 Changing faster today than at any other time  Cause – human activity (anthropogenic)

 Deforestation

 Greenhouse Gases & Greenhouse Effect

 Destruction of Ozone Layer

 Loss of Biodiversity

 Global Warming

 Global Environmental Issues ◦ Need to be informed to make intelligent decisions  Global Change in the Past ◦ Need to understand how planet was changing before humans ◦ Global change can occur on short (1000’s years) or long (millions of years) time scales  The Earth System ◦ Different components of Earth interact in response to forcings (internal and external influences)

 Global warming – an increase in Earth’s surface temperature caused by industrial and agricultural activities ◦ Release gases that increase greenhouse effect ◦ Intergovernmental Panel on Climate Change (IPPC) – 2007  “Warming of the climate system is unequivocal, as it is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.”

 1958 – 315 ppm  2008 – 386 ppm ◦ 1 cc of air = 2.7 x molecules ◦ 1ppm concentration = 2.7 x molecules  Most increase due to combustion of fossil fuels (coal, oil, natural gas) ◦ Tropical deforestation also contributes  Trend of increasing atmospheric CO 2 is real

 Use air bubbles trapped in polar ice ◦ Matches direct measurement well – reliable technique for determining long-term CO 2 concentrations  Pioneer Effect ◦ (before Industrial Age) ◦ Increased CO 2 due to deforestation of American West

 Methane (CH 4 ) & Nitrous Oxide (N 2 O) – from agriculture  CFCs ( Chlorofluorocarbons ) – destroy stratospheric ozone too  HUMANS HAVE ALTERED EARTH’S ATMOSPHERE

 Global Mean Surface Temperature ◦ increased 0.8 ℃ since 1900

 Understand the past in order to predict the future ◦ Little Ice Age ( )  Understand the whole Earth system in order to correctly interpret the changes that are occurring ◦ Sulfate aerosols  Understand the time scales on which global change occurs ◦ Sulfate aerosols removed in weeks, CO 2 stays for centuries

 Warming at the poles could raise sea level ◦ Greenland ice cap – sea level increase 6 meters (20 feet)

 Rise in sea level ◦ 10 cm in last 100 years  Thermal expansion  Melting ice  Impact agriculture ◦ Decreased soil moisture ◦ Spread of tropical pests  Stronger hurricanes  Earth has been significantly warmer in the past – past is the key to the present

 1985 – discovery of ozone hole above Antarctic  – ozone dropped by half (October)  Inverse relationship between ozone and ClO (chlorine monoxide)

 Humans have been altering the land surface for 10,000 years  Tends to reduce complexity of landscape  Reduces biodiversity ◦ Change in land can cause species unable to move ore adapt to become extinct ◦ Genetic information lost  Currently, greatest loss of species is in the tropical rainforests ◦ Rainforests most biodiverse habitats ◦ Rainforests disappearing the most

 Ozone Depletion? ◦ Omit CFCs - recovery in years  Increased CO 2 ? ◦ Stop CO 2 emissions – recovers in 1-2 million years  Loss of Biodiversity? ◦ Mass extinction – never recovers completely

 Glacial-Interglacial cycles  Mass Extinctions  Solar Luminosity Change

 The Geologic Time Scale – ◦ Divisions based on appearance/disappearance of organisms ◦ Earth is 4600 million years old (4.6 billion) ◦ Most of Earth time before animals with preservable hard parts appeared  Cambrian 544 mybp  Precambrian mybp

 Antarctica  Vostok and Dome C  800,000 years  CO 2 concentrations  Temperature ◦ Based on deuterium  Glacial/Interglacial Periods ◦ Last Ice Age ended 11,000 years ago

 Surface Temp , CO 2 & CH 4  ◦ associated with interglacial periods  21,000-11,000 ybp & 140, ,000 ybp  Why would CO 2, CH 4 & temperature co-vary? ◦ Greenhouse Effect ◦ Change in deep ocean circulation due to change in climate (brings more CO 2 )  Atmospheric CO 2 affects climate and climate affects atmospheric CO 2

 65 mybp ◦ Dinosaurs extinct ◦ 60-80% of marine species extinct ◦ Numerous terrestrial organisms  WHY?

 Clay layer at K-T boundary  Walter & Luis Alvarez ◦ Use iridium to determine rate of clay deposition ◦ Iridium 100 x higher than expected ◦ Iridium uncommon on Earth – reasoned that it came from the impact of a large extraterrestrial object

 The Earth system has recovered from large shocks in the past ◦ Recovery is slow ◦ Recovery generates a modified Earth

 As the sun ages and uses up its hydrogen fuel – its luminosity (brightness) increases ◦ 4,600 mybp Sun was 30% dimmer (less luminous) ◦ Luminosity has increased slowly, then rapidly ◦ Currently brightness increases 1% /100 x 10 6 years ◦ In 5,000 my – 2-3 times brighter than now  Early Earth colder (if other factors constant) ◦ Ocean should have been frozen – BUT NO  3.8 bya – sedimentary rocks  3.5 bya – organisms ◦ Faint Young Sun Paradox – solution?  Higher levels of Greenhouse gases in early atmosphere

 James Lovelock & Lynn Margulis  Earths is a self-regulating system in which the biota play an integral role ◦ The biota manipulate the environment for their own benefit, or by optimizing the conditions for life, for the benefit of all living organisms  Life itself is responsible for maintaining the stability of Earth’s climate  Climate stability implies self-regulation ◦ Biotic feedbacks (Gaia Hypothesis) ◦ Abiotic feedbacks (carbonate-silicate geochemical cycle)