Disruption of the carbon cycle by fossil fuel combustion

Fossil fuels, such as coal, oil, and gas, have been a primary energy source for industrial and domestic purposes since the Industrial Revolution in the UK during the mid-18th century. Their widespread use has significantly altered the natural balance of carbon in the environment. This occurs because fossil fuels store large amounts of carbon that have been locked away underground for millions of years.

When these fuels are burned, a process called combustion breaks down their chemical bonds, releasing heat energy along with carbon-based gases. This releases stored carbon into the atmosphere at a rapid rate, far exceeding natural processes.

Key greenhouse gases released from fossil fuel combustion

• Carbon dioxide (CO₂)
• Methane (CH₄)

Role of carbon sinks and sequestration

Although carbon sinks continue to sequester some of the excess carbon, the rate of greenhouse gas emissions from fossil fuels has outpaced this absorption. As a result, atmospheric concentrations of these gases have risen steadily.

Consequences for the carbon cycle

Fossil fuel combustion disrupts the natural balance of carbon within the carbon cycle by adding extra carbon that overwhelms natural processes, leading to an imbalance where more carbon enters the atmosphere than is removed. This disruption contributes to the enhanced greenhouse effect.

Impacts of climate change on global climate patterns

The enhanced greenhouse effect has led to a rise in average global temperatures, a phenomenon known as climate change. This warming influences weather systems and atmospheric circulation worldwide, often making patterns more extreme and unpredictable.

The thermohaline circulation system is likely to alter or weaken in certain areas

• Warmer temperatures cause ice sheets, such as those in Greenland, to melt faster, adding fresh water to the oceans.
• This reduces ocean salinity, making it less dense.
• Lower salinity disrupts downwelling.
• As a result, the thermohaline circulation may weaken or shift, affecting how air rises and falls between the equator and poles, which influences global wind patterns and weather.

Climate change alters rainfall distribution and intensity due to increased atmospheric warmth

• Dry regions are becoming drier.
• Wet regions are experiencing more rainfall.
• Overall, rainfall patterns have become unpredictable, with some areas facing extended droughts while others see unseasonal heavy precipitation.
• Extreme weather events, such as storms, are increasing in frequency and intensity due to warmer atmospheric conditions, which lead to increased evaporation and humidity.

Effects on the hydrological cycle

Rising global temperatures are intensifying the hydrological cycle, leading to imbalances in water distribution and availability.

Higher temperatures accelerate the melting of glaciers and ice sheets

• This increases the volume of water in glacier-fed rivers, raising the risk of flooding in downstream areas.
• Meltwater flows into the oceans, contributing to sea level rise.

Warming enhances evaporation, leading to shifts in precipitation patterns

• Increased precipitation in some areas leads to more frequent floods.
• These shifts disrupt the overall balance of the hydrological cycle.

Consequences for ecosystems and biodiversity

Ecosystems are highly sensitive to climate change driven by carbon cycle disruptions. Rising temperatures, altered water cycles, and other changes are reducing biodiversity.

Impacts on vegetation and permafrost

• Plants sensitive to temperature changes are declining in number, leading to reduced biodiversity in affected biomes.
• Permafrost is thawing due to warmer conditions, shortening frozen seasons and making it difficult for specialised vegetation adapted to cold, stable soils to survive.

Species migration and extinction risks

• Some species are migrating to new areas to remain within their required niche.
• Vulnerable species with low population numbers or fragile habitats face a higher risk of extinction.

Coastal and marine ecosystem losses

• Rising sea levels are submerging low-lying coastal areas, leading to ecosystem loss.
• Rising ocean temperatures are causing coral bleaching, and ocean acidification is weakening coral structures, which harms marine life and places coral reefs under severe threat.