend of carbon dioxide dissolved into the ocean from 1958 to 2018 as well as a decrease in seawater pH. In other words, ocean acidification is occurring in the sea surrounding the Hawaiian Islands, which could potentially transform the ocean ecosystem.

Source: NOAA

How does ocean acidification affect coral reefs?

Coral reefs are hyper-diverse marine ecosystems that provide important ecosystem services, such as coastline protection, fish habitat, and recreation. In addition to their importance in the oceanic ecosystem, coral reefs have have high economic value as well. Since Hawaii relies so heavily on tourism, this is an important factor to consider. A study of the economic values of coral reefs have been estimated that the net annual benefits of coral reefs worldwide are $33.6 billion per year.

This figure displays a healthy (the left image) vs bleached (the right image) comparison of the Rapture Reef in the French Frigate Shoals, the largest atoll in the Northwestern Hawaiian Islands. Source: The Weather Channel

However, coral reef ecosystems all across the globe have been declining rapidly due to factors such as overfishing, pollution, and habitat destruction. Climate change and greenhouse gas emissions have posed a new threat to coral reefs in recent years. Elevated sea-surface temperatures (SSTs) increase the risk of coral bleaching and the rising atmospheric carbon dioxide results in increased ocean acidification, which affects the process of coral growth (Lane et al., 2013).

According to a recent study conducted on Elkhorn coral, an endangered coral species, “ocean acidification could compromise the successful fertilization, larval settlement, and survivorship of the coral” (Albright et al. 2010). An increase in ocean acidification has also been shown to reduce the ability of reef-building coral to produce their skeletons, as well as significantly impact the ability of coral to recover from disturbances. As a result, coral reefs may begin to erode faster than they can be rebuilt. This could have devastating effects on the long-term variability of these ecosystems as well as the one million species that depend on the coral reef habitat.

So, why should we care?

The rapid decline of coral reefs will have devastating effects on the marine food chain. As a result, local fisheries will be greatly impacted by the decreasing number of fishermen who are able to earn their living from the ocean. In addition, coral reefs are also home to a type of sea slug that is actually an important ingredient in cancer-fighting compounds. Coral reefs also buffer shorelines from the effects of hurricanes. Without coral reefs, those in Hawaii who live near the shore will be at a greater risk during hurricane season.

Hawaii also faces a unique form of environmental injustice. Although many associate environmental injustice with the disproportionate exposure of low-income communities or communities of color to the burdens of climate change, for the indigenous people of Hawaii, environmental injustice is mostly about the cultural and economic self-determination. In other words, climate change threatens Native Hawaiian culture. Since indigenous culture is linked to Hawaii’s natural environment, these practices will be unable continue without the resources to support them. Despite the many challenges the indigenous people of Hawaii have faced, their culture continues to grow in the spirit of indigenous self-determination, which requires access to resources that support the cultural and religious practices.

Conclusion: Native Hawaiian activism and what we can do to help

Hawaii’s climate is changing as we experience rising air temperatures, increased ocean acidity, damaged coral reefs, and many more climate change impacts. It is more important now than ever for local leaders and experts to bring diverse minds to the table in order to work toward cliamte mitigation and adaptation. Researchers and policy makers need to provide provide room for the most vulnerable and at risk to speak out for themselves. In addition, researchers need to combine data and methodologies from political, social, and Earth-systems sciences to model risk holistically from local to global scales (Pelling and Garschagen, 2019).

Rosie Alegado is a University of Hawaii oceanography professor and a member of the Honolulu Climate Change Commission. In July of 2019, she was one of six women speaking on the opening panel of the Hawaii Conservation Conference. The panel discussed their perceptions of climate change from a traditional Native Hawaiian cultural lens. Alegado argues that the Indigenous people of Hawaii are experiencing a third wave of colonialism: the first was geographic displacement, the second was social and psychocultural (such as illegal occupation, forced assimilation, and militarism in Hawaii), and the third is climate change (driven by a consumer capitalist economy). Despite the looming threat of the climate crisis, Alegado brought an empowering attitude, which she attributed to the island mentality in relation to the role that survival has long played in the Hawaiian culture. Alegado emphasized the importance of community within the broader spectrum of climate change as a whole. In addition, Alegado pointed out how scientists have shifted their focus from saving individual species to restoring entire ecosystems, underlining their interconnectedness.

As residents of Hawaii, we should do our part in educating ourselves about these issues and raising awareness about climate change. The voices of affected communities and Indigenous people are essential to further understanding the issue of climate change and working toward climate mitigation and adaptation.

Works Cited

Albright, R., Mason, B., Miller, M., & Langdon, C. (2010). Ocean acidification compromises recruitment success of the threatened Caribbean coral Acropora palmata. Proceedings of the National Academy of Sciences, 107(47), 20400–20404. https://doi.org/10.1073/pnas.1007273107

DONEY, S. C., BALCH, W. M., FABRY, V. J., & FEELY, R. A. (2009). OCEAN ACIDIFICATION: A CRITICAL EMERGING PROBLEM FOR THE OCEAN SCIENCES. Oceanography, 22(4), 16–25. JSTOR.

Eagle, N. (2019, July 10). “We’re Not Scared”: Hawaii Confronts Next Wave Of Climate Change. Honolulu Civil Beat. https://www.civilbeat.org/2019/07/were-not-scared-hawaii-confronts-next-wave-of-climate-change/

Frauendorf, T. C., MacKenzie, R. A., Tingley, R. W., Frazier, A. G., Riney, M. H., & El‐Sabaawi, R. W. (2019). Evaluating ecosystem effects of climate change on tropical island streams using high spatial and temporal resolution sampling regimes. Global Change Biology, 25(4), 1344–1357. https://doi.org/10.1111/gcb.14584

Lane, D. R., Ready, R. C., Buddemeier, R. W., Martinich, J. A., Shouse, K. C., & Wobus, C. W. (2013). Quantifying and Valuing Potential Climate Change Impacts on Coral Reefs in the United States: Comparison of Two Scenarios. PLoS ONE, 8(12), 1–13. https://doi.org/10.1371/journal.pone.0082579

Pelling, M., & Garschagen, M. (2019). Put equity first in climate adaptation. Nature, 569(7756), 327–329. https://doi.org/10.1038/d41586-019-01497-9

Regional_releases_hawaii.pdf. (n.d.). Retrieved September 30, 2020, from https://www.edf.org/sites/default/files/content/regional_releases_hawaii.pdf

Showalter, K., López-Carr, D., & Ervin, D. (2019). Climate change and perceived vulnerability: Gender, heritage, and religion predict risk perception and knowledge of climate change in Hawaii. Geographical Bulletin, 60(1), 49–71.

What Climate Change Means for Hawaii. (n.d.). United States Environmental Protection Agency.

What is Ocean Acidification? (n.d.). Retrieved September 30, 2020, from https://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F