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Data Presentation

Dendrochronology

The analysis of tree rings to provide information on past climates.

Certain species of trees grow a new ring each year. This happens in trees that exist in areas where the climate halts their growth at some point during the year (such as cold temperatures or lack of water). So, this happens to trees in high altitude and high altitude areas (such as conifers and deciduous trees). Tropical tree do not grow rings each year.

Oldest Trees in the World? Ancient Bristlecone Pines!

White Mountains, California

1953, established a continuous tree-ring sequence of 8,253 years.

Go see them! https ://www.fs.usda.gov/detail/inyo/specialplaces/? cid=stelprdb5129900

Oxygen Isotope Analysis of Oceanic Sediments

Provides information on climate through the ratio of 16O and 18O

“Lighter” 16O evaporates more readily than 18O when temperatures are warmer.

This ratio can also be examined in ocean floor sediment.

Learn more here – https://earthobservatory.nasa.gov/Features/Paleoclimatology_OxygenBalance /

Pollen Analysis

Palynology – studies pollen trapped in sediment layers at the bottom of lakes and bogs

The sediment can be dated through radiocarbon dating,

Certain plants are better adapted to different climates, so the type of pollen in each layer can provide an indication of climate conditions when the layers were formed.

Ice Cores

Also provide data on 18O /16O ratio

Gas bubbles trapped in ice cores (see images on the next slide) also allow for the direct measurement of gasses such as carbon dioxide.

Dome C

Dome C is located 1750 kilometers from the South Pole, where the Antarctica ice cap is thickest (this is where we’ve extracted the longest ice core sample on Earth).

Ice coring under the European Project for Ice Coring in Antarctica (EPICA) has extracted core dating back 800,000 years (remember that timescale graph earlier?).

The Dome C climate record shows that the present concentration of CO2 in the atmosphere is higher than anytime during the past 800,000 years.

Also shows that increases and decreases in global temperature are closely correlated with changes in concentration—with temperatures high when concentrations are high, and vice versa.

Further, the findings at Dome C closely match the proxy climate record derived from the oxygen isotope analysis of the calcium carbonate in foraminifera (tiny marine creatures) found in oceanic sediments, adding to the scientists’ confidence in the soundness of the Dome C data.

Dome C Data – comparing carbon dioxide and methane concentrations to the overall temperature trend during the last 800,000 years. Do you see a correlation?

Now, let’s take a look at carbon dioxide a little more closely. Carbon dioxide (CO2) is one of the two most important greenhouse gases (the other is water vapor). These act like invisible blankets in our atmosphere. They allow short-wave radiation from the Sun to enter into the atmosphere and reach the surface of earth. The surface then heats up and emits long-wave radiation back out to space. BUT CO2 and water vapor do not allow long-wave radiation to escape as easily (hence the term ”blanket”) and trap that heat in the lower portion of the atmosphere. Most of the time this is a great process, known as the Greenhouse Effect. It keeps the surface of earth at a livable temperature for us. The problem though is when we increase the amount of CO2 in the atmosphere (i.e. add more and more blankets) and heat up the Earth’s surface temperature too much, too quickly. This is the case we are seeing now, and the reason why any solutions to climate change focus on reducing CO2 emissions. The graph above summarizes the concentrations of CO2 (measures in PPM or parts per million) As of April 2018, we are at 407 PPM.

Causes of Long-Term Climate Change

Plate Tectonics & Volcanic Activity

Variations in Earth-Sun relations (Milankovitch Cycles)

Fluctuations in Solar Output (Solar Flares)

Findings for the above – they are factors, but there hasn’t been significant enough changes to account for the most recent temperature trend

Feedback Mechanisms

Role of the Ocean

Role of Vegetation

Findings for the above – they are factors, but alone they do not account alter climate without other factors (such as carbon dioxide)

Greenhouse Gas Concentrations