Global temperatures are rising because of human activity, with more intense heatwaves and rising sea-levels among the consequences.
Things are likely to worsen in the coming decades, but urgent action can 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 is now about 1.1C warmer than in the late 19th Century.
Are humans causing climate change?
The climate has changed throughout the Earth's history. But natural causes cannot explain the particularly rapid warming of the past century.
It is mainly because of the widespread use of fossil fuels - coal, oil and gas - in homes, factories and transport.
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When fossil fuels burn, they release greenhouse gases - mostly carbon dioxide [CO2]. This traps extra energy in the atmosphere near the Earth's surface, causing the planet to heat up.
Since the start of the Industrial Revolution - when humans started burning large amounts of fossil fuels - the amount of CO2 in the atmosphere has risen by about 50%.
The CO2 from burning fossil fuels also has a distinctive chemical fingerprint. This matches the type increasing in the atmosphere.
What are the effects of climate change so far?
A global average temperature increase of 1.1C might not sound much.
However, it has had a huge effect on the environment, including:
- more frequent and intense extreme weather, such as heatwaves and heavy rainfall
- rapid melting of glaciers and ice sheets, contributing to sea-level rise
- huge declines in Arctic sea-ice
- ocean warming
People's lives are also changing.
For example, parts of East Africa recently suffered their worst drought in 40 years, putting more than 20 million people at risk of severe hunger. In 2022, European heatwaves led to an abnormal increase in deaths.
How will future climate change affect the world?
The more temperatures increase, the worse the impacts of climate change become.
Limiting long-term temperature rises to 1.5C is crucial, according to the UN's climate body, the IPCC.
The science is not completely certain, but the impacts of 2C global warming versus 1.5C could include:
- Extreme hot days would be on average 4C warmer at mid-latitudes [regions outside the poles and tropics], versus 3C at 1.5C
- Sea-level rise would be 0.1m higher than at 1.5C, exposing up to 10 million more people
- More than 99% of coral reefs would be lost, compared with 70-90% at 1.5C
- Twice the number of plants and vertebrates [animals with a backbone] would be exposed to unsuitable climate conditions across more than half their range
- Several hundred million more people may be exposed to climate-related risks and susceptible to poverty by 2050 than at 1.5C.
The 1.5C limit was partly designed to avoid crossing so-called "tipping points".
Beyond these points, changes could accelerate and become irreversible, such as the collapse of the Greenland Ice Sheet. However, it's not clear precisely where these thresholds sit.
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.
However, knock-on impacts could be felt over wide areas. For example, crop failures linked to extreme weather could raise global food prices.
What are governments doing about climate change?
In a landmark agreement signed in Paris in 2015, almost 200 countries pledged to try to keep global warming to 1.5C.
To achieve this, net zero CO2 emissions should be reached by 2050. Net zero means reducing greenhouse gas emissions as much as possible, and removing any remaining emissions from the atmosphere.
However, greenhouse gas levels are still rising quickly and the world is "likely" to warm beyond 1.5C, the IPCC says.
However, there has been progress in some areas like renewable energy and electric vehicles.
World leaders meet every year to discuss their climate commitments. The next summit [COP28] will be held in the United Arab Emirates between 30 November and 12 December 2023.
What can individuals do?
Major changes need to come from governments and businesses, but small changes by individuals can help:
- take fewer flights
- use less energy
- improve home insulation and energy efficiency
- switch to electric vehicles or live car-free
- replace gas central heating with electric systems like heat pumps
- eat less red meat
Top image from Getty Images. Climate stripes visualisation courtesy of Prof Ed Hawkins and University of Reading.
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