Global Warming Is Human-Induced Climate Change Going To Destroy The World? Ok… that’s a bit dramatic. But, good questions are: 1)What is the evidence for recent climate change? 2)Do we need to worry about it – what are the consequences? 3)What can we do about it? Data and diagrams from Richard Deem, Michael Mann, Lee Kump and the Intergovermental Panel on Climate Change

History of Earth’s Atmosphere/Climate Earth formed ~4.6 billion years ago Originally very hot, probably molten, early impact forming the moon Any early atmosphere removed by initiation of sun’s fusion reactions and solar wind Granitic crust and liquid water was present by ~4.3 billion years ago (zircon dating) However, much of Earth’s early history was erased during late heavy bombardment (~3.9 billion years ago)

First life appeared by ~3.8 Ga Photosynthesis began Ga, clear evidence for significant oxygen in the atmosphere by 2.0 Ga Photosynthesis introduced oxygen and removed carbon dioxide and methane (greenhouse gases) Earth began current cycles of glacial and interglacial periods ~3 Ma History of Earth’s Atmosphere/Climate

Sun Earth’s Temperature Solar Energy

Sun Earth’s Temperature Solar Energy Solar Energy Radiative Cooling Radiative Cooling

Sun Earth’s Temperature Solar Energy Solar Energy Radiative Cooling Radiative Cooling

Sun Earth’s Temperature Solar Energy Solar Energy Radiative Cooling Radiative Cooling

Greenhouse Effect Sun

Earth’s Atmospheric Gases Nitrogen (N 2 ) Oxygen (O 2 ) Water (H 2 O) Carbon Dioxide (CO 2 ) 99% Methane (CH 4 ) 1% Non- Greenhouse Gases Greenhouse Gases

Sun Runaway Greenhouse Effect 97% CO 2 3% N 2 Water & sulfuric acid clouds Temperature: 860°F (hotter than Mercury which is nearest to the sun) Venus

Time (YBP) CO 2 (ppm) Vostok Ice CoreDome Concordia Carbon Dioxide Levels 0 Muana Loa Readings CO 2 Levels Since CO 2 (ppm) 0

Worldwide Carbon Emissions Carbon (10 9 metric tons) Year Liquid fuel Total Gas fuel Solid fuel

Annual Carbon Emissions Annual carbon emissions Atmospheric CO 2 Atmospheric CO 2 average Year Carbon (10 9 metric tons)

Future Atmospheric CO 2 Levels? Increasing CO 2 emissions, especially in China and developing countries Likely to double within 150 years: Increased coal usage Increased natural gas usage Decreased petroleum usage (increased cost and decreasing supply)

Kyoto Protocol Adopted in 1997 Cut CO 2 emissions by 5% from 1990 levels for Really is symbolic only, since such levels of reduction will likely not significantly impact global warming

Year  Mean Temperature (°C) Recorded Worldwide Temperatures

Temperature Changes Compared to

Past Temperatures Measurement Proxy – a method that approximates a particular measurement (e.g., temperature) Ice cores Pollen records Plant macrofossils Sr/Ca isotope data Oxygen isotopes from speleothem calcite (stalactites and stalagmites)

Temperature History of the Earth Little ice age ( ) – 1°C cooler Medieval warm period ( ) – 1°C warmer than today Cool/warm cycles occur over ~1,500 years Mostly due to changes in thermohaline circulation system of the ocean

Temperature History of the Earth For the past 3 Ma, the Earth has been experiencing ~100 ka cycles of glaciation followed by ~10 ka interglacial periods These climate periods are largely the result of cycles in the earth’s orbit – precession, obliquity, and eccentricity

Orbital Parameters & Earth’s Climate Age (ka) Eccentricity (100 ka) Temperature Obliquity (41 ka) Precession (22 ka)

Temperature History of the Earth For the past 3 Ma the earth has been experiencing ~100 ka cycles of glaciation followed by ~10 ka interglacial periods Last ice age began ending 15,000 years ago, but was interrupted by the “Younger Dryas” event 12,900 years ago

“Hockey Stick” Controversey Year Temperature Change (°C) Direct temperature measurements Mann et al. 1999

Time (YBP) CO 2 (ppm) Antarctica SST (°C) Tropical Pacific CO 2 Concentration Vs. Temperature

Consequences of Global Warming: Primarily Impacts the Northern Hemisphere and Land Masses Year Temperature Change (°C) Year Northern vs. Southern LatitudeLand vs. Ocean Northern Hemisphere Southern Hemisphere Land Ocean

2007 Temperature Changes Compared to

Consqeuences of Global Warming: Ice Sheets Melting? GRACE (gravity measured by satellite) found melting in Antarctica equivalent to sea level rise of 0.4 mm/year (2 in/century) Zwally, 2005 (satellite radar altimetry) confirmed Antarctica melting Greenland ice melting on exterior, accumulating inland (higher precipitation) And - Glaciers are retreating all over the world.

Consqeuences of Global Warming: Rise in Sea Levels? Present rate is 1.8 ± 0.3 mm/yr (7.4 in/century) Accelerating at a rate of ± mm/yr 2 If acceleration continues, could result in 12 in/century sea level rise Scenarios claiming 1 meter or more rise are probably unrealistic

Consqeuences of Global Warming: How Much Temperature Increase? Some models propose up to 9°C increase this century Two studies put the minimum at 1.5°C and maximum at 4.5°C or 6.2°C Another study puts the minimum at 2.5°C Summary – most studies suggest ~4°C over the next century

Potential Worldwide Precipitation Changes

Mitigation of Global Warming? Conservation Reduce energy needs Recycling Alternate energy sources Nuclear Wind Geothermal Hydroelectric Solar Fusion?

Conclusions Global warming is happening Most warming is probably the result of human activities – but this is still under debate There will be positive and negative (mostly) repercussions from global warming The costs to mitigate global warming will be high – are they worthwhile?

Extra slides 2010 beyond this point

Winter Temperatures Year Summer Temperatures Year Annual Temperatures Year Temperature (°C) Historic Los Angeles Temperatures

Main Ocean Currents Adapted from IPCC SYR Figure 4-2

Younger Dryas Younger Dryas Event – Greenland Data Age (ka) Temperature (°C) Snow Accumulation (m/yr) Little Ice Age Ice Age Medieval Warm

Mann et al Esper et al Temperature Change (°C) 2000 Year Is the Hockey Stick Correct?

Year Temperature Change (°C) Mann et al Esper et al Moberg et al Mann et al. 2008

U.S. National Academy of Sciences: June Year Temperature Change (°C) “high level of confidence”“2:1 chance of being right”

Changing Sea Levels Relative Sea Level (cm) Adapted from IPCC SYR Figure 2-5 Amsterdam, Netherlands Brest, France Swinoujscie, Poland Global Temperature Change

Time (Ka) Sea Level (m) Sea Levels for 450,000 Years SST (°C) Tropical Pacific