Climate change

Climate is the long-term pattern of weather in a particular place, including factors such as temperature, rainfall, and wind. While weather describes day-to-day conditions, climate reflects the average weather patterns and variations experienced over many decades, typically 30 years or more.

Climate change refers to long-term changes in the Earth’s climate, including rising temperatures and shifts in weather patterns. While climate naturally changes over time, the rapid warming observed since the mid-20th century is mainly caused by human activities such as burning fossil fuels and deforestation, which increase the amount of greenhouse gases in the atmosphere.

Greenhouse gases trap heat, warming the planet and affecting the climate system. As a result, climate change is contributing to rising sea levels, melting ice, changing rainfall patterns, and more frequent or intense extreme weather events such as heatwaves, droughts, and heavy rainfall. Scientists know that human activities are the main driver of recent climate change because observations and climate models show that the warming seen today cannot be explained by natural factors alone.

Greenhouse gases are gases in the atmosphere that trap heat and help keep the Earth warm. They include carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O), which absorb some of the heat radiated from the Earth’s surface and prevent it from escaping into space.

This natural greenhouse effect is essential for life on Earth. However, human activities such as burning fossil fuels, deforestation, and agriculture have increased the concentration of greenhouse gases in the atmosphere, causing the planet to warm rapidly.

Atmospheric scientists measure climate change by collecting observations of the Earth’s atmosphere, oceans, ice, and land over long periods of time. They use data from weather stations, satellites, ocean buoys, aircraft, and ice cores to track changes in temperature, rainfall, greenhouse gases, sea level, and other indicators of climate change.

Scientists compare these observations over decades to identify long-term trends and use climate models to understand the causes of observed changes and predict how the climate may change in the future.

A climate model is a computer simulation of the Earth’s climate system, including the atmosphere, oceans, land, and ice. Scientists use climate models to understand how the climate works, and predict how the climate may change in the future under different scenarios.

Climate models are based on established physical laws and are continually tested against real-world observations, helping scientists improve climate predictions and assess the impacts of climate change.

As the climate warms, many regions are experiencing more frequent and intense extreme weather events, including heatwaves, heavy rainfall, droughts and wildfires.

A warmer atmosphere can hold more moisture and energy, increasing the likelihood of some types of extreme weather and changing weather patterns over time.

Climate change affects air quality by changing the weather conditions that influence how pollutants are formed, dispersed, and removed from the atmosphere. Rising temperatures, more frequent heatwaves, and increased wildfire activity can lead to higher levels of pollutants. Stronger winds and heavier rainfall can sometimes improve air quality by dispersing or removing pollution. Longer periods of hot, dry weather can allow pollutants to build up near the ground. Air pollution and climate change are closely linked, with each influencing the other.

Climate change is already affecting the UK, bringing warmer temperatures, more frequent and intense heatwaves, heavier rainfall, and an increased risk of flooding. Rising sea levels are also increasing the risk of coastal flooding and erosion in some areas. While hotter summers are becoming more common, changes in rainfall patterns can also increase the risk of droughts and water shortages.

The UK is also affected by climate impacts elsewhere in the world. More extreme weather can disrupt global food production, supply chains and energy systems, affecting the availability and cost of goods and services in the UK. Climate change can also increase risks to global ecosystems, human health, and infrastructure, creating challenges that extend beyond national borders.

1.5°C warming refers to an increase of 1.5°C in the Earth’s average global temperature compared to pre-industrial levels, before large-scale burning of fossil fuels began in the late 1800s.

Even a seemingly small rise in global temperature can have significant impacts. At 1.5°C of warming, we can expect more frequent and intense heatwaves, heavier rainfall, rising sea levels, and increased risks to ecosystems, food supplies, and human health. Limiting warming to 1.5°C is a key goal of international efforts to reduce the impacts of climate change.

Black carbon is a type of fine particulate matter produced when fuels or biomass do not burn completely. It is a major component of soot and consists of tiny black particles that absorb sunlight. Black carbon affects both air quality and climate. It can be inhaled deep into the lungs, and also absorbs heat in the atmosphere and contributes to global warming.

A climate tipping point is a critical climate threshold where minor changes trigger abrupt, irreversible shifts into a new stable state. Once a tipping point is crossed, the climate can move into a new state that is difficult or impossible to reverse on human timescales. Examples include the collapse of major ice sheets, widespread thawing of permafrost, and the dieback of tropical rainforests. Scientists study climate tipping points because crossing them could accelerate climate change and increase risks to people, societies, and the natural environment.