Dynamics of Climate Change

Climate change refers to rising temperatures and shifting precipitation patterns on Earth. People and scientists have observed that the climate of Earth is warming and is having significant impact on the quality of life. What is happening?

The Source of Earth’s Energy

The sun is a ball of hot plasma, heated by nuclear fusion reactions. The sun emits this energy as light, ultraviolet and infrared radiation. This energy heats the Earth. Over the millennia, some of this energy has accumulated and has been stored in the form of coal, gas, oil and calcium carbonate (CaCO_3, limestone and marble.) Since the invention of the automobile much stored energy has been burned, converting it to greenhouse gas.

Earth’s Systems

Earth has a complex web of systems interacting with feedbacks, delays, stocks and flows. Earth’s systems are the atmosphere, hydrosphere, biosphere and geosphere. All influence each other.

Feedbacks occur when warming leads to changes that further accelerate warming. For example:

• When icecaps melt, earth, rock and water, which absorb heat more than snow, are exposed causing further warming.
• Warmer oceans have less cooling effectiveness.
• Another accelerating feedback loop occurs when global warming leads to more forest fires that add more CO₂ to the atmosphere.

Delays or lags occur as follows. Warming temperatures melt icecaps and glaciers, and warm the oceans. It takes decades, sometime centuries for the ice to melt and oceans to warm. During the melting phase, stream flows increase. Only when the ice is gone (when the stock of ice has melted) does the stream flow slow and become more cyclical. Flows of water available for irrigation diminishing in summer when water is needed. Only when the oceans have warmed do they loose their cooling effect.

Changing balances in energy flows and the operation of Earth’s systems accelerate climate change at a faster and faster rate.

It has taken years for the burning of fossil fuels to build the stock of CO₂ in the atmosphere. Once CO₂ has accumulated in the air and temperatures have risen, it takes centuries for the biosphere and geosphere to remove the CO₂, for the icecaps to rebuild and for the oceans to cool.

The Atmosphere

The atmosphere is a thin layer of gases above the Earth’s surface. It contains the air that allows us to breathe. It is where many of the important processes of climate happen, where rain and storms are generated.

The composition of the atmosphere regulates the amount of energy from the sun that reaches the surface of the Earth. The atmosphere absorbs the sun’s energy during the day. That energy leaves Earth’s surface in three ways:

1. radiation – infrared heat escapes directly into space
2. convection –warm air rises, and
3. latent heat transfer occurs when water evaporates

Droplets reflect energy and reduce the amount of energy that reaches the Earth’s surface. The atmosphere hosts water vapour that creates clouds and leads to precipitation. It contains CO₂ that plants convert to cellulose, sugars and starch.

The Greenhouse Effect

The sun gives off energy in the form of shortwave radiation because it is hot. The Earth gives off long wave radiation.

The greenhouse effect is the additional energy Earth retains from the increasing concentration of CO² and other greenhouse gases in the atmosphere. Greenhouse gases include:

• Carbon dioxide CO₂ responsible for 24% of global warming
• Water H₂O which is responsible for 67% of global warming under clear sky conditions
• Nitrous Oxide N₂O
• Methane CH₄

Greenhouse gases in the air absorb particular wavelengths of radiation emitted by Earth’s surface, then re-emit the radiation in all directions, slowing the passage of energy back into space. Increasing concentration of greenhouse gasses in the atmosphere increases the greenhouse effect by further slowing the return of infrared energy back to space. The net effect is to warm the atmosphere, oceans and surfaces of the Earth.

The Carbon Cycle

Carbon is found in fossil fuels, (oil, coal and gas deposits) in rocks, oceans, soil, plants and trees. The atmosphere swaps hundreds of gigatons of carbon with the terrestrial biosphere (mainly plants) and with oceans. (See the Ecological Science).

By burning increasing amounts of fossil fuels, manufacturing cement, burning trees and other plants, people are increasing the amount of CO₂ in the atmosphere sufficiently to warm the planet. Warming the planet is having a harmful impact on the climate, leading to more intense storms, longer periods of drought, melting of glaciers and warming of oceans. (For more detail see Impact of Global Warming.)

Greenhouse gases remain on Earth for extended periods, leading to slow reduction of gas concentrations. Processes that remove CO₂ and other gases from the atmosphere occur slowly, leading to a significant lag time for removal of these gases from the atmosphere.

Some flows, those involving land plants and the surface of ocean, happen quickly and occur in seasonal ebbs and flows, but the output of hydrocarbons from human activities continuously increases the concentration of CO₂ in the atmosphere.

The primary process that removes CO₂ from circulation on long time scales are chemical weathering of silicate rock and carbon sinks (burial of organic carbon).

The Biosphere

(See Photosysthesis)

The Biosphere moderates the carbon cycle. Photosynthesis is a key process that reduces CO₂ in the atmosphere. Earth’s plants and animals absorb and store more carbon in the form of cellulose, starches and sugars than they return to the atmosphere through plant respiration.

The Hydrosphere – The Water Cycle

The circulation of water on Earth is called the water cycle. The atmosphere absorbs water. Water, evaporating from oceans, lakes and rivers, circulates in the atmosphere and returns to Earth in the form of precipitation. Evaporating water rises in air because the water vapour reduces the overall density of the air closer to the surface of the Earth. This convection helps transfer energy upward. The warmer upper atmosphere can radiate more energy into space.

Water vapour responds quickly to temperature changes, creating a feedback effect. With warmer temperatures there is more moisture in the atmosphere. When there is more water in the atmosphere there is increased warming.

Warming of lakes and oceans also amplifies the greenhouse effect. Carbon dioxide is released into the atmosphere from warmer water. Cold water has a capacity to hold more CO² than warm water.

Reflectivity

Warming of the Earth’s surface results in part from reduced reflectivity. Thirty percent of solar radiation is reflected from the Earth’s surface. The surface of oceans, lakes, glaciers and snowpacks both absorb and reflect the sun’s energy. Reduction of snow/ice surfaces leads to overall reduction of Earth’s reflective abilities. People alter Earth’s reflectivity by burning fossil fuels and changing land use.

The Geosphere

Over millennia, plants have contributed to the storage of carbon in the form of coal and gas. Coral reefs have contributed to the storage of carbon leading to the formation of limestone and marble. Volcanoes are temporary cooling devices, reflecting the sun’s energy and releasing tiny amounts of CO₂.

Human Impact

Since the start of the industrial revolution, humanity has increased the concentration of greenhouse gasses in the atmosphere. Fossil fuels account for 80% of our energy supply. Carbon emissions have grown from .003 Gigatons per year in 1751 to about 10 Gigatons per year in 2018. Forty five percent of our emissions stay in the atmosphere, accumulating over time.

Methane from swampy lands used for rice cultivation has increased the production of methane.