Chapter 19: Climate Change

Global Change

A change that occurs in the chemical, biological, and physical properties of the planet

Global Climate Change

A type of global change involving changes in the average weather that occurs in an area over a period of years or decades

Global Warming

The warming of the oceans, land masses, and the atmosphere of Earth

Greenhouse Effect

The absorption of infrared radiation by atmospheric gases and reradiation of the energy back towards Earth - ideal situration is that inputs of energy = outputs of energy - this relies on reflection vs. absorption (albedo) - increase in greenhouse gases makes this worse

Types of Greenhouse Gases

• Water Vapor (most common)

• Tropospheric Ozone

• CFCs

• CO₂

• Methane

• NO_x

Greenhouse Warming Potential

Estimates how much a molecule of any compound can contribute to global warming over a period of 100 years relative to a molecule of CO₂

Natural Sources of Greenhouse Gases

• Volcanic Eruptions (CO₂)

• Decomposition (CO₂ and methane)

• Digestion (methane)

• Denitrification (NO_x)

• Evaporation/Evapotranspiration (water vapor)

These lead to balance in the atmosphere

Anthropogenic Sources of Greenhouse Gases

• Combustion of Fossil Fuels (CO₂)

• Agriculture (CO₂ and methane)

• Deforestation (decreased CO₂ absorption)

• Landfills (methane)

• Industrial Production (CO₂, NO_x, SO_x, CFCs)

Measuring CO₂ Concentrations

Varies between seasons (spring/summer has less CO₂ because of more photosynthesis and biomass/crops) - there’s a clear trend of rising concentrations linked with fossil fuel use and deforestation - this is greater in developed countries, but developing countries are starting to surpass in concentrations due to industrialization (ex. China and India)

Indirect Measurement of CO₂

• Changes in species compositions of a group of protists called foraminifera - different species prefer different water temperatures which alters their activity

• Analyzing air bubbles in ice cores

• Examine the amount of isotopes in ice (Oxygen and Hydrogen) - different isotopes represent different temperatures

Positive Feedbacks and Climate Change

• Higher air temperature melts glaciers which decreases albedo which in turn increases ocean temperature

• An increase in biological activity of decomposers in soils releases more CO₂ - warmer soils lead to melting permafrost, causing standing water and anaerobic decomposition which releases methane

Negative Feedbacks and Climate Change

• More CO₂ can stimulate plant growth which reduces CO₂ by photosynthesis

• More CO₂ is absorbed by the ocean which helps the atmosphere but not oceans (ocean acidification)

Polar Ice Melting

Sea ice has declined about 13% per decade from 1979-2017 (triggers feedback loop) - the remaining ice is thinner - the arctic is predicted to warm an additional 4°C over the next 70 years - Antarctica and Greenland are melting

Glaciers Melting

Typically, glaciers partially melt in spring and summer and then grow back to their former size in winter - warmer summers lead to faster melting glaciers that can’t grow back all the way in winter - can lead to shortness of water supply

Melting Permafrost

Melting permafrost causes overlying lakes to become smaller - houses and pipelines can subside and slide away - organic matter will begin to decompose and release methane gas

Sea Levels Rising

Melting glaciers and ice sheets add to ocean volume - the ocean water gets warmer and will expand - these both cause ocean levels to rise - floods coastal cities and low-lying island nations

Negative Impacts of Climate Change

• Melting Polar Ice

• Melting Glaciers

• Melting Permafrost

• Sea Levels Rising

• Forced Species Adaptation (if they can)

Climate Change Impacts Organisms

Changes in the timing of plant flowering, animal behavior (mating, migration, etc.), the ability of plants and animals to disperse to more habitable habitats - temperature changes affect species that can’t adapt (ex. coral, polar bears)

Other Effects from Global Warming

• Heat Waves

• Cold Spells

• Precipitation Patterns

• Storm Intensity

• Ocean Currents

• Effects on Humans

Kyoto Protocol

Agreement to reduce greenhouse emissions by 5.2% by 2012 - looked at the use of carbon sequestration

Paris Climate Agreement

195 countries pledged to keep global warming less than 2°C above pre-industrial levels - went into effect in 2020