GLOBAL CLIMATE CHANGE

Global climate change is primarily caused by increases in certain gases in the atmosphere—known as greenhouse gases—that trap heat and prevent it from escaping into space, a phenomenon called the greenhouse effect.​

The chief cause of current global climate change is the dramatic rise in greenhouse gas emissions due to human activities since the Industrial Revolution. The most important of these greenhouse gases include:​

• Carbon dioxide (CO2): Released when burning fossil fuels (coal, oil, natural gas), deforestation, and some industrial processes.​
• Methane (CH4): Emitted by livestock, rice fields, landfills, and fossil fuel extraction and transport.​
• Nitrous oxide (N2O): Produced from agricultural practices such as fertilizer usage and burning of organic matter or fossil fuels.​
• Fluorinated gases: Industrial compounds used in a variety of applications such as refrigeration and air conditioning; more potent in trapping heat but present in smaller amounts.​

• Burning fossil fuels for energy production, transport, and industry is the biggest single cause of increased greenhouse gases.​
• Deforestation reduces the planet's ability to absorb CO2 and releases stored carbon from trees into the air.​
• Agriculture, especially livestock farming, releases methane, and the use of nitrogen-based fertilizers produces nitrous oxide.​
• Industrial processes and waste management release additional greenhouse gases including fluorinated gases.​

While natural factors like volcanic eruptions, solar radiation variations, and changes in Earth's orbit (Milankovitch cycles) do affect global climate over long timescales, scientific evidence shows that these cannot account for the rapid warming observed in recent decades.​

• Aerosols and air pollution can temporarily cool the Earth by reflecting sunlight, but most greenhouse gases persist longer and have a stronger warming effect.​
• Land use changes, such as urbanization and changes in land surface, also affect the climate by altering earth's reflectivity and carbon storage.​

CauseMechanismHuman/Natural?CO2 emissions (fossil fuels)Greenhouse effectHumanMethane emissionsGreenhouse effectHuman and naturalNitrous oxide (fertilizers)Greenhouse effectHumanFluorinated gas emissionsGreenhouse effectHumanDeforestationLoss of carbon sink, CO2 releaseHumanVolcanic eruptionsAerosols/greenhouse gasesNaturalSolar variation, orbital changesAffect energy received by EarthNatural

Human activity is the overwhelming driver of the rapid global climate changes being observed today, primarily through the combustion of fossil fuels, land-use change, and agriculture, all of which amplify the natural greenhouse effect

Over the last 20 years, the global climate has warmed at an accelerating rate, with rising temperatures driving more frequent and intense extreme weather, rapid glacial melt, and rising sea levels.​

• Every year from 2015 to 2025 is projected to be among the warmest on record, with the past three years ranking as the hottest, according to the World Meteorological Organization.​
• Average global temperatures from 2025–2029 are forecasted to be 1.2°C to 1.9°C warmer than the 1850–1900 pre-industrial baseline, with an 80% chance that one of these years exceeds the current record.​
• Arctic regions have warmed more than three and a half times faster than the global average, leading to significant loss of sea ice.​

• The decade 2011–2020 saw the most rapid glacier and ice-sheet loss ever recorded, with glaciers thinning by approximately 1 meter per year.​
• Antarctic continental ice sheet loss accelerated, nearly 75% higher in 2011–2020 than 2001–2010.​
• Sea level rise has nearly doubled its rate compared to previous decades and is expected to continue as ice loss accelerates.​

• Extreme weather events—heatwaves, droughts, floods, cyclones, and wildfires—have increased in both frequency and intensity over the past two decades.​
• Major floods, severe storms, and extreme heat events have become markedly more common, with heatwaves in Europe, Asia, and the Americas reaching new records and causing tens of thousands of deaths.​
• Climate change has intensified at least the 10 deadliest extreme weather events globally in the last 20 years, making them both more likely and more severe.​

• Atmospheric concentrations of key greenhouse gases—carbon dioxide, methane, nitrous oxide—reached new highs, driving more long-term warming.​
• Ocean heat content and acidification have also worsened, causing significant impacts on marine ecosystems.​

• Extreme weather events have caused large-scale displacement, food insecurity, and billions in economic losses globally.​
• The number of casualties from such disasters has decreased due to better warnings and disaster management, but the number affected and the scale of economic damage have risen.​

In summary, the last 20 years have seen a dramatic acceleration of climate change impacts, with unequivocal evidence of increased temperatures, more extreme weather, rapid polar ice loss, higher sea levels, and mounting social and economic costs—all driven overwhelmingly by human activities.​

If global climate change continues unabated, the consequences will be severe and widespread, impacting the environment, human health, economies, and societies worldwide.

• Temperature rise: Global average temperatures could increase by 2°C or more above pre-industrial levels by mid-century, leading to unprecedented heatwaves and altered climate patterns.​
• Sea level rise: Continued melting of glaciers and ice sheets will accelerate sea level rise, threatening coastal cities, small island nations, and low-lying areas with flooding, erosion, and saltwater intrusion.​
• Ecosystem disruption: More frequent extreme weather, droughts, and changing precipitation will disrupt habitats, causing loss of biodiversity and mass extinctions, especially in vulnerable ecosystems like coral reefs and Arctic habitats.​
• Ocean changes: Increased ocean warming and acidification will threaten marine species, fisheries, and coral reefs, undermining ocean food webs and biodiversity.​

• Heat-related illnesses: Rising temperatures will increase heat stress, heat strokes, and related deaths, particularly among vulnerable populations such as the elderly and those with preexisting conditions.​
• Food and water security: Droughts, floods, and changing growing seasons will reduce agricultural yields, threaten food supplies, and exacerbate water scarcity in many regions.​
• Displacement: Millions of people may be forced to migrate due to sea level rise, extreme weather events, and resource shortages, increasing pressure on urban areas and creating geopolitical tensions.​
• Disease spread: Changes in climate favor the spread of vector-borne diseases like malaria and dengue fever into new regions.​

• Damage to infrastructure: More frequent and intense storms, floods, and wildfires will cause increasing damage to infrastructure, homes, and transportation networks, raising repair and insurance costs.​
• Economic losses: The global economy could face trillions in losses due to decreased productivity, disaster recovery costs, and disruptions to trade and supply chains.​
• Inequality: Vulnerable and poorer communities will bear the brunt of climate impacts, exacerbating existing inequalities and social unrest.​

• Warming may trigger feedback loops like methane release from thawing permafrost and loss of ice-albedo effect, accelerating climate change beyond current projections.​
• Some changes, such as the loss of major ice sheets or extinction of key species, could become irreversible on human timescales.​

In conclusion, failure to limit global climate change will lead to catastrophic environmental degradation, severe threats to human health and livelihoods, large-scale economic damage, and increased social instability. Urgent global action to reduce greenhouse gas emissions and adapt to unavoidable changes is critical to mitigating these outcomes.​