Past, Present, and Probable Future of Atmospheric Carbon Dioxide Dr. Robert MacKay

Outline Introduction/ Motivation Natural and Anthropogenic sources of change Recent temperature record Past CO2 Present CO2 A simple mathematical/conceptual model Future projections Future emissions Discussion

Natural and Anthropogenic Climate Forcing

No Atmosphere http://cs.clark.edu/~mac/meteor/Animations/greenhouse.jnlp

Red circles are infrared photons and yellow are sunlight. Today’s Atmosphere

Greenhouse Gases Water Vapor Carbon Dioxide Ozone Methane Nitrous Oxide Chlorofluorocarbons

Cooling to offset warming

http://data.giss.nasa.gov/gistemp/graphs/ Most believe that the warming observed before 1950 was a result of increased solar luminosity and the warming after 1950 is from increase levels of greenhouse gases caused by human activity.

Increased ocean temperatures and decreased pH levels (increased acidity) can be detrimental to corral growth.

pH change between 1751 and 1990s. Estimate are that globally ocean surface water pH levels have decreased by as much as .12 units for atmospheric CO2 change from 280 to 360 ppm. http://www.terrain.org/articles/21/burns.htm

Carbon Dioxide in Prehistoric times CO2 levels in the early Cenozoic Era (~65 Myr ago) were 4 to 5 times higher than they are today. Some have speculated that the uplift of the Tibetan plateau resulted in increased weathering and a draw down of atmospheric CO2 levels bringing us into our present ice age state.

Climate and the carbon cycle have many time scales of interest.

The last Glacial Maximum occurred around 18,000 years ago

Vostok Ice Core data

Preindustrial levels of CO2 were 280 ppm and remained so until ~1800 Preindustrial levels of CO2 were 280 ppm and remained so until ~1800. Present values are around 383 ppm a 37% increase over preindustrial times. There has been a 70 ppm increase since 1958 .

The Bern Carbon Cycle model is used by the IPCC (Intergovernmental Panel on Climate Change) to estimate future CO2 levels for different assumed emission scenarios.

http://cs.clark.edu/~mac/physlets/GlobalPollution/CO2assign.htm

http://cs.clark.edu/~mac/physlets/GlobalPollution/carbon_dioxide.htm

Because of long time delays for the carbon cycle, drastically different scenarios yield very similar results for a 20 year time horizon, but drastically different result for a 50 to 100 year time horizon. http://cs.clark.edu/~mac/physlets/GlobalPollution/carbon_dioxide.htm

Recent results suggest that world wide emissions of carbon from fossil fuel use is growing at a rate corresponding to the largest projected emission scenario suggested by the 2001 IPCC report. http://www.newscientist.com/article/dn10507-carbon-emissions-rising-faster-than-ever.html

For the past 30 to 35 years emissions have been closely linked to population.

US Carbon emissions through 2004 http://cdiac.ornl.gov/trends/emis/em_cont.htm

China’s carbon emission through 2004 China’s total carbon emissions exceeded that of the US in late 2006. http://cdiac.ornl.gov/trends/emis/em_cont.htm

Russia’s carbon emission through 2004 http://cdiac.ornl.gov/trends/emis/em_cont.htm

India’s carbon emission through 2004 http://cdiac.ornl.gov/trends/emis/em_cont.htm

~40 yrs Oil ~80 yrs Natural gas ~200 years coal Fossil Fuel Reserves ~40 yrs Oil ~80 yrs Natural gas ~200 years coal

World Population http://www.physicstoday.org/vol-57/iss-7/p47.html

Fossil Fuel Reserves Oil http://www.physicstoday.org/vol-57/iss-7/p47.html

http://www.eia.doe.gov/pub/oil_gas/petroleum/feature_articles/2004/worldoilsupply/oilsupply04.html

Fossil Fuel Reserves Natural Gas http://www.physicstoday.org/vol-57/iss-7/p47.html

Fossil Fuel Reserves coal http://www.physicstoday.org/vol-57/iss-7/p47.html

http://chooseclimate.org/jcm/index.html

http://chooseclimate.org/jcm/index.html

A -developing countries B-Industrialize countries

http://cs.clark.edu/~mac/CarbonCycle.ppt