GEO 206: L.9 Environmental & Climatic Change

Ice Age and ice ages; what, when, and why

"Ice Age," a period in which giant glaciers extended down from the North Pole to cover Europe and much of North America. During ice ages the climate is colder and ice sheets are very large. BECAUSE WATER IS STORED IN GLACIERS, SEA LEVEL DROPS DURING THIS COLD PERIOD. Ice Retreat (interglacials): During interglacials, the climate warms and glaciers melt. Sea levels rise. New shorelines. Evidence for this fluctuation in sea level and climate is often preserved in old shoreline features, such as in the wave-cut terraces below. These features represent period of previously higher sea level. When sea level drops during glacial periods, these higher shoreline features are abandoned and are preserved for many years.

Human influences on the greenhouse effect

1. Deforestation : Less trees to absorb CO2. 2. Trees burned (Key: Young, growing forests remove more carbon dioxide than mature forests that have reached their growth limits.) 3. Burning Fossil Fuels (a majority of the electricity we use in the United States is generated from burning coal) ~~ Random: Logging ( Much of the world's timber harvest is used for paper products, though it is important to note that the trees used to manufacture paper generally come from managed plantations. )

Evidence in favor of anthropogenic climate change

1. The rapid increase in the atmospheric concentration of carbon dioxide following the onset of the Industrial Revolution.

Carbon and the carbon cycle

All life, as we know it, is based on carbon. CARBON SINKS (RESERVOIRS) Places that store carbon: living and dead organisms (not to be confused with decomposing organisms) fossil fuels sedimentary rocks (like limestone) soils the atmosphere the ocean *Carbon used in photosynthesis and respiration OCEAN AND CARBON: -Can directly dissolve into seawater -As it builds up in the oceans, it may precipitate out as calcium carbonate and form limestone rock on the ocean floor. Carbon can be locked up (or remain inactive) for millions of years in these rocks -Organisms within the oceans also extract calcium carbonate from the water to build their shells. Calcium carbonate is the main component of such things as coral, pearls, and seashells. -When organisms die, sink to ocean floor, accumulate and transform into sedimentary rock -As the temperature of the ocean water warms, the carbon dioxide tends to degas more readily -Carbon is stored in fossil fuels -Carbon is stored in plants (through photosynthesis) buried deep within Earth with high pressure, chemical/biological reactions and heat, transform the material matter into coal, oil, natural gas and other fossil fuels. The carbon within these fossils fuels is released out of the atmosphere when the fuels are burned to produce energy.

Greenhouse Gases

Are variable gases (meaning they vary in their proportion over time) -Although their amounts may increase or decrease, their relative proportion (extremely small) remains the same. SEVERAL, including: 1. water vapor (most abundant) 2. nitrous oxide (emitted by our cars and by the agricultural industry through the usage of nitrogen fertilizer in soils) 3. carbon dioxide (2nd most abundant and the one that humans most effect) 4. fluorinated gases 5. methane (released by decaying and burning plants, and livestock as they digest plants. Also released as fossil fuel combustion and rice production) 6. ozone 7. Chlorofluorocarbon (synthetic substances sometimes used in place of ozone-depleting substance)

Cross-dating

By comparing and matching ring width patterns among several trees in an area, an exact date can be found for each tree ring. This method, which is known as cross dating, is more precise than ring counting. Matching ring-width patterns across living and dead trees allows a continuous tree ring record to extend back for 10,000 years in the United States Southwest.

Atmospheric concentration of carbon dioxide

By looking at ice cores (remember from earlier in the lesson), we know that the pre-industrial atmosphere contained 288 parts CO2 for every one million parts of the atmosphere. In other words, the pre-industrial atmosphere contained 0.028% carbon dioxide. In contrast, as of July 2008, that number had risen to 384 ppm. In other words, the atmosphere now contains at least 0.038% CO2 (where 384 is the average level of carbon dioxide found in the atmosphere over one years time). This is an increase of a little more than 30% in roughly 200 years.

If a dendrochronologist wanted to develop a climate record that dates back before the oldest tree in a forest community, how would he or she do that?

Cross date the oldest living tree in that community with older or dead trees in the area.

Fossil pollen and how used

Each plant produces a unique pollen which can be preserved as fossils in sediment at the bottom of lakes and marshes. -Extract a core of a lake/pond/marsh sediment -Organic material at various levels within the core can be radiocarbon dated (see AAB for link) so that we know from what time period the pollen came -Rocks and soil are removed and pollen is viewed under a microscope In summary, palynologists and biogeographers can use the relative proportions of pollen grains found in a sediment core to determine what climate may have been like in an area during a period of time

Global Warming; changes in temperature and precipitation

Earth's average surface temperature has increased almost 0.6° C since 1880 -Global precip over land has increased by about 1% -Sea level has risen 4-8 inches during the past century

Fossil Fuels

Finally, we have the carbon that is stored in fossil fuels. The carbon was originally stored in plants through photosynthesis. The plants were then buried deep within the Earth for millions of years. The weight of the overlying sediments applied tremendous pressure on the buried materials. High heat, pressure, and chemical and biological reactions transformed the buried matter into coal, oil, natural gas, and other minor forms of fossil fuels. Evidence of fossilized plant material may still be found in coal.

Ice Sheets

Form where snow falls and does not melt completely during the summer months. -It is then BURIED by the following winter's snowfall. -If this process continues, it eventually becomes glacial ice. Key: Since water contains oxygen, and snow is crystallized water, the ice from any given ice sheet can reveal information on the atmospheric composition at the time the snow fell. IF ICE IS WELL PRESERVED, IT IS POSSIBLE TO COUNT THE NUMBER OF LAYERS OF SNOW ACCUMULATION AND RECONSTRUCT THE ATMOSPHERIC COMPOSITION FOR A GIVEN YEAR IN THE PREHISTORIC PAST.

Paris Agreement

In December 2015, 195 countries met once again at the Paris Climate Conference (COP21) to arrive at a legally binding, comprehensive climate plan--and by some accounts, this goal was finally realized.

IPCC

Intergovernmental Panel on Climate Change -Every year, hundreds of representatives, officials, and experts from relevant agencies, organizations, and research institutions in member countries come together to discuss issues related to global warming -During their annual meeting, members of the IPCC also determine whether they should issue a new report based on the most current scientific findings. -After the IPCC released their third assessment in 2001, humans began to adapt their activities to the changing climate.

Glacial landforms

Left distinctive evidence of their presence on the landscape in the form of glacial landforms; GLACIAL LANDFORMS; Topographic features found on the earth's surface of glacial origin. Key: As the ice advanced from the north in Canada southward through Michigan, rocks and sediment were plucked up from the ground and frozen into the ice. As the climate warmed, the ice melted and retreated progressively to the north. As the ice melted it dropped (deposited) the rocks and sediments previous trapped in the ice.

Prehistoric Climate Change

Major episodes of climate change have occured prehistorically, but naturally. There is strong evidence that multiple glacial cycles occurred on Earth in the past 2 million years.

Carbon dioxide

Most concerning in terms of global warming (because it is the most abundant GHG). -Responsible for as much as 80% of the enhancement of the greenhouse effect All life, as we know it, is based on carbon. Carbon combines with other elements like oxygen and hydrogen to form carbohydrates and proteins (our food and energy sources) and nucleic acids (DNA).

Anthropogenic

Most scientists agree that the present trend of global warming is largely anthropogenic (that is, caused by or related to human activity).

Geological evidence of global climate change

On Earth, there have been four long, generally cool periods during which continent-sized glaciers advanced and retreated. There are four factors that interact to produce conditions favoring the formation and movement of ice-sheets.

Geologic time: Quaternary; Pleistocene; Holocene

Period: Quaternary is the CURRENT PERIOD OF GEOLOGICAL time, which began about 1.8 million years ago. Epochs within the period: The beginning of the holocene was about 11,500 years ago. (like the animals living today). THE WARMER EPOCH. The beginning of the Pleistocene was about 1,806,000 years ago. (like living animals now but differences). Long periods of arctic conditions 'ice age'.

Sea-level change

See above

Skepticism surrounding global climate change

Skeptics argue that recent warming may be a natural phenomena, rather than a change brought about by human activities.

Kyoto Protocol

The Conference of the Parties meeting in Kyoto, Japan, in 1997, was one of the most significant to date. This meeting resulted in the Kyoto Protocol, which required developed countries to reduce greenhouse gas emissions to specific levels between 2008-2012. -The U.S. was 8% below 1990 levels -Allowed emissions trading (sell excess emissions to other countries) -Allowed buying of extra permits to exceed their target level -Bush said no, Russia said yes (2009) Many nations in attendance agreed to support the Copenhagen Accord--a pledge to reduce emissions and contribute financially to developing nations in order to mitigate climate change. Never became a legally binding agreement.

Global warming

The Earth is currently in a warm period or 'interglacial'. Began roughly 8k to 10k years ago. ***global warming is not synonymous with global climate change.

Greenhouse effect

The greenhouse effect is a natural mechanism that regulates temperatures on Earth making life, as we know it, possible. These gases are naturally found on Earth! NO GREENHOUSE EFFECT=NO LIFE ON EARTH Shortwave radiation pass in to atmosphere, traps long wave radiation. Earth's atmosphere allow shortwave radiation from the Sun to be transmitted to the Earth. This shortwave radiation is absorbed at the earth's surface. The absorbed energy is radiated back to the atmosphere as longwave radiation (called counter-radiation), some of which is absorbed by the greenhouse gases and re-radiated back to the Earth. This trapped energy heats the atmosphere. Key: Human activity is leading to increasing amounts of greenhouse gases in the atmosphere, thereby enhancing the greenhouse effect.

Glacials and interglacials

The periods of ice retreat are called INTERGLACIALS. During interglacials the climate warms and glaciers melt. The water previously locked up in the glacial ice returns to the sea and cause sea level rise. This resulted in new shorelines and coastal landforms are created at higher sea levels. The advances of ice are called GLACIAL periods or ice ages. During ice ages the climate is colder and ice sheets are very large. Because more water is stored in glaciers, sea level drops during this cold period. Most scientists agree that we are currently in an interglacial, which began about 10,000 to 11,000 years ago.

Palynology

The study of pollen/spore records, which can be used to indicate prehistoric climates.

Dendrochronology

The study of tree rings to reconstruct regional climatic histories.

Photosynthesis and the respiration

Through photosynthesis plants convert water and carbon dioxide into carbohydrates and oxygen. Respiration is basically the opposite of photosynthesis: plants release carbon dioxide, water, and heat into the environment.

UNFCC

United Nations Framework Convention on Climate Change (UNFCCC) -In 1992 many countries around the world agreed in the United Nations Framework Convention on Climate Change (UNFCCC) that people worldwide need to focus on the impacts of humans on the changing global climate. -Ultimate objectives and framework that allows governments to decide upon specific actions to take take as climate science develops. -The Convention makes America and Europe more responsible for combating global warming than less developed countries. (financially and technologically help poorer countries) -Conference of parties makes "countries" liable if they can't hit their targets.

Soils may form in sand dunes when the climate is cool and moist. If a scientist were studying soil development in a sand dune, how could they best infer climate and estimate when that soil may have formed?

Use pollen analysis to determine how the dominant vegetation changed over time.

18O, 16O; what they can tell us

VARIED ATOMIC WEIGHT. 18O (written superscript 18 "O"xygen) is heavier than 16O, therefore 16O evaporates more easily from ocean waters. Likewise, the heavier isotope, 18O, condenses more easily. As water evaporates from the oceans and travels poleward, most 18O is lost as precipitation along the way. This leaves a larger amount of 16O to be deposited as snow at higher latitudes. During glacial periods, this snow (containing large amounts of 16O) does not melt and return to the oceans, but rather remains trapped in the ice sheet. By studying the ratio of 18O to 16O in ice cores from places like Greenland and Antarctica, you can determine the temperatures of a time period: When the water is cooler (during a glacial cycle), the lighter 16O-containing water is evaporated, transported, and deposited onto glaciers. The oceans remain proportionately enriched with the heavier 18O isotope; whereas, the glacial ice is proportionately enriched in the 16O isotope. When the climate warms, the ice sheets melt and 16O returns to the oceans in the meltwater. During these warmer periods, the cores will have a lower concentration of 16O and the ocean's will be proportionately enriched with the 16O isotope.

Ice cores and how used

Vast ice sheets. -Only found in GREENLAND AND ANTARCTICA -Contain important record of past climates. ICE CORES: To reveal history, scientists drill into ice sheets and remove cylinders of ice. Ice cores can show the occurrence of volcanic eruptions and massive meteor strikes as well as fluctuations in the level of carbon dioxide in the atmosphere. OXYGEN ISOTOPES IN THE ICE CAN INDICATE THE AVERAGE TEMPERATURE DURING THE TIME AT WHICH THE SNOW FELL. Example: For example, an ice core from Greenland showed that 12,000 years ago the average temperature dropped by roughly 27 degrees Fahrenheit in less than five years. This cold period endured for about 1,300 years, ending just as abruptly as it began.

Tree rings and how used

Yearly growth rings in trees that represent annual accumulation of cells around the circumference of the trunk, just under the bark. -The cells formed early in the growing season are usually thinner and lighter-colored than the cells formed late in the growing season, which are generally thick and dark-colored. -The dark and light cells form to be TREE RINGS -Wide= healthy, thin=drought -Sometimes a core can have missing rings representing several years, either because the tree did not add a growth ring during a drought or the ring did not grow around the entire circumference of the tree.

Which of the following is not a carbon sink?

an automobile