Image source, Getty ImagesImage caption, Climate change is increasing the frequency and intensity of extreme heat events
ByMark Poynting and Alex BrianBBC News Climate & Science- Published23 September 2013
Human activities are causing world temperatures to rise, posing serious threats to people and nature.
Things are likely to worsen in the coming decades, but scientists argue urgent action can still limit the worst effects of climate change.
What is climate change?
Climate change is the long-term shift in the Earth's average temperatures and weather conditions.
The world has been rapidly warming for around a century, causing weather patterns to change.
Since the 1980s, each decade has been warmer than the previous one, the Met Office says.
2024 was Earth's hottest year on record, with climate change mainly responsible for the high temperatures.
It was also the first calendar year to surpass 1.5C of warming compared to "pre-industrial" levels of the late 1800s, according to the Copernicus climate service, external.
Temperatures remained high in 2025, despite a slight cooling from a natural weather pattern called La Niña.
The opposite El Niño pattern, combined with climate change, makes it likely that 2026 will also rank among the hottest years ever recorded.
How are humans causing climate change?
The climate has changed naturally throughout the Earth's history.
But natural causes cannot explain the particularly rapid warming seen over the last century, according to the UN's climate body, the Intergovernmental Panel on Climate Change (IPCC).
This has been without doubt caused by human activities, especially the widespread use of fossil fuels - coal, oil and gas - in homes, factories and transport systems.
When fossil fuels burn, they release greenhouse gases - mostly carbon dioxide (CO2). This CO2 acts like a blanket, trapping extra energy in the atmosphere near the Earth's surface. This causes the planet to heat up.
Since the start of the Industrial Revolution - when humans began burning large amounts of fossil fuels - the level of CO2 in the atmosphere has risen by more than 50%.
The CO2 released from burning fossil fuels, external has a distinctive chemical fingerprint. This matches the type of CO2 increasingly found in the atmosphere.
What effects of climate change have already been seen?
Climate change has already had a huge effect, including:
more frequent and intense extreme weather, such as heatwaves and heavy rainfall
rapid melting of glaciers and ice sheets, contributing to sea-level rises
the shrinking of Arctic sea-ice
warmer oceans, which can fuel more intense storms and harm sea life
These changes are already having serious consequences for people and economies around the world.
Image source, Getty ImagesImage caption, In August 2026, the partial collapse of a glacier caused an avalanche of ice and rock to descend on Nepal and Tibet
Flash floods in Nepal killed more than 1,400 people in August 2026. Nepal's Finance Minister, Swarnim Wagle, said it could cost up to a tenth of the economy to rebuild.
Climate change increased the chances of the glacier collapse which triggered the flood, World Weather Attribution group scientists said.
Why does 1.5C matter and how will future climate change affect the world?
The more the world warms, the worse the impacts of climate change become.
Nearly 200 countries pledged to try to limit global warming to 1.5C above pre-industrial levels in the 2015 Paris agreement.
That target is generally understood to mean an average annual increase of 1.5C over 20 years rather than a one-off rise in a single year.
Long-term warming of 1.5C would bring serious consequences for many populations.
But an increase of 2C or more would bring even greater impacts, the IPCC says.
These include:
more people exposed to extreme heat
increased risks to food security in some regions due to more extreme weather
greater chances of some climate-sensitive diseases spreading, such as dengue
more species being threatened with extinction
The call to restrict temperature rise to 1.5C was partly designed to avoid crossing so-called "tipping points".
It is not clear exactly where they sit, but once these thresholds are passed, changes could accelerate and become irreversible.
These could include the collapse of the Greenland Ice Sheet, warm Atlantic Ocean currents or further loss of the Amazon rainforest.
Image source, Getty ImagesImage caption, The Earth's poles are especially vulnerable to rising temperatures
About 3.3 to 3.6 billion people are highly vulnerable to climate change, the IPCC says.
People living in poorer countries are expected to suffer most as they have fewer resources to adapt.
This has led to questions about fairness, external, because these places have typically only been responsible for a small percentage of greenhouse gas emissions.
However, knock-on impacts could be felt over wide areas. For example, crop failures linked to extreme weather could raise food prices globally.
What are governments doing about climate change?
Reaching net zero CO2 emissions is essential to limit global warming, the IPCC says.
This means reducing emissions as much as possible and actively removing any remaining emissions from the atmosphere.
Most countries have, or are considering, net zero targets, external.
There has been encouraging progress in some areas, such as renewable energy and electric vehicles.
But humanity's CO2 emissions are still at record highs, causing long-term warming to reach 1.4C in 2025.
The latest UN Emissions Gap Report, external said the 1.5C limit was likely to be breached in the coming years.
A return to 1.5C by 2100 was possible, but it would require "urgent and stringent cuts to greenhouse emissions", the report added.
Otherwise, global warming could reach nearly 3C by the end of the century, the UN said.
World leaders meet every year to discuss their climate commitments.
In 2025, the COP30 climate conference ended without any new agreements on fossil fuels or deforestation in the final deal.
Countries had previously agreed on the need to "transition away from fossil fuels in energy systems" at the COP28 talks in 2023.
At COP29 in 2024, richer countries committed to giving developing nations at least $300bn (£223bn) a year by 2035 to help them tackle climate change. But this is far less than poorer countries say they need.
Governments are gathering in Turkey for the next round of talks, COP31, in November 2026.
What can individuals do about climate change?
Major changes need to come from governments and businesses, but individuals can help through actions like:
taking fewer flights
using less energy
improving their home's insulation and energy efficiency
switching to electric vehicles or living car-free
replacing gas boilers with electric systems like heat pumps
eating less red meat
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