Tag Archives: climate change

How corals can help us make predictions about our future under climate change (cross-posted from ReefBites)

This blog post originally appeared on ReefBites, the student blog of the International Society for Reef Studies.

Every two to seven years, the eastern equatorial Pacific climate oscillates between anomalously warm (El Niño) and cold (La Niña) conditions in a process known as the El Niño Southern Oscillation (ENSO). This process influences sea surface temperatures (SSTs), trade winds, and global teleconnection patterns, which together influence weather conditions all over the world (Collins 2010). Some scientists suggest that extreme El Niño events will happen more often with the warming climate (Federov and Philander 2000; Tudhope 2001; Cai 2014; Liu 2017), which would have profound impacts on communities around the world (for example, by altering patterns of global food production). Other scientists are undecided, pointing to the diversity of historical ENSO patterns, which confounds data that could suggest climate change is causing an impact (Collins 2010; Vecchi and Wittenburg 2010; Emile-Geay 2013, 2016). Fortunately, coral reefs hold a treasure trove of paleoclimate data that could be used to solve the mystery of past ENSO diversity, which would allow scientists to make more accurate predictions about how we can expect climate (and therefore weather) to change in the future.

It isn’t, however, an easy puzzle to solve. Scientists around the world have devoted huge amounts of resources to understanding how ENSO patterns will change as the climate continues to warm, but this has proven difficult because ENSO has historically exhibited differences in amplitude, temporal evolution, and spatial patterns (Capotondi 2015). Disagreements about what differences are caused by climate change and what is natural variation caused by radiative or orbital forcing have led to disagreement about future ENSO patterns. One thing that scientists do agree on, other than the absolute certainty that human-caused climate change is happening, is that in order to understand exactly what variations in ENSO are being influenced by a warming climate, scientists must first identify the background diversity of ENSO patterns, which requires going back potentially thousands of years (Collins 2010; Vecchi and Wittenburg 2010; Cobb 2013). This lack of information has limited the predicting power of climate models, leading to conflicting results.

So how can scientists get to the bottom of this? Instrumental records are limited in their usefulness because they tend to be short and sparse, particularly in remote regions of the Pacific where changes in SST are most pronounced (Emile-Geay 2013). Some proxy records, which are preserved physical characteristics of the environment that can stand in for direct measurements like ice cores and sediment records from lakes (NCDC NOAA, N.D.) may also be limited because they lack the temporal resolution needed to resolve ENSO patterns, which may vary seasonally (Cobb 2013). Luckily for us, coral reefs have been recording changes in the climate for hundreds of years at high resolutions. Similar to tree trunks, as they grow, corals record rings in their skeletons that reveal their age (Figure 1), and because corals are so sensitive to environmental fluctations, the chemistry in each ring can tell scientists about the temperature, rainfall, and water clarity from that year. By drilling into old corals and extracting a long sample (called a core), scientists can reconstruct monthly climate data over several hundred years. Corals therefore provide a hugely valuable source of data that could help us finally unravel the complicated history of ENSO, which in turn would help us accurately predict changes in our future climate.

Figure 1: Each of the light/dark bands in this x-ray of a cross-section of a coral core formed during a year of growth (NASA Earth Observatory 2005).

Stable isotopes, which are elements with the same number of protons but different numbers of neutrons, are a power tool to understanding past climate. The environmental conditions at the time a coral grows its skeleton can influence the number of neutrons an element has. For example, a number of scientists have used stable oxygen isotopes (δ18O and δ16O) to reconstruct the history of sea surface salinity (Figure 2) (e.g. Nurhati 2009). Other scientists have used ratios elements, such as Stronium to Calcium (Sr/Ca) to reconstruct temperature (e.g. Thompson and van Woesik 2009). A clearer picture of climate variability has begun to emerge through the use of these climate proxies from coral cores. We know, for example, that there are two different types of El Niño events, one in which warm water is centered over the central Pacific (known as “CP El Niño”) and one where warm water is over the eastern equatorial Pacific (“EP El Niño”), and that CP El Niño, which is projected to increase with global warming, has happened more frequently in the 21st century than EP El Niño (Wang 2016). But data from across the Pacific are limited, and many of the studies identifying ENSO patterns use proxies from just a few coral cores, highlighting the need for more studies.


Figure 2: Water vapor gradually loses 18O as it travels from the equator to the poles. Because water with heavy 18O isotopes in them condense more easily than normal water molecules, air becomes progressively depleted in 18O as it travels to high latitudes and becomes colder and drier. In turn, the snow that forms most glacial ice is also depleted in 18O. As glacial ice melts, it returns 16O-rich fresh water to the ocean. Therefore, oxygen isotopes preserved in ocean sediments [and coral cores] provide evidence for past ice ages and records of salinity (Riebeek 2005).

Another challenge is deciphering the cores themselves. Recent studies have called into question temperature data derived from coral cores using the common Sr/Ca proxy, because biological processes known as “vital effects” can influence and even override Sr/Ca relationships to temperature in corals during the biomineralization process (Alpert 2016, DeCarlo 2016). As a result, DeCarlo (2016) suggested a new proxy record that can be used to record past SST by combining Sr/Ca and the ratio of Uranium to Calcium (U/Ca) to create a new proxy, which they dubbed “the Sr-U thermometer.”

The need to address climate change only gets more urgent as time passes, which emphasizes how important this research is. Scientists cannot accurately predict the ways that climate change will influence humanity without understanding ENSO diversity. Coral have recorded climate variability in their skeletons for hundreds of years and are therefore a source of high-resolution, long-term data that could prove invaluable if we can only figure out the best way to decipher it. If scientists can understand ENSO’s patterns in the past, we can account for those patterns in climate models, and therefore predict how future ENSO will be influenced by climate change. This would allow us to make clear, accurate predictions about climate change in general, such as how rainfall patterns would impact food production, which could prove critical to the future of humanity.


 Alpert AE, Cohen AL, Oppo DW, DeCarlo TM, Gove JM, Young CW (2016) Comparison of equatorial Pacific sea surface temperature variability and trends with Sr/Ca records from multiple corals. Paleoceanography 31:252-265 (doi: 10.1002/2015PA002897)

Cai W, Borlace S, Lengaigne M, van Rensch P, Collins M, Vecchi G, Timmermann A, Santosa A, McPhaden MJ, Wu L, England MH, Wang G, Guilyardi E, Jin FF (2014) Increasing frequency of extreme El Niño events due to greenhouse warming. Nature Climate Change 4:111-116 (doi: 10.1038/nclimate2100)

Capotondi A, Wittenberg AT, Newman M, Di Lorenzo E, Yu JY, Bracconot P, Cole J, Dewitte B, Giese B, Guilyardi E, Jin FF, Karnauskas K, Kirtman B, Lee T, Schneider N, Xue Y, Yeh SW (2015) Understanding ENSO Diversity. American Meteorological Society 921-938 (doi: 10.1175/BAMS-D-13-00117.1)

Cobb KM, Westphal N, Sayani HR, Watson JT, Di Lorenzo E, CHeng H, Edwards RL, Charles CD (2013) Highly Variable El Niño-Southern Oscillation Throughout the Holocene. Science 339:67-70. (doi: 10.1126/science.1228246)

Collins M, An SI, Cai W, Ganachaud A, Guilyardi E, Jin FF, Jochum M, Lengaigne M, Power S, Timmermann A, Vecchi G, Wittenberg A (2010) The impact of global warming on the tropical Pacific Ocean and El Niño. Nature Geoscience 3:391-397. (doi: 10.1038/ngeo868)

DeCarlo TM, Gaetani GA, Cohen AL, Foster GL, Alpert AE, Stewart JA (2016) Coral Sr-U thermometry. Paleoceanography 3:626-638. (doi: 10.1002/2015PA002908)

Emile-Geay J, Cobb KM, Mann ME, Wittenberg AT (2013) Estimating Central Equatorial Pacific SST Variability over the Past Millennium. Part II: Reconstructions and Implications. Journal of Climate 26:2329-2352. (doi: 10.1175/JCLI-D-11-00511.1)

Emile-Geay J, Cobb KM, Carre M, Braconnot P, Leloup J, Zhou Y, Harrison SP, Correge T, McGregor HV, Collins M, Driscoll R, Elliot M, Schneider B, Tudhope A (2016) Links between tropical Pacific seasonal, interannual and orbital variability during the Holocene. Nature Geoscience 9:168-175. (doi: 10.1038/NGEO2608)

Federov AV, Philander SG (2001) A Stability Analysis of Tropical Ocean-Atmosphere Interactions: Bridging Measurements and Theory for El Niño. Journal of Climate 14:3086-3101. (doi: 10.1175/1520-0442(2001)014<3086:ASAOTO>2.0.CO;2)

Liu Y, Cobb KM, Song H, Li Q, Li CY, Nakatuska T, Zhisheng A, Zhou W, Cai Q, Li J, Leavitt SW, Sun C, Mei R, Shen CC, Chan MH, Sun J, Yan L, Lei Y, Ma Y, Li X, Chen D, Linderholm HW (2017) Recent enhancement of central Pacific El Niño variability relative to last eight centuries. Nature Communications:15386. (doi: 10.1038/ncomms15386)

NASA Earth Observatory (2005) Climate Close-up: Coral Reefs. From https://earthobservatory.nasa.gov/Features/Paleoclimatology_CloseUp/paleoclimatology_closeup_2.php. Accessed 18 October 2018.

National Climatic Data Center, National Ocean and Atmospheric Administration (N.D.) What Are “Proxy” Data? From http://www.ncdc.noaa.gov/news/what-are-proxy-data, accessed 14 October 2018.

Nurhati IS, Cobb KM, Charles CD, Dunbar RD (2009) Late 20th century warming and freshening in the central tropical Pacific. Geophysical Research Letters 36:L21606. (doi: 10.1029/2009GL040270)

Reibeek H (2005) Paleoclimatology: the Oxygen Balance. NASA Earth Observatory: https://earthobservatory.nasa.gov/Features/Paleoclimatology_OxygenBalance, accessed 18 October 2018.

Thompson DM, van Woesik R (2009) Corals escape bleaching in regions that recently and historically experienced frequent thermal stress. Proceedings of the Royal Society B 276:2893-2901 (doi: 10.1098/rspb.2009.0591)

Tudhope AW, Chilcott CP, McCulloch MT, Cook ER, Chappell J, Ellam RM, Lea DW, Lough JM, Shimmield GB (2001) Variability in the El Niño-Southern Oscillation Through a Glacial-Interglacial Cycle. Science Magazine 291:1511-1516. (doi: 10.1126/science.1057969)

Vecchi GA, Wittenberg AT (2010) El Niño and our future climate: where do we stand? WIREs Climate Change 1:260-270. (doi: 10.1002/wcc.33)

Wang C, Deser C, Yu JY, DiNezio P, Clement A (2016) El Niño-Southern Oscillation (ENSO): A review. In: Reefs of the Eastern Pacific, Glymn P, Manzello D, and Enochs I, Eds., Springer Science Publisher:85-106. (doi: 10.1007/978-94-017-7499-4_4)


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“We are not drowning, we are fighting”: Pacific Islanders want you to know that they still have hope for their islands

This blog post originally appeared on the Ocean Leaders blog, which highlights the work of Ocean Leaders fellows. Please consider giving them a follow on social media at @oceanleaders on Twitter or OceanLeadersUBC on Facebook!

This past weekend, I was on a discussion panel for the documentary film Anote’s Ark, which follows the former present of Kiribati, Anote Tong, in his quest to bring the plight of Kiribati’s people in the face of climate change to the western eye. This sounds harmless enough, but since the film was released a new president was elected, the filmmaker was banned from entering the country, and the Kiribati ambassador to the United States attempted to prevent the film from showing at Sundance Film Festival (this is according to the filmmaker, you can read his take here).

It’s important to know that the current president of Kiribati objects to this film not because he doesn’t believe in climate change, but because of the language and messaging the film employs. “We are not sinking, we are fighting” is a battle cry heard all throughout the Pacific. The dominant Western narrative about climate change is one in which people who live in the Pacific Islands are helpless in the face of rising sea levels and erosion, and Anote’s Ark uses language that reinforces this narrative. For example, the first thing you see when you visit the film’s website is the question, “What if your country was swallowed by the sea?” While it is true that Pacific Islanders are not responsible for creating climate change, they are far from helpless when it comes to facing its effects, and language such as that used in Anote’s Ark removes their autonomy.

Tokelau warriors participate in the Pacific Warrior Day of Action in 2013 (image via 350.org).

I was asked to be on the panel because I had just returned from Kiribati, where I spent two weeks scuba diving around Tarawa and Abaiang Atolls with my advisor, Simon Donner, and master’s student Heather Summers, to study the coral reefs for my Ph.D. fieldwork. While we were there, we worked closely with staff from the Kiribati Ministry of Fisheries and Marine Resources Development. I have also worked with communities on other “sinking islands”: in the Marshall Islands (just north of Kiribati) and in the outer islands of Yap in the Federated States of Micronesia. While these places are different in many ways, they are all united by their status as lands on the frontline of climate change. However, none of these communities are ready to give up the fight to save their homelands. Language evoking drowning and disappearing islands gives the impression that their fate has already been determined.

Before we left, we had an opportunity to share our research with people from various ministries in the Kiribati government (mainly, the Ministry of the Environment, Lands and Agricultural Development, the Ministry of Fisheries and Marine Resources Development, and the Ministry of Education). These ministries are being proactive and doing lots of great work to slow the effects of climate change. For example, the Ministry of the Environment has planted mangroves in various places in Tarawa’s lagoon to slow erosion, and they appear to be doing well. Healthy coral reefs can play an important role in protecting low-lying atolls like Tarawa and Abaiang from erosion because they break up waves that can cause erosion (in fact, coral reefs dissipate wave energy by an average of 97%). Everyone at the meeting was eager to brainstorm potential ways to protect and restore reefs around the atolls, and we discussed our preliminary findings and their potential implications for over an hour after the presentation. For me, the meeting was a much-needed reminder of how crucial healthy reefs really are to Pacific Island communities; this is easy to overlook from a Western viewpoint, in which people tend to think of their value mostly in terms of tourism and aesthetics.

Pacific Climate Warriors lead the People’s March in Bonn, Germany on November 4, 2017 (Image via Hoda Baraka, 350.org).

Anote’s Ark featured a scene from the COP23 meeting in Bonn, Germany, in which a group of Pacific Climate Warriors led the People’s March on November 4, 2017, a gathering of 20,000 people demanding action from the international community on climate change. This international congregation of people united behind the Climate Warriors who chanted as they marched, “We are not sinking, we are fighting”. One of these warriors was Kathy Jetñil-Kijiner, a Marshallese activist, poet, and teacher, who was also featured giving a speech. She has given talks all over the world, including one during the opening ceremony of the UN Climate Leaders Summit in 2014 (you can watch it here). Kathy has actively spoken against the narrative that Pacific Islanders are helplessly waiting to sink into the sea. I’ll end with a poem she shared that was written by another Pacific Climate Warrior named George:


Sounded like the calm ocean breeze blowing through the Baka Tree. The laughter of my Dreu’s* making jokes about the Baigani incident. The mixing of Yaqona at 10am and the call from across the village going mai, mai, mai, dua mada na bilinimua.

Yesterday tasted like sui mada by my mother. Fresh fish and Yaqona made by my people.

Yesterday looked like the Bula smiles and respectful gaze of my elders. It looked like hope.

Yesterday smelt like the voivoi picked to weave the finest mats, like the masi used to wrap my son and daughter the first time they came home.

Yesterday felt like 

We are not drowning.

We are fighting.



Yaqona – Kava
Mai, mai, mai, dua mada na bili ni mua – come, come, come, one farewell mix
Sui – meaty bone soup
Voivoi – pandanus leaves
Masi – Tapa
Baigani – Egg plant
Drue’s – traditional address for people from Vanua Levu, the other bigger island in Fiji.

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Tiabo for now, Kiribati

I’m currently sitting in the departure terminal in Tarawa, the capital of Kiribati. It is a small room made of mismatched wood paneling, with one wall open to the tarmac, and a concrete floor. There are no lights, and a huge fan in the corner keeps the air moving, although it’s still sweltering. My back is to the tarmac, and I can feel the heat rising off of the asphalt. It’s just before noon, the hottest part of the day, and we’re waiting for the plane to come in so we can board. We are getting ready to depart for Fiji, the first stop on my long trip back to Vancouver.

My time in Kiribati has come to a close, at least for now. My head is spinning slightly from just how quickly this trip flew by, which I’m sure is aided by whatever stomach bacteria I’ve been battling the last few days. Sadly, because I was sick, I spent most of our time in the beautiful Abaiang sleeping in a traditional sleeping hut and didn’t get to dive or explore much of the atoll. I did talk Max, one of the guys we’re working with from Fisheries, into giving me a motorcycle ride along the atoll’s single road the morning before we left (he said he could tell it was my first time on a motorcycle). Abaiang is lovely. People live in picturesque, mostly traditional style housing equipped with solar panels, and there is a surprisingly large kava bar with multiple pool tables and karaoke. Apparently, some of the guys sang karaoke our first night in Abaiang. I’m so sad that I missed it, but Heather thoughtfully recorded it for me so I could live vicariously through her. Fortunately, I brought antibiotics with me and started taking them as soon as I was feeling sick, so I was feeling better by the time we were heading back to Tarawa (we only spent two nights in Abaiang).



An Abaiang sunset.



IMG_0968 2

Our sleeping huts in Abaiang.


The highlight of the last few days in Tarawa was our presentation of our findings to various stakeholders, hosted and organized by the Phoenix Islands Protected Area (PIPA) Trust. We spoke to representatives from Kiribati’s Ministry of Fisheries and Marine Resources Development, the Ministry of Environment, Lands, and Agricultural Development, and the Ministry of Education (although Simon and Heather will give a more detailed presentation to the Ministry of Fisheries folks). People had a lot of great questions and I really hope that our work will be useful for them as they plan for the future of Kiribati. We spoke a lot about how coral reefs can help prevent erosion and therefore help protect against sea level rise. It’s an important reminder that those of us who travel to scuba dive on coral reefs tend to view them through a Western lens in that their value to us is in their beauty; to Pacific Islanders, the health of coral reefs is directly linked to the health of their communities and the survival of their islands. The meeting was a great reminder of how important this work is and it left me feeling motivated to do more.



Explaining the differences in coral diversity between less disturbed sites (N. Tarawa and Abaiang) and more disturbed sites (S. Tarawa).


My advisor, Heather, and Erietera and Max from Fisheries all accompanied me to the airport this morning. Heather and Simon will both be staying in Kiribati for an extra week, but I’m returning early because of family obligations (oh, the joys of being a single parent in academia). It’s hard leaving when I know there’s still work to be done, but I hope to return to Kiribati in the next couple of years to continue my work here, and to continue working with the Ministry of Fisheries. I’m so grateful that I had the opportunity to spend time in Kiribati and to learn so much from all the people I’ve met. So, until next time … Tiabo (goodbye, pronounced sabo), Kiribati!


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