Global Warming and Climate Change

The Earth's temperature has fluctuated over the last few centuries.
A dramatic increase in global temperatures has occurred since 1950, termed global warming.

Thermometer Readings: Annual global temperature increase (°C).
- Graph illustrates temperature increase from 1971 to 2021.

Definition: A natural process where greenhouse gases trap heat in the Earth’s atmosphere.
Process:
1. Solar radiation passes through the atmosphere as short-wave radiation and heats the Earth's surface.
2. The Earth's surface emits heat as long-wave radiation.
3. Greenhouse gases (e.g., methane, carbon dioxide, nitrous oxide) trap some of this outgoing heat, radiating it back toward the Earth, maintaining warmth.
- Importance: Without the greenhouse effect, Earth's surface would be too cold, affecting life forms.

Ongoing temperature recordings using thermometers show a clear increase in Earth's temperature over the decades.
Scientists found the Earth's average surface air temperature has increased by around 1°C since 1900.
The period from 2010 to 2020 was noted as the warmest decade on record.

Short-Wave Radiation: Passes through the atmosphere.
Long-Wave Radiation: Heat emitted by the Earth is absorbed and reflected by greenhouse gases.
More heat is absorbed due to the increased concentration of greenhouse gases, leading to less long-wave radiation escaping the atmosphere.

Burning Fossil Fuels
- Impact: Releases large amounts of carbon dioxide (CO₂), a major greenhouse gas.
- Data Point: In 2022, global CO₂ emissions from fossil fuels reached about 37 billion tonnes.
- Major sources include coal and oil-fired power stations, particularly in China and the USA.
Deforestation
- Trees absorb CO₂, acting as carbon sinks.
- Deforestation for agriculture and urban development reduces tree numbers; slash-and-burn methods release stored carbon.
- Example: Large areas of the Amazon rainforest were cleared for cattle farming, resulting in over 10,000 km² lost in 2020.
Agriculture
- Greenhouse Gases Produced: Methane (CH₄) and nitrous oxide (N₂O).
- Methane emissions originate from livestock digestion and rice paddies; nitrous oxide comes from fertilizers.
- Example: New Zealand’s agriculture sector produces nearly 50% of its total greenhouse gas emissions.
Industrial Processes
- Manufacturing processes release greenhouse gases, such as CO₂ during cement production.
- Data Point: Cement production accounts for 7-8% of global CO₂ emissions.
Waste Management
- Decomposition of organic waste produces methane (25 times more effective than CO₂).
- Landfills in the USA are a significant source of methane emissions.
Urbanization
- Increases energy demand and transport use while reducing green spaces.
- Urban areas are responsible for over 70% of global CO₂ emissions.

Warmer temperatures cause water expansion and melting ice.
Data Point: Average sea level has risen 23 cm since 1880 and is forecast to increase a further 30 cm by 2050.
Significance: Low-lying areas face increased flooding; certain islands may become uninhabitable.

Biome locations may shift north and south; polar and tundra biomes face extinction risks.
Example: The Arctic has lost 13% of sea ice cover, affecting polar bear populations who have declined by 30% since late 1980s due to starvation.
Changes also affect fish migration and animal hibernation patterns due to warmer temperatures.

Flooding, droughts, and wildfires lead to loss of habitats and decreased food sources, impacting food webs and vegetation.
Example: Wildfires in the western USA doubled between 1884-2015.

Changing climate conditions may force farmers to adapt or change crops and livestock types due to droughts and altered rainfall patterns.
Potential invasive species may thrive, increasing the risk to local agriculture.

Job opportunities in some sectors like tourism may decline due to climate impacts.
Farmers may need to change crops or livestock or leave farming altogether, affecting local economies.

Increased temperatures and extreme weather events raise the risk of disease spread and health issues.
Case Study: Italy saw malaria cases resurgence in 2017, previously malaria-free since ancient times.

Increased flooding may displace populations living in vulnerable areas.
Estimates indicate that 750,000 people in New Zealand reside near flood-prone areas, with high costs associated with property damages from extreme weather events.

Definition: Adjusting to the impact of climate change.
Possible strategies include:
- Water Supply Management: Transferring water from surplus to areas in need.
- Building Sea Defenses: Protecting areas at risk from sea-level rise through engineered defenses.

Definition: Reducing the causes of climate change.
Possible strategies include:
- Alternative Energy: Promoting solar, wind, and tidal energy; reducing fossil fuel dependency.
- Carbon Capture: Capturing CO₂ emissions from power stations and storing them underground.
- Planting Trees: Increasing afforestation for better CO₂ absorption.

Kyoto Protocol (2005): Countries pledged to reduce greenhouse gas emissions.
Paris Agreement (2016): Aims to limit global warming to below 2°C, preferably 1.5°C; annual COP meetings facilitate international cooperation on climate action.
COP28 held in Dubai from 30th November to 13th December 2023 to set further climate actions.