Geo 3B: Evidence for climate change Flashcards
Outline one major type of evidence for climate change through geological time
Evidence of climate change in the geological past can be seen 650 million years ago, during the Proterozoic period, commonly referred to as Snowball Earth. During this time, glaciers were located at the Equator. Global erratics/drop stones have been found in the Flinders Ranges(Australia) and Death Valley(USA), these are believed to have moved from higher latitudes by glaciers. These rocks are dissimilar to others found around them in their magnetism and rock structure indicate they were formed at different latitudes to that of their current locations. Plate tectonic theory indicates the position of Pangaea created significant chemical weathering across the tropics, leading to the removal of carbon dioxide from the atmosphere and causing a positive feedback in the climate system.
Outline one major type of evidence for climate change in recent human history
Climate change in recent human history is based on direct or instrumental data over the last 150 years. Currently in the interglacial period, temperatures have risen 0.75 over the past 100 years. Measured direct data includes ground-based weather stations, weather balloons and satellites, when combined with proxy data(ice core samples, dendrochronology) suggest temperature increases. Higher concentration of greenhouse gas emissions in the past 50 years are linked with recorded temperature increases. The melting of polar and mid latitude glaciers has been documented using cameras, both on the ground and from satellites. Glaciers are calving at unprecedented high rates in locations such as Columbia Bay in Alaska, as well as mid latitude glaciers such as Chacaltaya in Bolivia.
