THE PALEOCLIMATE. By Nick Cecil

Transcription

1 THE PALEOCLIMATE By Nick Cecil

2 What is the Paleoclimate? The term Paleoclimate refers to the climate of the Earth over its entire 4.6 billion year history.

3 Notes for Slide 1 Read definition (in a real presentation, the def n would not initially be visible). Explain some of the huge changes the climate has gone through v. early Earth with only hydrogen and helium. Then Earth with H2O, CO2, and Nitrogen from huge volcanism (more on this later) (this atmosphere is thought to have 100 times more gas than our current atmosphere). Then, the oxygen catastrophe ~2.5 bln years ago. Evolution of cyanobacteria and later plant life transforming CO2 to oxygen and helping remove CO2 from the atmosphere. Finally, the development of the ozone layer from continued release of Oxygen to the atmosphere, leading to what we know as the Earth s atmosphere with mostly nitrogen and oxygen. Even within this so-called third atmosphere, the climate varied dramatically, oscillating between huge tropic regions and vast ice sheets. (lead in to next slide). Sources: Monazite Canyons, by ~asetix. Via

4 Earth s Paleoclimate a Timeline An amalgam of our best temperature data for the last 542 million years of the Earth s climate (only a small fraction of Earth s history!).

5 Notes for Slide 2 Explain graphic temperature on the Y axis with a range of about 14 degrees C. Draw attention to the huge scale of time, and how it only represents a fraction of the Earth s history, and how the modern era in which humans have dominated the Earth is an even smaller fraction. The industrial age represents 2 MILLIONTHS of a percent of the represented time %. To put that in perspective, if you were the Earth, the Industrial Age started about an hour ago, compared to your 20 years of life. Note the huge maximums in the very prehistoric Earth, with temperatures as high as 8 degrees Celsius above the provided normal temperature, which is the average temperature over the last few thousand years. (This is a lead in to talk about how immensely huge a 3-4 degrees C rise in temperature would be over a 50 year period). Source of image: a collage of graphs from various research papers (sources given on wiki page).

6 Why should I care? Understanding prior changes in Earth s climate is absolutely critical to predicting the future, as well as determining whether the currently observed warming is natural or anthropogenic. As seen in the previous slide, Earth has undergone many huge climate changes in the last 500 million years. This appears to lend itself to the argument that what we re seeing is natural. The key is in the time scale.

7 Notes for Slide 3 Essentially just read the points out. Possibly go back to the previous slide and point out some of the glacial / temperature maximum periods. Use comparison to describe the time scale (refer back to graph to visualize): about 300 million years ago, the Earth s average temperature seems to have undergone an immense change from 2 degrees below the modern average temperature, to 6 degrees above average in an apparently short amount of time. However, this change actually occurred over the course of 50 million years. This amounts to a yearly average temperature change of just degrees/year. (Continue comparison on next slide). Sources: My brain.

8 To put climate change in perspective 542,000, ,000,000 years before present time 100 years before present 100 years after present Area of interest degrees C/year from 300 to 250 million years.04 to.015 degrees C / year from 2000 to 2100 (projected).

9 Notes for slide 4 Describe two graphs left is cutout from the earlier graph (point out the leap in temperature we re interested in). Right graph is from the 2008 IPCC report on predicted temperature change from 2000 to Read the number differences at the bottom of the graph. Sources: left graph cropped from image in slide 2. Right graph from the 2008 IPCC Climate Report.

10 Perspective (cont d) Modern Climate Paleoclimate Future change is 100,000 to 250,000 times more rapid than most rapid climate change on record.

11 Notes for Slide 5 Describe graph and stat graph is average of case of worst and best case IPCC scenarios, and the recorded temperature change between the Carboniferous and Permian periods. In reality, there are many things we can learn from the paleoclimate, but this is possibly the most important takeaway: yes, the Earth has undergone huge climate changes in the past, but we simply cannot comprehend just how long a time these changes have occurred over. Even the lowest estimates of ~1 degree Celsius change over the next 100 years is a huge jump, and one which we must take seriously. Thank everyone for their attention. Sources: My brain.