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Scientific Models

	Descriptive (classification) models, measurement & observation leads to descriptive models, e.g., cloud types, rock, classification of flora & fauna
	Explanatory models, natural selection, evolution, land-sea thermal properties & temporal temperature patterns, genetics
	Predictive models,
	example: gravity (deterministic)
	example: weather, genetics (stochastic or probability models)

Positive  & Normative Statements & Claims

Figure 3.2a. Change in mean glacial length Figure 3.2b. Reconstructed global mean temperature inferred from this change in glacial length

Climate change: present scientific knowledge & uncertainties

Lines of evidence

Figure 3.3. Annually averaged satellinte-measured Arctic sea ice area anomalies, 1973-2000, relative to the 1973-1996 average.

Figure 3.4. Time series for 1948-1998 of ocean temperature anomalies in the upper 300m for the global ocean.

Climate proxies

Figure 3.5.  Photo of cross-section of a tree.

Figure 3.6. Data from the Vostok ice core in Antarctica, from 410,000 years ago to the present.

Figure 3.7. Global ground temperature anomaly over the past 500 years.

Figure 3.8  Northern Hemisphere temperature anomaly, relative to the 1961-1990 average.

Figure 3.9  Temperature anomalies calculated from MSU satellite data & the surface thermometer record over the period 1979-2003.

Tqble 3.1.   A summary of measurements of changes iin the EarthÕs temperature.

Are human activities responsible for global warming?

Figure 3.10.   Global mean surface temperature anomalies from the surface thermometer record.

Figure 3.11.  CO2 emission scenarious used in models to predict future climate change.

Figure 3.12.   Gobally & annually averaged surface temperature anomaly predicted by climate models for 21st century, measured rletive to 1990.

Climate change: present scientific knowledge & uncertainties