Intergovernmental Panel on Climate Change (IPCC) Established by the UN and World Meteorological Organization in 1988Established by the UN and World Meteorological Organization in 1988 Role of the IPCC: to assess the scientific, technical, and socio-economic information relevant for the understanding of the risks of human-induced climate change.Role of the IPCC: to assess the scientific, technical, and socio-economic information relevant for the understanding of the risks of human-induced climate change. Assessments based on published and peer- reviewed literatureAssessments based on published and peer- reviewed literature

Intergovernmental Panel on Climate Change (IPCC) 2,500 of the world’s leading climate scientists and technical experts contribute to reports2,500 of the world’s leading climate scientists and technical experts contribute to reports Provides comprehensive and balanced assessments of climate change science, impacts, and adaptation and mitigation optionsProvides comprehensive and balanced assessments of climate change science, impacts, and adaptation and mitigation options Extensive peer-review and governmental review ensures scientific credibility and policy relevanceExtensive peer-review and governmental review ensures scientific credibility and policy relevance

Intergovernmental Panel on Climate Change (IPCC) Working Group I Climate change science Working Group II Impacts, adaptation and vulnerability Working Group III Mitigation Task force on national greenhouse gas inventories Technical support unit (TSU) in United Kingdom TSU in United States TSU in The Netherlands TSU in Japan Plenary IPCC Secretariat WMO/UNEPSwitzerland Experts, authors, contributors, reviewers Source: Redrawn from Vital Climate Graphics

IPCC Assessment Reports Standard reference workStandard reference work First Assessment Report (FAR) - published in 1990First Assessment Report (FAR) - published in 1990 –Projected increase in temperature of °F –Consequences: rising sea levels, increase in extreme weather events, serious pressure on aquatic and terrestrial ecosystems –“The size of the warming is broadly consistent with predictions of climate models,... but the unequivocal detection of the enhanced greenhouse effect from observations is not likely for a decade or more.”

IPCC Assessment report foci

Climate has changed over the past century Climate has changed over the past century – Global mean surface air temperature has increased.5-1 o F – Global sea level has risen 4-10 inches – Global precipitation over land has increased 1% “ Human signal still building... Nevertheless, the balance of evidence suggests a discernible human influence on global climate.” “ Human signal still building... Nevertheless, the balance of evidence suggests a discernible human influence on global climate.” IPCC Second Assessment Report Conclusions

Climate has changed over the past century Climate has changed over the past century – Global mean surface air temperature has increased.5-1 o F – Global sea level has risen 4-10 inches – Global precipitation over land has increased 1% “ Human signal still building... Nevertheless, the balance of evidence suggests a discernible human influence on global climate.” “ Human signal still building... Nevertheless, the balance of evidence suggests a discernible human influence on global climate.” Climate is expected to continue to change in the future Climate is expected to continue to change in the future – Projected temperature increase of o F by 2100 – Projected sea-level rise of 6-37 inches by 2100 – Likely increase in extreme weather events IPCC Second Assessment Report Conclusions

Kyoto Protocol SAR provided key input to the negotiations that led to the adoption of the Kyoto Protocol in 1997SAR provided key input to the negotiations that led to the adoption of the Kyoto Protocol in 1997 Is an international agreement that establishes binding targets for reduction of greenhouse gases emitted by developed countries.Is an international agreement that establishes binding targets for reduction of greenhouse gases emitted by developed countries.

Emission Scenarios SAR - used scenarios developed in 1992, known as the IS92 seriesSAR - used scenarios developed in 1992, known as the IS92 series Alternative projections of population, affluence, and technological change were used to come up with a range of future GHG emission scenariosAlternative projections of population, affluence, and technological change were used to come up with a range of future GHG emission scenarios IPCC evaluated the IS92 scenarios, recommended that a new set of scenarios be developed - Special Report on Emission Scenarios IPCC evaluated the IS92 scenarios, recommended that a new set of scenarios be developed - Special Report on Emission Scenarios TAR - projections are underlain by the full range of SRES scenariosTAR - projections are underlain by the full range of SRES scenarios

Third Assessment Report of the IPCC Published in 2001Published in 2001 Emphasizes information from the last 5 yearsEmphasizes information from the last 5 years Places climate change in the context of sustainable development, emphasizing equity issuesPlaces climate change in the context of sustainable development, emphasizing equity issues Policy relevant, but not policy prescriptivePolicy relevant, but not policy prescriptive

IPCC Third Assessment Report Key Findings of Working Group I “An increasing body of observations gives a collective picture of a warming world and other changes in the climate system.”

Source: IPCC TAR 2001 Variations of the Earth’s Surface Temperature* *relative to average

Global Annual Temperature Trends: Source: Watson 2000

U.S. Temperature Trends: 1901 to 1998 Red circles = warming; Blue circles = cooling All stations/trends displayed regardless of statistical significance. Source: National Climatic Data Center/NESDIS/NOAA

U.S. Precipitation Trends: 1901 to 1998 Source: National Climatic Data Center/NESDIS/NOAA Green = increasing, Brown = decreasing All stations/trends displayed regardless of statistical significance

Extreme Precipitation Events in the U.S. Source: Karl, et.al

Increase in catastrophic flood events

Increase in frequency and intensity of droughts Source: OSTP

Snow cover and ice extent have decreased

Global average sea level has risen and ocean heat content has increased

IPCC Third Assessment Report Key Findings of Working Group I “Emissions of greenhouse gases and aerosols due to human activities continue to alter the atmosphere in ways that are expected to affect the climate.”

Indicators of the Human Influence on the Atmosphere during the Industrial Era Source: IPCC TAR 2001

IPCC Third Assessment Report Key Findings of Working Group I “Confidence in the ability of models to project future climate has increased.”

IPCC Third Assessment Report Key Findings of Working Group I “There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.”

IPCC Third Assessment Report Key Findings of Working Group I “Human influences will continue to change atmospheric composition throughout the 21st century.”

IPCC Third Assessment Report Key Findings of Working Group I “Global average temperature and sea level are projected to rise under all IPCC scenarios.”

Main Findings of WG I Extensive and wide-spread evidence that the earth is warming; we are already seeing the first clear signals of a changing climate.Extensive and wide-spread evidence that the earth is warming; we are already seeing the first clear signals of a changing climate. Human activities are changing the atmospheric concentrations of greenhouse gases.Human activities are changing the atmospheric concentrations of greenhouse gases. New and stronger evidence of a human influence on climate.New and stronger evidence of a human influence on climate. Global temperature will rise from 2.5 to 10.4°F over this century. Precipitation patterns will change, sea level will rise and extreme weather events will increase.Global temperature will rise from 2.5 to 10.4°F over this century. Precipitation patterns will change, sea level will rise and extreme weather events will increase. Human influence will continue to grow during the next century unless measures are taken to reduce GHG emissions.Human influence will continue to grow during the next century unless measures are taken to reduce GHG emissions.

IPCC History: Evolution of Our Knowledge FAR (1990): “The size of the warming is broadly consistent with predictions of climate models,... but the unequivocal detection of the enhanced greenhouse effect from observations is not likely for a decade or more.”FAR (1990): “The size of the warming is broadly consistent with predictions of climate models,... but the unequivocal detection of the enhanced greenhouse effect from observations is not likely for a decade or more.” SAR (1996): “The balance of evidence suggests a discernible human influence on climate.”SAR (1996): “The balance of evidence suggests a discernible human influence on climate.” TAR (2001): “There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.”TAR (2001): “There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.”

IPCC Scenario formulation

Data vs. Models in Science Data tell us about the past –But in nonlinear systems (like climate), past trends not necessarily predictive of future Models project the future –Connect theory with data –Can work with nonlinear systems But how do we know models are correct? –Right answers for wrong reasons

Climate Models 3-dimensional mathematical simulations –based on “first principles”: physical equations of motion and state –transport of heat, moisture, energy –grids (4-5° latitude, or km) –time steps (15-30 minutes) –long-term simulations (years to centuries) Computationally expensive –hundreds of supercomputer hours per run

General Circulation Models Governed by physics: - Law of Continuity - Equation of State - Conservation of energy - Conservation of momentum Input: solar forcing, Earth rotation, seasons, initial conditions, greenhouse gas levels Output: temperature, precip, pressures, winds, ocean currents, heat transport, deep ocean circulation…

Run a GCM on your computer? One “experiment” takes 3-4 days of cpu time

SRES Scenarios

The A1 storyline and scenario family describes a future world of very rapid economic growth, low population growth, and the rapid introduction of new and more efficient technologies. Major underlying themes are convergence among regions, capacity building, and increased cultural and social interactions, with a substantial reduction in regional differences in per capita income. The A2 storyline and scenario family describes a very heterogeneous world. The underlying theme is self-reliance and preservation of local identities. Fertility patterns across regions converge very slowly, which results in high population growth. Economic development is primarily regionally oriented. The B1 storyline and scenario family describes a convergent world with the same low population growth as in the A1 storyline, but with rapid changes in economic structures toward a service and information economy, with reductions in material intensity, and the introduction of clean and resource-efficient technologies. Global solutions to economic, social, and environmental sustainability, including improved equity, but without additional climate initiatives. The B2 storyline and scenario family describes a world in which the emphasis is on local solutions to economic, social, and environmental sustainability. It is a world with moderate population growth, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines. While the scenario is also oriented toward environmental protection and social equity, it focuses on local and regional levels.

CO 2 and SO 2 in the 21 st Century Source: IPCC TAR 2001

Global average temperature is projected to increase by °C by 2100 Projected temperature increases are greater than those in the SAR Projected rate of warming is unprecedented for last 10,000 years Temperature Projections Source: IPCC TAR 2001

1000AD to 1861, N. Hemisphere, proxy data 1861 to 2000, Global, instrumental 2000 to 2100, SRES projections Source: IPCC TAR 2001 Variations of the Earth’s Surface Temperature to 2100

Projected Changes in Annual Temperatures for the 2050s The projected change is compared to the present day with a ~1% increase per year in equivalent CO 2 Source: The Met Office. Hadley Center for Climate Prediction and Research

A probabilistic view… “With the climatological probability of a hot summer represented by two faces (say painted red) of a six- faced die, judging from our model by the 1990s three or four of the six die faces will be red. It seems to us that this is a sufficient ‘loading’ of the dice that it will be noticeable to the man in the street.” Hansen et al., J. Geophys. Res. 93, , 1988.

Metro NYC region: Impact study 31 counties in 3 states (NY, NJ, CT) 21 million residents 13,000 square miles Variety of pop densities & land uses

Estimated Increases in Ozone Excedences ( 1 hour >120 ppb) for the New York Metro Region by Hottest Summer Climate 2050 A2 Hottest Summer Climate 1990 air pollutant emissions 7863, A2 air pollutant emissions 1,7457,489 (from C. Hogrefe et al, 2003) (+122%) (+315%) (+749%)

Temperature & Mortality Relationship in 11 Eastern US Cities (Curreiro et al, 2002)

Public Health Impacts (PHI) Model STUDY POP x BASE RISK x CHANG E IN ENV x EXP- RISK COEF F = # ADD’L PHIs IN FUTURE

Public Health Impacts (PHI) Model STUDY POP x BASE RISK x CHANG E IN ENV x EXP- RISK COEF F = # ADD’L PHIs IN FUTURE Census 2000 county pop

Public Health Impacts (PHI) Model STUDY POP x BASE RISK x CHANG E IN ENV x EXP- RISK COEF F = # ADD’L PHIs IN FUTURE average annual non-heat- rel mortality risk

Public Health Impacts (PHI) Model STUDY POP x BASE RISK x CHANG E IN ENV x EXP- RISK COEF F = # ADD’L PHIs IN FUTURE (# days > MMT range)* (average #degrees F above MMT range on those days) Source: R Goldberg & C Rosenzweig, NASA-GISS

Public Health Impacts (PHI) Model STUDY POP x BASE RISK x CHANG E IN ENV x EXP- RISK COEF F = # ADD’L PHIs IN FUTURE 1.305% increase RR mortality per deg F>MMT range (“hot slope”)

Public Health Impacts (PHI) Model STUDY POP x BASE RISK x CHANG E IN ENV x EXP- RISK COEF F = # ADD’L PHIs IN FUTURE Additional # impacts (e.g. deaths) from env change

NYC “optimal mortality temperature range” ~ F – F from Curreiro et al. (2002 revision, ms. submitted) Relative Risk of Mortality Average Daily Temperature (deg F)

NYCHP, Phase I: Preliminary Heat-Mortality Results Summers: Observed 1990s vs. GISS-modeled 2050s Population Growth consistent with IPCC A2 & B2 scenarios* In a typical SUMMER (June 1 - August 31): 1990sGISS A2 2050sGISS B2 2050s Regional non-temperature-related deaths, all internal causes 42,11764,50952,312 Regional population21,491,89832,917,88926,694,229 # Heat-related deaths1,7344,7593,272 % Heat-related vs. Same-yr non-temperature-related deaths 4.1% 7.4% 6.3% # Additional heat-related deaths, 2050s vs. 1990s 3,0251,538 % Increase above 1990s heat- related deaths 174.5%88.7% Heat-related mortality risk in regional population 8.1/100K14.5/100K (6.4/100 K incr) 12.3/100K (4.2/100K incr) * Regional population growth consistent with B2 population growth projections in 5-yr steps from 1990 to 2100 by Stuart Gaffin & Xiaoshi Xing (CIESIN, 2002); same for A2 population growth projections by Wolfgang Lutz at IIASA (CIESIN, 2002)

Precipitation Projections Global average water vapor and global mean precipitation will increaseGlobal average water vapor and global mean precipitation will increase Larger year to year variations in precipitationLarger year to year variations in precipitation

Projected Changes in Annual Precipitation for the 2050s Source: The Met Office. Hadley Center for Climate Prediction and Research The projected change is compared to the present day with a ~1% increase per year in equivalent CO 2

Change in PhenomenonConfidence in projected change* Increase in tropical cyclone peak wind and precipitation intensities Likely, over some areas Increased summer continental drying & associated risk of drought More intense precipitation events Increase of heat index Higher minimum temperatures, fewer cold days and frost days Higher maximum temperatures, more hot days Likely, over most mid-latitude continental interiors Very likely, over most areas Very likely, over many areas Very likely Extreme Events *Judgmental estimates of confidence by IPCC: very likely % chance, likely % chance. Source: IPCC TAR 2001

Global average sea level is projected to rise by 4 to 35 inches between 1990 and 2100 Global average sea level is projected to rise by 4 to 35 inches between 1990 and 2100 Projected rise is slightly lower than the range presented in the SAR (6 to 37 inches) Projected rise is slightly lower than the range presented in the SAR (6 to 37 inches) Sea level will continue to rise for hundreds of years after stabilization of greenhouse gas concentrations Sea level will continue to rise for hundreds of years after stabilization of greenhouse gas concentrations Sea-Level Rise Projections Source: IPCC TAR 2001

Sea-Level Rise Commitment Thermal expansion and land ice melt after an initial 1% increase in CO 2 for 70 years Source: The Met Office. Hadley Center for Climate Prediction and Research

Jim Hansen’s View (NASA/GISS) 1. Climate is Changing (Global Warming) 2. Human (Greenhouse Gas) Role is Probable 3. Global Warming Increases Hydrologic Extremes (droughts/fires and heavy rain/floods) 4. With Large Climate Change, Detrimental Effects Probably Exceed Beneficial Ones 5. Common Sense Steps to limit emissions are warranted 6. Steps also to reverse CO2 trends (sequestration)

Discussion question What should we do? Nothing, it’s a hoax. Wait until climate change is certain? Take precautionary measures to reduce emissions? Take drastic measures to reduce emissions?

Acknowledgement For more information about UCS, visit.