How Low Does CO2 Go?

by Emil Morhardt

Atmospheric CO2 levels are always lower during glacial periods than during interglacials like the one we are in now. During the last glacial maximum 20,000 years ago, for example, they were at 190 parts per million (ppm), whereas during the most recent 10,000 years, almost up to the present, they have been about 280 ppm. [We have now succeeded in raising them to over 400 ppm and still counting, but that’s a different story.] Eric Galbraith and S. Eggleston (Galbraith and Eggleston, 2017) argue that as far as we know, atmospheric CO2 levels have never gone below the typical glacial levels of 190 ppm, even in extended snowball earth conditions. Why not? Well, a carefully-reasoned 2009 paper they cite (Pagani et al., 2009) suggests that even in the mostly warm conditions of the last 24 million years, when CO2 levels fell below 190 ppm, terrestrial plants stopped effectively photosynthesizing, thus they not only stopped removing CO2 from the atmosphere directly, but they also stopped the active root growth which increases the acidity of soils and enhances chemical silicate weathering from the rocks which removes CO2 from the soil, and ultimately from the atmosphere. Galbraith and Eggleston argue that the same thing has been happening during the glacial periods of the last 800,000 years, and extend the argument to the photosynthesis of oceanic phytoplankton. To wit, when CO2 levels get below 190 ppm, CO2 removal from the atmosphere by photosynthesis and chemical weathering is sharply reduced, so they decline no further. Continue reading

Is Climate Change to Blame for the Rise in Shark Attacks?

by Alex McKenna

After the release of Jaws in 1975, people started thinking twice before getting in the water. Decades later, they still remember the stories, newspaper articles, and photographs of swimmers collapsed on the shore, covered in shark bites. But do they have reason to be concerned? Recent trends in climate change suggest that they actually do. Over the past 30 years, the frequency of unprovoked shark attacks has drastically increased, with the majority of bites being recorded in Florida, South Africa, Australia, and the Bahamas. While researchers argue that there are many reasons behind this influx, Dr. Blake Chapman, professor at Bond University in Australia, points to climate change as one of the principle explanations. He believes that rising temperatures, heavy rains, and anomalous weather patterns, all results of climate change, fundamentally alter marine ecosystems and are ultimately to blame for the recent spike in shark attacks. Continue reading

Schneider and Louisville’s Green Initiative

by Vikramaditya Jhunjhunwala

In the spring of 2011, the mayor of Louisville created a commission dedicated to planting more trees. This commission was to be co-chaired by none other than Katy Schneider, former deputy mayor of Louisville and advocate of environmental issues. Madeline Ostrander (2016) outlines Schneider’s efforts in creating a healthier environment for her city, and reminds the people of urban America of the environmental dangers their concrete worlds face in the absence of greenery.

Ostrander recounts that Schneider’s journey began in early 2012 when Schneider approached Brian Stone, a professor at the Georgia Institute of Technology, to find out the extent of temperature changes in Louisville. Stone proceeded to reveal that Louisville’s temperature had increased by about 1.7 degrees every decade since 1960. Stone also noticed that urban areas were heating more than rural areas. He discovered that this situation was primarily caused by what meteorologists call the urban heat-island effect whereby dark and paved surfaces absorb solar radiation consequently causing the air temperature to rise. Continue reading

Ocean Acidification can Mediate Biodiversity Shifts by changing Biogenic Habitat

by Elizabeth Rodarte

Ocean acidification is the process in which the pH of the world’s oceans decreases due to the production of atmospheric CO2. The increase of CO2 and decrease in pH leads to changes in calcification, growth, and abundance of species such as coral reefs, mussels, seagrass, and macroalgae. Habitats experience the indirect effects of such CO2 increases. They must remain resistant to sudden changes in pH and CO2 in order to benefit the organisms they support. By modeling the effects of lowering pH in habitats with corals, mussels, seagrass, and microalgae, we can determine the costs to these species. Coral reefs and mussels are calcifying organisms that are negatively affected by the pH which limits survival and stunts, or even stops, growth and development. Lower pH decreases the species complexity of corals and mussels and ultimately the species richness in habitats. Mytilus mussels, for example, require specific pH to function. The species of mussels, other than Mytilus, that survive decreases in pH lack “structural complexity” to support dense surrounding vegetation. Therefore, the loss of Mytilus mussels due to ocean acidification allows for a more stable yet less diverse habitat. Continue reading

Pacific Islanders Fear for Future Amidst Trump’s Climate Rhetoric

by Aurora Brachman

The future of Pacific Island nations requires the United States solidarity on climate change action to protect people in vulnerable developing nations from the environmental destruction they imminently face. As a result of rising sea levels and changing weather patterns, a consequence of global warming, Pacific Islands have begun to experience significant costal erosion and increasingly severe natural disasters that threaten the continued existence of these small island nations. Unfortunately, United States president Donald Trump has endorsed skepticism about human contributions to climate change and his climate policy as of January is consistent with these views. In Trump’s 100-day action plan, which he issued during his campaign, he claims intentions to cancel billions of dollars in funds to the United Nation’s climate change programs, which assist people in developing countries. He has also vowed to approve trillions of dollars’ worth of energy projects involving shale, coal, natural gas and oil, all industries that perpetuate climate change and whose continued use pose a threat to the future of these island nations. Continue reading

Climate Change and Archeology

by Alejandro Sandell-Gandara

Adam Johnson describes how archeologists are observing tsunami surges as a way to predict the impact of rising sea levels on archeological sites. In 2011 the 9.0 magnitude Tohoku earthquake created a tsunami that caused damage to Japan and communities across the pacific. The costal archaeological sites at Pu’uhonua o Honaunau National Historical Park on Hawai’i were affected by the tsunami.

The Pu’uhonua archaeological site in the coast of Kona is significant due to its ceremonial complex. On the site there is the Hale o Keawe temple which served as a royal mausoleum. The site is located on the coast line and surrounded by a stone wall to the east and south. The site has been excavated by several archeologists and determined to be originally related to chief Ehu-kai-milano in the 1500s. In the 1600s, Umi-a-Liloa built the stone wall around the site. An analysis and excavation of the bedrock shoreline shows evidence of activities such as dyeing of fishnets, processing seaweed, and pounding fish bait.

Tsunamis, hurricanes, and high surf caused damage to this site. The first documented tsunami occurred in 1819; a two-meter-high wave caused by a submarine fault in Chile struck the archeological site from the northwest, filled the royal fishponds with stones and sand, and broke down the northern part of the stone wall. Since 1900, twenty-four tsunamis have been recorded in Hawai’i with eleven causing significant damage.

In 1992, hurricane Iniki struck Hawai’i and caused 143 mph winds and water levels thirty feet above normal. The hurricane damaged the archaeological site by destroying structures and removing surface sand and sediments.

The damage caused by rising sea levels, hurricanes, and tsunamis can be analyzed and used to predict the effects of climate change. The destruction caused by these natural disasters confirm that climate change would cause major damage to archeological sites in coastal areas.

Adam Johnson, Lisa Marrack & Sara Dolan (2015) Threats to Coastal Archaeological Sites and the Effects of Future Climate Change: Impacts of the 2011 Tsunami and an Assessment of Future Sea-Level Rise at Hōnaunau, Hawai’i, The Journal of Island and Coastal Archaeology, 10:2, 232-252, DOI: 10.1080/15564894.2014.980472


The Great Climate Debate Circa 2006

by Paola Salomon

There is still much controversy about whether human activity is causing global warming, and whether what appears to be a climate change is simply normal climate variability. Assenza and Reddy (2006) mainly debate the causes and consequences of climate change and discuss two different points of views: that of sceptics and supporters. While the sceptics do not want to take action, the supporters claim that we cannot postpone dealing with this issue anymore. Supporters are afraid that the environmental and socio-economic costs of climate change are significant, while the sceptics are fearful about the economic consequences of attempting to reverse climate change. Continue reading