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Ever Wondered? Episode 8


Climate change

In Episode 8 of Ever Wondered?, Dr John Watt investigates how scientists monitor changes in atmospheric gas levels and looks at some innovative ways to reduce greenhouse gas emissions.
Using ice cores to map past greenhouse gas levels

NIWA's Dr Katja Reidel collects ice cores from Antarctica. She shows John some glacial ice that is about 1,000 years old.

The ice core has gas bubbles that form in winter and summer, like the growth rings on trees. To collect the gases, Katja slices through the core and places a sample in an ice grater. This breaks up the ice, releasing the bubbles into an airtight container. Liquid helium traps the gases. Katja analyses the ice for gas levels and to find out the temperature at the time the ice formed. This enables her to compare past CO2 levels with corresponding temperatures.

Measuring gases at ground level

Baring Head is a NIWA monitoring station near Wellington. Gordon Brailsford explains how the air arriving at Baring Head originates from the Southern Ocean. It hasn't been over land for 5-10 days, so it's not influenced by human activities. Baring Head began measuring CO2 in 1972 and has the longest continuous CO2 measurements in the Southern Hemisphere. Their data shows a steep rise in CO2 levels, fitting global trends.

Measuring gases at the atmospheric level

John visits a second NIWA monitoring station at Lauder, Central Otago. Dr Vanessa Sherlock explains a new technique for measuring greenhouse gases. The technique, total column measurement, uses a telescope that points at the centre of the Sun. Individual greenhouse gas molecules absorb sunlight in a unique way. By splitting the sunlight into its full spectrum, she can see which parts of the spectrum are missing, giving her very precise gas measurements.

Using phytoplankton as a carbon sink

Dr Cliff Law found that adding iron oxide to seawater promotes phytoplankton growth - microscopic plants capable of absorbing huge amounts of CO2. When phytoplankton dies, some of it sinks to the ocean floor, locking the carbon away for hundreds of years. Companies selling carbon credits are interested in Cliff's research. However, decaying phytoplankton produces nitrous oxide and methane, so Cliff is now investigating the overall effect of adding iron to seawater.

Reducing methane emissions

John moves inland, visiting the Agricultural Gas Research Centre in Palmerston North. Dr Harry Clark explains that each dairy cow emits 90kg of methane per year. The yearly emissions from a single cow have a CO2 equivalent of 860 litres of petrol. Demand for milk and meat means we can't eliminate animals but we can reduce the amount of methane they produce. Dr Gerald Cosgrove shows John test facilities that mimic animal digestion. He tests various plant materials to find correlations between food sources and methane production.

Dr Kerry Hancock is an AgResearch scientist also working to reduce animal methane emissions. Kerry's research involves genetically engineering white clover to produce condensed tannins, chemicals that decrease digestive methane in cows by up to 15%. Because of New Zealand's strict regulations regarding genetically engineered plants, field trials involving white clover take place offshore.

Activity idea

In conjunction with this episode of Ever Wondered?, your students may enjoy these activities.

In this activity, students interpret graphs using actual CO2 and 12C data from the Baring Head monitoring station.
www.sciencelearn.org.nz/Contexts/The-Ocean-in-Action/Teaching-and-Learning-Approaches/Using-radiocarbon-carbon-dioxide-data
 
Students explore this interactive diagram to learn more about the carbon cycle. Short video clips and images explain different parts of the cycle, including phytoplankton's role in sequestering carbon.
www.sciencelearn.org.nz/Contexts/The-Ocean-in-Action/Sci-Media/Animations-and-Interactives/Carbon-cycle

Context links

To further investigate climate change, check out these Science Learning Hub contexts.

Icy-Ecosystems: In this context, you'll find research articles and videos of Dr Katja Reidel explaining how she uses ice cores to learn more about climate change.
www.sciencelearn.org.nz/Contexts/Icy-Ecosystems/NZ-Research/Icy-Ecosystems

The Ocean in Action: In this context, you'll find research articles and videos detailing the work of New Zealand scientists in relation to CO2 in the atmosphere and the ocean.
www.sciencelearn.org.nz/Contexts/The-Ocean-in-Action/NZ-Research/The-Ocean-in-Action






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