Climate Change

Climate and Geology are Linked Climate impacts geologic processes Geologic processes impact climate Study of sediments, fossils, sedimentary rocks clearly documents this Climate – natural variability through time

The Climate System Multidimensional System, many interacting parts Atmosphere, hydrosphere, geosphere, biosphere, and cryosphere Exchange of energy and moisture

The Climate System

How is climate change detected? Techniques for analyzing Earth’s climate history Seafloor sediments – numbers and types of organic remains are indicative of past sea- surface temperatures Oxygen isotope analysis – ratio of 18 O/ 16 O in shells of microorganisms reflect past temperatures

Figure 21.4 Microfossils in deep sea cores contain clues about paleoclimate

Climate has changed throughout geologic time. Mesozoic earth was warmer than today’s climate. The most recent large temperature increase in earth’s climate is called the Paleocene- Eocene Thermal Maximum (PETM) at about 55 million years ago.

Why did this happen? This is still widely debated. The most obvious feedback mechanism that could amplify the initial perturbation is that of clathrates. Under certain temperature and pressure conditions, methane – which is being produced continually by decomposing microbes in sea bottom sediments – is stable in a complex with water, which forms ice-like cages trapping the methane in solid form. As temperature rises, the pressure required to keep this clathrate configuration stable increases, so shallow clathrates dissociate, releasing methane gas to make its way into the atmosphere. Since biogenic clathrates have a δ 13 C signature of −60 ‰ (inorganic clathrates are the still rather large −40 ‰), relatively small masses can produce large δ 13 C excursions. Further, methane is a potent greenhouse gas as it is released into the atmosphere, so it causes warming, and as the ocean transports this warmth to the bottom sediments, it destabilizes more clathrates.

Gas hydrate—frozen methane beneath sea floor. These are present underlying the seafloor in vast regions of the ocean.

How is climate change detected? Techniques for analyzing Earth’s climate history Other sources of data for studying past climates include –Growth of tree rings –Pollen contained in sediment and coral reefs –Information found in historical documents

Figure 21.5A Temperature can be inferred from isotopic composition of oxygen in ice cores from Antarctica and Greenland. CO 2 can be directly measured in bubbles in the ice. CO 2 concentration in the atmosphere today is the highest in >100,000 years

How is Climate Change Detected? Seafloor Sediments Oxygen Isotopes Glacial Ice Cores Corals Pollen Historical Data

The infamous “hockey-stick” graph

The historic record of global temperature from actual temperature measurements.

Some atmospheric basics Composition of the atmosphere Air is a mixture of many discrete gases –Composition varies over time and distances After water vapor, dust, and other variable components are removed, nitrogen and oxygen make up 99% of the clean dry air CO 2, although present in minute amounts (0.0338%), greatly influences the heating of the atmosphere

Figure 21.9

Some atmospheric basics Composition of the atmosphere Two important variable components of air are water vapor and aerosols –Water vapor absorbs ultraviolet radiation given off by Earth similar to CO 2 –Aerosols (tiny solid and liquid particles) are important because they act as surfaces for condensation and also are good absorbers and reflectors

Some atmospheric basics Energy from the Sun Electromagnetic radiation is energy emitted in the form of rays, or waves –Key difference among electromagnetic waves is their wavelength Some basic laws governing radiation –All objects emit radiant energy –Hotter objects radiate more total energy than do colder objects

Some atmospheric basics Energy from the Sun Some basic laws governing radiation –The hotter the radiating body, the shorter the wavelengths of maximum radiation –Objects that are good absorbers of radiation are good emitters as well

Some atmospheric basics The fate of incoming solar energy Approximately 50% of the solar energy that strikes the atmosphere reaches Earth’s surface –30% is reflected back to space –20% is absorbed by clouds and the atmosphere’s gases

Incoming solar radiation

Some atmospheric basics The greenhouse effect Radiant energy that is absorbed heats Earth and eventually is reradiated skyward –Radiation is in the form of longwave infrared radiation –Atmospheric gases, primarily H 2 O and CO 2, are more efficient absorbers of longwave radiation –This selective absorption, called the greenhouse effect, results in warming of the atmosphere

The greenhouse effect

Natural causes of climate change Several explanations have been formulated to explain climate change including Plate tectonics Variations in Earth orbit – eccentricity, obliquity, and precession Volcanic activity Changes in the Sun’s output associated with sunspots

Human impact on global climate Humans have been modifying the environment for thousands of years Ground cover has been altered by –Fire –Overgrazing Results in modification of climatological factors such as reflectivity, evaporation rates, and surface winds

Natural Causes for Climate Change Volcanoes Solar Variability Sunspots

Volcanoes

Solar Variability

Sunspots

Human impact on global climate Humans have been modifying the environment for thousands of years Addition of carbon dioxide and other trace gases to the atmosphere are likely contributing to global climate change –Trace gases include methane, nitrous oxide, and chlorofluorocarbons

Environmental effects of burning fossil fuels Urban air pollution Air pollutants are airborne particles and gases that occur in concentrations that endanger the heath of organisms and disrupt the orderly functioning of the environment

Environmental effects of burning fossil fuels Two types of pollutants Primary pollutants - emitted directly from identifiable sources Secondary pollutants - formed when chemical reactions take place among primary pollutants

Environmental effects of burning fossil fuels Carbon dioxide and global warming Burning fossil fuels produces carbon dioxide which is one of the gases responsible for warming the lower atmosphere

Environmental effects of burning fossil fuels Carbon dioxide and global warming Greenhouse effect – the atmosphere is transparent to incoming short-wavelength solar radiation. However, the outgoing long-wave radiation emitted by Earth is absorbed in the lower atmosphere, keeping the air near the ground warmer

Heating of the atmosphere

The Greenhouse Effect vs. Global Climate Change Greenhouse effect = natural Global Climate change = caused by humans

Human-created Causes for Climate Change Industrialization Fire Agriculture Altering Ground Cover

Gases and Climate Change Carbon Dioxide Methane Nitrous Oxides CFC’s

Gases and Climate Change

Figure 21.25

Figure 21.24

e

Consequences of Climate Change Sea Level Rise The Changing Arctic Melting Permafrost Increasing Ocean Acidity

Sea Level Rise

Acidity of the Oceans

Wildcards – Surprises? What if the Pacific Ocean warms in such a way that El Niño events become much more extreme? This could reduce the frequency, but perhaps not the strength, of hurricanes along the East Coast, while on the West Coast, more severe winter storms, extreme precipitation events, and damaging winds could become common. What if large quantities of methane, a potent greenhouse gas currently frozen in icy Arctic tundra and sediments, began to be released to the atmosphere by warming, potentially creating an amplifying “feedback loop” that would cause even more warming? We simply do not know how far the climate system or other systems it affects can be pushed before they respond in unexpected ways.

Which one is it? You've got to ask yourself one question: 'Do I feel lucky?' Well, do ya punk?”

Lunar eclipse over Mount St. Helens. Photo by Larry Workman, Quinault Reservation. The End