Introduction

Weather is what we feel on a day-to day basis but climate is defined as "the weather we expect to occur in the future based on our past experience". When changes in this expected weather occur, we call it climate change. Climate change is not always directly related to geology but the two are usually connected in some way. For instance we have already talked about cosmic and volcanic winters in previous units. These are global climate changes directly related to impacts from space and volcanism respectively. In other cases the link is less obvious but still there, because most of the evidence of ancient climate comes directly from the study of fossils, ocean sediments and ice, all branches of geological science.

Climate change happened on Earth long before humans arrived and it will continue long after we are gone. In this unit we will first look briefly at Earth's long-term climatic cycles, some of which are hundreds of millions of years long. This section will be short, because these long-term, gradual changes in climate do not have the ability to cause "disaster". We will then look at the history of short-term climate change. Of course in geology "short-term" can still mean thousands or even hundreds of thousands of years, not nearly abrupt enough to be called disastrous. The term "disaster" will be reserved for very short-term climate changes over a period of decades or centuries; too fast for humans to adjust to easily.

We will also look at the clever ways in which geologists can work out the past climate of Earth from a time before humans collected records, as well as the possible causes of the climate change that is now happening. There is now reasonable consensus amongst earth scientists that our planet is becoming a warmer place, in large part because of the burning of fossil fuels (a geological resource). We need to look at the implications for the human race as well as some of the ways in which we might prevent further warming from happening.

Learning Objectives

Upon completion of this unit you should be able to:

1. Discuss long-term climate changes that move the Earth between icehouse and greenhouse periods.
2. Recount in general the history of short-term climate change over the past 1.7 million years or so and how the Earth has fluctuated between glacial and interglacial periods.
3. Describe how oxygen isotope data from fossils are useful in working out ocean water temperatures.
4. Describe the process by which atmospheric precipitation and ocean water can become enriched in various oxygen isotopes.
5. Discuss how oxygen isotope ratios in continental ice can be used to work out ancient temperature.
6. Say how ancient climate can be deciphered by looking at growth rings in trees
7. Discuss the type of information that air bubbles trapped in polar ice caps can give us about ancient atmospheric composition.
8. List at least 4 other things that can be found in polar ice cores and what they can tell us about ancient climate.
9. Discuss the way in which foraminifera in deep ocean sediments can be used to estimate past ocean temperature.
10. Describe a Heinrich Event and what type of sedimentary processes and sediments are characteristic of it as well as what this signifies about the behavior of continental ice sheets and climate change.
11.  Explain the processes that could cause changes in ocean circulation patterns and how this could relate to sudden climate change.
12. Explain the greenhouse effect and why burning of fossil fuels might lead to global warming.
13. Explain in general, other ways that the amount of solar energy retained at the surface of the Earth could change. This includes surface reflectivity, dust and aerosols and the intensity of sunlight.
14. Discuss the major dangers associated with climate change.
15. Discuss the ways that global warming could be reduced or halted.

Required Readings

Read Abbott, P.L., 2012. Natural Disasters, Eighth Edition:

Chapter 9: External Energy, Fuels, Weather and Climate. p. 224-227
Chapter 12: Climate Change. p. 309-341

Web Resources

Manchester Metropolitan University - Climate Change
http://www.ace.mmu.ac.uk/eae/Climate_Change/climate_change.html

Miami University-Climate Change
http://jrscience.wcp.muohio.edu/html/globalchange.html#anchor4239967

NOAA- Paleoclimatology
http://www.ncdc.noaa.gov/paleo/slides/slideset/

RealClimate -BLOG
http://www.realclimate.org/index.php

Rapid Climate Change
http://www.aip.org/history/climate/rapid.htm

Readings From the Old Book

Abbott, P.L., 2009. Natural Disasters, Seventh Edition:

Chapter 2: Energy Flows in Earth History and Natural Disasters. p. 38-45.
Chapter 12: Climate Change. pp. 323-357.