Climate change

Climate change describes a broad range of global phenomena affecting Earth's climate system. It includes changes in temperature, precipitation patterns, and extreme weather events. A major component of this is global warming, which is the upward trend in global average surface temperature. While global warming focuses on heat, climate change is a more accurate scientific term for the total impact. It accounts for ocean acidification, sea level rise, and shifting rainfall. These changes can happen through natural processes or human activities.

The mechanism behind modern warming involves greenhouse gases. These gases, such as carbon dioxide, methane, and nitrous oxide, trap heat in the lower atmosphere. When the Earth warms from sunlight, it radiates heat back toward space. Greenhouse gases absorb some of this heat instead of letting it escape. This process creates an energy imbalance. Since the pre-industrial era, carbon dioxide levels have risen by roughly 50%. This has brought concentrations to levels not seen for millions of years.

Human activities drive most of this modern warming. The burning of fossil fuels like coal, oil, and natural gas is a primary cause. Deforestation and certain industrial or agricultural practices also release these gases. Between the 18th century and 1970, there was little net warming. This was because sulfur dioxide emissions created sulfate aerosols. These aerosols reflect sunlight and cause global dimming, which offset greenhouse warming. However, after 1970, the accumulation of greenhouse gases began to outpace this cooling effect.

Scientists have tracked these changes using various data sets. For the 2014–2023 decade, observed warming was 1.19 °C. Of that amount, 1.19 °C was human-induced. The warming is not uniform across the planet. Land surface air temperatures have risen nearly twice as much as the global average. The oceans play a massive role in managing this heat. They absorb over 90% of the heat from global warming. This leads to rising ocean heat content and ocean acidification.

The impacts of a warming planet are widespread and severe. In the Arctic, warming is amplified, leading to thawing permafrost. This contributes to the retreat of glaciers and the decline of sea ice. The shrinking cryosphere includes loss from ice sheets and reduced snow cover. Other regions face expanding deserts and land degradation. Extreme weather is also becoming more common. This includes more intense storms, droughts, and heat waves. These rapid changes force many species to relocate or face extinction.

Human societies face significant risks from these environmental shifts. Climate change threatens people with increased flooding and extreme heat. It also leads to food and water scarcity, more disease, and economic loss. These pressures can cause human migration and conflict. The World Health Organization views climate change as a major threat to global health. While some communities use adaptation, such as flood control or drought-resistant crops, there are limits. Some ecosystems have already reached "hard" adaptation limits. Poorer communities are often the most vulnerable because they have the least ability to adapt.

Global efforts are underway to mitigate these risks. Under the 2015 Paris Agreement, nations agreed to keep warming well under 2 °C. Currently, projections suggest warming could reach 2.6 °C to 2.8 °C based on existing pledges. To prevent this, many countries have adopted net-zero pledges. This means they aim to stop emitting greenhouse gases. One solution is transitioning to clean energy sources. These include wind, solar, hydro, and nuclear power. We can also remove carbon from the air by increasing forest cover or using specific farming methods.