Intergovernmental Panel on Climate Change (IPCC) The IPCC is the leading international body for the assessment of climate change. It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts. The IPCC is a scientific body. It reviews and assesses the most recent scientific, technical and socio-economic information produced worldwide relevant to the understanding of climate change. It does not conduct any research nor does it monitor climate related data or parameters. The IPCC is an intergovernmental body. It is open to all member countries of the United Nations (UN) and WMO. Currently 194 countries are members of the IPCC.

Climate Scenarios and Emissions Scenarios Scenario Definition Image of future Neither forecast nor prediction Each scenario is one possible future– Set of scenarios possible future developments of complex systems Useful tool for not fully understood complex systems, whose prediction is impossible, e.g. population growth, use of fossil fuels and GreenHouse Gases (GHG) emissions Emission scenario ≠ climate scenario Future levels of global GHG emissions are the products of a very complex, ill- understood dynamic system, driven by forces such as population growth, socio- economic development, and technological progress; thus to predict emissions accurately is virtually impossible. However, near-term policies may have profound long-term climate impacts. Consequently, policy-makers need a summary of what is understood about possible future GHG emissions, and given the uncertainties in both emissions models and our understanding of key driving forces, scenarios are an appropriate tool for summarizing both current understanding and current uncertainties.

Scenarios can be viewed as a linking tool that integrates qualitative narratives or stories about the future and quantitative formulations based on formal modeling. As such they enhance our understanding of how systems work, behave and evolve. How are scenarios formulated? Scenarios are formulated with the help of numeric or analytic formal models. Scenario development 1990 IPCC SA90 emission scenarios; 1992 IPCC IS92 emission scenarios 1999 IPCC Special Report on Emission Scenarios (SRES) 2007 IPCC AR4 uses SRES and IS92 scenarios 2009 Representative Concentration Pathways (RCPs) 2014 IPCC AR5 uses RCPs

Emission

SRES: Special Report on Emission Scenarios used in AR4 Main driving forces of future emissions: 1. Population prospects 2. Economic development 3. Energy intensities and demand, structure of its use 4. Resource availability 5. Technological change 6. Prospects for future energy systems 7. Land-use changes different future developments GHG total emissions 40 different scenarios

Storylines of scenarios A1:Rapid economic growth. Peak population mid-21 st century, then, declining. Rapid introduction of new and more efficient technologies. Substantial reduction of regional difference in per-capita income. A2: Regional solutions to environmental and social equity issues. Continuously rising world population. Slow per-capita income growth technological development B1: Rapid changes in economic structures. Peak population mid-21 st century, then, declining, as in A1. Reduction in intensity of demand for materials. Introduction of clean and resource efficient technologies. Global solutions to environmental and social equity issues. B2: Intermediate economic development. Moderate population growth. Less rapid and more diverse technological change than in the B1 and A1. Regional solutions to environmental and social equity issues.

A1FI: Fossil fuel intensive A1B: Balanced emphasis on all energy sources A1T: Non-fossil fuel intensive A1FI A1B A1T

Uncertainties and Scenario Analysis Three types of uncertainties: data uncertainties, modeling uncertainties, completeness uncertainties. Data uncertainties arise from the quality or appropriateness of the data used as inputs to models. Modeling uncertainties arise from an incomplete understanding of the modeled phenomena, or from approximations that are used in formal representation of the processes. Completeness uncertainties refer to all omissions due to lack of knowledge. They are, in principle, non-quantifiable and irreducible. Uncertainties may be caused by socio-economic conditions, technology, policy environment, representations of processes in assessment models, ‘rare’ events, …

CMIP: Coupled Model Intercomparison Project Program for Climate Model Diagnosis and Intercomparison (PCMDI) Standard experimental protocol for coupled atmosphere-ocean general circulation models (AOGCMs) Since 1995 Phase 1: control runs (constant emissions) Phase 2: idealized global warming scenarios Phase 3: ‘realistic’ climate scenarios – CMIP3 models used for IPCC AR4 Phase 4: testing climate models for forecasting abilities Phase 5: improved Phase 3 – CMIP5 used for IPCC AR5

Range of global surface warming