Weather vs Climate Weather the day to day state of the atmosphere with respect to temperature precipitation wind and pressure Generally controlled by regional changes in atmosphere and conditions Can locally be controlled by geographic features such as mountains and lakes Variations occur in short periods of time Climate the average prevailing weather conditions of a region throughout the year averaged over a series of years Variations occur on much longer cycles decades to tens of thousands of years Controlled by long term changes in temperature humidity atmospheric pressure wind and precipitation Earth System The earth functions as a complex interactive system that transfers energy and matter to the five earth spheres Lithosphere all the solid rock material sediment and molten rock from the surface down to the core Atmosphere envelope of gases held to Earth by gravity extending 100s of km upward Hydrosphere all liquid water at the surface rivers lakes oceans etc as well as groundwater Cryosphere all solid ice in the form of glaciers snowcaps sea ice permafrost etc Biosphere all living organism on planet Earth Anthropogenic the parts of the environment that are influenced or modified by human activity What happens in one sphere will eventually inevitably affect aspects of the other spheres Life on Earth is due to interactions between the Lithosphere Atmosphere and Hydrosphere The Earth System is comprised of these physical components interacting with the biosphere The link between the physical and biological are transformed due to global changes There are many ways to describe changes Rate gradual vs catastrophic Type unidirectional vs cyclic Frequency once vs repeated Agency gelogenic vs anthropogenic Unidirectional Change Evolution of the solid Earth Melting and differentiation Iron sank to the center and produced a layered Earth Iron alloy core with a rocky mantle Formation of the Moon Mars sized proto planet collides with earth The earth s mantle is blasted into space and the debris collects to form the moon Evolution of the atmosphere and oceans Volcanic gases created an early atmosphere Liquid water condensed to form the oceans Physical cycles The Super Continent cycle Plate tectonics drives continental movement Ocean basins open and close continental landmasses collide and rift apart Supercontinents like Pangaea have formed several times The Sea Level SL cycle SL is historically unstable and has risen and fallen many times over the Earth s history Transgression SL rise The shoreline moves towards the land Regression SL fall The shoreline moves towards the sea Sedimentary rocks preserve evidence of sea level change Transgression regression cycles are bounded by large scale unconformities The most recent sea level rise is from deglaciation The Rock cycle Contrary to popular belief rocks are not permanent Biogeochemical cycles The hydrologic cycle Water moves between biological and physical reservoirs Biological o All living organisms Physical o Oceans o Atmosphere o Surface water o Ground water o Glaciers o Soil moisture The Carbon cycle A biogeochemical cycle that regulates climate Volcanic CO2 adds carbon to the atmosphere Atmospheric CO2 is removed in several ways o It dissolves in water as carbonic acid and bicarbonate o Photosynthesis removes CO2 o Weathering Carbon may be stored for long periods of time Organic shales Limestones Fossil fuels coal and oil Methane hydrates Carbon is returned to the atmosphere Biotic respiration creates CO2 from organic matter Rapid oxidation burning of organic matter creates CO2 Metamorphism of carbonate rocks liberates CO2 Degassing removes dissolved CO2 from water Global Climate change The Earth s climate has changed many times Long term climate change is changes over millions to tens of millions of years in scale Short term climate change is changes over tens to hundreds of thousands of years in scale Climate studies reveal past climates and predict future climates Determine the effects on earth They distinguish the types of climate change Establish the rates at which these changes occurred Methods of study Paleoclimates investigations of past climatic variation Computer simulations modeling past and future changes Paleoclimates past climates that are interpreted from climate sensitive and datable Earth materials Stratigraphic records sequences of rock strata Depositional environments are often climate sensitive o Glacial tills cold and continental o Coral reefs tropical marine Paleo climatic evidence o Paleontological faunal assemblages reflect climate o Assemblage changes record climatic shifts Oxygen isotopes two isotopes 16O and 18O 16O evaporates faster than 18O during an ice age o 16O in seawater evaporates faster o Seas become 16O depleted 18O enriched o 18O 16O increases in remaining seawater o Shells grown in this sea will reflect the altered 18O 16O ratio o Ice cores reveal the ratio of 16O and 18O over time Oxygen isotope ratios are preserved in carbonate shells of organisms The oxygen in CaCO3 shells mirrors oceanic 18O 16O Sea floor sediments preserve ocean chemistry changes Growth rings tree rings can easily be dated Ring thickness reflects climatic changes Wetter warmer thicker drier colder thinner Overlapping sequences from many trees yield a time scale Ring widths form time sequences Long Term Climate Change Earth s climate history has been largely deciphered Greenhouse warmer climates Icehouse colder climates Last 100 million years Warm climate at the end of the Mesozoic Climate cooling since the Oligocene CO2 and CH4 are greenhouse gases Unaffected by incoming UV radiation from the sun Absorb infrared energy reflected from Earth s surface Greenhouse gases exert a strong control on climate More greenhouse gases warmer less cooler Processes that add or remove greenhouse gases alter climate Complex interactions across the Earth System cause long term climate change Plate tectonics modifies the position of continents o Positioned at high or low latitudes o Oceanic currents closing the Isthmus of Panama Volcanic gases trap heat promote global warming o Cretaceous rifting and expanding mid ocean ridges o Increased volcanic activity added gases to atmosphere o Lead to overall climate warming Mountain building leads to increased weathering o Chemical weathering absorbs CO2 o Leads to overall climatic cooling o Uplift of the Himalayas may have led to Cenozoic cooling Biological influences Formation of organic deposits