Introduction
Climate change is one of the defining environmental and development challenges of the 21st century. Rising greenhouse gas concentrations are warming the atmosphere and oceans, changing rainfall patterns, accelerating ice loss and increasing risks from extreme heat, heavy rainfall, drought and other climate hazards.
The scientific evidence is clear about the central cause: human activities, particularly the release of greenhouse gases from fossil fuels, land-use change and other sources, have unequivocally caused global warming. The Intergovernmental Panel on Climate Change (IPCC) estimates that global surface temperature was already about 1.1°C above the 1850–1900 average during 2011–2020.
The latest observations show that warming has continued. The World Meteorological Organization (WMO) reports that 2015–2025 were the 11 warmest years on record, while 2025 was approximately 1.43°C above the 1850–1900 average.
Climate change does not mean that every weather event is caused by global warming. Rather, a changing climate alters the likelihood and intensity of many extremes, while increasing risks to human health, food and water security, economies and natural ecosystems.
What Is Climate Change?
Climate change refers to long-term changes in Earth’s climate, including changes in average temperatures, precipitation, wind patterns and the frequency or intensity of some extreme events.
Earth’s climate has changed naturally throughout geological history. However, the rapid warming observed since the industrial era is primarily driven by human activities that increase concentrations of heat-trapping greenhouse gases.
The most important human-related sources include:
- Burning coal, oil and natural gas for electricity, transport, heating and industry
- Deforestation and other land-use changes
- Agriculture and livestock production
- Industrial processes
- Waste and methane emissions
- Energy production and distribution
Carbon dioxide (CO₂) is the largest contributor to long-term human-caused warming, although methane and nitrous oxide are also important greenhouse gases.
The Latest Evidence Shows a Rapidly Warming Planet
Climate change is no longer only a projection of what might happen decades from now. Many of its physical effects are already measurable.
According to the WMO’s State of the Global Climate 2025, the 11-year period from 2015 through 2025 was the warmest such sequence in the instrumental record. The same assessment found that ocean heat content reached a record high in 2025.
Global mean sea level has also continued to rise. WMO reports that the 2025 level was about 11 centimetres higher than at the beginning of the satellite altimetry record in 1993, with the long-term rate of rise increasing compared with the earlier part of that record.
These indicators matter because warming does not stop at the atmosphere. Extra heat is accumulating in the ocean, ice is being lost and sea levels are rising, creating risks that can persist long after individual heatwaves or storms have ended.
Major Impacts of Climate Change
1. More Dangerous Extreme Heat
One of the clearest consequences of global warming is an increase in extreme heat.
As the average temperature rises, unusually hot conditions become more likely. Heat can directly cause illness and death, while also reducing labour productivity, increasing pressure on electricity systems and worsening drought and wildfire conditions in some regions.
The risks are particularly significant for older people, children, outdoor workers and communities with limited access to cooling and healthcare.
2. Rising Sea Levels and Coastal Risks
Sea-level rise is driven mainly by the expansion of warming seawater and the loss of land-based ice.
Higher seas increase the risk of coastal flooding, erosion and saltwater intrusion into freshwater systems. Low-lying coastal communities and small island states face particularly serious long-term challenges.
WMO reports that global mean sea level in 2025 remained near record-high levels and that the rate of rise since 2012 was higher than during 1993–2011.
3. Threats to Food and Water Security
Climate change can disrupt agriculture through higher temperatures, changing rainfall patterns, drought, floods and other extreme events.
The effects vary by location and crop, but increasing climate hazards can make food production less predictable and place additional pressure on water resources.
Climate change can also compound existing problems such as poverty, land degradation and inadequate infrastructure. This means the consequences are often greatest where communities have the fewest resources to adapt.
4. Damage to Ecosystems and Biodiversity
Plants and animals are responding to changes in temperature, rainfall, ocean conditions and seasonal cycles.
Some species can move or adapt, while others face increasingly difficult conditions. Coral reefs, polar environments, forests, freshwater ecosystems and other climate-sensitive systems are particularly exposed to multiple pressures.
The IPCC warns that climate risks increase with every additional increment of global warming, making rapid emissions reductions and effective adaptation increasingly important.
5. Growing Risks to Human Health
Climate change is also a major public-health concern.
The World Health Organization identifies heatwaves, floods, storms, disrupted food systems, infectious diseases and other pathways through which climate change can affect health. It estimates that approximately 3.6 billion people already live in areas highly susceptible to climate change.
WHO also projects approximately 250,000 additional deaths per year between 2030 and 2050 from a limited group of climate-sensitive causes—malnutrition, malaria, diarrhoea and heat stress alone. This figure does not represent the full health burden of climate change.
The burden is also unevenly distributed. People and countries with fewer resources to adapt can face disproportionately severe consequences despite often contributing less to historical greenhouse gas emissions.
Why 1.5°C Matters
The 1.5°C figure is frequently discussed because the Paris Agreement calls for efforts to limit the increase in global average temperature to 1.5°C above pre-industrial levels while also holding warming well below 2°C.
These thresholds are not a simple point at which climate change suddenly becomes safe or dangerous. Climate risks increase progressively with warming.
The practical implication is important: every fraction of a degree of additional warming matters.
UNEP’s Emissions Gap Report 2025 estimates that full implementation of the latest national climate pledges would still leave the world on a trajectory toward approximately 2.3–2.5°C of warming this century, while current policies point toward about 2.8°C.
In September 2026, UNEP further reported that exceeding 1.5°C over a multi-decadal period is now widely assessed as unavoidable, making the reduction of peak warming and the duration of any overshoot increasingly important.
This does not mean that climate action has become pointless. On the contrary, limiting additional warming can still substantially reduce future risks and damages.
Climate Change and the Global Economy
The economic consequences of climate change extend well beyond direct damage from storms, floods or wildfires.
Climate-related disruption can affect :
- Agriculture and food prices
- Infrastructure and housing
- Energy systems
- Supply chains
- Labour productivity
- Public health
- Insurance and financial markets
- Government budgets
- Poverty reduction and development
The World Bank estimates that climate change could push an additional 132 million people into extreme poverty by 2030, highlighting how climate risks can undermine progress in reducing poverty.
The economic consequences are not predetermined, however. Investments in resilient infrastructure, clean energy, efficient buildings, public transport, early-warning systems and climate-smart agriculture can reduce exposure and create wider social and economic benefits.
What Can Be Done About Climate Change?
Addressing climate change requires two complementary approaches: mitigation and adaptation.
Mitigation : Reducing the Causes
Mitigation means reducing greenhouse gas emissions or increasing the removal of carbon dioxide from the atmosphere.
Key measures include :
- Expanding renewable energy such as solar and wind power.
- Improving energy efficiency in buildings, industry and transport.
- Electrifying transport and other energy uses where practical.
- Reducing methane emissions from energy, agriculture and waste.
- Protecting and restoring forests and other ecosystems.
- Reducing food loss and waste.
- Developing low-carbon industrial technologies.
- Using effective climate policies and investment to accelerate the transition.
The IPCC has found that the costs of several key low-emission technologies have fallen substantially. It also identifies solar power, wind energy, energy efficiency, reduced ecosystem conversion and methane reductions among options with significant emissions-reduction potential.
Adaptation : Preparing for a Changing Climate
Some climate impacts can no longer be avoided, making adaptation essential.
Adaptation measures can include:
- Early-warning systems for extreme weather
- Heat-health action plans
- Flood protection and improved drainage
- Drought-resistant agricultural practices
- Water conservation
- Climate-resilient infrastructure
- Urban cooling and green spaces
- Stronger health systems
- Coastal planning and ecosystem restoration
Adaptation cannot eliminate every climate risk, particularly at higher levels of warming. But well-designed adaptation can significantly reduce vulnerability and protect lives, livelihoods and infrastructure.
Climate Action Is Also a Health and Development Opportunity
Climate policies are not simply about avoiding future damage. Many measures can deliver immediate benefits.
For example, replacing polluting fossil-fuel combustion with cleaner energy can reduce both greenhouse gas emissions and air pollution. Better public transport, walking and cycling infrastructure can reduce emissions while supporting physical activity. More efficient buildings can lower energy use and improve comfort.
The IPCC concludes that low-emission transitions can provide multiple co-benefits, including improvements in air quality and health.
The challenge is therefore not simply whether societies can respond to climate change, but whether governments, businesses and communities can accelerate the transition at sufficient scale and speed while ensuring that its costs and benefits are distributed fairly.
Key Facts About Climate Change
| Finding | Latest evidence |
|---|---|
| Human cause of warming | Human activities have unequivocally caused global warming, according to the IPCC. |
| Recent temperature trend | 2015–2025 were the 11 warmest years on record, according to WMO. |
| 2025 global temperature | About 1.43°C above the 1850–1900 average. |
| Ocean warming | Ocean heat content reached a record high in 2025. |
| Sea-level rise | Global mean sea level was about 11 cm above the 1993 satellite baseline in 2025. |
| Current climate trajectory | UNEP estimates 2.3–2.5°C of warming this century if current national pledges are fully implemented. |
| Health vulnerability | About 3.6 billion people live in areas highly susceptible to climate change, according to WHO. |
Sources: IPCC, WMO, UNEP and WHO.
What Does Climate Change Mean for the Future of the Planet?
The future is not determined by a single temperature threshold or one climate model. It depends heavily on decisions made over the coming years.
Higher emissions generally mean greater warming and greater risks. Conversely, rapid reductions in greenhouse gas emissions can limit the amount of additional warming and reduce the severity of many future impacts.
Even if global warming temporarily exceeds 1.5°C, climate action remains important. UNEP’s latest assessment emphasizes that limiting the magnitude and duration of an overshoot can reduce risks, while the IPCC continues to show that lower-warming pathways are associated with substantially lower climate risks.
This makes the climate challenge both a warning and a choice. The scientific evidence shows that delay increases risks, but it also shows that practical solutions already exist.
Conclusion : Climate Change Is a Challenge We Can Still Influence
Climate change is already altering Earth’s atmosphere, oceans, ecosystems and societies. The evidence is no longer limited to long-term projections: record temperatures, rising seas, increasing ocean heat and growing climate-related risks are being observed today.
The challenge is serious, but describing climate change only as an environmental threat misses part of the picture. It is also a health, economic, infrastructure, food-security and development issue.
The most effective response combines rapid greenhouse gas reductions with climate adaptation, resilient infrastructure, technological innovation and international cooperation. Every fraction of a degree of warming avoided can reduce future risks.
The future of the planet will not be determined by climate change alone. It will also be shaped by how quickly societies respond to the evidence. The scientific message is clear: the longer emissions remain high, the greater the risks; the faster the world moves toward a low-emissions and climate-resilient future, the more damage can be avoided.
Sources
- Intergovernmental Panel on Climate Change (IPCC) — Climate Change 2023: Synthesis Report. IPCC Climate Change 2023: Synthesis Report
- World Meteorological Organization (WMO) — State of the Global Climate 2025, published March 2026. WMO State of the Global Climate 2025
- United Nations Environment Programme (UNEP) — Emissions Gap Report 2025: Off Target. UNEP Emissions Gap Report 2025
- United Nations Environment Programme (UNEP) — Limiting Overshoot: Navigating exceedance of 1.5°C and pathways towards return, September 2026. UNEP Limiting Overshoot report
- World Health Organization (WHO) — Climate Change and Health. WHO Climate Change and Health
- World Bank — Health and Climate Change, 2025. World Bank Health and Climate Change
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