History of climate change and the causes

Over the past century, climate change has evolved from a scientific curiosity to a global crisis. The Earth’s climate, which once changed gradually over millennia due to natural forces, has now been drastically altered by human activities within just a few generations. These changes have profound implications for ecosystems, human societies, and the planet’s future stability.

Early Recognition of Climate Change

In the early 20th century, scientists first began to recognize that human activities, especially the burning of fossil fuels, could impact the Earth's climate. In the 1930s, British engineer Guy Stewart Callendar made the connection between rising global temperatures and increased levels of carbon dioxide (CO2) from industrial activities. His work laid the groundwork for future climate research. However, it wasn’t until the 1950s that precise measurements confirmed these changes, most notably through the work of Charles David Keeling, who developed the Keeling Curve to track rising atmospheric CO2 concentrations at Mauna Loa Observatory in Hawaii. His data showed a steady and alarming rise in CO2 levels, which has continued to this day.

The Causes of Climate Change

The primary cause of climate change is the increase in greenhouse gases (GHGs) in the atmosphere, especially CO2, methane (CH4), and nitrous oxide (N2O). These gases trap heat in the Earth’s atmosphere, creating a “greenhouse effect” that leads to global warming. Human activities, primarily the burning of fossil fuels such as coal, oil, and natural gas, have been the major driver of GHG emissions.

• Fossil Fuel Combustion: Since the Industrial Revolution, the burning of fossil fuels for energy has dramatically increased the concentration of CO2 in the atmosphere. Power plants, transportation, and industrial processes all contribute to this rise. The rapid expansion of the global economy after World War II fuelled a significant increase in energy consumption, leading to a corresponding spike in emissions.
• Deforestation: Forests act as carbon sinks, absorbing CO2 from the atmosphere. However, deforestation, particularly in tropical rainforests like the Amazon, has reduced the planet's capacity to absorb CO2, further exacerbating climate change. The conversion of forests into agricultural land, especially for cattle grazing and soy production, has led to large-scale deforestation.
• Agriculture and Land Use: Agricultural activities, such as rice cultivation and livestock farming, release significant amounts of methane and nitrous oxide, both potent GHGs. Methane, produced by cattle digestion and manure management, is about 25 times more effective than CO2 at trapping heat in the atmosphere. Nitrous oxide, released from fertilizers, is even more potent, contributing to both climate change and ozone layer depletion.
• Industrial and Waste Processes: Industrial processes, including cement production, also contribute to GHG emissions. Waste management practices, such as the decomposition of organic waste in landfills, release methane.

The Impacts of Climate Change

As a result of these activities, global temperatures have risen by approximately 1.1°C since the late 19th century. This warming trend has accelerated over the last few decades, with the 21st century experiencing record-breaking temperatures almost every year. The consequences of this warming are wide-ranging and severe.

• Melting Ice and Rising Sea Levels: Polar ice caps and glaciers have been melting at unprecedented rates, contributing to sea level rise. This threatens coastal communities, with millions of people at risk of displacement due to flooding.
• Extreme Weather Events: Climate change has led to more frequent and intense weather events, including heatwaves, hurricanes, floods, and droughts. These events cause widespread damage to infrastructure, disrupt agriculture, and threaten water supplies.
• Ocean Acidification: As oceans absorb more CO2, they become more acidic, which negatively affects marine ecosystems, particularly coral reefs and species that rely on calcium carbonate to form shells or skeletons.
• Biodiversity Loss: Warming temperatures and habitat destruction have led to the decline of many species, with scientists warning of a potential sixth mass extinction.

Responses to Climate Change

The scientific consensus on climate change has led to international efforts to address the crisis. The 1997 Kyoto Protocol was the first global agreement aimed at reducing GHG emissions, but its impact was limited by non-participation from key countries. The 2015 Paris Agreement marked a significant step forward, with nearly every country committing to limit global warming to below 2°C, with efforts to keep it below 1.5°C.

Despite these efforts, progress has been slow. Many countries continue to rely heavily on fossil fuels, and global emissions have yet to peak. However, there are growing movements toward renewable energy, sustainable agriculture, and conservation, offering hope for mitigating the worst impacts of climate change.