Intergovernmental Panel on Climate Change (IPCC) International Scientific Consensus and Climate Model Projections

Outline The IPCC as an organization What inputs do they use – review of some global warming evidence How do they make models? What are the projections? Conclusion

IPCC - Why was it created? “Human activities now occur on a scale that is starting to interfere with complex natural systems” “Climate change poses a serious challenge to policymakers” “Policymakers … need an objective source of the most widely accepted scientific, technical and socio-economic information available about climate change” “The World Meteorological Organization (WMO) and the UN Environment Programme (UNEP) established the IPCC in The Panel does not conduct new research or monitor climate-related data. Its mandate is to assess … peer-reviewed literature … to ensure a balanced reporting of viewpoints…” All quotes from “Introduction to the IPCC” -

IPCC Organization WG I Science WG II Impacts WG III Mitigation Task Force on GHG IPCC Bureau IPCC Chair

IPCC Reports First Assessment Report (1990) - Helped lead to work at Rio de Janeiro Earth Summit (1992) and UNFCCC Second Assessment Report (1996) - Contributed to negotiations that lead to Kyoto Protocol (1997) Third Assessment Report (2001) - Update concentrating on findings after 1995; looks at regional as well as global effects Fourth Assessment Report – Due in 2007

IPCC Process Approximately 1000 experts directly involved in drafting and revising the reports About 2500 participate in the review process IPCC authors are nominated by governments and international organizations, and represent universities, research centers, business and environmental groups from 120 countries

IPCC Process “...(T)eams of lead authors are assembled … Every chapter team must represent a range of prevailing scientific-technical viewpoints and expertise, and ensure appropriate representation of experts from developing and developed countries …”

Temperature Change - Century

Temperature Change - Millenium

Energy Balance “Earth’s Energy Imbalance: Confirmation and Implications” James Hansen, et al. Science 3 June : – Current imbalance of 0.85±0.15 W/m 2

Model “Forcings”

Natural or anthropogenic?

Model scenario indicators

Model projections

IPCCmodelscenarios

IPCC Projections 66%-90% 90%-99%

Carbon Budget Watson, IPCC

Natural CO 2 changes 2100 Petit et al, Nature v.399 (6735), pp (1999) 2100 today

CO 2 Concentrations

Methane Fluctuations Petit et al, Nature v.399 (6735), pp (1999) 1500 ppbv (today)

Probability distributions “Interpretation of High Projections for Global-Mean Warming” T.M.L. Wigley and S.C.B. Raper 20 JULY 2001 VOL 293 SCIENCE

Stop burning fossil fuels? “The Climate Change Commitment” T. M. L. Wigley 18 MARCH 2005 VOL 307 SCIENCE

Keep burning at same rate? “The Climate Change Commitment” T. M. L. Wigley 18 MARCH 2005 VOL 307 SCIENCE

Questions Is the current evidence convincing (especially for non-scientists)? Are models + scenarios convincing (as a way to project to the future)?