bio220 lecture 10

Introduction to Greenhouse Gases and Climate Change

• Overview of natural climate changes throughout Earth's history.

• Major shifts in species diversity and distribution due to climatic changes.

• Current climate conditions relate to cycles of glacial (ice) and interglacial (warmer) periods.

Historical Climate Data

• The Earth has entered major ice ages, with the most recent one starting 2.5 million years ago.

• Sea level fluctuations drastically altered coastal geography over million-year timescales.

• Example: 55 million years ago, much of Florida and certain areas in South America were underwater.

• Evidence for climate cycles primarily comes from ice core data.

Ice Ages and Temperature Cycles

• Ice ages are characterized by alternating glacial (cold) and interglacial (warm) phases.

• Ice core data provides insight into temperature deviations from long-term averages.

• Cycles of ice volume and temperature exhibit clear periodicity, estimated to last tens of thousands of years.

Human Influence on Climate

• Current climate predictions differ dramatically due to human activities compared to natural patterns.

• Historical figures contributing to climate science:

  • John Tyndall (1861): Identified how gases absorb heat, especially water vapor and CO2.

  • Eunice Foote (1856): Explored absorbing properties of gases and their role in climate change, published before Tyndall.

  • Svante Arrhenius: Early predictions on CO2 doubling and its effect on global temperatures during the industrial revolution.

  • Lewis Fry Richardson: Developed early weather prediction methods using complex equations and highlighted computing limitations.

Weather vs Climate

• Weather: Short-term atmospheric conditions; unpredictable beyond a few days.

• Climate: Long-term averages and statistics of weather patterns.

• The International Panel on Climate Change (IPCC) was established to create consensus among climate research groups.

Energy Balance and Greenhouse Effect

• The sun emits energy, with half absorbed by the Earth or reflected back by atmospheric components.

• Greenhouse gases trap infrared radiation, leading to a warming effect.

• Albedo effect: Different materials reflect percentages of solar energy back into space; for instance, fresh snow reflects 75%, while water only reflects 5%.

• Feedback loops: Reduced ice/snow cover leads to greater warming due to lower albedo, creating a self-reinforcing cycle.

The Keeling Curve

• Atmospheric CO2 levels fluctuate seasonally, influenced by photosynthesis: concentrations drop in summer and rise in winter.

• Long-term trend shows a steady increase in atmospheric CO2, from 280 parts per million (pre-industrial) to about 426 ppm currently.

• Significant human contributions to greenhouse gas concentrations have been observed.

Greenhouse Gas Contributions

• Gases ranked by potency:

  • CO2 (1 unit), Methane (30 units), Nitrous Oxide (200 units), CFCs (30,000 units).

• Major greenhouse gas producers discussed in context of national emissions and populations.

• China's rank as the largest emitter overall, while countries like Canada and Australia lead per capita due to industrial activities.

Climate Data Analysis

• Trends indicate increasing temperatures, sea levels, and decreasing ice extent: measured against historical averages and current observations.

• Globally coherent temperature increases signal climate changes across regions, dismissing localized weather anomalies as explanations.

Recent Findings on Greenhouse Gas Levels

• Current methane and CO2 levels have reached unprecedented heights compared to historical data.

• Potential future projections stress the consequences of continued fossil fuel consumption, with disastrous effects if CO2 levels rise to 2200 ppm.

Observations of Climate Change

• Documented changes in Greenland's land cover: significant decreases in ice and increases in vegetation reflecting higher temperatures.

• Rising sea levels affected by thermal expansion and melting ice, with accelerating rates of sea level rise.

• Observations in Arctic conditions indicate dramatic shifts in ice cover and geographic accessibility.

Conclusion

• Synthesized data points towards a clear signal of global climate change backed by physical measurements.

• The historical understanding of climate and modern data suggest urgent attention to greenhouse gas emissions and climatic shifts.