BaCCC/Module 1/Lesson 3/Part 2

Measuring and monitoring

How do we know what the climate was like in the past?

Did you know that even today scientists are still studying past climate? The study of past climate is known as “palaeoclimatology.” The factors that make up climate (such as temperature and precipitation) have been measured directly since the 1860s. However, to understand what climate was like before that, scientists use “proxies” or indirect measurements that have a well-defined relationship to temperature or other climatic variables.

Activity

1. Search for three of the most common proxies, briefly explain each one in your learning journal, and then state your source of information.

2. “Concentrations of the key greenhouse gases have all increased since the Industrial Revolution due to human activities.” Search for and give statistical data to prove this point.

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Some common proxies include: Ice cores – The ratio of oxygen isotopes in the ice can indicate the temperature at the time the ice was formed. Air bubbles trapped in ice can show what the greenhouse gas concentration of the atmosphere was at the time of formation. Ocean sediment cores – The remains of small hard-shelled creatures (foraminifera) are preserved in ocean sediments. The composition of their shells can reveal ocean temperatures at the time of their formation. Pollen records – Fossilised pollen grains can indicate what types of plants were present at the time the fossils were formed. Tree rings – The width of annual tree rings in temperate climates depends in part on soil moisture and temperature and can, therefore, reveal information about these variables. Past climate is often “reconstructed” by looking at many of these measurements together. More examples can be found at these sources: "What are proxy data?" "How do we determine past climate?"

As you searched for information, you likely discovered that the process of monitoring climate change began in the 1950s with the measurement of carbon dioxide or CO2 at the summit of a mountain (at the Mauna Loa Observatory) on the island of Hawaii. The measurements continue to confirm that atmospheric levels of CO₂ are increasing at an alarming rate. The use of computer simulations in the late 1960s and the later development of (computerised) climate models confirmed a link between continued CO₂ emissions and global warming. You may find it interesting that with these models, scientists could date this link back centuries. Climate scientists have confirmed that over the past 100 years, global average surface temperatures have increased by just over 1°C.

Activity

It is generally believed that one way of “doing science” is to make a claim and then find or use evidence (proof). In your learning journal, confirm six of the given claims (in the chart below) via evidence from various sources, especially the Internet. Include the source of your evidence for each claim. .

Claim and evidence game

Claims	Local visible evidence (videos/ photographs/ interviews)	Research-based evidence (scientific journals)	Evidence from other sources (media)
Increases in atmospheric moisture content
Increased summer temperatures
Food shortages and water scarcity
Torrential rainstorms
More flooding and severe drought events
Further rise in ocean levels
More intense hurricanes
More extreme heatwaves
Further melting of ice caps and glaciers
Ocean acidification
Extinction of species
Coral reefs degraded