What role does the Ocean play in Global Climate Change?

The Global Greenhouse

How the Greenhouse Effect Works

Emission Spectra of Sun and Earth and Absorption Spectra of Atmosphere

Interplanetary Comparisons: Venus: Higher concentrations: 400 o C Mars: Lower concentrations: -50 o C

Intergovernmental Panel on Climate Change (IPCC) Established by the UN and World Meteorological Organization in 1988 Established by the UN and World Meteorological Organization in 1988 Mission of the IPCC: to assess the scientific, technical, and socio- economic information relevant for the understanding of the risks of human-induced climate change Mission of the IPCC: to assess the scientific, technical, and socio- economic information relevant for the understanding of the risks of human-induced climate change 2,500 of the world’s leading climate scientists and technical experts contribute to reports 2,500 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 options Provides 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 relevance Extensive peer-review and governmental review ensures scientific credibility and policy relevance

Observed Changes in Greenhouse Gas Concentrations

Predicted Increases in CO 2 Emissions and Concentrations (from IPCC SAR 1995)

Global Temperature and Atmospheric CO 2 over Geological Time Current level of CO 2 is outside bounds of natural variability Current level of CO 2 is outside bounds of natural variability Rate of change of CO 2 is also unprecedented Rate of change of CO 2 is also unprecedented Clear correlation between atmospheric CO 2 and temperature over last 160,000 years Clear correlation between atmospheric CO 2 and temperature over last 160,000 years

Observed Changes in Global Mean Temperature (measured and proxy data) *relative to average

IPCC Global Mean Temperature Predictions: Global average temperature is projected to increase by 1.5 to 5.5° C (2.5 to 10.4° F) from 1990 to 2100 Global average temperature is projected to increase by 1.5 to 5.5° C (2.5 to 10.4° F) from 1990 to 2100 Projected temperature increases in TAR are greater than those in SAR. Projected temperature increases in TAR are greater than those in SAR. Projected rate of warming is unprecedented for last 10,000 years Projected rate of warming is unprecedented for last 10,000 years

1861 to 2000: 1861 to 2000: Instrumental data 1000 to 1861: 1000 to 1861: Proxy data 2000 to 2100: 2000 to 2100: Model projections Model projections Predicted Temperature Change in the Context of Last 1000 Years

Observed Changes in Spatial Patterns of Land and Sea Surface Temperature Surface temperature change between 20 year mean and 20 year mean

Predicted Changes in Spatial Patterns of Land and Sea Surface Temperature Model-predicted surface temperature change by 2050

Atmospheric CO 2 and Sea Level Rise

Global average sea level is projected to rise by 10 to 80 cm (4 to 35 inches) between 1990 and 2100 Global average sea level is projected to rise by 10 to 80 cm (4 to 35 inches) between 1990 and 2100 Projected rise is slightly lower than the range presented in the SAR. Projected rise is slightly lower than the range presented in the SAR. 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 IPCC Global Sea Level Rise Predictions:

Components of Sea Level Rise Thermal expansion and land ice melt after an initial 1% increase in CO 2 Thermal expansion and land ice melt after an initial 1% increase in CO 2 for 70 years Eventually. most of sea-level rise will be due to thermal expansion of ocean, Eventually. most of sea-level rise will be due to thermal expansion of ocean, not melting of ice

Predicted Changes in Annual Precipitation by 2050 The projected change is compared to the present day with a ~1% increase per year in equivalent CO 2

Increase in Extreme Precipitation Events in the U.S.

Number of Billion Dollar Weather Disasters

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 Weather Events *Judgmental estimates of confidence by IPCC: very likely % chance, likely % chance.

Economic losses from catastrophic weather events have increased 10-fold in recent decades Economic losses from catastrophic weather events have increased 10-fold in recent decades Increasing losses are due in part to socioeconomic factors and in part to climatic factors Increasing losses are due in part to socioeconomic factors and in part to climatic factors Because of expensive coastal development and projection of more extreme events - insurance damages, claims, and costs are likely to increase Because of expensive coastal development and projection of more extreme events - insurance damages, claims, and costs are likely to increase Significant challenges in the future if high impact events occur or if catastrophes are closely- spaced Significant challenges in the future if high impact events occur or if catastrophes are closely- spaced Impacts of Climate Change on Insurance

IPCC Policy-Makers Summary: Observations Human activities are changing the atmospheric concentrations of greenhouse gases. Human activities are changing the atmospheric concentrations of greenhouse gases. Extensive and wide-spread evidence that the earth has warmed ° C over the last century; however, this warming has not been uniform. Extensive and wide-spread evidence that the earth has warmed ° C over the last century; however, this warming has not been uniform. Global sea level has risen 10 – 20 cm over the last century. Global sea level has risen 10 – 20 cm over the last century. Forecasts Global average temperature is projected to increase by 1.5 to 5.5° C (2.5 to 10.4° F) from 1990 to 2100 Global average temperature is projected to increase by 1.5 to 5.5° C (2.5 to 10.4° F) from 1990 to 2100 Global average sea level is projected to rise by 10 to 80 cm (4 to 35 inches) between 1990 and 2100 Global average sea level is projected to rise by 10 to 80 cm (4 to 35 inches) between 1990 and 2100 Likely to be an increase in extreme weather events Likely to be an increase in extreme weather events

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.”

Unpredictability: What if our models are not complete?

Greater warming, lesser warming, but what about cooling?

Example: Shutdown of NADW Formation and Collapse of Ocean Thermohaline Circulation?