Global Warming: Estimating Future Carbon Emissions CS 1210 Spring 2004

“A world thrown into turmoil by drought, floods, typhoons. Whole countries rendered uninhabitable. The capital of the Netherlands submerged. The borders of the US and Australia patrolled by armies firing into waves of starving boat people desperate to find a new home. Fishing boats armed with cannon to drive off competitors. Demands for access to water and farmland backed up with nuclear weapons. Sound like the ravings of doom-saying environmental extremists? It's actually the latest Pentagon report on how to ready America for the coming climate Armageddon.” Coming to a planet near you…

Review: Heat-Trapping Gasses Water Vapor – most powerful greenhouse gas Carbon Dioxide Methane Chlorofluorocarbons (also involved in ozone depletion)

Review: Climate modeling All climate models based on heat balance Zero-dimensional model: Earth as a single point One-dimensional model: Earth as a set of latitude zones General circulation models: 4-D grid

Review: Zero-D model Energy incoming from sun is constant Energy radiated out depends on T Adjust T so that Energy out = Energy in Result: T = zero degrees F! Difference between model and reality is natural greenhouse effect

General Circulation Models Uses 4-D grid Limited by available supercomputer power Starley pun: need a “Congressional Resolution”

Starley Thompson’s smoking gun

Starley’s Grand Challenge Existing climate models: Assumed CO2 levels  Climate change Models we need: Assumed human emissions  CO2 levels and climate change

Moving from Specified to Predicted CO 2 Currently, projections of climate change do this: Currently, projections of climate change do this: More credible projections will need to do this: More credible projections will need to do this: Specified Atmospheric CO 2 Concentration ClimateModel Future Climate Specified CO 2 Emissions Combined Climate and Carbon Cycle Model Future Climate CO 2 Concentration

Human & Natural Carbon Flows Natural carbon flows are much larger than anthropogenic flows Possible indirect effects of human activity on natural carbon flows could be very important

Summary: model uncertainties Cloud processes (can heat or cool) Effects on natural carbon flows How much human-emitted carbon? Effects of global warming (possibly include THC collapse)

Predicting Human Carbon Emissions Use the IPAT formula: I = P A T Future human P opulation: unknown Future human A ffluence: unknown Future human T echnology: unknown

The IPCC Scenarios The Intergovernmental Panel on Climate Change (IPCC) attempts to project possible future CO2 emissions IPCC generated 40 scenarios, grouped into four storylines Each storyline is a possible general trend of the history of the 21 st century

Storylines of 21 st Century History Actual direction will depend on conscious human choices US has disproportionate influence on future direction of the world

A1 storyline: successful globalization High economic growth Investment in education and technology Incomes of rich and poor nations converge

Scenarios within A1 storyline B scenario: Baseline (average) case FI scenario: Fossil-fuel intensive T scenario: new technologies used (solar, wind, nuclear)

A2 storyline: differentiated world Differences between rich and poor nations persist High population growth in poor nations Many resources devoted to feeding 15 billion people Few resources devoted to pollution control

B1 Storyline: Global Sustainable Development Coherent international approach to sustainable development High social and environmental consciousness Economic gains invested in social institutions environment Massive income redistribution towards income equality

B1 population and economics Population reaches 9 billion by 2050 Declines to 7 billion by 2100 Lower average income than A1, but higher environmental quality and less poverty

B2 storyline: sustainable focus Strong emphasis on environmental problems Decentralized and community-based Less global planning and tech focus than B1 Strong education and welfare systems lead to small, well-educated population

B2 Population and Economics Population reaches 10 billion by 2100 (compare to B1, with more coordination) Slightly less average income than B1 More inequality, but more local control

Emission Scenario Results Baseline assumptions: no explicit climate polity Note high emissions for A1FI, lower for A1T A1T and B1 have lowest emissions No scenarios reduce CO 2 to pre-2000 level

Global warming: possible futures Uncertainty in models plus uncertainty in emission scenarios