Climate Change: A 21st Century Issue

Earth Is a Greenhouse Planet

• Earth's temperature allows water to exist in liquid form, which is essential for life.

• Factors determining Earth's temperature:

  • Distance from the sun.

  • Energy output of the sun.

  • Presence of carbon dioxide in the atmosphere.

• Greenhouse gases:

  • Transparent to ultraviolet and visible light but absorb infrared radiation.

  • Allow sunlight to penetrate the atmosphere and be absorbed by the Earth’s surface.

  • Absorb some of the reradiated infrared radiation (heat).

• Carbon dioxide:

  • Significant greenhouse gas, despite its small amount in the atmosphere.

  • Without carbon dioxide, Earth’s temperature would be about $-18^\circ C$ ($0^\circ F$) instead of $15^\circ C$ ($60^\circ F$).

  • The greenhouse effect makes Earth suitable for life.

Geologic Evidence of Climate Change

• Global warming refers to an average increase in Earth's atmospheric temperature.

• Climate change encompasses various changes resulting from global warming.

• Geologic studies show significant climate changes throughout Earth’s history, including hotter and colder periods.

• Evidence of past continental glaciers indicates climate change in the recent geologic past.

Growth in Knowledge of Global Warming and Climate Change

• The average temperature of the Earth has been increasing.

• Correlation between greenhouse gas concentrations and global temperatures over 160,000 years.

• Computer models predict that increasing greenhouse gases will lead to warmer temperatures and various climate changes.

• Other evidence of climate change:

  • Steady increase in atmospheric carbon dioxide.

  • Gas bubbles trapped in glaciers indicating pre-industrial revolution atmosphere (lower carbon dioxide levels).

  • Satellite photos showing altered snow and ice conditions.

  • Changes in terrestrial and marine animal migration behavior.

  • Ocean studies showing changes in $CO_2$ content and pH (lower pH).

  • Longer growing seasons.

  • Physical measurements of retreating glaciers and thinning ice sheets.

  • Effects of increased carbon dioxide on photosynthesis.

  • Changes in wind patterns and ocean currents.

  • Impact of particulates from natural and human activities.

  • Rising sea levels.

  • Frequency and strength of tropical storms.

Sources and Impacts of Principal Greenhouse Gases

• Most important greenhouse gases:

  • Carbon dioxide ($CO_2$).

  • Methane ($CH_4$).

  • Chlorofluorocarbons (CFCs), primarily ($CCl<em>3F$ and $CCl</em>2F_2$).

  • Nitrous oxide ($N_2O$).

• Carbon dioxide ($CO_2$):

  • Most abundant greenhouse gas, responsible for about 65% of global warming.

  • Natural consequence of respiration and fermentation.

  • Released from burning fossil fuels.

  • Deforestation reduces carbon storage in trees, contributing to increased concentration of carbon dioxide.

• Measurements at Mauna Loa Observatory in Hawaii show carbon dioxide levels increased from about 317 ppm in 1960 to over 411 ppm in 2019, a nearly 30% increase. Furthermore, the current concentration represents an increase of 47 percent over preindustrial concentrations (280 ppm).

• Methane ($CH_4$):

  • Second most abundant greenhouse gas, responsible for about 17% of global warming.

  • From biological sources and fossil-fuel use.

  • Released by microorganisms in wetlands and rice paddies.

  • Released from the digestive systems of animals (ruminants and termites).

  • Natural gas is primarily methane, and oil and coal contain some methane.

  • Preindustrial concentrations were about 700 parts per billion (ppb), current concentrations are about 1,870 ppb.

• Nitrous oxide ($N_2O$):

  • Enters the atmosphere through fertilizer use and fossil fuels.

  • Nitrogen-containing fertilizers and animal manure are converted to nitrous oxide by soil bacteria.

  • Formed during the burning of fossil fuels.

• Chlorofluorocarbons (CFCs):

  • Synthetic compounds with no natural sources.

  • Used as refrigerant gases, cleaning solvents, propellants, and expanders.

  • Extremely efficient greenhouse gases (15,000 times more efficient than carbon dioxide at retarding heat loss).

  • Production and use have been sharply reduced due to ozone destruction, scheduled to be eliminated by 2020, atmospheric levels are decreasing.

The Current State of Knowledge about Climate Change

• The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by the United Nations Environment Programme and the World Meteorological Organization to study the issue and make recommendations.

• The IPCC provides assessments of the state of knowledge about climate change at regular intervals.

• IPCC is organized into working groups:

  • Working Group I: physical science of climate change.

  • Working Group II: impacts of climate change.

  • Working Group III: mitigation of climate change.

• Working Group I published its portion of the Fifth Assessment Report, Climate Change 2013: The Physical Science Basis, in September 2013.

• Key conclusions from the Fifth Assessment Report:

  1. Human activity is clearly influencing climate.

  2. Increased greenhouse gas concentrations, especially carbon dioxide, are causing increased temperatures.

  3. Evidence of increased temperature is clear.

• Specific findings from the report:

  • Average Earth temperature has increased $0.65-1.06^\circ C$ ($1.2 to 1.9^\circ F$) since 1880.

  • Spring snow and ice have decreased in the Northern Hemisphere, with earlier melting.

  • The number of cold days has decreased, and the number of warm days has increased.

  • The Arctic region is warming 2 to 3 times faster than the rest of the world.

  • Permafrost temperatures have increased $2 to 3^\circ C$ ($3.6 to 5.4^\circ F$), and permafrost layer thickness and area have decreased.

  • Reduction in Arctic sea ice coverage at the end of summer.

  • Greenland and Antarctic ice sheets are losing mass.

  • Glaciers are melting.

  • The arrival of spring is earlier in many parts of the world.

• Increased carbon dioxide and temperature are affecting oceans:

  • About 28% of carbon dioxide emissions end up in the ocean.

  • Increased $CO_2$ dissolved in water has decreased pH by 0.1 pH unit (a 26% increase in hydrogen ion concentration).

  • About 90% of additional energy added to the Earth has been stored in the oceans, resulting in an increase of about $0.44^\circ C$ ($0.8^\circ F$) in the temperature of the upper 75 meters of the oceans in the last 40 years.

  • Sea level has risen about 19 cm (7.5 in.) between 1901 and 2010.

  • The rate of sea level rise has been increasing and was about 3.2 mm/year (0.125 inches/year) from 1993 to 2010 (in 2019, sea level was rising about 3.4 mm/year).

Consequences of Climate Change

• A small increase in average Earth temperature can trigger significant regional climate changes

• Computer models suggest rising temperatures will alter the hydrologic cycle, sea level, human health, organism survival, and natural resource use.

• Some ecosystems and settlements can adapt, while others cannot.

• Poorer nations are more vulnerable due to climate-sensitive economies and limited resources.

• The IPCC identifies Africa as most vulnerable due to widespread poverty limiting adaptation.

• Working Group II of IPCC lists 8 major risks:

  1. Risk of death or harm from coastal flooding.

  2. Risk to health and livelihoods from inland flooding.

  3. Risk of severe weather disrupting infrastructure and public services.

  4. Risk of death and illness due to extreme heat.

  5. Risk of food insecurity due to warming, drought, or flooding.

  6. Risk to agricultural productivity due to water shortage.

  7. Risk of loss of marine and coastal ecosystem services.

  8. Risk of loss of terrestrial and freshwater ecosystem services.

• Oceans are closely linked to climate:

  • Equatorial waters are warmer, causing wind patterns.

  • Oceans are the primary water vapor source for precipitation.

  • Winds and water vapor from oceans drive weather patterns.

  • Increased ocean temperature: About 90% of additional heat from climate change is absorbed by the oceans. In 2019, the average surface temperature of the ocean was about $0.8^\circ C$ ($1.4^\circ F$) above the long- term average.

  • Oceans are becoming more acidic: About 25% of carbon dioxide released is absorbed into them. Dissolved carbon dioxide creates carbonic acid, leading to about a 0.1 pH unit decrease (approximately a 33% increase in acidity). Many marine organisms face difficulties in constructing and maintaining skeletal structures.

• Hydrologic cycle disruption:

  • Driven by Earth's temperature, which depends on solar energy and the greenhouse effect.

  • Changes in temperature are expected to alter weather and climate.

  • Weather: Short-term activities (temperature, rain, winds, clouds).

  • Climate: Long-term average of weather patterns.

  • Higher temperatures increase evaporation.

  • Some areas become drier (drought, less water in lakes/rivers), while others get more rainfall (floods, severe storms, wetter soil).

  • Snowfall patterns are also expected to change.

• Recent data suggest:

  • Spring snow has decreased.

  • Snow is melting earlier.

  • Hurricanes are more powerful.

  • There are more hot days and fewer cold days.

  • Spring is arriving earlier.

Rising Sea Level

• A warmer Earth causes rising sea levels due to:

  • Thermal expansion of water.

  • Melting glaciers adding water to oceans.

• Rising sea level leads to:

  • Erosion of beaches and coastal wetlands.

  • Inundation of low-lying areas.

  • Increased vulnerability to flooding from storm surges and rainfall.

• IPCC projects a sea-level rise of 26 to 98 centimeters (10 to 39 inches) by 2100.

• A 50-centimeter (20-inch) rise will cause substantial coastal land loss in North America, especially along the southern Atlantic and Gulf coasts.

• Many coastal cities will be significantly affected.

• About 600 million people worldwide live in low-lying coastal areas.

• Land area of some island nations and countries like Bangladesh would change dramatically due to flooding.

Changes to Ecosystems

• Geographic distribution of organisms will change.

  • Terrestrial plants and animals are shifting their range toward poles.

  • Tundra regions are converting to forests.

  • Ocean organisms (plankton, fish, mammals) are shifting their ranges.

• Coral reefs are affected by increased ocean temperature and acidity.

• Mangrove forests and marshes on shorelines are being affected by sea-level rise and storm surges.

Health Effects

• Direct effect: hotter temperatures increase deaths (from various causes).

  • People with heart problems are vulnerable.

  • Heat exhaustion and respiratory problems increase.

• Climate change worsens air pollution:

  • Higher temperatures increase ground-level ozone, injuring lung tissue and increasing respiratory disease, asthma, and allergies.

  • Children and the elderly are more vulnerable.

• Tropical diseases could migrate to former temperate regions:

  • Vector-borne diseases (malaria, dengue fever, yellow fever, encephalitis) could become more prevalent.

  • Some scientists believe that algal blooms could occur more frequently as temperatures rise.

Challenges to Agriculture and the Food Supply

• Climate strongly affects crop yields.

  • Yields fall in regions with increased drought and heat stress.

  • Yields should increase in regions with increased rainfall and warming temperatures.

  • Severe weather will cause crop damage.

  • A warmer climate will alter the kinds of crops that can be grown and increase irrigation demands.

  • Expansion of insect pests could increase vulnerability and pesticide use.

• Total world agricultural productivity is not likely to change much, but regional changes will occur, with some areas experiencing reduced productivity. Poor regions will suffer decreased productivity.

Addressing Climate Change

• Energy Efficiency and Green Energy:

  • Improving energy efficiency reduces carbon dioxide release and conserves energy resources.

  • Increase energy efficiency even if global warming is not a concern.

  • A tax on carbon emissions would increase the cost of fuels and stimulate demand for fuel-efficient products, as well as encourage the development of alternative fuels and fund research.

  • Increases in energy efficiency and reductions in greenhouse gas emissions are likely to have important related benefits that could offset the costs, such as reduced air pollution and lower healthcare costs.

• Switching to green sources of energy such as wind, solar, and hydroelectric, as well as nuclear power do not release carbon dioxide and lead to reduced carbon dioxide emissions.

• Role of Biomass:

  • Forests tie up carbon for centuries.

  • Preserving forests slows the rate of increase of atmospheric carbon dioxide, especially in tropical forests as they are very efficient at capturing carbon dioxide.

  • The burning of tropical rainforests adds carbon dioxide to the atmosphere and reduces the rainforests’ ability to remove carbon dioxide from the atmosphere. A commonly cited estimate is that 10 percent of the additional carbon dioxide entering the atmosphere is due to deforestation.

  • Planting trees has also been supported as a way to reduce atmospheric carbon dioxide.

• Technological Approaches:

  • The U.S. Department of Energy has concluded that, relying primarily on already proven technology, the United States could reduce its carbon emissions by almost 400 million metric tons, enough to stabilize U.S. emissions at 1990 levels.

  • Alternative energy sources like wind, solar, hydroelectric, geothermal, and nuclear power do not release carbon dioxide and can replace current fossil-fuel energy sources.

  • Prevent carbon dioxide from being released into the atmosphere:

    • Carbon dioxide can be reacted to produce solid carbonate minerals that could be stored in landfills.

    • Carbon dioxide can be captured and stored underground.

  • Technological changes come with a cost that will be paid by the consumer; government policies that stimulate the deployment of these technologies will be needed.

• International Agreements:

  • Montreal Protocol—Dealing with Chlorofluorocarbons. Established to phase out chlorofluorocarbon production which has resulted in CFCs in the atmosphere declining and had the side benefit of reducing the release of a potent greenhouse gas.

  • Kyoto Protocol—Dealing with Greenhouse Gases. Established in 1997, it required economically developed countries to limit their greenhouse gas emissions below 1990 levels by 2012. Economically developing countries did NOT have requirements. The United States did not officially ratify the treaty. In 2006 China became the largest emitter of greenhouse gases, followed the United States and European Union. The Kyoto Protocol expired in 2012, and an agreement was reached to extend the protocol through 2020, it required that ALL countries publish plans for reducing greenhouse gases.

  • Paris Agreement—Establishing Goals to Cut Greenhouse Gas Emissions: A follow-up to the Kyoto Protocol. The goals of the agreement are to prevent human activity from causing a $2^\circ C$ increase in global temperature this century and strive to keep it below $1.5^\circ C$. Each country publishes its plans to reduce greenhouse gas emissions (Nationally Determined Contributions (NDCs)) and report every 5 years on progress and revise plans. Developed countries pledged to provide funding to help developing countries (Green Climate Fund). The United States withdrew from the Paris Agreement in 2017 but will likely rejoin. Funding for Green Climate Fund is not meeting the goal of $100 billion.

  • Madrid Climate Change Meeting (2019) had goals to establish how each countries NDCs will be measured, establish carbon credit trading mechanism and develop plan for compensating developing countries. However, no agreement was reached, and further action was deferred to the next meeting, as current NDCs do not meet the goal of limiting temperature increase to $2^\circ C$.

  • The Kigali Agreement—Dealing with Chlorofluorocarbons and Hydrofluorocarbons, is an amendment to the Montreal Protocol which phases out the production of hydrofluorocarbons.

Summary

• Climate change is not new, with geological studies showing changes throughout Earth’s history.

• Today’s climate change is likely caused by human activities.

• The primary greenhouse gases are carbon dioxide, nitrous oxide, methane, and chlorofluorocarbons which are strongly linked to an increase in Earth's average temperature, leading to major climate changes.

• These include:

  • Warming of the Earth, particularly near the poles.

  • Melting of permafrost, glaciers, and sea ice.

  • Changes in rain and snowfall patterns.

  • Shifts in the distribution of plants and animals.

  • More intense heat waves and severe storms.

  • A rise in sea level.

  • Acidification of the oceans.

• Other likely effects are:

  • Health effects in humans.

  • Extinction of some plants and animals.

  • Flooding of cities.

  • Changes in agricultural productivity.

• The primary factor involved in climate change appears to be the carbon dioxide released from the burning of fossil fuels, but since fossil fuel use is closely tied to economic development, many developing countries are unwilling to accept limits to their use of fossil fuels.