What Is Climate Change?

Climate change is the long-term alteration of average weather conditions such as temperature and rainfall. This can happen on a local, regional or global scale.

Human activities are causing climate change by burning fossil fuels (coal, oil and gas) that release greenhouse gases into the atmosphere. These gases trap heat from the sun and warm Earth.

Changes in Temperature

The average temperature of the Earth has gone up about a degree Fahrenheit in the last century. This may not seem like a lot, but it can have big effects on plants and animals.

Climate refers to the long-term regional or global average of temperature, humidity and rainfall patterns over seasons, years or decades. Weather changes quickly - usually in just a few hours - but climate changes over longer timeframes.

Human-induced climate change is the result of burning fossil fuels, cutting down forests and farming livestock. This causes greenhouse gases to build up in the atmosphere, trapping heat from the sun and warming the earth's surface.

The warming is affecting the natural world and poses a risk to our health. As the temperature increases, more extreme weather events are expected. Those extremes can include heavy rainfall, drought and heat waves. These weather conditions can cause stress and illness, leading to greater mortality in people and other creatures.

Changes in Rainfall

Climate change affects many aspects of human life - from water availability and energy supply to transportation and wildlife. But it also has a direct effect on rainfall.

Precipitation is the movement of water from the atmosphere to the surface and it depends on the patterns of air circulation and ocean flow. It is a critical element of the water cycle.

As the Earth warms, warmer air can hold more water vapour than colder air can. This means that it can rain more frequently and more intensely.

But if there is more evaporation than rainfall, it can lead to drought conditions. This can have a serious impact on human health and ecosystems.

A study shows that the majority of the world's population rely on a predictable rainfall pattern to plan agriculture (rain-fed). If the pattern changes erraticly, food insecurity will result.

Changes in Ocean Temperature

The ocean covers more than 70% of the Earth’s surface, and it absorbs excess heat and energy from rising levels of greenhouse gas emissions. The warming ocean leads to unprecedented cascading effects such as ice-melting, sea-level rise, marine heatwaves, and ocean acidification.

The top 2,000 meters of the ocean’s water is the warmest, with temperatures that are similar to those in the air. Below that, colder water is found.

Climate change has caused the global average ocean temperature to rise, and it continues to increase. It is causing unprecedented changes in the marine ecosystem, affecting food supplies and economies.

The ocean also absorbed excess carbon dioxide from fossil fuels released into the atmosphere. It has been reducing oxygen in the water, which can be harmful to marine life.

Changes in Sea Levels

Sea levels can rise in two ways: as glaciers and ice sheets melt or expand due to global warming, or when water shifts from land to the ocean. A third, much smaller contributor is a decline in the amount of liquid water on land.

This shift can be caused by groundwater pumping, lakes and reservoirs that empty into the ocean, and rivers that dry out. The combined effects of these changes make coastal flooding worse.

Coastal communities and infrastructure are particularly vulnerable to rising seas, as is a growing number of people living in low-lying coastal areas less than five meters above high tide. These impacts can be devastating, with many islands and coastlines becoming uninhabitable and countless people forced to migrate.