week 12 Flashcards
Why can’t tectonic forcing explain climate change?
Completely different time-scale
5-10°C over 50 - 100 million
years
Why can’t Orbital forcing explain climate change?
Based on current orbital configuration Earth should be
cooling
CO2 outside of range over Quaternary
Why can’t Millennial-scale forcing explain climate change?
millennial-scale events relied on presence of Laurentide ice sheet
pattern would be bi-polar not global
Why can’t Solar forcing forcing explain climate change?
not large enough to account for observed warming
11-year solar variation cycle
Why can’t Volcanic forcing forcing explain climate change?
Short-lived - impact lasts only a few years
would expect cooling as well
Why can’t Variation in climate modes explain climate change?
too small and short lived
Strongest El Niño years i raised average global temperature by 0.1 - 0.2°C – only for that year
What has been the warming caused by humans?
0.8°C to 1.3°C warming relative to 1850-1900
What is the Paleoclimate record key to?
- Placing the current changes in context
- Understanding how the climate system operates
- Developing and testing models that are used to predict future changes
What is the Anthropocene?
a proposed new geological epoch, representing that human activities are having a significant impact on the Earth system
What is the argument that Early agriculture should be the start of the Anthropocene?
Early anthropogenic hypothesis
Increase in CO2 ~7000 years ago
Increase in CH4 ~5000 years ago
What is the argument that Collison of Old and New Worlds should be the start of the Anthropocene?
Colombia exchange’: mixing/homogenisation of biotas
lead to rapid reorganisation of life
Establishment of ‘world system’
What is the argument that Industrial revolution should be the start of the Anthropocene?
- 1760-1880 in northwest Europe
- Marking when we first made use of other energies
What are the problems with using the Industrial revolution as the start as the Anthropocene?
industrial type production wasn’t new and initial
spread was slow
• Local rather than regional scale
• Gradual build up
•Hard to define a marker
When is the start of the Anthropocene?
Great Acceleration and year 1950
What are the markers of the Great Acceleration?
• Global array of signals in recent strata
• Plastic, aluminium, concrete particles, artificial
radionuclides, changes to carbon and nitrogen isotope
patterns, fly ash particles, sediment distribution etc
What is the great acceleration?
Global ramping up of post-war industrial activity contributing to major changes inthe character, composition, and behaviour of the atmosphere, ocean, cryosphere and land surfaces
What is a golden spike?
- marker denoting the Global Boundary Stratotype Section and Point (GSSP)
• Reference point that can be dated
• Event should be traceable globally
What features are needed in defining the Defining the Anthropocene?
- Must be fairly synchronous in time across the globe
- Must be large enough to be detectable in the stratigraphic record
Why can’t megafauna extinction be defined as the start of the Anthropocene?
- Likely a series of different events in different regions
- Degree that humans were responsible is debated
