global warming. climate climate: the average weather conditions over a period of years in a...

Global Warming

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 record

The Climate System

• Multidimensional System, many interacting parts

• Atmosphere, hydrosphere, geosphere, biosphere, and cryosphere

• Exchange of energy and moisture

Remember Environmental Unity!

Remember Open and Closed Systems!

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.

Paleoclimatology – Study of past climatesWhat can paleoclimatology

tell us about climate change that is relevant to society in the future?

• 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?

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 Data

Proxy climate indicators and their useful time range

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 14th century. Trends in these records show changes in climate, as the harvest started earlier or later in the year.

Tree rings

•Trees can live for thousands of years.

•The width of tree rings provides information about growing conditions, including temperature conditions and CO2 concentrations.

Oxygen Isotope Analysis

One of the most important ways that proxy data indicators reveal climate information is through the use of oxygen isotope analysis.

Paleoclimatology: The Ice Core Story

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.

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.

The modern atmosphere

• Two most abundant gases:– 78% N2 – 21% O2

• Less abundant gases (< 1%)– Argon– Water vapor – CO2 (only about .035%) It’s up to almost .040% now!

• Non-gaseous components– water droplets– dust, pollen, soot and other particulates

Fig. 17.6, p.437

How CO2 in atmosphere relates to temperature

• Until the 19th century, ice core data show atmospheric CO2 levels at less than 300 parts per million (ppm)

• Rapid increase in CO2 concentrations since the Industrial Revolution (mid 19th century) is apparent

• Present-day levels exceed 390 ppm. This represents a 30% increase.

In 1958, Roger Revelle and Charles David Keeling started direct monitoring of atmospheric CO2 from the Mauna Loa Observatory.

Addition of Keeling Curve to the Vostok Ice Core Data

Temperature Deviation Map for 2009. Note Arctic

Changes in the Qori Kalis Glacier, Quelccaya Ice Cap, Peru, are shown between 1978 (top) and 2002. The glacier retreat during this time was 1,100 meters.

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.

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.

Typical Albedos of Materials on the Earth

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.

“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.

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 -200

C (00 F).

Does this mean that human activity is responsible for global warming?

American Impact on ClimateAdds up to over 16 metric tons annually

CO2 emissions by country (1995)

B. Per capita emissions by country

US number closer to 40 metric tons

Haves vs. have-nots