global climate change

1. What is climate? What is the main source of energy at the earth's surface? What are positive and negative feedbacks in the climate system? What is meant by a "tippy balance"?

Climate: average weather conditions of an area. The sun is the main source of energy on earth. Positive feedback: a change in the system promotes continued change in the same direction. These changes are destabilizing. Negative Feedback: a change in the system leads to events that reverse the direction of change. These changes are stabilizing. "Tippy balance" means pushing the climate system envelope by smaller, additive changes to a point where the system moves rapidly from its previous state to another, possibly very different and unpredictable state.

4. What is the greenhouse effect? What are the five most important greenhouse gases? Which four of these gases have become more abundant in the atmosphere as a result of human activities? Why does deforestation promote global warming? What are methane hydrates and why do they represent a climate "wild card"? What is global dimming and how and to what degree does it affect estimates of global warming due to increased atmospheric concentrations of greenhouse gases?

Greenhouse effect is certain gases tend to absorb energy in which warms the atmosphere and makes earth habitable. Five most important greenhouse gases are carbon dioxide, methane, nitrous oxide, chloroflurocarbons. Deforestation increases atmospheric CO2 concentrations by reducing the size of an important carbon dioxide sink. methane hydrates crystalline solid mixtures of water ice and methane. They cause warmer ocean temperatures and have a huge effect on climate by dumping huge amount of methane into the atmosphere. They are called wild cards bc warming of oceans will cause increasing amounts of methane. Global dimming is a cooling effect that has masked a significant portion (50%) of the warming effect of greenhouse gases increases. 10 to 30 percent "dim the sun" around the globe and mask half the effect of CO2.

2. Why is it important to understand past climate fluctuations? What types of evidence can be used to track past global climate change? How are ice cores used to determine past atmospheric composition? Paleotemperatures?

Past climate change is essential if we are to delineate future climate variations. Evidence includes: temperature records, written accounts of general conditions, paleoclimate proxy records (organisms and rocks or other deposits that record changes in climate or in phenomena that can be related to climate over time: corals, tree rings, pollen in lake sediments, ice core data, plankton shells in ocean sediments, sedimentary rock layers. Paleoatmospheric composition: trapped air bubbles in the ice preserve air samples from the time of snow/ice formation and measuring gas abundances in these bubbles gives direct information about past atmospheric compositions, including greenhouse gas concentrations. Paleotemperature data shows oxygen isotope composition of ice layers variance over time and these variations can be directly related to global avg. temperatures.

6. What possible changes may result from global warming caused by a human-increased greenhouse effect? What can be done to limit the predicted increases in global temperatures due to the greenhouse effect?

Reduce fossil fuel combustion and reduce atmospheric CO2 levels.

5. Why is it so difficult to predict the effects of increased atmospheric CO2 on global climate?

Results suggest uneven patterns of change in precipitation and other factors. Even though no single model may be correct, we can learn by comparing their results in light of how each model works. We may never be able to prove climate predictions, but may instead be forced to rely upon a preponderance of evidence to suggest that we MAY be correct about certain aspects of the climate.

climate change

causes: external to earth: solar output and earth orbit fluctuations internal to earth: plate tectonics and other earth cycles

greenhouse effect

certain gases in the atmosphere tend to absorb this energy (energy coming from sun is electromagnetic radiation and thus surface materials are heated by solar radiation) which warms the atmosphere and makes earth habitable.

external

change amount or distribution of solar energy reaching earth. solar output variations may have been larger in past . orbital fluctuations are separate cycles on different time scales but experience collective reinforcement that are enough to cause significant global climate change.

"tippy balance"

climate change occur very quickly once a threshold is reached.

3. What are the possible external and internal causes for global climate change? What factors affect CO2 abundance in the atmosphere? Why was Earth's climate so warm about 100 Ma? Why did it cool down between 50 and 2 Ma? By what percentage has human activity increased atmospheric CO2 abundance over the last 150 years?

external causes: solar output and orbital fluctuations. internal: plate tectonic changes, changes in rate of volcanic activity, and changes in the balances of biogeochemical cycles. CO2 abundance is impacted by [volcanism, respiration, combustion of fossil fuels--- add CO2] and [chemical weathering of silicate rocks, photosynthesis--- remove CO2]. 100 Ma-- Middle Cretaceous Period- initially due to opening of atlantic ocean. increased volcanism. 50 and 2 Ma: Cenozoic Cooling. cooled down bc of plate tectonics. and changes in oceanic circulation. 35%

predicting

general circulation models: mathematical compute models that try and predict global climate. mimic most important interactions of earths subsystems.

knowledge of past climates is essential if we are to delineate future climate variations

geology provides most of this info

ice cores provide two types of data

paleoatmospheric composition: trapped air bubbles in the ice preserve air samples from time of snow/ice formation. paleotemperature data: oxygen isotope composition of ice layers varies over time. variations can be directly related to past average global temps

global dimming

particulate pollution associated with fossil fuel combustion has resulted in a cooling effect that has masked a significant portion of the warming effect of greenhouse gas increases. particles reflect sunlight and overall effect is to "dim the sun" in areas around the globe and mask about half of the effect of increased CO2 levels in atmosphere

internal

plate tectonic changes change ocean and atmospheric circulation patterns and lass masses needed at high latitudes for glaciation. changes in rate of volcanic activity add CO2 to atmosphere. changes in balance of biogeochem cycles impact climate

climate: average weather conditions of an area controlling factors: atmosphere, hydrosphere, cryosphere, lithosphere, biosphere.

positive feedback: promotes continued change in same direction- destabilizing negative feedback: leads to events. reverse direction of change. stabilizing

four important greenhouse gases : carbon dioxide, methane, nitrous oxide, chlorofluorocarbons. gases aren't created equal.

processes that add CO2 : volcanism, reparation, combustion of fossil fuels. processes that remove CO2 chemical weathering of silicate rocks and photosynthesis. THUS AFFECT ATMOSPHERIC CO2 ABUNDANCE.

mitigation of human-induced global warming

reduce fossil fuel combustion. reduce atmospheric CO2 levels..

global warming effects

shifts in climatic zones, declines in food production, less fresh water, increasing incidence of violent weather, disease, floods and droughts, ice sheet melting, ocean acidification and dead zone dev., economic and political instability

tracking earths climate over time

temperature records, written accounts of general conditions, etc: landscape paintings paleoclimate proxy records: organism and rocks or other deposits that record changes in climate or in phenomena that can be related to climate over time. ex: corals, tree rings, pollen in lake sediments, ice core data, plankton shells in ocean sediments, sedimentary rock layers.

isotopic mass fractionation

water molecules made with O 16 are lighter and vibrate faster thus they evaporate preferentially. and thus water vapor is enriched and any precipitation travels to poles. and is enriched more so. effect is greatest when its coldest