8_PresentClimateChange_LectureSlides

Climate Change Overview

• Climate change involves the interactions among Earth’s spheres and their impact on climate.

• As open systems, these spheres contribute to various climate factors.

• Global Temperature Trends: Since 1880, human activity has contributed to an increase of 0.8°C (1.4°F) in global temperatures.

• Temperature Data: NASA/GISS has documented land-ocean temperature trends relative to the global average from 1951-1980.

Ice Melt

• Atmospheric Heating: Increased temperatures are leading to rapid melting of sea and land ice.

• Arctic Sea Ice: Melting contributes to further global warming through positive feedback mechanisms.

  • Significant increases in summer melting of Greenland (30% increase from 1979 to 2006).

  • Irreversible decline of West Antarctica Ice Sheet noted.

• Types of Arctic Ice:

  • Floating sea ice (frozen seawater).

  • Glacier ice (frozen freshwater).

• **Trends in Sea Ice: ** Overall reduction in Arctic sea ice since 1979, with significant losses in 2005-2007.

• Concerns: Potential future disruptions in thermohaline circulation due to freshening of the Arctic Ocean.

Antarctica and Global Warming

• Ice Shelf Disintegration: Six Antarctic ice shelves have collapsed since 1993, eliminating over 8000 km² of ice.

• Larsen Ice Shelf: Notable retreats include:

  • Larsen A in 1995.

  • Larsen B’s collapse in 2002, occurring further south than previous collapses.

• Mass Loss Data: Remote sensing technology (e.g., Jason-1 and Jason-2) shows a 4.5 cm rise in global mean sea level from 1993-2008 due to thermal expansion and melting ice contributing to sea-level rise.

• Future Rise Predictions: Sea levels are projected to rise 1.0-1.4 meters by century's end.

Coastal Inundation

• Rising Sea Levels: A one-meter rise could lead to extensive flooding, especially in regions like Miami.

The Greenhouse Effect

• Importance of Greenhouse Gases: They are vital for maintaining Earth's temperature.

• Human Impact: Excessive emissions can disrupt this balance.

  • Historical data show that global temperatures are nearing highs experienced in the last 125,000 years.

Carbon Dioxide Dynamics

• Sources and Sinks of CO2:

  • Major sources include coal, oil, and gas.

  • Sinks primarily involve oceans and plants through photosynthesis.

• Trends in CO2 Levels: Since 1958, CO2 has steadily increased due to fossil fuel combustion and deforestation.

• Methane: The second most significant greenhouse gas is escalating at a rate surpassing CO2.

  • Nitrous oxide concentrations have increased 19% since 1750, now at historically high levels.

• Radiative Forcing: Measures how much energy emitted by the Earth is deviating from equilibrium, predominantly driven by greenhouse gases.

Climate Feedback Mechanisms

• Water-Vapor Feedback: Higher temperatures increase evaporation, further elevating temperatures.

• Permafrost-Carbon Feedback: Thawing permafrost releases additional CO2 and methane.

• Wildfire-Carbon Feedback: Increased wildfires contribute more greenhouse gases, enhancing climate change.

Climate Models and Predictions

• General Circulation Models (GCMs): Complex computational models simulating interactions among various climate systems (atmosphere, oceans, land, cryosphere, biosphere).

• Future Climate Scenarios: Assessed based on varying input parameters.

• Anthropogenic vs. Natural Forcing: Models highlight the significance of anthropogenic factors in climate warming.

Consequences of Climate Change

• Ecosystem Impacts: Loss of glaciers, coral reefs, and coastal wetlands leading to extinction and ecosystem migration.

• Ocean Acidification: Absorption of CO2 by oceans results in more acidic waters, threatening marine life.

• Extreme Weather Events: Increased frequency and severity of hurricanes, floods, heatwaves, and droughts noted.

• Socioeconomic Effects: Climate change may lead to crop failures and diminished water supply, with poorer nations most vulnerable.

Paris Agreement and Global Action

• 2015 Accord: Aimed at limiting global temperature rise to below 2°C above pre-industrial levels, with goals set for emission reductions.

• COP26 Summit (2021): Urged to limit warming to 1.5°C; outlined necessary emission cuts.

• Individual Action: Personal initiatives encouraged to reduce atmospheric CO2 levels.

Research Sources for Climate Change

• Agencies and organizations provide continued scientific research and data, including:

  • United Nations Environment Programme

  • Intergovernmental Panel on Climate Change

  • NASA and various climate monitoring organizations.