Our Earth is experiencing unusually rapid warming compared to changes over the previous 2,000 years. This global warming is clearly the result of greenhouse gas emissions caused by human activities, particularly the burning of fossil fuels such as coal, oil and natural gas, used in transportation and energy. Global warming and the associated climate change are leading to increasingly serious and harmful consequences for people and the ecosystems that support us. These consequences are manifested in deteriorating health, safety, security and prosperity.

Climate change is often referred to as a challenge or crisis because of its severe impacts, the urgency of finding solutions, and the complexity of the problem. Already, climate change is increasing pressure on the physical infrastructure and social, economic, and political systems we rely on, while also threatening the health and well-being of people and all life on Earth.

Some future climate change is inevitable and/or irreversible, such as the loss of ice sheets and the permanent flooding of coastal areas. However, these changes can be limited by significant and rapid reductions in global greenhouse gas emissions. Urgent action to reduce emissions and scale up adaptation in this decade is crucial to minimize impacts on people and ecosystems. Rapid action would also bring a number of benefits, particularly for air quality and health. These transitions would involve large-scale changes in technology, infrastructure, land use, behaviour and governance structures.

Greenhouse gases emitted by human activities include carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O) and fluorinated gases. Increased amounts of these gases in the atmosphere are causing global warming, with widespread consequences for the climate system.

Climate change has broad impacts on the health and well-being of people and ecosystems. These include more frequent and intense floods, droughts, stronger storms, and fires; changes in food availability and crop production methods; threats to water supplies; and increases in vector-borne diseases, mental health problems, and heat-related illnesses and deaths. Together, these impacts can increase risks to national security.

While some people and regions may experience limited or short-term benefits from climate change, the negative impacts already outweigh most of the positive effects, and with continued warming, any benefits will be further eroded.

Although climate change affects everyone, its impacts are not the same for everyone. Some individuals and communities face higher health risks depending on factors such as age, where they work or live, access to resources, and pre-existing health conditions. These factors are influenced by social and economic context. For example, low-income communities and communities of color face greater risks and harms because they are more likely to live or work in areas exposed to climate hazards and often have fewer resources to respond to their impacts. In rural areas, these risks may be even higher due to a lack of resources or infrastructure to adapt. Young people will also face increasing pressures from climate change throughout their lives. An important part of climate literacy is understanding how and why people perceive the impacts of climate change differently and how social and cultural contexts influence their ability to respond. Spring

Glossary of key terms

• Adaptation: In human systems, it is the process of adapting to actual or expected climate and its effects in order to mitigate damage or take advantage of advantageous opportunities. In natural systems, it is the process of adapting to actual climate and its effects.
• Aerosols: A suspension of airborne solid or liquid particles with a typical particle size ranging from a few nanometers to a few tens of micrometers.
• Biodiversity: The diversity of life, including the number of plant and animal species, other life forms, genetic types, habitats, and biomes in an ecosystem.
• Carbon cycle: The set of processes by which carbon compounds flow between reservoirs in the environment.
• Circulation (ocean): The large-scale movement of water in an ocean basin, which is a key regulator of climate.
• Climate: The average weather conditions of an area over a longer period of time.
• Climate change: Changes in average weather conditions that persist for several decades or longer.
• Climate justice: Recognition of diversity of values and past and present harms.
• Climate model: Numerical representation of the climate system based on physical, chemical and biological properties.
• Climate system: Matter, energy, and processes involved in the interactions between the Earth's atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere.
• Climate variability: Deviations of climate variables from a given average state.
• Co-production (of knowledge): Integration of different knowledge systems.
• Decent work: Productive work for people in conditions of freedom, equality, security and human dignity.
• Discrimination: Unequal treatment of an individual or group of people based on, for example, their race, gender, age or disability.
• Drought: An exceptional period of water shortage.
• Earth system: The function of the Earth as a system of interconnected parts.
• Eco-anxiety: Chronic fear of environmental destruction.
• Eco system: A functional unit consisting of living organisms, their non-living environment, and their interactions with each other.
• Emissions: Release of gases and aerosols into the atmosphere.
• Environmental injustice: Environmental actions, behaviors, laws, and policies that are not fair.
• Equality: The principle of being fair and impartial.
• Extreme events: Weather events that are rare in a particular place and time.
• Extreme heat: Temperatures that are much higher and/or more humid than average.
• Flood: Overflowing of the normal boundaries of a watercourse.
• Food Network: Diagram of the connections between species in an ecosystem.
• Fossil fuels: Carbon fuels from fossil hydrocarbon deposits, including coal, oil, and natural gas.
• Global warming: Increase in global surface temperature.
• Greenhouse effect: The process by which heat is trapped near the Earth's surface by greenhouse gases.
• Greenhouse gas (GHG): Gaseous components of the atmosphere that absorb and emit radiation.
• Danger: The potential occurrence of a natural or man-made physical event.
• Heat wave: A period of abnormally hot weather.
• Tide flooding: It occurs when sea level rise combines with local factors.
• Ice shield: A continental-sized ice body.
• Impact (climatic): Consequences of realized risks on natural and human systems.
• Indigenous Knowledge (IK): Bodies of dynamic and experiential knowledge acquired over time by indigenous peoples.
• Industrial Era: The period from the beginning of large-scale industrial activity around 1750 to the present.
• Inequality: Unfair difference in resource distribution.
• Intergovernmental Panel on Climate Change: An organization that provides scientific information for climate policymaking.
• Just transition: A set of principles, processes and practices that ensure that no one is left behind in the transition to a low-carbon economy.
• Maladaptation: It occurs when actions are taken that may lead to an increased risk of adverse climate-related consequences.
• Marginalized population/community: A community excluded from mainstream social, economic and cultural life.
• Migration (of people): The movement of a person or group of persons across international borders or within a nation.
• Mitigation: Measures to reduce the amount and speed of future climate change.
• Ocean acidification: The process by which the pH value of seawater shifts towards more acidic values.
• Congested community: A population or geographic area that experiences disproportionate environmental and climate damage and risks.
• Paris Agreement: The 2015 international climate agreement.
• Participatory processes: Approaches to research and planning in which those most affected by the results are actively involved in the process.
• Renewable energy: Any form of energy that is replenished by natural processes.
• Resistance (climatic): The ability of interconnected social, economic and ecological systems to cope with climate change.
• Risk: Threat to life, health, safety, environment, economic well-being and other valuables.
• Sea level rise: Sea level rise.
• Social systems: Institutions, policies, programs, practices, values, and behavior.
• Storm surge: A temporary rise in sea level due to extreme weather conditions.
• Transformational adaptation: Adaptation that changes the fundamental attributes of a socio-ecological system.
• Critical point: The point at which climate change triggers a major environmental event.
• Uncertainty (statistical): An expression of the extent to which a quantity or process is unknown.
• Neglected community: A community that experiences disproportionate environmental and climate harms and risks due to ongoing systemic discrimination.
• Vector (diseases): An organism that transmits disease-causing microorganisms.
• Vulnerability (climatic): The extent to which physical, biological and socio-economic systems are vulnerable to the adverse impacts of climate change.
• Weather: The state of the atmosphere, especially with regard to its effects on life and human activities.
• Well-being (human): A state of existence that fulfills various human needs.
• Fire: Wildland fire.