Global Climate Change: A Geographical Overview

• The unit explores the geographical dimensions of global climate change.

Climate Change Fundamentals

• Earth is around 4,500 million years old and has experienced significant climatic changes.
• Early atmospheric conditions made life impossible due to heat retention.
• The Earth originated during the Hadean eon, ending 3,800 million years ago.

Geological Time Scale

• Eons include Hadean, Archaean, Proterozoic, and Phanerozoic.
• Eras are subdivisions of eons; the Phanerozoic eon includes Paleozoic, Mesozoic, and Cenozoic eras.
• Periods are divisions within eras; the Cenozoic era includes the Tertiary and Quaternary periods.
• Epochs are divisions within periods; the Quaternary period includes the Pleistocene and Holocene epochs, with the Holocene epoch starting 10,000 years ago.

Climate Evolution Across Geological Eras

• During the Archaean eon, the atmosphere contained methane and ammonia, later toxic to life.
• The first life forms (primitive bacteria) appeared in the oceans during the Archaean eon.
• The Proterozoic eon saw the diversification of life in the seas, with eukaryotic cells and multicellular organisms emerging.
• The Paleozoic era, beginning 542 million years ago, saw the rise of various life forms like trilobites; life transitioned from marine to terrestrial environments.
• The Paleozoic climate had fluctuations, with warmer, stable periods, high sea levels, and reduced land area, along with glacial periods that caused species displacement and extinctions.
• During the Paleozoic era, giant ferns grew up to 30 meters tall, and animals like the Meganeura dragonfly (70 cm), Stenodyctia cockroach (10 cm), and Diplovertebron amphibian existed.
• The Mesozoic era started 251 million years ago, ending 65 million years ago, marking the "age of reptiles" with dinosaurs and other large reptiles, as well as plants like ferns, gymnosperms, and conifers.
• The Mesozoic climate was influenced by the supercontinent Pangea, creating diverse climates, with humid coastal regions and dry inland conditions.
• In early Mesozoic, there were tropical rainforests, grasslands, and coniferous forests, while the breakup of Pangea led to increased humidity and warmer temperatures in more areas.
• Near the end of the Mesozoic era, a meteor impact caused a major climate shift with a dust cloud covering the planet, leading to a prolonged winter and the extinction of many species, including dinosaurs.
• The Cenozoic era began 65 million years ago, defined by radical changes and the survival of species after the Mesozoic extinction event; it saw the development of current dominant groups (mammals).

Climate Oscillations and Glaciations

• The Cenozoic era experienced significant climate oscillations, with an initially warm and wet climate, followed by cooler periods alternating with temperate ones.
• Over the past 1,800 million years, Earth has alternated between cold phases with extensive ice cover and warmer interglacial periods, with present times being in a less cold phase.
• Geological periods with early hominids saw glacial and interglacial cycles; intense cold led to lower sea levels, exposing previously submerged lands, while warmer phases increased sea levels.
• Glaciations and interglaciations caused climate changes like droughts in tropical areas; these changes tested the intelligence of early humans, leading to migrations and social adaptations like forming tribes.

Climate Changes in the Last Millennium

• The Medieval Warm Period (700-1300) saw warmer conditions than today, benefiting agriculture and allowing crops like grapes to grow in new regions, such as England, leading to population growth.
• The Medieval Warm Period allowed Arctic ice to recede, enabling Viking expansion into areas like Iceland and Greenland.
• This period had droughts in the Mediterranean and a drop in the Caspian Sea level.
• The Little Ice Age (1350-1850) was marked by declining temperatures, manifested mainly in severe winters, causing the disappearance of vineyards in England and ending agricultural prosperity in Iceland and Greenland.
• Glaciers in the Alps expanded, destroying villages, and rivers like the Thames in London froze, posing unusual issues.
• Scientists are studying causes of the Little Ice Age, including reduced solar radiation and volcanic eruptions.
• Volcanic activity affects climate variations; the eruption of the Huaynaputina volcano in Peru (1600) caused a temperature drop of 0.8°C in the Northern Hemisphere the following summer.
• Benjamin Franklin noted decreased solar radiation in 1783 due to the eruption of the Laki volcano in Iceland, causing glacial cold in Europe and North America.

Climate Change Studies from the 19th Century to Present

• The Industrial Revolution from the 19th century increased greenhouse gas accumulation, accelerating Earth's warming through coal use, which initiated air pollution with industrial gases.
• In the 19th century, scientists began studying climate conditions; Joseph Fourier (1824) proposed that the Earth would be much colder without an atmosphere.
• By 1850, scientists concluded that carbon dioxide (CO₂) and water vapor trapped heat, causing global warming.
• The 20th century saw specific temperature measurements in the U.S., confirming a rise in temperature over the previous 50 years, as well as increased methane concentration in the atmosphere.
• A climate conference in Austria (1985) aimed to raise awareness of climate change, but lacked government support for environmental policies.
• In 1988, the Intergovernmental Panel on Climate Change (IPCC) was established by the UN and the World Meteorological Organization (WMO) to investigate climate change, including future scenarios and its impact on life.
• In the 1990s, climate change studies intensified, using ice cores from Antarctica and tree rings to reveal links between carbon dioxide levels and global temperatures.
• The Framework Convention on Climate Change (1992) was signed by 150 nations to reduce human impact on climate, defining climate change as "a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods."

Climate Change and the Greenhouse Effect

• Humans are facing climate variations, termed global climate change, with current climate change happening faster.
• Investigations confirm that the global average temperature has risen in the last 100 years (between 0.3°C and 0.6°C from 1860 to 2000).
• The IPCC estimates a potential global temperature increase of 1.5°C by the end of the 21st century, compared to 1850-1900 levels.
• The greenhouse effect is a natural process where solar radiation enters the atmosphere, is filtered, and interacts with Earth's surface, with some radiation being reflected and some absorbed by greenhouse gases.
• Greenhouse gases (GHG) include water vapor, carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and ozone (O₃), maintaining an average surface temperature of 15 °C, essential for life. Without this effect, Earth's average temperature would be -17 °C.
• The hypothesis is that an enhanced greenhouse effect results from increased greenhouse gases due to human activities.
• This is increasing pollution through increased emissions of carbon dioxide, methane, and chlorofluorocarbons due to burning fossil fuels, electricity production, vehicle emissions, deforestation, and fires.
• Chlorofluorocarbons are regulated due to their impact on the environment and were previously used in aerosols and refrigeration.

Natural vs. Accentuated Greenhouse Effect

• The natural greenhouse effect is essential for maintaining Earth's temperature, while the accentuated greenhouse effect is due to human activities.
• Gases involved in the greenhouse effect include water vapor, carbon dioxide, methane, nitrous oxide, and ozone.
• Human activities contributing to the accentuated greenhouse effect include burning fossil fuels, electricity generation, vehicle emissions, and deforestation.

Greenhouse Gases

• Water vapor is the most abundant GHG, unaffected by human influence.
• Carbon dioxide is necessary for photosynthesis and comes from fossil fuel combustion and deforestation.
• Nitrous oxide is naturally produced in oceans and from human activities like agriculture and burning fuels.
• Methane is important for tropospheric oxidation, coming from livestock manure, rice cultivation, burning pastures, and solid waste decomposition.
• Ozone protects against solar radiation and is formed by photochemical reactions from pollutants (smog).
• Before the Industrial Revolution (pre-industrial era), carbon dioxide concentration was approximately 275 ppm in 1750.
• By 2015, global carbon dioxide concentrations reached 400 ppm, a 44% increase from pre-industrial levels.

Historical Carbon Dioxide Emissions

• From 1850 to 1960, the largest carbon dioxide emitters were the United States, England, Russia, Germany, and China.
• England was the top polluter from 1850 to around 1890.
• The United States became the primary carbon dioxide source between 1890 and 1960, while China’s emissions increased around 1950

Fossil Fuels

• The increased greenhouse effect is from human activities like burning fossil fuels.
• Fossil fuels are energy sources formed from ancient remains of living organisms.
• The main fossil fuels include petroleum, coal, and natural gas.

Petroleum

• Petroleum comes from the remains of organisms, requiring a refining process to separate elements like gasoline, kerosene, diesel, lubricating oils, asphalt, and paraffin.
• Gasoline, kerosene, and diesel are widely used but emit significant amounts of CO₂.
• Derivatives of petroleum have different applications in transport, construction, and industry.
• Asphalt is used for roads, floors, and tiles.
• Ether is used as a solvent.
• Paraffin is used in lubricants, cosmetics, pharmaceuticals, paper, and candles.
• Lubricating oils are used to protect engines from corrosion.
• Gasoline, kerosene, and diesel power vehicles, stoves, and lamps.

Coal

• Coal is the most abundant fossil energy source, found in solid form with derivatives.
• Coke is used to melt iron and steel.
• Tar is used in heating, as an anti-corrosive agent, and in medicinal creams.
• Gas from coal is used to generate electricity.
• Burning coal for electricity is damaging to the environment due to less efficient machinery, resulting in greater carbon dioxide emissions.
• China is the largest coal consumer for electricity, followed by the US, India, Japan, Germany, and South Africa.

Natural Gas

• Natural gas is a mixture of gases, mainly methane, in subsurface rock formations.
• Natural gas is used for cooking, heating, and electricity generation.
• Natural gas emits less carbon dioxide and fewer pollutants compared to petroleum and coal when burned.