Climate is influenced by a variety of processes including geologic processes Volcanism Seafloor spreading Configuration of landmasses due to plate tectonics Climate changes impact geologic processes ID: 685588
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Slide1
Global WarmingSlide2
Climate
Climate: the average weather conditions over a period of years in a particular place
Climate is influenced by a variety of processes, including geologic processes
Volcanism
Sea-floor spreading
Configuration of landmasses due to plate tectonics
Climate changes impact geologic processes
Rates of erosion and deposition
Types of sediments deposited and sedimentary rocks formed
Geomorphology (surface features)
Fossil recordSlide3
The Climate System
Multidimensional System, many interacting parts
Atmosphere, hydrosphere, geosphere, biosphere, and cryosphere
Exchange of energy and moistureSlide4
The Climate SystemSlide5
Paleoclimatology – the study of past climates.
Earth’s climate varies in cyclical fashion over a number of time-scales
The study of natural climate processes is important to understand the role of humans in climate change.
Scientists measure climate change in the past in many different ways, depending on the time-scale.Slide6
Paleoclimatology – Study of past climates
What can paleoclimatology tell us about climate change that is relevant to society in the future?Slide7
Is the last century of climate change unprecedented relative to the last 500, 2000, and 20,000 years?
Do recent global temperatures represent new highs, or are they just part of a longer cycle of natural variability?
Is the recent rate of climate change unique to the present or was it commonplace in the past?
Can we find evidence in the paleoclimate record for mechanisms or climate forcings that could be causing recent climate change? Slide8
Proxy Climate Indicators
Instrumental records (from thermometers, rain gauges, etc.) only exist for the last 150 years.
Proxy climate indicators
provide indirect indications of climate change. These include:
Seafloor Sediments
Oxygen Isotopes
Glacial Ice Cores
Corals
Pollen
Historical DataSlide9
Proxy climate indicators and their useful time rangeSlide10
Climate Data from Historical Records
Wine is a serious business in Europe!
Careful records of the first day of the grape harvest in Europe have been kept since the 14
th
century. Trends in these records show changes in climate, as the harvest started earlier or later in the year. Slide11
Tree rings
Trees can live for thousands of years.
The width of tree rings provides information about growing conditions, including temperature conditions and CO
2
concentrations.Slide12
Oxygen Isotope Analysis
One of the most important ways that proxy data indicators reveal climate information is through the use of oxygen isotope analysis.Slide13
Oxygen Isotope Analysis
Isotope – varieties of an element with different numbers of neutrons, resulting in different atomic masses.
The most common isotope of oxygen has an atomic mass of 16 and is called
16
O. A heavier, less common variant is
18
O. Both occur naturally, and neither is radioactive. You breathe both kinds. Both isotopes bond with 2 hydrogen atoms to make water, H
2
O.
Water made of
16
O evaporates more easily. Water made of
18
O condenses more easily.
18
O has two extra neutronsSlide14
Oxygen Isotope Analysis
During colder weather, more light
16
O evaporates, leaving ocean water with more heavy
18
O.
This oxygen is incorporated into coral, plankton shells and sediments at the ocean bottom.
In colder climates, these proxy indicators will be enriched in
18
O.
The ratio of
18
O to
16
O, (
δ
18
O) can be correlated to temperature. For benthic (deep-water sediments), colder temperatures are related to higher values of
δ
18
O. Slide15
Reading the Graph
Horizontal (x) axis: Note older data as you move right.
Left vertical (y) axis -
δ
18
O ratios. A value of zero indicates the “standard” value for ocean water. The higher the value, the more
18
O, and the colder the ocean waters. Note colder is down on this graph.
Right vertical (y) axis - ∆T (temperature difference from “normal” annual average ocean temperature) Zero (dashed line) indicates “normal”. Slide16
Conversely, glacial ice cores are made of evaporated water that precipated.
Precipitation water always has a negative value of of
δ
18
O.
Colder temperatures are related to lower (negative values) of
δ
18
O.
The arrow points to a sudden cooling event that occurred over 10, 000 years ago, known as the Younger Dryas Event.
Oxygen Isotope AnalysisSlide17
Great website explaining oxygen isotope analysis
http://earthobservatory.nasa.gov/Features/Paleoclimatology_OxygenBalance/Slide18
Left: The type of fossil can indicate the temperature range in ocean waters.
Their shells can be analyzed chemically to measure CO
2
concentrations and oxygen isotope ratios
Oxygen isotope analysis (below): the ratio of O-18 (heavier, less common) to O-16 (lighter, more common) is a proxy measurement of temperature. Slide19
Ice Cores – a very valuable proxy data indicator
Ice cores have annual rings, like trees, so age of core can be determined
Air bubbles trapped in the ice can be analyzed for oxygen-isotope data, carbon dioxide concentration, presence of aerosols etc.
The ice itself can be melted and analyzed for these proxy data indicators.Slide20
Vostok Ice Core Data
This is partial data from an ice core from Antarctica.
Temperature data from oxygen/hydrogen isotopes.
Interglacial” is a warm period between ice ages.
Peak of last ice age about 20,000 years ago.Slide21
The modern atmosphere
Two most abundant gases:
78% N
2
21% O
2
Less abundant gases (< 1%)
Argon
Water vapor
CO
2
(only about .035%) It’s up to almost .040% now!
Non-gaseous components
water droplets
dust, pollen, soot and other particulatesSlide22
Fig. 17.6, p.437Slide23
Thermal Structure of Atmosphere: Upper Layers
Troposphere - Extends to about 12 km (40,000 ft) elevation. Where we live.
Stratosphere – heated primarily by solar radiation
Ozone (O
3
) layer absorbs UV energy, causing temperatures to rise
Above 55km (stratopause) temps fall again
Mesosphere – thin air (can’t absorb energy), very cold up to 80km
Thermosphere – above 80km, temps rise rapidly (to just below freezing!)Slide24
Solar Energy (Insolation)
Also called solar radiation, although NOT radioactive!
Composed of electromagnetic waves with different properties depending on wavelength, frequency
Longwave (low frequency): includes heat (infrared), radio waves
Shortwave (high frequency): includes visible light as well as ultraviolet, x rays, gamma rays
Electromagnetic spectrum – shows EM wavelengths by frequency and wavelength.Slide25
Electromagnetic SpectrumSlide26
Solar Radiation in the atmosphere
Reflection/scattering – bounces off with no effect
Absorption – eventual re-emission in a different formSlide27
Reflection and Albedo
Reflection–electromagnetic radiation bouncing of from a surface without absorption or emission, no change in material or energy wavelength
Albedo – proportional reflectance of a surface
a perfect mirror has an albedo of 100%
Glaciers & snowfields approach 80-90%
Clouds – 50-55%
Pavement and some buildings – only 10-15%
Ocean only 5%! Water absorbs energy.Slide28
Typical Albedos of Materials on the EarthSlide29
Absorption and Emission
Absorption of radiation – electrons of absorbing material are “excited” by increase in energy
Increase in temperature; physical/chemical change
Examples: sunburn, cancer
Emission of radiation – excited electrons return to original state; radiation emitted as light or
heat
Earth
absorbs
short wave radiation from sun (i.e. visible light) and
emits
longwave
(infrared or heat) into the
atmosphere.Slide30
“Greenhouse
gases” (water vapor, carbon dioxide, methane, etc.) let shortwave energy pass, but absorb
longwave energy radiated upward by the Earth
. The
longwave
energy is
then re-radiated by the gases in
all directions, some of it returning to the Earth’s surface. Slide31
The greenhouse effect keeps
our atmosphere at a livable temperature of about 15 degrees C (59 degrees F
). If all heat escaped, the average temperature of Earth would be about -20
0
C (0
0
F).Slide32